import { describe, it } from 'mocha';
import assert from 'assert'
// @ts-ignore
import { BloomFilter } from './helpers/sync'
import { create, load, SyncState, Automerge, decodeChange, initSyncState, decodeSyncMessage, decodeSyncState, encodeSyncState, encodeSyncMessage } from '..'
import { Value, DecodedSyncMessage, Hash } from '..';

function sync(a: Automerge, b: Automerge, aSyncState = initSyncState(), bSyncState = initSyncState()) {
  const MAX_ITER = 10
  let aToBmsg = null, bToAmsg = null, i = 0
  do {
    aToBmsg = a.generateSyncMessage(aSyncState)
    bToAmsg = b.generateSyncMessage(bSyncState)

    if (aToBmsg) {
      b.receiveSyncMessage(bSyncState, aToBmsg)
    }
    if (bToAmsg) {
      a.receiveSyncMessage(aSyncState, bToAmsg)
    }

    if (i++ > MAX_ITER) {
      throw new Error(`Did not synchronize within ${MAX_ITER} iterations`)
    }
  } while (aToBmsg || bToAmsg)
}

describe('Automerge', () => {
  describe('basics', () => {

    it('should create, clone and free', () => {
      const doc1 = create()
      const doc2 = doc1.clone()
      doc2.free()
    })

    it('should be able to start and commit', () => {
      const doc = create()
      doc.commit()
    })

    it('getting a nonexistent prop does not throw an error', () => {
      const doc = create()
      const root = "_root"
      const result = doc.getWithType(root, "hello")
      assert.deepEqual(result, undefined)
    })

    it('should be able to set and get a simple value', () => {
      const doc: Automerge = create("aabbcc")
      const root = "_root"
      let result

      doc.put(root, "hello", "world")
      doc.put(root, "number1", 5, "uint")
      doc.put(root, "number2", 5)
      doc.put(root, "number3", 5.5)
      doc.put(root, "number4", 5.5, "f64")
      doc.put(root, "number5", 5.5, "int")
      doc.put(root, "bool", true)
      doc.put(root, "time1", 1000, "timestamp")
      doc.put(root, "time2", new Date(1001))
      doc.putObject(root, "list", []);
      doc.put(root, "null", null)

      result = doc.getWithType(root, "hello")
      assert.deepEqual(result, ["str", "world"])
      assert.deepEqual(doc.get("/", "hello"), "world")

      result = doc.getWithType(root, "number1")
      assert.deepEqual(result, ["uint", 5])
      assert.deepEqual(doc.get("/", "number1"), 5)

      result = doc.getWithType(root, "number2")
      assert.deepEqual(result, ["int", 5])

      result = doc.getWithType(root, "number3")
      assert.deepEqual(result, ["f64", 5.5])

      result = doc.getWithType(root, "number4")
      assert.deepEqual(result, ["f64", 5.5])

      result = doc.getWithType(root, "number5")
      assert.deepEqual(result, ["int", 5])

      result = doc.getWithType(root, "bool")
      assert.deepEqual(result, ["boolean", true])

      doc.put(root, "bool", false, "boolean")

      result = doc.getWithType(root, "bool")
      assert.deepEqual(result, ["boolean", false])

      result = doc.getWithType(root, "time1")
      assert.deepEqual(result, ["timestamp", new Date(1000)])

      result = doc.getWithType(root, "time2")
      assert.deepEqual(result, ["timestamp", new Date(1001)])

      result = doc.getWithType(root, "list")
      assert.deepEqual(result, ["list", "10@aabbcc"]);

      result = doc.getWithType(root, "null")
      assert.deepEqual(result, ["null", null]);
    })

    it('should be able to use bytes', () => {
      const doc = create()
      doc.put("_root", "data1", new Uint8Array([10, 11, 12]));
      doc.put("_root", "data2", new Uint8Array([13, 14, 15]), "bytes");
      const value1 = doc.getWithType("_root", "data1")
      assert.deepEqual(value1, ["bytes", new Uint8Array([10, 11, 12])]);
      const value2 = doc.getWithType("_root", "data2")
      assert.deepEqual(value2, ["bytes", new Uint8Array([13, 14, 15])]);
    })

    it('should be able to make subobjects', () => {
      const doc = create()
      const root = "_root"
      let result

      const submap = doc.putObject(root, "submap", {})
      doc.put(submap, "number", 6, "uint")
      assert.strictEqual(doc.pendingOps(), 2)

      result = doc.getWithType(root, "submap")
      assert.deepEqual(result, ["map", submap])

      result = doc.getWithType(submap, "number")
      assert.deepEqual(result, ["uint", 6])
    })

    it('should be able to make lists', () => {
      const doc = create()
      const root = "_root"

      const sublist = doc.putObject(root, "numbers", [])
      doc.insert(sublist, 0, "a");
      doc.insert(sublist, 1, "b");
      doc.insert(sublist, 2, "c");
      doc.insert(sublist, 0, "z");

      assert.deepEqual(doc.getWithType(sublist, 0), ["str", "z"])
      assert.deepEqual(doc.getWithType(sublist, 1), ["str", "a"])
      assert.deepEqual(doc.getWithType(sublist, 2), ["str", "b"])
      assert.deepEqual(doc.getWithType(sublist, 3), ["str", "c"])
      assert.deepEqual(doc.length(sublist), 4)

      doc.put(sublist, 2, "b v2");

      assert.deepEqual(doc.getWithType(sublist, 2), ["str", "b v2"])
      assert.deepEqual(doc.length(sublist), 4)
    })

    it('lists have insert, set, splice, and push ops', () => {
      const doc = create()
      const root = "_root"

      const sublist = doc.putObject(root, "letters", [])
      doc.insert(sublist, 0, "a");
      doc.insert(sublist, 0, "b");
      assert.deepEqual(doc.materialize(), { letters: ["b", "a"] })
      doc.push(sublist, "c");
      const heads = doc.getHeads()
      assert.deepEqual(doc.materialize(), { letters: ["b", "a", "c"] })
      doc.push(sublist, 3, "timestamp");
      assert.deepEqual(doc.materialize(), { letters: ["b", "a", "c", new Date(3)] })
      doc.splice(sublist, 1, 1, ["d", "e", "f"]);
      assert.deepEqual(doc.materialize(), { letters: ["b", "d", "e", "f", "c", new Date(3)] })
      doc.put(sublist, 0, "z");
      assert.deepEqual(doc.materialize(), { letters: ["z", "d", "e", "f", "c", new Date(3)] })
      assert.deepEqual(doc.materialize(sublist), ["z", "d", "e", "f", "c", new Date(3)])
      assert.deepEqual(doc.length(sublist), 6)
      assert.deepEqual(doc.materialize("/", heads), { letters: ["b", "a", "c"] })
    })

    it('should be able delete non-existent props', () => {
      const doc = create()

      doc.put("_root", "foo", "bar")
      doc.put("_root", "bip", "bap")
      const hash1 = doc.commit()

      assert.deepEqual(doc.keys("_root"), ["bip", "foo"])

      doc.delete("_root", "foo")
      doc.delete("_root", "baz")
      const hash2 = doc.commit()

      assert.deepEqual(doc.keys("_root"), ["bip"])
      assert.deepEqual(doc.keys("_root", [hash1]), ["bip", "foo"])
      assert.deepEqual(doc.keys("_root", [hash2]), ["bip"])
    })

    it('should be able to del', () => {
      const doc = create()
      const root = "_root"

      doc.put(root, "xxx", "xxx");
      assert.deepEqual(doc.getWithType(root, "xxx"), ["str", "xxx"])
      doc.delete(root, "xxx");
      assert.deepEqual(doc.getWithType(root, "xxx"), undefined)
    })

    it('should be able to use counters', () => {
      const doc = create()
      const root = "_root"

      doc.put(root, "counter", 10, "counter");
      assert.deepEqual(doc.getWithType(root, "counter"), ["counter", 10])
      doc.increment(root, "counter", 10);
      assert.deepEqual(doc.getWithType(root, "counter"), ["counter", 20])
      doc.increment(root, "counter", -5);
      assert.deepEqual(doc.getWithType(root, "counter"), ["counter", 15])
    })

    it('should be able to splice text', () => {
      const doc = create()
      const root = "_root";

      const text = doc.putObject(root, "text", "");
      doc.splice(text, 0, 0, "hello ")
      doc.splice(text, 6, 0, ["w", "o", "r", "l", "d"])
      doc.splice(text, 11, 0, ["!", "?"])
      assert.deepEqual(doc.getWithType(text, 0), ["str", "h"])
      assert.deepEqual(doc.getWithType(text, 1), ["str", "e"])
      assert.deepEqual(doc.getWithType(text, 9), ["str", "l"])
      assert.deepEqual(doc.getWithType(text, 10), ["str", "d"])
      assert.deepEqual(doc.getWithType(text, 11), ["str", "!"])
      assert.deepEqual(doc.getWithType(text, 12), ["str", "?"])
    })

    it('should be able to insert objects into text', () => {
      const doc = create()
      const text = doc.putObject("/", "text", "Hello world");
      const obj = doc.insertObject(text, 6, { hello: "world" });
      assert.deepEqual(doc.text(text), "Hello \ufffcworld");
      assert.deepEqual(doc.getWithType(text, 6), ["map", obj]);
      assert.deepEqual(doc.getWithType(obj, "hello"), ["str", "world"]);
    })

    it('should be able save all or incrementally', () => {
      const doc = create()

      doc.put("_root", "foo", 1)

      const save1 = doc.save()

      doc.put("_root", "bar", 2)

      const saveMidway = doc.clone().save();

      const save2 = doc.saveIncremental();

