Change JSON parsing

Since ActionLogger will only be responsible for logging, the parsing part will be done here, so it involves slightly more complicated logic by building the tree structure from the ground up

Author: wenli-cai

workflow-trace-viewer/src/jvmMain/kotlin/com/squareup/workflow1/traceviewer/ui/FrameSelectTab.kt

@@ -38,7 +38,7 @@ public fun FrameSelectTab(
     ) {
       items(frames.size) { index ->
         Text(
-          text = "State ${index + 1}",
+          text = "Frame ${index + 1}",
           color = if (index == currentIndex) Color.Black else Color.LightGray,
           modifier = Modifier
             .clip(RoundedCornerShape(16.dp))

workflow-trace-viewer/src/jvmMain/kotlin/com/squareup/workflow1/traceviewer/ui/WorkflowTree.kt

@@ -64,8 +64,6 @@ public fun RenderDiagram(
   if (!isLoading) {
     DrawTree(frames[frameInd], onNodeSelect)
   }
-
-  // TODO: catch errors and display UI here
 }
 
 /**

workflow-trace-viewer/src/jvmMain/kotlin/com/squareup/workflow1/traceviewer/util/JsonParser.kt

@@ -9,7 +9,8 @@ import io.github.vinceglb.filekit.PlatformFile
 import io.github.vinceglb.filekit.readString
 
 /**
- * Parses a given file's JSON String into [Node] with Moshi adapters.
+ * Parses a given file's JSON String into a list of [Node]s with Moshi adapters. Each of these nodes
+ * count as the root of a tree which forms a Frame.
  *
  * @return A [ParseResult] representing result of parsing, either an error related to the
  * format of the JSON, or a success and a parsed trace.
@@ -19,18 +20,58 @@ public suspend fun parseTrace(
 ): ParseResult {
   return try {
     val jsonString = file.readString()
-    val moshi = Moshi.Builder()
-      .add(KotlinJsonAdapterFactory())
-      .build()
-    val workflowList = Types.newParameterizedType(List::class.java, Node::class.java)
-    val workflowAdapter: JsonAdapter<List<Node>> = moshi.adapter(workflowList)
-    val trace = workflowAdapter.fromJson(jsonString)
-    ParseResult.Success(trace)
+    val workflowAdapter = createMoshiAdapter()
+    val unParsedTrace = workflowAdapter.fromJson(jsonString)
+
+    val parsedTrace = mutableListOf<Node>()
+    unParsedTrace?.forEach { renderPass ->
+      val parsed = getFrameFromRenderPass(renderPass)
+      parsedTrace.add(parsed)
+    }
+
+    ParseResult.Success(parsedTrace)
   } catch (e: Exception) {
     ParseResult.Failure(e)
   }
 }
 
+/**
+ * Creates a Moshi adapter for parsing the JSON trace file.
+ */
+private fun createMoshiAdapter(): JsonAdapter<List<List<Node>>> {
+  val moshi = Moshi.Builder()
+    .add(KotlinJsonAdapterFactory())
+    .build()
+  val workflowList = Types.newParameterizedType(List::class.java,
+    Types.newParameterizedType(List::class.java, Node::class.java))
+  val adapter: JsonAdapter<List<List<Node>>> = moshi.adapter(workflowList)
+  return adapter
+}
+
+/**
+ * We take an unparsed render pass and build up a tree structure from it to form a Frame.
+ */
+private fun getFrameFromRenderPass(renderPass: List<Node>): Node {
+  val childrenByParent = renderPass.groupBy { it.parent }
+  val root = childrenByParent["root"]?.single()
+  return buildTree(root!!, childrenByParent)
+}
+
+/**
+ * Recursively builds a tree using each node's children.
+ */
+private fun buildTree(node: Node, childrenByParent: Map<String, List<Node>>): Node {
+  val children = (childrenByParent[node.name] ?: emptyList())
+  return Node(
+    name = node.name,
+    parent = node.parent,
+    props = node.props,
+    state = node.state,
+    children = children.map { buildTree(it, childrenByParent) },
+    id = node.id
+  )
+}
+
 sealed interface ParseResult {
   class Success(val trace: List<Node>?) : ParseResult
   class Failure(val error: Throwable) : ParseResult