From ec5562876dd5cede97d125aea18af1d86cc9ca21 Mon Sep 17 00:00:00 2001
From: Diego Beraldin <diego.beraldin@gmail.com>
Date: Tue, 19 Sep 2023 23:01:22 +0200
Subject: [PATCH] fix(common-ui): comment ordering in post detail

---
 .../postdetail/PostDetailViewModel.kt         | 68 ++++++++++++++++++-
 .../domain/lemmy/data/CommentModel.kt         |  5 ++
 2 files changed, 70 insertions(+), 3 deletions(-)

diff --git a/core-commonui/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/core/commonui/postdetail/PostDetailViewModel.kt b/core-commonui/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/core/commonui/postdetail/PostDetailViewModel.kt
index f586af006..6fd164f23 100644
--- a/core-commonui/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/core/commonui/postdetail/PostDetailViewModel.kt
+++ b/core-commonui/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/core/commonui/postdetail/PostDetailViewModel.kt
@@ -146,9 +146,12 @@ class PostDetailViewModel(
                 page = currentPage,
                 sort = sort,
                 maxDepth = CommentRepository.MAX_COMMENT_DEPTH,
-            )
+            ).let {
+                processCommentsToGetNestedOrder(it)
+            }
             currentPage++
-            val canFetchMore = commentList.size >= CommentRepository.DEFAULT_PAGE_SIZE
+            val topLevelItems = commentList.filter { it.depth == 0 }
+            val canFetchMore = topLevelItems.size >= CommentRepository.DEFAULT_PAGE_SIZE
             mvi.updateState {
                 val newcomments = if (refreshing) {
                     commentList
@@ -180,7 +183,9 @@ class PostDetailViewModel(
                 parentId = parentId,
                 sort = sort,
                 maxDepth = CommentRepository.MAX_COMMENT_DEPTH,
-            )
+            ).let {
+                processCommentsToGetNestedOrder(it)
+            }
             val newList = uiState.value.comments.let { list ->
                 val index = list.indexOfFirst { c -> c.id == parentId }
                 list.toMutableList().apply {
@@ -452,3 +457,60 @@ class PostDetailViewModel(
         }
     }
 }
+
+
+private data class Node(
+    val comment: CommentModel?,
+    val children: MutableList<Node> = mutableListOf(),
+)
+
+private fun findNode(id: String, node: Node): Node? {
+    if (node.comment?.id.toString() == id) {
+        return node
+    }
+    for (c in node.children) {
+        val res = findNode(id, c)
+        if (res != null) {
+            return res
+        }
+    }
+    return null
+}
+
+
+private fun linearize(node: Node, list: MutableList<CommentModel>) {
+    if (node.children.isEmpty()) {
+        if (node.comment != null) {
+            list.add(node.comment)
+        }
+        return
+    }
+    for (c in node.children) {
+        linearize(c, list)
+    }
+    if (node.comment != null) {
+        list.add(node.comment)
+    }
+}
+
+private fun processCommentsToGetNestedOrder(items: List<CommentModel>): List<CommentModel> {
+    val root = Node(null)
+    // reconstructs the tree
+    for (c in items) {
+        val parentId = c.parentId
+        if (parentId == null) {
+            root.children += Node(c)
+        } else {
+            val parent = findNode(parentId, root)
+            if (parent != null) {
+                parent.children += Node(c)
+            }
+        }
+    }
+
+    // linearize the tree depth first
+    val result = mutableListOf<CommentModel>()
+    linearize(root, result)
+
+    return result.reversed().toList()
+}
\ No newline at end of file
diff --git a/domain-lemmy/data/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/domain/lemmy/data/CommentModel.kt b/domain-lemmy/data/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/domain/lemmy/data/CommentModel.kt
index 80b628dfe..8e1560867 100644
--- a/domain-lemmy/data/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/domain/lemmy/data/CommentModel.kt
+++ b/domain-lemmy/data/src/commonMain/kotlin/com/github/diegoberaldin/raccoonforlemmy/domain/lemmy/data/CommentModel.kt
@@ -14,4 +14,9 @@ data class CommentModel(
     val path: String = "",
 ) : JavaSerializable {
     val depth: Int get() = (path.split(".").size - 2).coerceAtLeast(0)
+    val parentId: String?
+        get() = path.split(".")
+            .let {
+                it.getOrNull(it.lastIndex - 1)
+            }?.takeIf { it != "0" }
 }