introduce AutobaseHostCalls abstraction (#216)

* introduce HostCalls abstraction

* remove test on private method

* _removeWriter is sync

* expose removeable from base

* increase blocks in simple ff test

* applyState is source of truth

* rename to AutobaseHostCalls

index.js

@@ -300,7 +300,7 @@ module.exports = class Autobase extends ReadyResource {
       : { key: null, indexedLength: 0, indexersUpdated: false, fastForwarding: false, heads: null }
   }
 
-  interrupt (reason) {
+  _interrupt (reason) {
     assert(this._applyState.applying, 'Interrupt is only allowed in apply')
     this._interrupting = true
     if (reason) this.interrupted = reason
@@ -1371,13 +1371,10 @@ module.exports = class Autobase extends ReadyResource {
   }
 
   // triggered from apply
-  async addWriter (key, { indexer = true, isIndexer = indexer } = {}) { // just compat for old version
+  async _addWriter (key, sys) { // just compat for old version
     assert(this._applyState.applying, 'System changes are only allowed in apply')
 
-    const sys = this._applyState.system
-    await sys.add(key, { isIndexer })
-
-    const writer = (await this._getWriterByKey(key, -1, 0, false, true, null)) || this._makeWriter(key, 0, true, false)
+    const writer = (await this._getWriterByKey(key, -1, 0, false, true, sys)) || this._makeWriter(key, 0, true, false)
     await writer.ready()
 
     if (!this.activeWriters.has(key)) {
@@ -1390,27 +1387,18 @@ module.exports = class Autobase extends ReadyResource {
     this._queueBump()
   }
 
-  removeable (key, sys = this.system) {
-    if (sys.indexers.length !== 1) return true
-    return !b4a.equals(sys.indexers[0].key, key)
-  }
-
   // triggered from apply
-  async removeWriter (key) { // just compat for old version
-    assert(this._applyState.applying, 'System changes are only allowed in apply')
-
-    if (!this.removeable(key, this._applyState.system)) {
-      throw new Error('Not allowed to remove the last indexer')
-    }
-
-    await this._applyState.system.remove(key)
-
+  _removeWriter (key) { // just compat for old version
     const w = this.activeWriters.get(key)
     if (w) w.isRemoved = true
 
     this._queueBump()
   }
 
+  removeable (key) {
+    return this._applyState ? this._applyState.removeable(key) : false
+  }
+
   _updateAckThreshold () {
     if (this._ackThreshold === 0) return
     if (this._ackTimer) this._ackTimer.bau()

lib/apply-state.js

@@ -11,6 +11,32 @@ const safetyCatch = require('safety-catch')
 // must not be set too low (stretched with num of indexers)
 const SHOULD_WRITE_THRESHOLD = 16
 
+class AutobaseHostCalls {
+  constructor (state) {
+    this.state = state
+    this.base = state.base
+    this.system = state.system
+  }
+
+  async addWriter (key, { indexer = true, isIndexer = indexer } = {}) { // just compat for old version
+    await this.system.add(key, { isIndexer })
+    await this.base._addWriter(key, this.system)
+  }
+
+  async removeWriter (key) { // just compat for old version
+    if (!this.state.removeable(key)) {
+      throw new Error('Not allowed to remove the last indexer')
+    }
+
+    await this.system.remove(key)
+    this.base._removeWriter(key)
+  }
+
+  interrupt (reason) {
+    this.base._interrupt(reason)
+  }
+}
+
 class CheckpointCore {
   constructor (view, core, signer) {
     this.view = view
@@ -186,6 +212,7 @@ module.exports = class ApplyState extends ReadyResource {
     this.view = null
     this.views = []
     this.systemRef = null
+    this.hostCalls = null
 
     this.updates = []
 
@@ -255,6 +282,11 @@ module.exports = class ApplyState extends ReadyResource {
     return false
   }
 
+  removeable (key) {
+    if (this.system.indexers.length !== 1) return true
+    return !b4a.equals(this.system.indexers[0].key, key)
+  }
+
   isLocalIndexer () {
     return !!this.localCheckpoint
   }
@@ -297,6 +329,7 @@ module.exports = class ApplyState extends ReadyResource {
     this.indexersUpdated = boot.indexersUpdated
     this.stretchedThreshold = this.system.indexers.length * SHOULD_WRITE_THRESHOLD
     this.quorum = sysCore.manifest ? sysCore.manifest.quorum : 0
+    this.hostCalls = new AutobaseHostCalls(this)
 
     const added = new Set()
 
@@ -769,7 +802,7 @@ module.exports = class ApplyState extends ReadyResource {
 
       if (applyBatch.length && this.base._hasApply === true) {
         this.applying = true
-        await this.base._handlers.apply(applyBatch, this.view, this.base)
+        await this.base._handlers.apply(applyBatch, this.view, this.hostCalls)
         this.applying = false
       }
 

test/basic.js

@@ -421,7 +421,6 @@ test('basic - throws', async t => {
 
   await t.exception(b.append('not writable'))
   await t.exception(a.view.append('append outside apply'))
-  await t.exception(() => a.addWriter(b.local.key))
 })
 
 test('basic - add 5 writers', async t => {

test/fast-forward.js

@@ -26,7 +26,7 @@ test('fast-forward - simple', async t => {
 
   const [a, b] = bases
 
-  for (let i = 0; i < 200; i++) {
+  for (let i = 0; i < 1000; i++) {
     await a.append('a' + i)
   }