feat: add Memo post thread endpoint

src/adapters/post-query.js

@@ -90,6 +90,30 @@ class PostQuery {
 
     return posts
   }
+
+  async buildReplyCountMap () {
+  const counts = new Map()
+  let total = 0
+
+  for await (const [childTxid, child] of this.postChildrenDb.iterator()) {
+    total++
+
+    console.log('Indexed reply:', {
+      childTxid,
+      child,
+      parentTxid: child?.parentTxid
+    })
+
+    const parentTxid = child?.parentTxid
+    if (!parentTxid) continue
+
+    counts.set(parentTxid, (counts.get(parentTxid) || 0) + 1)
+  }
+
+  console.log(`Total postChildrenDb records: ${total}`)
+
+  return counts
+}
 }
 
 export default PostQuery

src/controllers/rest-api/posts/controller.js

@@ -17,6 +17,7 @@ class PostsRESTControllerLib {
 
     this.getRecentPosts = this.getRecentPosts.bind(this)
     this.getPostsByAddr = this.getPostsByAddr.bind(this)
+    this.getPostThread = this.getPostThread.bind(this)
     this.handleError = this.handleError.bind(this)
   }
 
@@ -98,6 +99,18 @@ class PostsRESTControllerLib {
       this.handleError(ctx, err)
     }
   }
+
+  async getPostThread (ctx) {
+    try {
+      const { txid } = ctx.params
+
+      ctx.body = await this.useCases.getPostThread.execute({
+        txid
+      })
+    } catch (err) {
+      this.handleError(ctx, err)
+    }
+  }
 }
 
 export default PostsRESTControllerLib

src/controllers/rest-api/posts/index.js

@@ -26,6 +26,7 @@ class PostsRouter {
   attach (app) {
     this.router.get('/recent', this.postsRESTController.getRecentPosts)
     this.router.get('/by/:addr', this.postsRESTController.getPostsByAddr)
+    this.router.get('/:txid/thread',this.postsRESTController.getPostThread)
     app.use(this.router.routes())
     app.use(this.router.allowedMethods())
   }

src/use-cases/get-post-thread.js

@@ -0,0 +1,101 @@
+/*
+  Retrieve a Memo post and its nested replies.
+*/
+
+class GetPostThread {
+  constructor (localConfig = {}) {
+    this.adapters = localConfig.adapters
+
+    if (!this.adapters) {
+      throw new Error(
+        'Adapters required when instantiating GetPostThread.'
+      )
+    }
+
+    this.execute = this.execute.bind(this)
+    this.buildThreadNode = this.buildThreadNode.bind(this)
+  }
+
+  async execute ({ txid } = {}) {
+    if (!txid || typeof txid !== 'string') {
+      const err = new Error('A transaction ID is required.')
+      err.status = 400
+      throw err
+    }
+
+    const rootPost = await this.buildThreadNode(txid)
+
+    if (!rootPost) {
+      const err = new Error('Post not found.')
+      err.status = 404
+      throw err
+    }
+
+    return {
+      post: rootPost
+    }
+  }
+
+  async buildThreadNode (txid, visited = new Set()) {
+    if (visited.has(txid)) return null
+
+    visited.add(txid)
+
+    let post
+
+    try {
+      post = await this.adapters.postQuery.postsDb.get(txid)
+    } catch (err) {
+      if (err.notFound || err.code === 'LEVEL_NOT_FOUND') {
+        return null
+      }
+
+      throw err
+    }
+
+    const childTxids = []
+
+    for await (
+      const [, child]
+      of this.adapters.postQuery.postChildrenDb.iterator()
+    ) {
+      if (child?.parentTxid !== txid) continue
+      if (!child?.childTxid) continue
+
+      childTxids.push(child.childTxid)
+    }
+
+    const replies = []
+
+    for (const childTxid of childTxids) {
+      const reply = await this.buildThreadNode(childTxid, visited)
+
+      if (reply) {
+        replies.push(reply)
+      }
+    }
+
+    replies.sort((a, b) => {
+      const blockDifference =
+        (a.blockHeight ?? 0) - (b.blockHeight ?? 0)
+
+      if (blockDifference !== 0) {
+        return blockDifference
+      }
+
+      return (a.seen ?? 0) - (b.seen ?? 0)
+    })
+
+    return {
+      txid,
+      addr: post.addr,
+      text: post.text,
+      seen: post.seen,
+      blockHeight: post.blockHeight ?? 0,
+      replyCount: replies.length,
+      replies
+    }
+  }
+}
+
+export default GetPostThread

src/use-cases/index.js

@@ -5,26 +5,46 @@
 import ListRecentProfiles from './list-recent-profiles.js'
 import ListRecentPosts from './list-recent-posts.js'
 import ListPostsByAddr from './list-posts-by-addr.js'
+import GetPostThread from './get-post-thread.js'
 
 class UseCases {
   constructor (localConfig = {}) {
     this.adapters = localConfig.adapters
+
     if (!this.adapters) {
-      throw new Error('Adapters required when instantiating UseCases.')
+      throw new Error(
+        'Adapters required when instantiating UseCases.'
+      )
     }
 
     this.listRecentProfiles = null
     this.listRecentPosts = null
     this.listPostsByAddr = null
+    this.getPostThread = null
   }
 
   async start () {
-    this.listRecentProfiles = new ListRecentProfiles({ adapters: this.adapters })
-    this.listRecentPosts = new ListRecentPosts({ adapters: this.adapters })
-    this.listPostsByAddr = new ListPostsByAddr({ adapters: this.adapters })
+    this.listRecentProfiles = new ListRecentProfiles({
+      adapters: this.adapters
+    })
+
+    this.listRecentPosts = new ListRecentPosts({
+      adapters: this.adapters
+    })
+
+    this.listPostsByAddr = new ListPostsByAddr({
+      adapters: this.adapters
+    })
+
+    this.getPostThread = new GetPostThread({
+      adapters: this.adapters
+    })
+
     console.log('Use cases initialized.')
+
     return true
   }
 }
 
 export default UseCases
+