feat(crdt): support delete operation in CRDT

CLAUDE.md

@@ -0,0 +1,12 @@
+# CLAUDE.md
+
+## Build & Test
+
+- **Tests:** `npx vitest run` (run all tests) or `npx vitest run test/<file>` (run a single test file)
+- **Lint:** `npm run lint` (uses [standard](https://standardjs.com/) — no semicolons, no trailing commas)
+
+## Conventions
+
+- All changes should include tests where possible
+- Tests must pass before submitting
+- Lint must pass before submitting

src/batch/api.ts

@@ -51,6 +51,11 @@ export interface Batcher {
    * overwritten.
    */
   put: (key: string, value: UnknownLink) => Promise<void>
+  /**
+   * Delete the value for the given key. If the key is not found no operation
+   * occurs.
+   */
+  del: (key: string) => Promise<void>
   /**
    * Encode all altered shards in the batch and return the new root CID and
    * difference blocks.

src/batch/index.js

@@ -38,6 +38,15 @@ class Batcher {
     return put(this.blocks, this, key, value)
   }
 
+  /**
+   * @param {string} key The key of the value to delete.
+   * @returns {Promise<void>}
+   */
+  async del (key) {
+    if (this.#committed) throw new BatchCommittedError()
+    return del(this.blocks, this, key)
+  }
+
   async commit () {
     if (this.#committed) throw new BatchCommittedError()
     this.#committed = true
@@ -165,6 +174,31 @@ export const put = async (blocks, shard, key, value) => {
   shard.entries = Shard.putEntry(asShardEntries(targetEntries), asShardEntry(entry))
 }
 
+/**
+ * @param {API.BlockFetcher} blocks
+ * @param {API.BatcherShard} shard
+ * @param {string} key The key of the value to delete.
+ * @returns {Promise<void>}
+ */
+export const del = async (blocks, shard, key) => {
+  const shards = new ShardFetcher(blocks)
+  const dest = await traverse(shards, shard, key)
+
+  const entryidx = dest.shard.entries.findIndex(([k]) => k === dest.key)
+  if (entryidx === -1) return
+
+  const entry = dest.shard.entries[entryidx]
+  if (Array.isArray(entry[1])) {
+    // cannot delete a shard-only entry (no value)
+    if (entry[1][1] == null) return
+    // remove value but keep shard link
+    dest.shard.entries[entryidx] = [entry[0], /** @type {API.ShardEntryLinkValue | API.ShardEntryShardValue} */ ([entry[1][0]])]
+  } else {
+    // remove the entry entirely
+    dest.shard.entries.splice(entryidx, 1)
+  }
+}
+
 /**
  * Traverse from the passed shard through to the correct shard for the passed
  * key.

src/crdt/batch/index.js

@@ -54,6 +54,16 @@ class Batcher {
     this.ops.push({ type: 'put', key, value })
   }
 
+  /**
+   * @param {string} key The key of the value to delete.
+   * @returns {Promise<void>}
+   */
+  async del (key) {
+    if (this.#committed) throw new BatchCommittedError()
+    await Batch.del(this.blocks, this, key)
+    this.ops.push({ type: 'del', key })
+  }
+
   async commit () {
     if (this.#committed) throw new BatchCommittedError()
     this.#committed = true