      doc.put("_root", "baz", 3);

      const save3 = doc.saveIncremental();

      const saveA = doc.save();
      const saveB = new Uint8Array([...save1, ...save2, ...save3]);

      assert.notDeepEqual(saveA, saveB);

      const docA = load(saveA);
      const docB = load(saveB);
      const docC = load(saveMidway)
      docC.loadIncremental(save3)

      assert.deepEqual(docA.keys("_root"), docB.keys("_root"));
      assert.deepEqual(docA.save(), docB.save());
      assert.deepEqual(docA.save(), docC.save());
    })

    it('should be able to splice text', () => {
      const doc = create()
      const text = doc.putObject("_root", "text", "");
      doc.splice(text, 0, 0, "hello world");
      const hash1 = doc.commit();
      doc.splice(text, 6, 0, "big bad ");
      const hash2 = doc.commit();
      assert.strictEqual(doc.text(text), "hello big bad world")
      assert.strictEqual(doc.length(text), 19)
      assert.strictEqual(doc.text(text, [hash1]), "hello world")
      assert.strictEqual(doc.length(text, [hash1]), 11)
      assert.strictEqual(doc.text(text, [hash2]), "hello big bad world")
      assert.strictEqual(doc.length(text, [hash2]), 19)
    })

    it('local inc increments all visible counters in a map', () => {
      const doc1 = create("aaaa")
      doc1.put("_root", "hello", "world")
      const doc2 = load(doc1.save(), "bbbb");
      const doc3 = load(doc1.save(), "cccc");
      const heads = doc1.getHeads()
      doc1.put("_root", "cnt", 20)
      doc2.put("_root", "cnt", 0, "counter")
      doc3.put("_root", "cnt", 10, "counter")
      doc1.applyChanges(doc2.getChanges(heads))
      doc1.applyChanges(doc3.getChanges(heads))
      let result = doc1.getAll("_root", "cnt")
      assert.deepEqual(result, [
        ['int', 20, '2@aaaa'],
        ['counter', 0, '2@bbbb'],
        ['counter', 10, '2@cccc'],
      ])
      doc1.increment("_root", "cnt", 5)
      result = doc1.getAll("_root", "cnt")
      assert.deepEqual(result, [
        ['counter', 5, '2@bbbb'],
        ['counter', 15, '2@cccc'],
      ])

      const save1 = doc1.save()
      const doc4 = load(save1)
      assert.deepEqual(doc4.save(), save1);
    })

    it('local inc increments all visible counters in a sequence', () => {
      const doc1 = create("aaaa")
      const seq = doc1.putObject("_root", "seq", [])
      doc1.insert(seq, 0, "hello")
      const doc2 = load(doc1.save(), "bbbb");
      const doc3 = load(doc1.save(), "cccc");
      const heads = doc1.getHeads()
      doc1.put(seq, 0, 20)
      doc2.put(seq, 0, 0, "counter")
      doc3.put(seq, 0, 10, "counter")
      doc1.applyChanges(doc2.getChanges(heads))
      doc1.applyChanges(doc3.getChanges(heads))
      let result = doc1.getAll(seq, 0)
      assert.deepEqual(result, [
        ['int', 20, '3@aaaa'],
        ['counter', 0, '3@bbbb'],
        ['counter', 10, '3@cccc'],
      ])
      doc1.increment(seq, 0, 5)
      result = doc1.getAll(seq, 0)
      assert.deepEqual(result, [
        ['counter', 5, '3@bbbb'],
        ['counter', 15, '3@cccc'],
      ])

      const save = doc1.save()
      const doc4 = load(save)
      assert.deepEqual(doc4.save(), save);
    })

    it('paths can be used instead of objids', () => {
      const doc = create("aaaa")
      doc.putObject("_root", "list", [{ foo: "bar" }, [1, 2, 3]])
      assert.deepEqual(doc.materialize("/"), { list: [{ foo: "bar" }, [1, 2, 3]] })
      assert.deepEqual(doc.materialize("/list"), [{ foo: "bar" }, [1, 2, 3]])
      assert.deepEqual(doc.materialize("/list/0"), { foo: "bar" })
    })

    it('should be able to fetch changes by hash', () => {
      const doc1 = create("aaaa")
      const doc2 = create("bbbb")
      doc1.put("/", "a", "b")
      doc2.put("/", "b", "c")
      const head1 = doc1.getHeads()
      const head2 = doc2.getHeads()
      const change1 = doc1.getChangeByHash(head1[0])
      const change2 = doc1.getChangeByHash(head2[0])
      assert.deepEqual(change2, null)
      if (change1 === null) { throw new RangeError("change1 should not be null") }
      assert.deepEqual(decodeChange(change1).hash, head1[0])
    })

    it('recursive sets are possible', () => {
      const doc = create("aaaa")
      doc.registerDatatype("text", (n: Value[]) => new String(n.join("")))
      const l1 = doc.putObject("_root", "list", [{ foo: "bar" }, [1, 2, 3]])
      const l2 = doc.insertObject(l1, 0, { zip: ["a", "b"] })
      doc.putObject("_root", "info1", "hello world") // 'text' object
      doc.put("_root", "info2", "hello world")  // 'str'
      const l4 = doc.putObject("_root", "info3", "hello world")
      assert.deepEqual(doc.materialize(), {
        "list": [{ zip: ["a", "b"] }, { foo: "bar" }, [1, 2, 3]],
        "info1": new String("hello world"),
        "info2": "hello world",
        "info3": new String("hello world"),
      })
      assert.deepEqual(doc.materialize(l2), { zip: ["a", "b"] })
      assert.deepEqual(doc.materialize(l1), [{ zip: ["a", "b"] }, { foo: "bar" }, [1, 2, 3]])
      assert.deepEqual(doc.materialize(l4), new String("hello world"))
    })

    it('only returns an object id when objects are created', () => {
      const doc = create("aaaa")
      const r1 = doc.put("_root", "foo", "bar")
      const r2 = doc.putObject("_root", "list", [])
      const r3 = doc.put("_root", "counter", 10, "counter")
      const r4 = doc.increment("_root", "counter", 1)
      const r5 = doc.delete("_root", "counter")
      const r6 = doc.insert(r2, 0, 10);
      const r7 = doc.insertObject(r2, 0, {});
      const r8 = doc.splice(r2, 1, 0, ["a", "b", "c"]);
      //let r9 = doc.splice(r2,1,0,["a",[],{},"d"]);
      assert.deepEqual(r1, null);
      assert.deepEqual(r2, "2@aaaa");
      assert.deepEqual(r3, null);
      assert.deepEqual(r4, null);
      assert.deepEqual(r5, null);
      assert.deepEqual(r6, null);
      assert.deepEqual(r7, "7@aaaa");
      assert.deepEqual(r8, null);
      //assert.deepEqual(r9,["12@aaaa","13@aaaa"]);
    })

    it('objects without properties are preserved', () => {
      const doc1 = create("aaaa")
      const a = doc1.putObject("_root", "a", {});
      const b = doc1.putObject("_root", "b", {});
      const c = doc1.putObject("_root", "c", {});
                doc1.put(c, "d", "dd");
      const saved = doc1.save();
      const doc2 = load(saved);
      assert.deepEqual(doc2.getWithType("_root", "a"), ["map", a])
      assert.deepEqual(doc2.keys(a), [])
      assert.deepEqual(doc2.getWithType("_root", "b"), ["map", b])
      assert.deepEqual(doc2.keys(b), [])
      assert.deepEqual(doc2.getWithType("_root", "c"), ["map", c])
      assert.deepEqual(doc2.keys(c), ["d"])
      assert.deepEqual(doc2.getWithType(c, "d"), ["str", "dd"])
    })

    it('should allow you to fork at a heads', () => {
      const A = create("aaaaaa")
      A.put("/", "key1", "val1");
      A.put("/", "key2", "val2");
      const heads1 = A.getHeads();
      const B = A.fork("bbbbbb")
      A.put("/", "key3", "val3");
      B.put("/", "key4", "val4");
      A.merge(B)
      const heads2 = A.getHeads();
      A.put("/", "key5", "val5");
      assert.deepEqual(A.fork(undefined, heads1).materialize("/"), A.materialize("/", heads1))
      assert.deepEqual(A.fork(undefined, heads2).materialize("/"), A.materialize("/", heads2))
    })

    it('should handle merging text conflicts then saving & loading', () => {
      const A = create("aabbcc")
      const At = A.putObject('_root', 'text', "")
      A.splice(At, 0, 0, 'hello')

      const B = A.fork()

      assert.deepEqual(B.getWithType("_root", "text"), ["text", At])

      B.splice(At, 4, 1)
      B.splice(At, 4, 0, '!')
      B.splice(At, 5, 0, ' ')
      B.splice(At, 6, 0, 'world')

