chore: rename to CoreSyncState and update API (#308)

* move and rename core-sync-state

* cleanup API for CoreSyncState

* delete test for old code

* Apply suggestions from code review

Co-authored-by: Andrew Chou <andrewchou@fastmail.com>

* rename param

* rename test file

---------

Co-authored-by: Andrew Chou <andrewchou@fastmail.com>

src/core-manager/core-replication-state.js → src/sync/core-sync-state.js

@@ -1,6 +1,8 @@
 import { TypedEmitter } from 'tiny-typed-emitter'
 import { keyToId } from '../utils.js'
-import RemoteBitfield, { BITS_PER_PAGE } from './remote-bitfield.js'
+import RemoteBitfield, {
+  BITS_PER_PAGE,
+} from '../core-manager/remote-bitfield.js'
 
 /**
  * @typedef {RemoteBitfield} Bitfield
@@ -31,29 +33,29 @@ import RemoteBitfield, { BITS_PER_PAGE } from './remote-bitfield.js'
  * @property {Record<PeerId, RemotePeerSimpleState>} remoteStates map of state of all known peers
  */
 /**
- * @typedef {object} CoreReplicationEvents
+ * @typedef {object} CoreSyncEvents
  * @property {() => void} update
  */
 
 /**
- * Track replication state for a core identified by `discoveryId`. Can start
- * tracking state before the core instance exists locally, via the "preHave"
- * messages received over the project creator core.
+ * Track sync state for a core identified by `discoveryId`. Can start tracking
+ * state before the core instance exists locally, via the "preHave" messages
+ * received over the project creator core.
  *
  * Because deriving the state is expensive (it iterates through the bitfields of
  * all peers), this is designed to be pull-based: an `update` event signals that
  * the state is updated, but does not pass the state. The consumer can "pull"
- * the state when it wants it via `coreReplicationState.getState()`.
+ * the state when it wants it via `coreSyncState.getState()`.
  *
  * Each peer (including the local peer) has a state of:
  *   1. `have` - number of blocks the peer has locally
  *   2. `want` - number of blocks the peer wants, and at least one peer has
  *   3. `wanted` - number of blocks the peer has that at least one peer wants
  *   4. `missing` - number of blocks the peer wants but no peer has
  *
- * @extends {TypedEmitter<CoreReplicationEvents>}
+ * @extends {TypedEmitter<CoreSyncEvents>}
  */
-export class CoreReplicationState extends TypedEmitter {
+export class CoreSyncState extends TypedEmitter {
   /** @type {import('hypercore')<'binary', Buffer>} */
   #core
   /** @type {InternalState['remoteStates']} */
@@ -92,10 +94,9 @@ export class CoreReplicationState extends TypedEmitter {
   }
 
   /**
-   * Attach a core. The replication state can be initialized without a core
-   * instance, because we could receive peer want and have states via extension
-   * messages before we have the core key that allows us to create a core
-   * instance.
+   * Attach a core. The sync state can be initialized without a core instance,
+   * because we could receive peer want and have states via extension messages
+   * before we have the core key that allows us to create a core instance.
    *
    * @param {import('hypercore')<'binary', Buffer>} core
    */
@@ -137,14 +138,15 @@ export class CoreReplicationState extends TypedEmitter {
   /**
    * Add a pre-emptive "have" bitfield for a peer. This is used when we receive
    * a peer "have" via extension message - it allows us to have a state for the
-   * peer before the peer actually starts replicating this core
+   * peer before the peer actually starts syncing this core
    *
    * @param {PeerId} peerId
-   * @param {Bitfield} bitfield
+   * @param {number} start
+   * @param {Uint32Array} bitfield
    */
-  setHavesBitfield(peerId, bitfield) {
+  insertPreHaves(peerId, start, bitfield) {
     const peerState = this.#getPeerState(peerId)
-    peerState.setPreHavesBitfield(bitfield)
+    peerState.insertPreHaves(start, bitfield)
     this.#update()
   }
 
