From 448bd44a41fa0734feb50cd0d21b74cfa7622231 Mon Sep 17 00:00:00 2001
From: Andre Staltz <andre@staltz.com>
Date: Fri, 7 Apr 2023 17:57:53 +0300
Subject: [PATCH] lipmaa in multi-author tangles

---
 lib/feed-v1/index.js         | 26 ++++++++---
 test/feed-v1-tangles.test.js | 86 ++++++++++++++++++++++++++++++++++++
 2 files changed, 105 insertions(+), 7 deletions(-)

diff --git a/lib/feed-v1/index.js b/lib/feed-v1/index.js
index 70b2cc0..6079547 100644
--- a/lib/feed-v1/index.js
+++ b/lib/feed-v1/index.js
@@ -86,11 +86,19 @@ function toPlaintextBuffer(opts) {
   return Buffer.from(stringify(opts.content), 'utf8')
 }
 
-function calculateDepth(existing) {
+function readDepth(msg, tangleId = null) {
+  if (tangleId) {
+    return msg.metadata.tangles?.[tangleId]?.depth ?? 0
+  } else {
+    return msg.metadata.depth
+  }}
+
+function calculateDepth(existing, tangleId = null) {
   let max = -1
   for (const msg of existing.values()) {
-    if (msg.metadata.depth > max) {
-      max = msg.metadata.depth
+    const depth = readDepth(msg, tangleId)
+    if (depth > max) {
+      max = depth
     }
   }
   return max + 1
@@ -124,10 +132,10 @@ function lipmaa(n) {
   return n - po3
 }
 
-function calculatePrev(existing, depth, lipmaaDepth) {
+function calculatePrev(existing, depth, lipmaaDepth, tangleId = null) {
   const prev = []
   for (const msg of existing.values()) {
-    const msgDepth = msg.metadata.depth
+    const msgDepth = readDepth(msg, tangleId)
     if (msgDepth === lipmaaDepth || msgDepth === depth - 1) {
       prev.push(getMsgHash(msg))
     }
@@ -168,6 +176,9 @@ function prevalidateExisting(existing, tangleId = null) {
         } else {
           hasDepthZeroMsg = true
         }
+      } else if (!p.metadata.tangles?.[tangleId]) {
+        // prettier-ignore
+        return new Error(`existing must refer to the tangleId ${tangleId}`)
       }
     }
   }
@@ -197,9 +208,10 @@ function create(opts) {
       if ((err = validateMsgHash(rootId))) throw err
       const existing = opts.tangles[rootId]
       if ((err = prevalidateExisting(existing, rootId))) throw err
-      const depth = calculateDepth(existing)
+
+      const depth = calculateDepth(existing, rootId)
       const lipmaaDepth = lipmaa(depth + 1) - 1
-      const prev = calculatePrev(existing, depth, lipmaaDepth)
+      const prev = calculatePrev(existing, depth, lipmaaDepth, rootId)
       tangles ??= {}
       tangles[rootId] = { depth, prev }
     }
diff --git a/test/feed-v1-tangles.test.js b/test/feed-v1-tangles.test.js
index f3509d4..da39951 100644
--- a/test/feed-v1-tangles.test.js
+++ b/test/feed-v1-tangles.test.js
@@ -37,3 +37,89 @@ tape('simple multi-author tangle', (t) => {
 
   t.end()
 })
+
+tape('lipmaa in multi-author tangle', (t) => {
+  const keysA = generateKeypair('alice')
+  const keysB = generateKeypair('bob')
+
+  const content = { text: 'Hello world!' }
+  const when = 1652037377204
+  const existingA = new Map()
+  const existingB = new Map()
+  const tangleExisting = new Map()
+
+  const msg1 = FeedV1.create({
+    keys: keysA,
+    content,
+    type: 'post',
+    existing: existingA,
+    when: when + 1,
+  })
+  const msgHash1 = FeedV1.getMsgHash(msg1)
+  existingA.set(msgHash1, msg1)
+  tangleExisting.set(msgHash1, msg1)
+
+  t.notOk(msg1.metadata.tangles, 'A:msg1 has no extra tangles')
+
+  const msg2 = FeedV1.create({
+    keys: keysB,
+    content,
+    type: 'post',
+    existing: existingB,
+    tangles: {
+      [msgHash1]: tangleExisting,
+    },
+    when: when + 2,
+  })
+  const msgHash2 = FeedV1.getMsgHash(msg2)
+  existingB.set(msgHash2, msg2)
+  tangleExisting.set(msgHash2, msg2)
+
+  t.deepEquals(
+    msg2.metadata.tangles[msgHash1].prev,
+    [msgHash1],
+    'B:msg2 points to A:msg1'
+  )
+
+  const msg3 = FeedV1.create({
+    keys: keysB,
+    content,
+    type: 'post',
+    existing: existingB,
+    tangles: {
+      [msgHash1]: tangleExisting,
+    },
+    when: when + 3,
+  })
+  const msgHash3 = FeedV1.getMsgHash(msg3)
+  existingB.set(msgHash3, msg3)
+  tangleExisting.set(msgHash3, msg3)
+
+  t.deepEquals(
+    msg3.metadata.tangles[msgHash1].prev,
+    [msgHash2],
+    'B:msg3 points to B:msg2'
+  )
+
+  const msg4 = FeedV1.create({
+    keys: keysA,
+    content,
+    type: 'post',
+    existing: existingA,
+    tangles: {
+      [msgHash1]: tangleExisting,
+    },
+    when: when + 4,
+  })
+  const msgHash4 = FeedV1.getMsgHash(msg4)
+  existingB.set(msgHash4, msg4)
+  tangleExisting.set(msgHash4, msg4)
+
+  t.deepEquals(
+    msg4.metadata.tangles[msgHash1].prev,
+    [msgHash1, msgHash3],
+    'A:msg4 points to A:msg1,B:msg3'
+  )
+
+  t.end()
+})