      A.merge(B)

      const binary = A.save()

      const C = load(binary)

      assert.deepEqual(C.getWithType('_root', 'text'), ['text', '1@aabbcc'])
      assert.deepEqual(C.text(At), 'hell! world')
    })
  })

  describe('patch generation', () => {
    it('should include root object key updates', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.put('_root', 'hello', 'world')
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['hello'], value: 'world', conflict: false }
      ])
    })

    it('should include nested object creation', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.putObject('_root', 'birds', { friday: { robins: 3 } })
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: [ 'birds' ], value: {}, conflict: false },
        { action: 'put', path: [ 'birds', 'friday' ], value: {}, conflict: false },
        { action: 'put', path: [ 'birds', 'friday', 'robins' ], value: 3, conflict: false},
      ])
    })

    it('should delete map keys', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.put('_root', 'favouriteBird', 'Robin')
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.delete('_root', 'favouriteBird')
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: [ 'favouriteBird' ], value: 'Robin', conflict: false },
        { action: 'del', path: [ 'favouriteBird' ] }
      ])
    })

    it('should include list element insertion', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.putObject('_root', 'birds', ['Goldfinch', 'Chaffinch'])
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: [ 'birds' ], value: [], conflict: false },
        { action: 'splice', path: [ 'birds', 0 ], values: ['Goldfinch', 'Chaffinch'] },
      ])
    })

    it('should insert nested maps into a list', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.putObject('_root', 'birds', [])
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.insertObject('1@aaaa', 0, { species: 'Goldfinch', count: 3 })
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.popPatches(), [
        { action: 'splice', path: [ 'birds', 0 ], values: [{}] },
        { action: 'put', path: [ 'birds', 0, 'species' ], value: 'Goldfinch', conflict: false },
        { action: 'put', path: [ 'birds', 0, 'count', ], value: 3, conflict: false }
      ])
    })

    it('should calculate list indexes based on visible elements', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.putObject('_root', 'birds', ['Goldfinch', 'Chaffinch'])
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.delete('1@aaaa', 0)
      doc1.insert('1@aaaa', 1, 'Greenfinch')
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc1.getWithType('1@aaaa', 0), ['str', 'Chaffinch'])
      assert.deepEqual(doc1.getWithType('1@aaaa', 1), ['str', 'Greenfinch'])
      assert.deepEqual(doc2.popPatches(), [
        { action: 'del', path: ['birds', 0] },
        { action: 'splice', path: ['birds', 1], values: ['Greenfinch'] }
      ])
    })

    it('should handle concurrent insertions at the head of a list', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc'), doc4 = create('dddd')
      doc1.putObject('_root', 'values', [])
      const change1 = doc1.saveIncremental()
      doc2.loadIncremental(change1)
      doc3.loadIncremental(change1)
      doc4.loadIncremental(change1)
      doc1.insert('1@aaaa', 0, 'c')
      doc1.insert('1@aaaa', 1, 'd')
      doc2.insert('1@aaaa', 0, 'a')
      doc2.insert('1@aaaa', 1, 'b')
      const change2 = doc1.saveIncremental(), change3 = doc2.saveIncremental()
      doc3.enablePatches(true)
      doc4.enablePatches(true)
      doc3.loadIncremental(change2); doc3.loadIncremental(change3)
      doc4.loadIncremental(change3); doc4.loadIncremental(change2)
      assert.deepEqual([0, 1, 2, 3].map(i => (doc3.getWithType('1@aaaa', i) || [])[1]), ['a', 'b', 'c', 'd'])
      assert.deepEqual([0, 1, 2, 3].map(i => (doc4.getWithType('1@aaaa', i) || [])[1]), ['a', 'b', 'c', 'd'])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'splice', path: ['values', 0], values:['a','b','c','d'] },
      ])
      assert.deepEqual(doc4.popPatches(), [
        { action: 'splice', path: ['values',0], values:['a','b','c','d'] },
      ])
    })

    it('should handle concurrent insertions beyond the head', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc'), doc4 = create('dddd')
      doc1.putObject('_root', 'values', ['a', 'b'])
      const change1 = doc1.saveIncremental()
      doc2.loadIncremental(change1)
      doc3.loadIncremental(change1)
      doc4.loadIncremental(change1)
      doc1.insert('1@aaaa', 2, 'e')
      doc1.insert('1@aaaa', 3, 'f')
      doc2.insert('1@aaaa', 2, 'c')
      doc2.insert('1@aaaa', 3, 'd')
      const change2 = doc1.saveIncremental(), change3 = doc2.saveIncremental()
      doc3.enablePatches(true)
      doc4.enablePatches(true)
      doc3.loadIncremental(change2); doc3.loadIncremental(change3)
      doc4.loadIncremental(change3); doc4.loadIncremental(change2)
      assert.deepEqual([0, 1, 2, 3, 4, 5].map(i => (doc3.getWithType('1@aaaa', i) || [])[1]), ['a', 'b', 'c', 'd', 'e', 'f'])
      assert.deepEqual([0, 1, 2, 3, 4, 5].map(i => (doc4.getWithType('1@aaaa', i) || [])[1]), ['a', 'b', 'c', 'd', 'e', 'f'])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'splice', path: ['values', 2], values: ['c','d','e','f'] },
      ])
      assert.deepEqual(doc4.popPatches(), [
        { action: 'splice', path: ['values', 2], values: ['c','d','e','f'] },
      ])
    })

    it('should handle conflicts on root object keys', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc'), doc4 = create('dddd')
      doc1.put('_root', 'bird', 'Greenfinch')
      doc2.put('_root', 'bird', 'Goldfinch')
      const change1 = doc1.saveIncremental(), change2 = doc2.saveIncremental()
      doc3.enablePatches(true)
      doc4.enablePatches(true)
      doc3.loadIncremental(change1); doc3.loadIncremental(change2)
      doc4.loadIncremental(change2); doc4.loadIncremental(change1)
      assert.deepEqual(doc3.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc3.getAll('_root', 'bird'), [['str', 'Greenfinch', '1@aaaa'], ['str', 'Goldfinch', '1@bbbb']])
      assert.deepEqual(doc4.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc4.getAll('_root', 'bird'), [['str', 'Greenfinch', '1@aaaa'], ['str', 'Goldfinch', '1@bbbb']])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Greenfinch', conflict: false },
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true },
      ])
      assert.deepEqual(doc4.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: false },
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true },
      ])
    })

    it('should handle three-way conflicts', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc')
      doc1.put('_root', 'bird', 'Greenfinch')
      doc2.put('_root', 'bird', 'Chaffinch')
      doc3.put('_root', 'bird', 'Goldfinch')
      const change1 = doc1.saveIncremental(), change2 = doc2.saveIncremental(), change3 = doc3.saveIncremental()
      doc1.enablePatches(true)
      doc2.enablePatches(true)
      doc3.enablePatches(true)
      doc1.loadIncremental(change2); doc1.loadIncremental(change3)
      doc2.loadIncremental(change3); doc2.loadIncremental(change1)
      doc3.loadIncremental(change1); doc3.loadIncremental(change2)
      assert.deepEqual(doc1.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc1.getAll('_root', 'bird'), [
        ['str', 'Greenfinch', '1@aaaa'], ['str', 'Chaffinch', '1@bbbb'], ['str', 'Goldfinch', '1@cccc']
      ])
      assert.deepEqual(doc2.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc2.getAll('_root', 'bird'), [
        ['str', 'Greenfinch', '1@aaaa'], ['str', 'Chaffinch', '1@bbbb'], ['str', 'Goldfinch', '1@cccc']
      ])
      assert.deepEqual(doc3.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc3.getAll('_root', 'bird'), [
        ['str', 'Greenfinch', '1@aaaa'], ['str', 'Chaffinch', '1@bbbb'], ['str', 'Goldfinch', '1@cccc']
      ])
      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Chaffinch', conflict: true },
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true }
      ])
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true },
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true }
      ])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true },
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: true }
      ])
    })

    it('should allow a conflict to be resolved', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc')
      doc1.put('_root', 'bird', 'Greenfinch')
      doc2.put('_root', 'bird', 'Chaffinch')
      doc3.enablePatches(true)
      const change1 = doc1.saveIncremental(), change2 = doc2.saveIncremental()
      doc1.loadIncremental(change2); doc3.loadIncremental(change1)
      doc2.loadIncremental(change1); doc3.loadIncremental(change2)
      doc1.put('_root', 'bird', 'Goldfinch')
      doc3.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc3.getAll('_root', 'bird'), [['str', 'Goldfinch', '2@aaaa']])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Greenfinch', conflict: false },
        { action: 'put', path: ['bird'], value: 'Chaffinch', conflict: true },
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: false }
      ])
    })

    it('should handle a concurrent map key overwrite and delete', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.put('_root', 'bird', 'Greenfinch')
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.put('_root', 'bird', 'Goldfinch')
      doc2.delete('_root', 'bird')
      const change1 = doc1.saveIncremental(), change2 = doc2.saveIncremental()
      doc1.enablePatches(true)
      doc2.enablePatches(true)
      doc1.loadIncremental(change2)
      doc2.loadIncremental(change1)
      assert.deepEqual(doc1.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc1.getAll('_root', 'bird'), [['str', 'Goldfinch', '2@aaaa']])
      assert.deepEqual(doc2.getWithType('_root', 'bird'), ['str', 'Goldfinch'])
      assert.deepEqual(doc2.getAll('_root', 'bird'), [['str', 'Goldfinch', '2@aaaa']])
      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: false }
      ])
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Goldfinch', conflict: false }
      ])
    })

    it('should handle a conflict on a list element', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc'), doc4 = create('dddd')
      doc1.putObject('_root', 'birds', ['Thrush', 'Magpie'])
      const change1 = doc1.saveIncremental()
      doc2.loadIncremental(change1)
      doc3.loadIncremental(change1)
      doc4.loadIncremental(change1)
      doc1.put('1@aaaa', 0, 'Song Thrush')
      doc2.put('1@aaaa', 0, 'Redwing')
      const change2 = doc1.saveIncremental(), change3 = doc2.saveIncremental()
      doc3.enablePatches(true)
      doc4.enablePatches(true)
      doc3.loadIncremental(change2); doc3.loadIncremental(change3)
      doc4.loadIncremental(change3); doc4.loadIncremental(change2)
      assert.deepEqual(doc3.getWithType('1@aaaa', 0), ['str', 'Redwing'])
      assert.deepEqual(doc3.getAll('1@aaaa', 0), [['str', 'Song Thrush', '4@aaaa'], ['str', 'Redwing', '4@bbbb']])
      assert.deepEqual(doc4.getWithType('1@aaaa', 0), ['str', 'Redwing'])
      assert.deepEqual(doc4.getAll('1@aaaa', 0), [['str', 'Song Thrush', '4@aaaa'], ['str', 'Redwing', '4@bbbb']])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'put', path: ['birds',0], value: 'Song Thrush', conflict: false },
        { action: 'put', path: ['birds',0], value: 'Redwing', conflict: true }
      ])
      assert.deepEqual(doc4.popPatches(), [
        { action: 'put', path: ['birds',0], value: 'Redwing', conflict: false },
        { action: 'put', path: ['birds',0], value: 'Redwing', conflict: true }
      ])
    })