@@ -225,40 +227,39 @@ export class CoreReplicationState extends TypedEmitter {
 }
 
 /**
- * Replication state for a core for a peer. Uses an internal bitfield from
- * Hypercore to track which blocks the peer has. Default is that a peer wants
- * all blocks, but can set ranges of "wants". Setting a want range changes all
- * other blocks to "not wanted"
+ * Sync state for a core for a peer. Uses an internal bitfield from Hypercore to
+ * track which blocks the peer has. Default is that a peer wants all blocks, but
+ * can set ranges of "wants". Setting a want range changes all other blocks to
+ * "not wanted"
  *
  * @private
  * Only exported for testing
  */
 export class PeerState {
-  /** @type {Bitfield | undefined} */
-  #preHaves
+  /** @type {Bitfield} */
+  #preHaves = new RemoteBitfield()
   /** @type {Bitfield | undefined} */
   #haves
-  /** @type {Bitfield | undefined} */
-  #wants
+  /** @type {Bitfield} */
+  #wants = new RemoteBitfield()
   connected = false
+  #wantAll
+  constructor({ wantAll = true } = {}) {
+    this.#wantAll = wantAll
+  }
   /**
-   * @param {Bitfield} bitfield
+   * @param {number} start
+   * @param {Uint32Array} bitfield
    */
-  setPreHavesBitfield(bitfield) {
-    this.#preHaves = bitfield
+  insertPreHaves(start, bitfield) {
+    return this.#preHaves.insert(start, bitfield)
   }
   /**
    * @param {Bitfield} bitfield
    */
   setHavesBitfield(bitfield) {
     this.#haves = bitfield
   }
-  /**
-   * @param {Bitfield} bitfield
-   */
-  setWantsBitfield(bitfield) {
-    this.#wants = bitfield
-  }
   /**
    * Set a range of blocks that a peer wants. This is not part of the Hypercore
    * protocol, so we need our own extension messages that a peer can use to
@@ -269,7 +270,7 @@ export class PeerState {
    * @param {{ start: number, length: number }} range
    */
   setWantRange({ start, length }) {
-    if (!this.#wants) this.#wants = new RemoteBitfield()
+    this.#wantAll = false
     this.#wants.setRange(start, length, true)
   }
   /**
@@ -279,11 +280,7 @@ export class PeerState {
    * @param {number} index
    */
   have(index) {
-    return this.#haves
-      ? this.#haves.get(index)
-      : this.#preHaves
-      ? this.#preHaves.get(index)
-      : false
+    return this.#haves ? this.#haves.get(index) : this.#preHaves.get(index)
   }
   /**
    * Return the "haves" for the 32 blocks from `index`, as a 32-bit integer
@@ -294,16 +291,16 @@ export class PeerState {
    */
   haveWord(index) {
     if (this.#haves) return getBitfieldWord(this.#haves, index)
-    if (this.#preHaves) return getBitfieldWord(this.#preHaves, index)
-    return 0
+    return getBitfieldWord(this.#preHaves, index)
   }
   /**
    * Returns whether this peer wants block at `index`. Defaults to `true` for
    * all blocks
    * @param {number} index
    */
   want(index) {
-    return this.#wants ? this.#wants.get(index) : true
+    if (this.#wantAll) return true
+    return this.#wants.get(index)
   }
   /**
    * Return the "wants" for the 32 blocks from `index`, as a 32-bit integer
@@ -313,9 +310,11 @@ export class PeerState {
    * the 32 blocks from `index`
    */
   wantWord(index) {
-    if (this.#wants) return getBitfieldWord(this.#wants, index)
-    // This is a 32-bit number with all bits set
-    return 2 ** 32 - 1
+    if (this.#wantAll) {
+      // This is a 32-bit number with all bits set
+      return 2 ** 32 - 1
+    }
+    return getBitfieldWord(this.#wants, index)
   }
 }