From 6074f0fa831abc45b40177ea498a2e0fbb3eeb32 Mon Sep 17 00:00:00 2001
From: Alex Potsides <alex@achingbrain.net>
Date: Sat, 3 Jun 2023 20:09:11 +0100
Subject: [PATCH] feat: add black hole stores (#227)

Sometimes it's useful to not store anything, for example calculating
the CID of a datastructure without actually storing any of the data.
---
 packages/blockstore-core/README.md         | 16 +++++++++--
 packages/blockstore-core/package.json      |  4 +++
 packages/blockstore-core/src/black-hole.ts | 27 +++++++++++++++++++
 packages/datastore-core/README.md          | 21 +++++++++++----
 packages/datastore-core/package.json       |  4 +++
 packages/datastore-core/src/black-hole.ts  | 31 ++++++++++++++++++++++
 6 files changed, 96 insertions(+), 7 deletions(-)
 create mode 100644 packages/blockstore-core/src/black-hole.ts
 create mode 100644 packages/datastore-core/src/black-hole.ts

diff --git a/packages/blockstore-core/README.md b/packages/blockstore-core/README.md
index 1e4a5f61..bde24348 100644
--- a/packages/blockstore-core/README.md
+++ b/packages/blockstore-core/README.md
@@ -15,6 +15,7 @@
 - [Usage](#usage)
   - [BaseBlockstore](#baseblockstore)
   - [MemoryBlockstore](#memoryblockstore)
+  - [BlackHoleBlockstore](#blackholeblockstore)
 - [API Docs](#api-docs)
 - [License](#license)
 - [Contribute](#contribute)
@@ -35,8 +36,9 @@ Loading this module through a script tag will make it's exports available as `Bl
 
 ## Implementations
 
-- Base: [`src/base`](src/base.js)
-- Memory: [`src/memory`](src/memory.js)
+- Base: [`src/base`](src/base.ts)
+- Memory: [`src/memory`](src/memory.ts)
+- BlackHole: ['src/blackhole](src/blackhole.ts)
 
 ## Usage
 
@@ -70,6 +72,16 @@ import { MemoryBlockstore } from 'blockstore-core/memory'
 const store = new MemoryBlockstore()
 ```
 
+### BlackHoleBlockstore
+
+A Blockstore that does not store any blocks.
+
+```js
+import { BlackHoleBlockstore } from 'blockstore-core/black-hole'
+
+const store = new BlackHoleBlockstore()
+```
+
 ## API Docs
 
 - <https://ipfs.github.io/js-stores/modules/blockstore_core.html>
diff --git a/packages/blockstore-core/package.json b/packages/blockstore-core/package.json
index 80cdf454..0149677c 100644
--- a/packages/blockstore-core/package.json
+++ b/packages/blockstore-core/package.json
@@ -55,6 +55,10 @@
       "types": "./dist/src/base.d.ts",
       "import": "./dist/src/base.js"
     },
+    "./black-hole": {
+      "types": "./dist/src/black-hole.d.ts",
+      "import": "./dist/src/black-hole.js"
+    },
     "./errors": {
       "types": "./dist/src/errors.d.ts",
       "import": "./dist/src/errors.js"
diff --git a/packages/blockstore-core/src/black-hole.ts b/packages/blockstore-core/src/black-hole.ts
new file mode 100644
index 00000000..ab1b5a61
--- /dev/null
+++ b/packages/blockstore-core/src/black-hole.ts
@@ -0,0 +1,27 @@
+import { BaseBlockstore } from './base.js'
+import * as Errors from './errors.js'
+import type { Pair } from 'interface-blockstore'
+import type { Await, AwaitIterable } from 'interface-store'
+import type { CID } from 'multiformats/cid'
+
+export class BlackHoleBlockstore extends BaseBlockstore {
+  put (key: CID): Await<CID> {
+    return key
+  }
+
+  get (): Await<Uint8Array> {
+    throw Errors.notFoundError()
+  }
+
+  has (): Await<boolean> {
+    return false
+  }
+
+  async delete (): Promise<void> {
+
+  }
+
+  async * getAll (): AwaitIterable<Pair> {
+
+  }
+}
diff --git a/packages/datastore-core/README.md b/packages/datastore-core/README.md
index 0b822a73..3afefb1b 100644
--- a/packages/datastore-core/README.md
+++ b/packages/datastore-core/README.md
@@ -37,11 +37,12 @@ Loading this module through a script tag will make it's exports available as `Da
 ## Implementations
 
 - Wrapper Implementations
-  - Mount: [`src/mount`](src/mount.js)
-  - Keytransform: [`src/keytransform`](src/keytransform.js)
-  - Sharding: [`src/sharding`](src/sharding.js)
-  - Tiered: [`src/tiered`](src/tirered.js)
-  - Namespace: [`src/namespace`](src/namespace.js)
+  - Mount: [`src/mount`](src/mount.ts)
+  - Keytransform: [`src/keytransform`](src/keytransform.ts)
+  - Sharding: [`src/sharding`](src/sharding.ts)
+  - Tiered: [`src/tiered`](src/tirered.ts)
+  - Namespace: [`src/namespace`](src/namespace.ts)
+  - BlackHole: [`src/black-hole`](src/black-hole.ts)
 
 ## Usage
 
@@ -83,6 +84,16 @@ import {
 const store = new MountStore({prefix: new Key('/a'), datastore: new MemoryStore()})
 ```
 
+### BlackHoleDatastore
+
+A datastore that does not store any data.
+
+```js
+import { BlackHoleDatastore } from 'datastore-core/black-hole'
+
+const store = new BlackHoleDatastore()
+```
+
 ## Contribute
 
 Feel free to join in. All welcome. Open an [issue](https://github.com/ipfs/js-ipfs-unixfs-importer/issues)!
diff --git a/packages/datastore-core/package.json b/packages/datastore-core/package.json
index f5181ef7..2efef0fb 100644
--- a/packages/datastore-core/package.json
+++ b/packages/datastore-core/package.json
@@ -55,6 +55,10 @@
       "types": "./dist/src/base.d.ts",
       "import": "./dist/src/base.js"
     },
+    "./black-hole": {
+      "types": "./dist/src/black-hole.d.ts",
+      "import": "./dist/src/black-hole.js"
+    },
     "./errors": {
       "types": "./dist/src/errors.d.ts",
       "import": "./dist/src/errors.js"
diff --git a/packages/datastore-core/src/black-hole.ts b/packages/datastore-core/src/black-hole.ts
new file mode 100644
index 00000000..9c7b3d3e
--- /dev/null
+++ b/packages/datastore-core/src/black-hole.ts
@@ -0,0 +1,31 @@
+import { BaseDatastore } from './base.js'
+import * as Errors from './errors.js'
+import type { Pair } from 'interface-datastore'
+import type { Key } from 'interface-datastore/key'
+import type { Await, AwaitIterable } from 'interface-store'
+
+export class BlackHoleDatastore extends BaseDatastore {
+  put (key: Key): Await<Key> {
+    return key
+  }
+
+  get (): Await<Uint8Array> {
+    throw Errors.notFoundError()
+  }
+
+  has (key: Key): Await<boolean> {
+    return false
+  }
+
+  delete (key: Key): Await<void> {
+
+  }
+
+  * _all (): AwaitIterable<Pair> {
+
+  }
+
+  * _allKeys (): AwaitIterable<Key> {
+
+  }
+}