    it('should handle a concurrent list element overwrite and delete', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc'), doc4 = create('dddd')
      doc1.putObject('_root', 'birds', ['Parakeet', 'Magpie', 'Thrush'])
      const change1 = doc1.saveIncremental()
      doc2.loadIncremental(change1)
      doc3.loadIncremental(change1)
      doc4.loadIncremental(change1)
      doc1.delete('1@aaaa', 0)
      doc1.put('1@aaaa', 1, 'Song Thrush')
      doc2.put('1@aaaa', 0, 'Ring-necked parakeet')
      doc2.put('1@aaaa', 2, 'Redwing')
      const change2 = doc1.saveIncremental(), change3 = doc2.saveIncremental()
      doc3.enablePatches(true)
      doc4.enablePatches(true)
      doc3.loadIncremental(change2); doc3.loadIncremental(change3)
      doc4.loadIncremental(change3); doc4.loadIncremental(change2)
      assert.deepEqual(doc3.getAll('1@aaaa', 0), [['str', 'Ring-necked parakeet', '5@bbbb']])
      assert.deepEqual(doc3.getAll('1@aaaa', 2), [['str', 'Song Thrush', '6@aaaa'], ['str', 'Redwing', '6@bbbb']])
      assert.deepEqual(doc4.getAll('1@aaaa', 0), [['str', 'Ring-necked parakeet', '5@bbbb']])
      assert.deepEqual(doc4.getAll('1@aaaa', 2), [['str', 'Song Thrush', '6@aaaa'], ['str', 'Redwing', '6@bbbb']])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'del', path: ['birds',0], },
        { action: 'put', path: ['birds',1], value: 'Song Thrush', conflict: false },
        { action: 'splice', path: ['birds',0], values: ['Ring-necked parakeet'] },
        { action: 'put', path: ['birds',2], value: 'Redwing', conflict: true }
      ])
      assert.deepEqual(doc4.popPatches(), [
        { action: 'put', path: ['birds',0], value: 'Ring-necked parakeet', conflict: false },
        { action: 'put', path: ['birds',2], value: 'Redwing', conflict: false },
        { action: 'put', path: ['birds',0], value: 'Ring-necked parakeet', conflict: false },
        { action: 'put', path: ['birds',2], value: 'Redwing', conflict: true }
      ])
    })

    it('should handle deletion of a conflict value', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), doc3 = create('cccc')
      doc1.put('_root', 'bird', 'Robin')
      doc2.put('_root', 'bird', 'Wren')
      const change1 = doc1.saveIncremental(), change2 = doc2.saveIncremental()
      doc2.delete('_root', 'bird')
      const change3 = doc2.saveIncremental()
      doc3.enablePatches(true)
      doc3.loadIncremental(change1)
      doc3.loadIncremental(change2)
      assert.deepEqual(doc3.getAll('_root', 'bird'), [['str', 'Robin', '1@aaaa'], ['str', 'Wren', '1@bbbb']])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Robin', conflict: false },
        { action: 'put', path: ['bird'], value: 'Wren', conflict: true }
      ])
      doc3.loadIncremental(change3)
      assert.deepEqual(doc3.getWithType('_root', 'bird'), ['str', 'Robin'])
      assert.deepEqual(doc3.getAll('_root', 'bird'), [['str', 'Robin', '1@aaaa']])
      assert.deepEqual(doc3.popPatches(), [
        { action: 'put', path: ['bird'], value: 'Robin', conflict: false }
      ])
    })

    it('should handle conflicting nested objects', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc1.putObject('_root', 'birds', ['Parakeet'])
      doc2.putObject('_root', 'birds', { 'Sparrowhawk': 1 })
      const change1 = doc1.saveIncremental(), change2 = doc2.saveIncremental()
      doc1.enablePatches(true)
      doc2.enablePatches(true)
      doc1.loadIncremental(change2)
      doc2.loadIncremental(change1)
      assert.deepEqual(doc1.getAll('_root', 'birds'), [['list', '1@aaaa'], ['map', '1@bbbb']])
      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['birds'], value: {}, conflict: true },
        { action: 'put', path: ['birds', 'Sparrowhawk'], value: 1, conflict: false }
      ])
      assert.deepEqual(doc2.getAll('_root', 'birds'), [['list', '1@aaaa'], ['map', '1@bbbb']])
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['birds'], value: {}, conflict: true },
        { action: 'splice', path: ['birds',0], values: ['Parakeet'] }
      ])
    })

    it('should support date objects', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb'), now = new Date()
      doc1.put('_root', 'createdAt', now)
      doc2.enablePatches(true)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.getWithType('_root', 'createdAt'), ['timestamp', now])
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['createdAt'], value: now, conflict: false }
      ])
    })

    it('should capture local put ops', () => {
      const doc1 = create('aaaa')
      doc1.enablePatches(true)
      doc1.put('_root', 'key1', 1)
      doc1.put('_root', 'key1', 2)
      doc1.put('_root', 'key2', 3)
      doc1.putObject('_root', 'map', {})
      doc1.putObject('_root', 'list', [])

      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['key1'], value: 1, conflict: false },
        { action: 'put', path: ['key1'], value: 2, conflict: false },
        { action: 'put', path: ['key2'], value: 3, conflict: false },
        { action: 'put', path: ['map'], value: {}, conflict: false },
        { action: 'put', path: ['list'], value: [], conflict: false },
      ])
    })

    it('should capture local insert ops', () => {
      const doc1 = create('aaaa')
      doc1.enablePatches(true)
      const list = doc1.putObject('_root', 'list', [])
      doc1.insert(list, 0, 1)
      doc1.insert(list, 0, 2)
      doc1.insert(list, 2, 3)
      doc1.insertObject(list, 2, {})
      doc1.insertObject(list, 2, [])

      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['list'], value: [], conflict: false },
        { action: 'splice', path: ['list', 0], values: [2,1,[],{},3]  },
      ])
    })

    it('should capture local push ops', () => {
      const doc1 = create('aaaa')
      doc1.enablePatches(true)
      const list = doc1.putObject('_root', 'list', [])
      doc1.push(list, 1)
      doc1.pushObject(list, {})
      doc1.pushObject(list, [])

      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['list'], value: [], conflict: false },
        { action: 'splice', path: ['list',0], values: [1,{},[]] },
      ])
    })

    it('should capture local splice ops', () => {
      const doc1 = create('aaaa')
      doc1.enablePatches(true)
      const list = doc1.putObject('_root', 'list', [])
      doc1.splice(list, 0, 0, [1, 2, 3, 4])
      doc1.splice(list, 1, 2)

      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['list'],  value: [], conflict: false },
        { action: 'splice', path: ['list',0], values: [1,4] },
      ])
    })

    it('should capture local increment ops', () => {
      const doc1 = create('aaaa')
      doc1.enablePatches(true)
      doc1.put('_root', 'counter', 2, 'counter')
      doc1.increment('_root', 'counter', 4)

      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['counter'], value: 2, conflict: false },
        { action: 'inc', path: ['counter'], value: 4 },
      ])
    })


    it('should capture local delete ops', () => {
      const doc1 = create('aaaa')
      doc1.enablePatches(true)
      doc1.put('_root', 'key1', 1)
      doc1.put('_root', 'key2', 2)
      doc1.delete('_root', 'key1')
      doc1.delete('_root', 'key2')
      assert.deepEqual(doc1.popPatches(), [
        { action: 'put', path: ['key1'], value: 1, conflict: false },
        { action: 'put', path: ['key2'], value: 2, conflict: false },
        { action: 'del', path: ['key1'], },
        { action: 'del', path: ['key2'], },
      ])
    })

    it('should support counters in a map', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc2.enablePatches(true)
      doc1.put('_root', 'starlings', 2, 'counter')
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.increment('_root', 'starlings', 1)
      doc2.loadIncremental(doc1.saveIncremental())
      assert.deepEqual(doc2.getWithType('_root', 'starlings'), ['counter', 3])
      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['starlings'], value: 2, conflict: false },
        { action: 'inc', path: ['starlings'], value: 1 }
      ])
    })

    it('should support counters in a list', () => {
      const doc1 = create('aaaa'), doc2 = create('bbbb')
      doc2.enablePatches(true)
      const list = doc1.putObject('_root', 'list', [])
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.insert(list, 0, 1, 'counter')
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.increment(list, 0, 2)
      doc2.loadIncremental(doc1.saveIncremental())
      doc1.increment(list, 0, -5)
      doc2.loadIncremental(doc1.saveIncremental())

      assert.deepEqual(doc2.popPatches(), [
        { action: 'put', path: ['list'], value: [], conflict: false },
        { action: 'splice', path: ['list',0], values: [1] },
        { action: 'inc', path: ['list',0], value: 2 },
        { action: 'inc', path: ['list',0], value: -5 },
      ])
    })

    it('should delete a counter from a map') // TODO
  })

  describe('sync', () => {
    it('should send a sync message implying no local data', () => {
      const doc = create()
      const s1 = initSyncState()
      const m1 = doc.generateSyncMessage(s1)
      if (m1 === null) { throw new RangeError("message should not be null") }
      const message: DecodedSyncMessage = decodeSyncMessage(m1)
      assert.deepStrictEqual(message.heads, [])
      assert.deepStrictEqual(message.need, [])
      assert.deepStrictEqual(message.have.length, 1)
      assert.deepStrictEqual(message.have[0].lastSync, [])
      assert.deepStrictEqual(message.have[0].bloom.byteLength, 0)
      assert.deepStrictEqual(message.changes, [])
    })

    it('should not reply if we have no data as well', () => {
      const n1 = create(), n2 = create()
      const s1 = initSyncState(), s2 = initSyncState()
      const m1 = n1.generateSyncMessage(s1)
      if (m1 === null) { throw new RangeError("message should not be null") }
      n2.receiveSyncMessage(s2, m1)
      const m2 = n2.generateSyncMessage(s2)
      assert.deepStrictEqual(m2, null)
    })

    it('repos with equal heads do not need a reply message', () => {
      const n1 = create(), n2 = create()
      const s1 = initSyncState(), s2 = initSyncState()

