Move to takes session (#634)

* update moveTo

* update tests

* add missing length on boot

* fix issue and tests

* drop support for atomic moveTo

---------

Co-authored-by: Christophe Diederichs <chm-diederichs@protonmail.com>

lib/core.js

@@ -240,6 +240,7 @@ module.exports = class Core {
 
     const treeInfo = {
       fork: header.tree.fork,
+      length: header.tree.length,
       signature: header.tree.signature,
       roots: header.tree.length ? await tree.getRoots(header.tree.length) : [],
       prologue

lib/session-state.js

@@ -39,7 +39,7 @@ module.exports = class SessionState {
     this.signature = treeInfo.signature || null
 
     const deps = this.storage.dependencies
-    this.dependencyLength = deps.length ? deps[deps.length - 1].length : Infinity
+    this.dependencyLength = deps.length ? deps[deps.length - 1].length : 0
 
     if (treeInfo.length < this.dependencyLength) this.dependencyLength = treeInfo.length
     if (treeInfo.roots.length) this.setRoots(treeInfo.roots)
@@ -237,24 +237,6 @@ module.exports = class SessionState {
       this.storage.updateDependencyLength(src.dependencyLength)
     }
 
-    // handle migration
-    if (src.core !== this.core) {
-      if (this.lingers === null) this.lingers = []
-      this.lingers.push(this.storage)
-
-      this.prologue = src.prologue
-      this.storage = await src.core.state.storage.resumeSession(this.name)
-      this.tree = new MerkleTree(this.storage)
-
-      for (let i = this.core.sessionStates.length - 1; i >= 0; i--) {
-        const state = this.core.sessionStates[i]
-        if (state === this) continue
-        if (state.name === this.name) state._moveToCore(src.core)
-      }
-
-      this._moveToCore(src.core)
-    }
-
     const truncated = (bitfield && bitfield.truncated !== -1)
       ? bitfield.truncated
       : src.dependencyLength
@@ -814,9 +796,9 @@ module.exports = class SessionState {
     await this.mutex.lock()
 
     try {
-      if (state.storage && (await state.storage.resumeSession(this.name)) !== null) {
-        throw STORAGE_CONFLICT('Batch has already been created')
-      }
+      // if (state.storage && (await state.storage.resumeSession(this.name)) !== null) {
+      //   throw STORAGE_CONFLICT('Batch has already been created')
+      // }
 
       const treeLength = this.length
 
@@ -831,12 +813,12 @@ module.exports = class SessionState {
 
         // todo: validate treeInfo
 
-        if (!this.storage.atom) {
-          this.storage = await state.storage.createSession(this.name, treeInfo)
+        const resumed = await state.storage.resumeSession(this.name)
+
+        if (resumed) {
+          this.storage = resumed
         } else {
-          const s = state.storage.atomize(this.storage.atom)
-          this.storage = await s.createSession(this.name, treeInfo)
-          await s.close()
+          this.storage = await state.storage.createSession(this.name, treeInfo)
         }
 
         this.tree = new MerkleTree(this.storage)
@@ -847,22 +829,20 @@ module.exports = class SessionState {
         this.roots = await this.tree.getRoots(length)
 
         if (truncation) {
-          const { dependency, tree, flushed } = truncation
+          const { dependency, tree } = truncation
 
           if (dependency) this.storage.updateDependencyLength(this.dependencyLength)
-          this.ontruncate(tree, tree.length, treeLength, flushed)
+          this.ontruncate(tree, tree.length, treeLength, true)
         }
       }
 
-      if (!this.storage.atom) {
-        for (let i = this.core.sessionStates.length - 1; i >= 0; i--) {
-          const state = this.core.sessionStates[i]
-          if (state === this) continue
-          if (state.name === this.name) state._moveToCore(core)
-        }
+      for (let i = this.core.sessionStates.length - 1; i >= 0; i--) {
+        const state = this.core.sessionStates[i]
+        if (state === this) continue
+        if (state.name === this.name) state._moveToCore(core.core)
       }
 
-      this._moveToCore(core)
+      this._moveToCore(core.core)
     } finally {
       this.mutex.unlock()
     }

test/atomic.js

@@ -366,60 +366,6 @@ test('atomic - overwrite and user data', async function (t) {
   await core2.close()
 })
 
-test('atomic - move to', async function (t) {
-  const storage = await createStorage(t)
-
-  const core = new Hypercore(storage)
-  const core2 = new Hypercore(storage)
-
-  await core.ready()
-  await core2.ready()
-
-  await core.append('hello')
-  await core.append('world')
-
-  await core2.append('hello')
-
-  t.is(core.length, 2)
-  t.is(core2.length, 1)
-
-  const session = core.session({ name: 'moveable' })
-  await session.ready()
-
-  let truncates = 0
-  session.on('truncate', () => { truncates++ })
-
-  t.is(session.length, 2)
-  t.ok(session.core === core.core)
-  t.is(truncates, 0)
-
-  const atom = core.state.storage.createAtom()
-
-  const atomic = session.session({ atom })
-  await atomic.ready()
-
-  await atomic.state.moveTo(core2.core, 1)
-
-  t.is(atomic.length, 1)
-  t.is(session.length, 2)
-  t.ok(session.core === core.core)
-  t.is(truncates, 0)
-
-  t.is(atomic.length, 1)
-  await atom.flush()
-
-  t.is(session.length, 1)
-  t.ok(session.core !== core.core)
-  t.ok(session.core === core2.core)
-  t.is(truncates, 1)
-
-  await session.close()
-  await atomic.close()
-
-  await core.close()
-  await core2.close()
-})
-
 test('atomic - truncate', async function (t) {
   const core = await create(t)
 

test/move-to.js

@@ -38,7 +38,7 @@ test('move - basic', async function (t) {
 
   sess.once('migrate', key => { t.alike(key, core2.key) })
 
-  await sess.state.moveTo(core2.core, core2.length)
+  await sess.state.moveTo(core2, core2.length)
   await sess.append('4')
 
   await core2.commit(sess)
@@ -92,7 +92,7 @@ test('move - snapshots', async function (t) {
 
   t.is(core2.length, 2)
 
-  await snap.state.moveTo(core2.core, core2.length)
+  await snap.state.moveTo(core2, core2.length)
 
   t.is(snap.length, 3)