      // make two nodes with the same changes
      const list = n1.putObject("_root", "n", [])
      n1.commit("", 0)
      for (let i = 0; i < 10; i++) {
        n1.insert(list, i, i)
        n1.commit("", 0)
      }
      n2.applyChanges(n1.getChanges([]))
      assert.deepStrictEqual(n1.materialize(), n2.materialize())

      // generate a naive sync message
      const m1 = n1.generateSyncMessage(s1)
      if (m1 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(s1.lastSentHeads, n1.getHeads())

      // heads are equal so this message should be null
      n2.receiveSyncMessage(s2, m1)
      const m2 = n2.generateSyncMessage(s2)
      assert.strictEqual(m2, null)
    })

    it('n1 should offer all changes to n2 when starting from nothing', () => {
      const n1 = create(), n2 = create()

      // make changes for n1 that n2 should request
      const list = n1.putObject("_root", "n", [])
      n1.commit("", 0)
      for (let i = 0; i < 10; i++) {
        n1.insert(list, i, i)
        n1.commit("", 0)
      }

      assert.notDeepStrictEqual(n1.materialize(), n2.materialize())
      sync(n1, n2)
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should sync peers where one has commits the other does not', () => {
      const n1 = create(), n2 = create()

      // make changes for n1 that n2 should request
      const list = n1.putObject("_root", "n", [])
      n1.commit("", 0)
      for (let i = 0; i < 10; i++) {
        n1.insert(list, i, i)
        n1.commit("", 0)
      }

      assert.notDeepStrictEqual(n1.materialize(), n2.materialize())
      sync(n1, n2)
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should work with prior sync state', () => {
      // create & synchronize two nodes
      const n1 = create(), n2 = create()
      const s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 5; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      // modify the first node further
      for (let i = 5; i < 10; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      assert.notDeepStrictEqual(n1.materialize(), n2.materialize())
      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should not generate messages once synced', () => {
      // create & synchronize two nodes
      const n1 = create('abc123'), n2 = create('def456')
      const s1 = initSyncState(), s2 = initSyncState()

      let message
      for (let i = 0; i < 5; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }
      for (let i = 0; i < 5; i++) {
        n2.put("_root", "y", i)
        n2.commit("", 0)
      }

      // n1 reports what it has
      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }

      // n2 receives that message and sends changes along with what it has
      n2.receiveSyncMessage(s2, message)
      message = n2.generateSyncMessage(s2)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(message).changes.length, 5)
      //assert.deepStrictEqual(patch, null) // no changes arrived

      // n1 receives the changes and replies with the changes it now knows that n2 needs
      n1.receiveSyncMessage(s1, message)
      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(message).changes.length, 5)

      // n2 applies the changes and sends confirmation ending the exchange
      n2.receiveSyncMessage(s2, message)
      message = n2.generateSyncMessage(s2)
      if (message === null) { throw new RangeError("message should not be null") }

      // n1 receives the message and has nothing more to say
      n1.receiveSyncMessage(s1, message)
      message = n1.generateSyncMessage(s1)
      assert.deepStrictEqual(message, null)
      //assert.deepStrictEqual(patch, null) // no changes arrived

      // n2 also has nothing left to say
      message = n2.generateSyncMessage(s2)
      assert.deepStrictEqual(message, null)
    })

    it('should allow simultaneous messages during synchronization', () => {
      // create & synchronize two nodes
      const n1 = create('abc123'), n2 = create('def456')
      const s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 5; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }
      for (let i = 0; i < 5; i++) {
        n2.put("_root", "y", i)
        n2.commit("", 0)
      }

      const head1 = n1.getHeads()[0], head2 = n2.getHeads()[0]

      // both sides report what they have but have no shared peer state
      let msg1to2, msg2to1
      msg1to2 = n1.generateSyncMessage(s1)
      msg2to1 = n2.generateSyncMessage(s2)
      if (msg1to2 === null) { throw new RangeError("message should not be null") }
      if (msg2to1 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(msg1to2).changes.length, 0)
      assert.deepStrictEqual(decodeSyncMessage(msg1to2).have[0].lastSync.length, 0)
      assert.deepStrictEqual(decodeSyncMessage(msg2to1).changes.length, 0)
      assert.deepStrictEqual(decodeSyncMessage(msg2to1).have[0].lastSync.length, 0)

      // n1 and n2 receive that message and update sync state but make no patch
      n1.receiveSyncMessage(s1, msg2to1)
      n2.receiveSyncMessage(s2, msg1to2)

      // now both reply with their local changes the other lacks
      // (standard warning that 1% of the time this will result in a "need" message)
      msg1to2 = n1.generateSyncMessage(s1)
      if (msg1to2 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(msg1to2).changes.length, 5)
      msg2to1 = n2.generateSyncMessage(s2)
      if (msg2to1 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(msg2to1).changes.length, 5)

      // both should now apply the changes and update the frontend
      n1.receiveSyncMessage(s1, msg2to1)
      assert.deepStrictEqual(n1.getMissingDeps(), [])
      //assert.notDeepStrictEqual(patch1, null)
      assert.deepStrictEqual(n1.materialize(), { x: 4, y: 4 })

      n2.receiveSyncMessage(s2, msg1to2)
      assert.deepStrictEqual(n2.getMissingDeps(), [])
      //assert.notDeepStrictEqual(patch2, null)
      assert.deepStrictEqual(n2.materialize(), { x: 4, y: 4 })

      // The response acknowledges the changes received and sends no further changes
      msg1to2 = n1.generateSyncMessage(s1)
      if (msg1to2 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(msg1to2).changes.length, 0)
      msg2to1 = n2.generateSyncMessage(s2)
      if (msg2to1 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(msg2to1).changes.length, 0)

      // After receiving acknowledgements, their shared heads should be equal
      n1.receiveSyncMessage(s1, msg2to1)
      n2.receiveSyncMessage(s2, msg1to2)
      assert.deepStrictEqual(s1.sharedHeads, [head1, head2].sort())
      assert.deepStrictEqual(s2.sharedHeads, [head1, head2].sort())
      //assert.deepStrictEqual(patch1, null)
      //assert.deepStrictEqual(patch2, null)

      // We're in sync, no more messages required
      msg1to2 = n1.generateSyncMessage(s1)
      msg2to1 = n2.generateSyncMessage(s2)
      assert.deepStrictEqual(msg1to2, null)
      assert.deepStrictEqual(msg2to1, null)

      // If we make one more change and start another sync then its lastSync should be updated
      n1.put("_root", "x", 5)
      msg1to2 = n1.generateSyncMessage(s1)
      if (msg1to2 === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(msg1to2).have[0].lastSync, [head1, head2].sort())
    })

    it('should assume sent changes were received until we hear otherwise', () => {
      const n1 = create('01234567'), n2 = create('89abcdef')
      const s1 = initSyncState(), s2 = initSyncState()
      let message = null

      const items = n1.putObject("_root", "items", [])
      n1.commit("", 0)

      sync(n1, n2, s1, s2)

      n1.push(items, "x")
      n1.commit("", 0)
      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(message).changes.length, 1)

      n1.push(items, "y")
      n1.commit("", 0)
      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(message).changes.length, 1)

      n1.push(items, "z")
      n1.commit("", 0)

      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(message).changes.length, 1)
    })

    it('should work regardless of who initiates the exchange', () => {
      // create & synchronize two nodes
      const n1 = create(), n2 = create()
      const s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 5; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      // modify the first node further
      for (let i = 5; i < 10; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      assert.notDeepStrictEqual(n1.materialize(), n2.materialize())
      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should work without prior sync state', () => {
      // Scenario:                                                            ,-- c10 <-- c11 <-- c12 <-- c13 <-- c14
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8 <-- c9 <-+
      //                                                                      `-- c15 <-- c16 <-- c17
      // lastSync is undefined.

      // create two peers both with divergent commits
      const n1 = create('01234567'), n2 = create('89abcdef')
      //const s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 10; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2)

      for (let i = 10; i < 15; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      for (let i = 15; i < 18; i++) {
        n2.put("_root", "x", i)
        n2.commit("", 0)
      }

      assert.notDeepStrictEqual(n1.materialize(), n2.materialize())
      sync(n1, n2)
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should work with prior sync state', () => {
      // Scenario:                                                            ,-- c10 <-- c11 <-- c12 <-- c13 <-- c14
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8 <-- c9 <-+
      //                                                                      `-- c15 <-- c16 <-- c17
      // lastSync is c9.

      // create two peers both with divergent commits
      const n1 = create('01234567'), n2 = create('89abcdef')
      let s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 10; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      for (let i = 10; i < 15; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }
      for (let i = 15; i < 18; i++) {
        n2.put("_root", "x", i)
        n2.commit("", 0)
      }

      s1 = decodeSyncState(encodeSyncState(s1))
      s2 = decodeSyncState(encodeSyncState(s2))

      assert.notDeepStrictEqual(n1.materialize(), n2.materialize())
      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should ensure non-empty state after sync', () => {
      const n1 = create('01234567'), n2 = create('89abcdef')
      const s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 3; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      assert.deepStrictEqual(s1.sharedHeads, n1.getHeads())
      assert.deepStrictEqual(s2.sharedHeads, n1.getHeads())
    })

    it('should re-sync after one node crashed with data loss', () => {
      // Scenario:     (r)                  (n2)                 (n1)
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8
      // n2 has changes {c0, c1, c2}, n1's lastSync is c5, and n2's lastSync is c2.
      // we want to successfully sync (n1) with (r), even though (n1) believes it's talking to (n2)
      const n1 = create('01234567'), n2 = create('89abcdef')
      let s1 = initSyncState()
      const s2 = initSyncState()

      // n1 makes three changes, which we sync to n2
      for (let i = 0; i < 3; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      // save a copy of n2 as "r" to simulate recovering from a crash
      let r
      let rSyncState
      ;[r, rSyncState] = [n2.clone(), s2.clone()]

      // sync another few commits
      for (let i = 3; i < 6; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      // everyone should be on the same page here
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())

      // now make a few more changes and then attempt to sync the fully-up-to-date n1 with the confused r
      for (let i = 6; i < 9; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      s1 = decodeSyncState(encodeSyncState(s1))
      rSyncState = decodeSyncState(encodeSyncState(rSyncState))

      assert.notDeepStrictEqual(n1.getHeads(), r.getHeads())
      assert.notDeepStrictEqual(n1.materialize(), r.materialize())
      assert.deepStrictEqual(n1.materialize(), { x: 8 })
      assert.deepStrictEqual(r.materialize(), { x: 2 })
      sync(n1, r, s1, rSyncState)
      assert.deepStrictEqual(n1.getHeads(), r.getHeads())
      assert.deepStrictEqual(n1.materialize(), r.materialize())
      r = null
    })

    it('should re-sync after one node experiences data loss without disconnecting', () => {
      const n1 = create('01234567'), n2 = create('89abcdef')
      const s1 = initSyncState(), s2 = initSyncState()

      // n1 makes three changes, which we sync to n2
      for (let i = 0; i < 3; i++) {
        n1.put("_root", "x", i)
        n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())

      const n2AfterDataLoss = create('89abcdef')

      // "n2" now has no data, but n1 still thinks it does. Note we don't do
      // decodeSyncState(encodeSyncState(s1)) in order to simulate data loss without disconnecting
      sync(n1, n2AfterDataLoss, s1, initSyncState())
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should handle changes concurrent to the last sync heads', () => {
      const n1 = create('01234567'), n2 = create('89abcdef'), n3 = create('fedcba98')
      const s12 = initSyncState(), s21 = initSyncState(), s23 = initSyncState(), s32 = initSyncState()

      // Change 1 is known to all three nodes
      //n1 = Automerge.change(n1, {time: 0}, doc => doc.x = 1)
      n1.put("_root", "x", 1); n1.commit("", 0)

      sync(n1, n2, s12, s21)
      sync(n2, n3, s23, s32)

      // Change 2 is known to n1 and n2
      n1.put("_root", "x", 2); n1.commit("", 0)

      sync(n1, n2, s12, s21)

      // Each of the three nodes makes one change (changes 3, 4, 5)
      n1.put("_root", "x", 3); n1.commit("", 0)
      n2.put("_root", "x", 4); n2.commit("", 0)
      n3.put("_root", "x", 5); n3.commit("", 0)

      // Apply n3's latest change to n2. If running in Node, turn the Uint8Array into a Buffer, to
      // simulate transmission over a network (see https://github.com/automerge/automerge/pull/362)
      let change = n3.getLastLocalChange()
      if (change === null) throw new RangeError("no local change")
      //ts-ignore
      if (typeof Buffer === 'function') change = Buffer.from(change)
      if (change === undefined) { throw new RangeError("last local change failed") }
      n2.applyChanges([change])

      // Now sync n1 and n2. n3's change is concurrent to n1 and n2's last sync heads
      sync(n1, n2, s12, s21)
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should handle histories with lots of branching and merging', () => {
      const n1 = create('01234567'), n2 = create('89abcdef'), n3 = create('fedcba98')
      n1.put("_root", "x", 0); n1.commit("", 0)
      const change1 = n1.getLastLocalChange()
      if (change1 === null) throw new RangeError("no local change")
      n2.applyChanges([change1])
      const change2 = n1.getLastLocalChange()
      if (change2 === null) throw new RangeError("no local change")
      n3.applyChanges([change2])
      n3.put("_root", "x", 1); n3.commit("", 0)

      //        - n1c1 <------ n1c2 <------ n1c3 <-- etc. <-- n1c20 <------ n1c21
      //       /          \/           \/                              \/
      //      /           /\           /\                              /\
      // c0 <---- n2c1 <------ n2c2 <------ n2c3 <-- etc. <-- n2c20 <------ n2c21
      //      \                                                          /
      //       ---------------------------------------------- n3c1 <-----
      for (let i = 1; i < 20; i++) {
        n1.put("_root", "n1", i); n1.commit("", 0)
        n2.put("_root", "n2", i); n2.commit("", 0)
        const change1 = n1.getLastLocalChange()
        if (change1 === null) throw new RangeError("no local change")
        const change2 = n2.getLastLocalChange()
        if (change2 === null) throw new RangeError("no local change")
        n1.applyChanges([change2])
        n2.applyChanges([change1])
      }

      const s1 = initSyncState(), s2 = initSyncState()
      sync(n1, n2, s1, s2)

      // Having n3's last change concurrent to the last sync heads forces us into the slower code path
      const change3 = n2.getLastLocalChange()
      if (change3 === null) throw new RangeError("no local change")
      n2.applyChanges([change3])
      n1.put("_root", "n1", "final"); n1.commit("", 0)
      n2.put("_root", "n2", "final"); n2.commit("", 0)

      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
      assert.deepStrictEqual(n1.materialize(), n2.materialize())
    })

    it('should handle a false-positive head', () => {
      // Scenario:                                                            ,-- n1
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8 <-- c9 <-+
      //                                                                      `-- n2
      // where n2 is a false positive in the Bloom filter containing {n1}.
      // lastSync is c9.
      let n1 = create('01234567'), n2 = create('89abcdef')
      let s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 10; i++) {
        n1.put("_root", "x", i); n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)
      for (let i = 1; ; i++) { // search for false positive; see comment above
        const n1up = n1.clone('01234567');
        n1up.put("_root", "x", `${i} @ n1`); n1up.commit("", 0)
        const n2up = n2.clone('89abcdef');
        n2up.put("_root", "x", `${i} @ n2`); n2up.commit("", 0)
        if (new BloomFilter(n1up.getHeads()).containsHash(n2up.getHeads()[0])) {
          n1 = n1up; n2 = n2up; break
        }
      }
      const allHeads = [...n1.getHeads(), ...n2.getHeads()].sort()
      s1 = decodeSyncState(encodeSyncState(s1))
      s2 = decodeSyncState(encodeSyncState(s2))
      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.getHeads(), allHeads)
      assert.deepStrictEqual(n2.getHeads(), allHeads)
    })


    describe('with a false-positive dependency', () => {
      let n1: Automerge, n2: Automerge, s1: SyncState, s2: SyncState, n1hash2: Hash, n2hash2: Hash

      beforeEach(() => {
        // Scenario:                                                            ,-- n1c1 <-- n1c2
        // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8 <-- c9 <-+
        //                                                                      `-- n2c1 <-- n2c2
        // where n2c1 is a false positive in the Bloom filter containing {n1c1, n1c2}.
        // lastSync is c9.
        n1 = create('01234567')
        n2 = create('89abcdef')
        s1 = initSyncState()
        s2 = initSyncState()
        for (let i = 0; i < 10; i++) {
          n1.put("_root", "x", i); n1.commit("", 0)
        }
        sync(n1, n2, s1, s2)

        let n1hash1, n2hash1
        for (let i = 29; ; i++) { // search for false positive; see comment above
          const n1us1 = n1.clone('01234567')
          n1us1.put("_root", "x", `${i} @ n1`); n1us1.commit("", 0)

          const n2us1 = n2.clone('89abcdef')
          n2us1.put("_root", "x", `${i} @ n1`); n2us1.commit("", 0)

          n1hash1 = n1us1.getHeads()[0]; n2hash1 = n2us1.getHeads()[0]

          const n1us2 = n1us1.clone();
          n1us2.put("_root", "x", `final @ n1`); n1us2.commit("", 0)

          const n2us2 = n2us1.clone();
          n2us2.put("_root", "x", `final @ n2`); n2us2.commit("", 0)

          n1hash2 = n1us2.getHeads()[0]; n2hash2 = n2us2.getHeads()[0]
          if (new BloomFilter([n1hash1, n1hash2]).containsHash(n2hash1)) {
            n1 = n1us2; n2 = n2us2; break
          }
        }
      })

      it('should sync two nodes without connection reset', () => {
        sync(n1, n2, s1, s2)
        assert.deepStrictEqual(n1.getHeads(), [n1hash2, n2hash2].sort())
        assert.deepStrictEqual(n2.getHeads(), [n1hash2, n2hash2].sort())
      })

      it('should sync two nodes with connection reset', () => {
        s1 = decodeSyncState(encodeSyncState(s1))
        s2 = decodeSyncState(encodeSyncState(s2))
        sync(n1, n2, s1, s2)
        assert.deepStrictEqual(n1.getHeads(), [n1hash2, n2hash2].sort())
        assert.deepStrictEqual(n2.getHeads(), [n1hash2, n2hash2].sort())
      })

      it('should sync three nodes', () => {
        s1 = decodeSyncState(encodeSyncState(s1))
        s2 = decodeSyncState(encodeSyncState(s2))

        // First n1 and n2 exchange Bloom filters
        let m1, m2
        m1 = n1.generateSyncMessage(s1)
        m2 = n2.generateSyncMessage(s2)
        if (m1 === null) { throw new RangeError("message should not be null") }
        if (m2 === null) { throw new RangeError("message should not be null") }
        n1.receiveSyncMessage(s1, m2)
        n2.receiveSyncMessage(s2, m1)

        // Then n1 and n2 send each other their changes, except for the false positive
        m1 = n1.generateSyncMessage(s1)
        m2 = n2.generateSyncMessage(s2)
        if (m1 === null) { throw new RangeError("message should not be null") }
        if (m2 === null) { throw new RangeError("message should not be null") }
        n1.receiveSyncMessage(s1, m2)
        n2.receiveSyncMessage(s2, m1)
        assert.strictEqual(decodeSyncMessage(m1).changes.length, 2) // n1c1 and n1c2
        assert.strictEqual(decodeSyncMessage(m2).changes.length, 1) // only n2c2; change n2c1 is not sent

        // n3 is a node that doesn't have the missing change. Nevertheless n1 is going to ask n3 for it
        const n3 = create('fedcba98'), s13 = initSyncState(), s31 = initSyncState()
        sync(n1, n3, s13, s31)
        assert.deepStrictEqual(n1.getHeads(), [n1hash2])
        assert.deepStrictEqual(n3.getHeads(), [n1hash2])
      })
    })

    it('should not require an additional request when a false-positive depends on a true-negative', () => {
      // Scenario:                         ,-- n1c1 <-- n1c2 <-- n1c3
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-+
      //                                   `-- n2c1 <-- n2c2 <-- n2c3
      // where n2c2 is a false positive in the Bloom filter containing {n1c1, n1c2, n1c3}.
      // lastSync is c4.
      let n1 = create('01234567'), n2 = create('89abcdef')
      let s1 = initSyncState(), s2 = initSyncState()
      let n1hash3, n2hash3

      for (let i = 0; i < 5; i++) {
        n1.put("_root", "x", i); n1.commit("", 0)
      }
      sync(n1, n2, s1, s2)
      for (let i = 86; ; i++) { // search for false positive; see comment above
        const n1us1 = n1.clone('01234567')
        n1us1.put("_root", "x", `${i} @ n1`); n1us1.commit("", 0)

        const n2us1 = n2.clone('89abcdef')
        n2us1.put("_root", "x", `${i} @ n2`); n2us1.commit("", 0)

        //const n1us1 = Automerge.change(Automerge.clone(n1, {actorId: '01234567'}), {time: 0}, doc => doc.x = `${i} @ n1`)
        //const n2us1 = Automerge.change(Automerge.clone(n2, {actorId: '89abcdef'}), {time: 0}, doc => doc.x = `${i} @ n2`)
        const n1hash1 = n1us1.getHeads()[0]

        const n1us2 = n1us1.clone()
        n1us2.put("_root", "x", `${i + 1} @ n1`); n1us2.commit("", 0)

        const n2us2 = n2us1.clone()
        n2us2.put("_root", "x", `${i + 1} @ n2`); n2us2.commit("", 0)

        const n1hash2 = n1us2.getHeads()[0], n2hash2 = n2us2.getHeads()[0]

        const n1us3 = n1us2.clone()
        n1us3.put("_root", "x", `final @ n1`); n1us3.commit("", 0)

        const n2us3 = n2us2.clone()
        n2us3.put("_root", "x", `final @ n2`); n2us3.commit("", 0)

        n1hash3 = n1us3.getHeads()[0]; n2hash3 = n2us3.getHeads()[0]

        if (new BloomFilter([n1hash1, n1hash2, n1hash3]).containsHash(n2hash2)) {
          n1 = n1us3; n2 = n2us3; break
        }
      }
      const bothHeads = [n1hash3, n2hash3].sort()
      s1 = decodeSyncState(encodeSyncState(s1))
      s2 = decodeSyncState(encodeSyncState(s2))
      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.getHeads(), bothHeads)
      assert.deepStrictEqual(n2.getHeads(), bothHeads)
    })

    it('should handle chains of false-positives', () => {
      // Scenario:                         ,-- c5
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-+
      //                                   `-- n2c1 <-- n2c2 <-- n2c3
      // where n2c1 and n2c2 are both false positives in the Bloom filter containing {c5}.
      // lastSync is c4.
      const n1 = create('01234567')
      let n2 = create('89abcdef')
      let s1 = initSyncState(), s2 = initSyncState()

      for (let i = 0; i < 5; i++) {
        n1.put("_root", "x", i); n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      n1.put("_root", "x", 5); n1.commit("", 0)

      for (let i = 2; ; i++) { // search for false positive; see comment above
        const n2us1 = n2.clone('89abcdef')
        n2us1.put("_root", "x", `${i} @ n2`); n2us1.commit("", 0)
        if (new BloomFilter(n1.getHeads()).containsHash(n2us1.getHeads()[0])) {
          n2 = n2us1; break
        }
      }
      for (let i = 141; ; i++) { // search for false positive; see comment above
        const n2us2 = n2.clone('89abcdef')
        n2us2.put("_root", "x", `${i} again`); n2us2.commit("", 0)
        if (new BloomFilter(n1.getHeads()).containsHash(n2us2.getHeads()[0])) {
          n2 = n2us2; break
        }
      }
      n2.put("_root", "x", `final @ n2`); n2.commit("", 0)

      const allHeads = [...n1.getHeads(), ...n2.getHeads()].sort()
      s1 = decodeSyncState(encodeSyncState(s1))
      s2 = decodeSyncState(encodeSyncState(s2))
      sync(n1, n2, s1, s2)
      assert.deepStrictEqual(n1.getHeads(), allHeads)
      assert.deepStrictEqual(n2.getHeads(), allHeads)
    })

    it('should allow the false-positive hash to be explicitly requested', () => {
      // Scenario:                                                            ,-- n1
      // c0 <-- c1 <-- c2 <-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8 <-- c9 <-+
      //                                                                      `-- n2
      // where n2 causes a false positive in the Bloom filter containing {n1}.
      let n1 = create('01234567'), n2 = create('89abcdef')
      let s1 = initSyncState(), s2 = initSyncState()
      let message

      for (let i = 0; i < 10; i++) {
        n1.put("_root", "x", i); n1.commit("", 0)
      }

      sync(n1, n2, s1, s2)

      s1 = decodeSyncState(encodeSyncState(s1))
      s2 = decodeSyncState(encodeSyncState(s2))

      for (let i = 1; ; i++) { // brute-force search for false positive; see comment above
        const n1up = n1.clone('01234567'); n1up.put("_root", "x", `${i} @ n1`); n1up.commit("", 0)
        const n2up = n1.clone('89abcdef'); n2up.put("_root", "x", `${i} @ n2`); n2up.commit("", 0)

        // check if the bloom filter on n2 will believe n1 already has a particular hash
        // this will mean n2 won't offer that data to n2 by receiving a sync message from n1
        if (new BloomFilter(n1up.getHeads()).containsHash(n2up.getHeads()[0])) {
          n1 = n1up; n2 = n2up; break
        }
      }

      // n1 creates a sync message for n2 with an ill-fated bloom
      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.strictEqual(decodeSyncMessage(message).changes.length, 0)

      // n2 receives it and DOESN'T send a change back
      n2.receiveSyncMessage(s2, message)
      message = n2.generateSyncMessage(s2)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.strictEqual(decodeSyncMessage(message).changes.length, 0)

      // n1 should now realize it's missing that change and request it explicitly
      n1.receiveSyncMessage(s1, message)
      message = n1.generateSyncMessage(s1)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.deepStrictEqual(decodeSyncMessage(message).need, n2.getHeads())

      // n2 should fulfill that request
      n2.receiveSyncMessage(s2, message)
      message = n2.generateSyncMessage(s2)
      if (message === null) { throw new RangeError("message should not be null") }
      assert.strictEqual(decodeSyncMessage(message).changes.length, 1)

      // n1 should apply the change and the two should now be in sync
      n1.receiveSyncMessage(s1, message)
      assert.deepStrictEqual(n1.getHeads(), n2.getHeads())
    })

    describe('protocol features', () => {
      it('should allow multiple Bloom filters', () => {
        // Scenario:           ,-- n1c1 <-- n1c2 <-- n1c3
        // c0 <-- c1 <-- c2 <-+--- n2c1 <-- n2c2 <-- n2c3
        //                     `-- n3c1 <-- n3c2 <-- n3c3
        // n1 has {c0, c1, c2, n1c1, n1c2, n1c3, n2c1, n2c2};
        // n2 has {c0, c1, c2, n1c1, n1c2, n2c1, n2c2, n2c3};
        // n3 has {c0, c1, c2, n3c1, n3c2, n3c3}.
        const n1 = create('01234567'), n2 = create('89abcdef'), n3 = create('76543210')
        let s13 = initSyncState()
        const s12 = initSyncState()
        const s21 = initSyncState()
        let s32 = initSyncState(), s31 = initSyncState(), s23 = initSyncState()
        let message1, message3

        for (let i = 0; i < 3; i++) {
          n1.put("_root", "x", i); n1.commit("", 0)
        }

        // sync all 3 nodes
        sync(n1, n2, s12, s21) // eslint-disable-line no-unused-vars -- kept for consistency
        sync(n1, n3, s13, s31)
        sync(n3, n2, s32, s23)
        for (let i = 0; i < 2; i++) {
          n1.put("_root", "x", `${i} @ n1`); n1.commit("", 0)
        }
        for (let i = 0; i < 2; i++) {
          n2.put("_root", "x", `${i} @ n2`); n2.commit("", 0)
        }
        n1.applyChanges(n2.getChanges([]))
        n2.applyChanges(n1.getChanges([]))
        n1.put("_root", "x", `3 @ n1`); n1.commit("", 0)
        n2.put("_root", "x", `3 @ n2`); n2.commit("", 0)

        for (let i = 0; i < 3; i++) {
          n3.put("_root", "x", `${i} @ n3`); n3.commit("", 0)
        }
        const n1c3 = n1.getHeads()[0], n2c3 = n2.getHeads()[0], n3c3 = n3.getHeads()[0]
        s13 = decodeSyncState(encodeSyncState(s13))
        s31 = decodeSyncState(encodeSyncState(s31))
        s23 = decodeSyncState(encodeSyncState(s23))
        s32 = decodeSyncState(encodeSyncState(s32))


        // Now n3 concurrently syncs with n1 and n2. Doing this naively would result in n3 receiving
        // changes {n1c1, n1c2, n2c1, n2c2} twice (those are the changes that both n1 and n2 have, but
        // that n3 does not have). We want to prevent this duplication.
        message1 = n1.generateSyncMessage(s13) // message from n1 to n3
        if (message1 === null) { throw new RangeError("message should not be null") }
        assert.strictEqual(decodeSyncMessage(message1).changes.length, 0)
        n3.receiveSyncMessage(s31, message1)
        message3 = n3.generateSyncMessage(s31) // message from n3 to n1
        if (message3 === null) { throw new RangeError("message should not be null") }
        assert.strictEqual(decodeSyncMessage(message3).changes.length, 3) // {n3c1, n3c2, n3c3}
        n1.receiveSyncMessage(s13, message3)

        // Copy the Bloom filter received from n1 into the message sent from n3 to n2. This Bloom
        // filter indicates what changes n3 is going to receive from n1.
        message3 = n3.generateSyncMessage(s32) // message from n3 to n2
        if (message3 === null) { throw new RangeError("message should not be null") }
        const modifiedMessage = decodeSyncMessage(message3)
        modifiedMessage.have.push(decodeSyncMessage(message1).have[0])
        assert.strictEqual(modifiedMessage.changes.length, 0)
        n2.receiveSyncMessage(s23, encodeSyncMessage(modifiedMessage))

        // n2 replies to n3, sending only n2c3 (the one change that n2 has but n1 doesn't)
        const message2 = n2.generateSyncMessage(s23)
        if (message2 === null) { throw new RangeError("message should not be null") }
        assert.strictEqual(decodeSyncMessage(message2).changes.length, 1) // {n2c3}
        n3.receiveSyncMessage(s32, message2)

        // n1 replies to n3
        message1 = n1.generateSyncMessage(s13)
        if (message1 === null) { throw new RangeError("message should not be null") }
        assert.strictEqual(decodeSyncMessage(message1).changes.length, 5) // {n1c1, n1c2, n1c3, n2c1, n2c2}
        n3.receiveSyncMessage(s31, message1)
        assert.deepStrictEqual(n3.getHeads(), [n1c3, n2c3, n3c3].sort())
      })

      it('should allow any change to be requested', () => {
        const n1 = create('01234567'), n2 = create('89abcdef')
        const s1 = initSyncState(), s2 = initSyncState()
        let message = null

        for (let i = 0; i < 3; i++) {
          n1.put("_root", "x", i); n1.commit("", 0)
        }

        const lastSync = n1.getHeads()

        for (let i = 3; i < 6; i++) {
          n1.put("_root", "x", i); n1.commit("", 0)
        }

        sync(n1, n2, s1, s2)
        s1.lastSentHeads = [] // force generateSyncMessage to return a message even though nothing changed
        message = n1.generateSyncMessage(s1)
        if (message === null) { throw new RangeError("message should not be null") }
        const modMsg = decodeSyncMessage(message)
        modMsg.need = lastSync // re-request change 2
        n2.receiveSyncMessage(s2, encodeSyncMessage(modMsg))
        message = n2.generateSyncMessage(s2)
        if (message === null) { throw new RangeError("message should not be null") }
        assert.strictEqual(decodeSyncMessage(message).changes.length, 1)
        assert.strictEqual(decodeChange(decodeSyncMessage(message).changes[0]).hash, lastSync[0])
      })

      it('should ignore requests for a nonexistent change', () => {
        const n1 = create('01234567'), n2 = create('89abcdef')
        const s1 = initSyncState(), s2 = initSyncState()
        let message = null

        for (let i = 0; i < 3; i++) {
          n1.put("_root", "x", i); n1.commit("", 0)
        }

        n2.applyChanges(n1.getChanges([]))
        message = n1.generateSyncMessage(s1)
        if (message === null) { throw new RangeError("message should not be null") }
        message = decodeSyncMessage(message)
        message.need = ['0000000000000000000000000000000000000000000000000000000000000000']
        message = encodeSyncMessage(message)
        n2.receiveSyncMessage(s2, message)
        message = n2.generateSyncMessage(s2)
        assert.strictEqual(message, null)
      })

      it('should allow a subset of changes to be sent', () => {
        //       ,-- c1 <-- c2
        // c0 <-+
        //       `-- c3 <-- c4 <-- c5 <-- c6 <-- c7 <-- c8
        const n1 = create('01234567'), n2 = create('89abcdef'), n3 = create('76543210')
        let s1 = initSyncState(), s2 = initSyncState()
        let msg

        n1.put("_root", "x", 0); n1.commit("", 0)
        n3.applyChanges(n3.getChangesAdded(n1)) // merge()
        for (let i = 1; i <= 2; i++) {
          n1.put("_root", "x", i); n1.commit("", 0)
        }
        for (let i = 3; i <= 4; i++) {
          n3.put("_root", "x", i); n3.commit("", 0)
        }
        const c2 = n1.getHeads()[0], c4 = n3.getHeads()[0]
        n2.applyChanges(n2.getChangesAdded(n3)) // merge()

        // Sync n1 and n2, so their shared heads are {c2, c4}
        sync(n1, n2, s1, s2)
        s1 = decodeSyncState(encodeSyncState(s1))
        s2 = decodeSyncState(encodeSyncState(s2))
        assert.deepStrictEqual(s1.sharedHeads, [c2, c4].sort())
        assert.deepStrictEqual(s2.sharedHeads, [c2, c4].sort())

        // n2 and n3 apply {c5, c6, c7, c8}
        n3.put("_root", "x", 5); n3.commit("", 0)
        const change5 = n3.getLastLocalChange()
        if (change5 === null) throw new RangeError("no local change")
        n3.put("_root", "x", 6); n3.commit("", 0)
        const change6 = n3.getLastLocalChange(), c6 = n3.getHeads()[0]
        if (change6 === null) throw new RangeError("no local change")
        for (let i = 7; i <= 8; i++) {
          n3.put("_root", "x", i); n3.commit("", 0)
        }
        const c8 = n3.getHeads()[0]
        n2.applyChanges(n2.getChangesAdded(n3)) // merge()

        // Now n1 initiates a sync with n2, and n2 replies with {c5, c6}. n2 does not send {c7, c8}
        msg = n1.generateSyncMessage(s1)
        if (msg === null) { throw new RangeError("message should not be null") }
        n2.receiveSyncMessage(s2, msg)
        msg = n2.generateSyncMessage(s2)
        if (msg === null) { throw new RangeError("message should not be null") }
        const decodedMsg = decodeSyncMessage(msg)
        decodedMsg.changes = [change5, change6]
        msg = encodeSyncMessage(decodedMsg)
        const sentHashes: any = {}

        sentHashes[decodeChange(change5).hash] = true
        sentHashes[decodeChange(change6).hash] = true

        s2.sentHashes = sentHashes
        n1.receiveSyncMessage(s1, msg)
        assert.deepStrictEqual(s1.sharedHeads, [c2, c6].sort())

        // n1 replies, confirming the receipt of {c5, c6} and requesting the remaining changes
        msg = n1.generateSyncMessage(s1)
        if (msg === null) { throw new RangeError("message should not be null") }
        n2.receiveSyncMessage(s2, msg)
        assert.deepStrictEqual(decodeSyncMessage(msg).need, [c8])
        assert.deepStrictEqual(decodeSyncMessage(msg).have[0].lastSync, [c2, c6].sort())
        assert.deepStrictEqual(s1.sharedHeads, [c2, c6].sort())
        assert.deepStrictEqual(s2.sharedHeads, [c2, c6].sort())

        // n2 sends the remaining changes {c7, c8}
        msg = n2.generateSyncMessage(s2)
        if (msg === null) { throw new RangeError("message should not be null") }
        n1.receiveSyncMessage(s1, msg)
        assert.strictEqual(decodeSyncMessage(msg).changes.length, 2)
        assert.deepStrictEqual(s1.sharedHeads, [c2, c8].sort())
      })
    })
  })
})