fix: make trickle dag importer compatible with go (#29)

* fix: make trickle dag importer compatible with go

* chore: fix typo

Author: achingbrain

src/dag-builder/file/trickle.js

@@ -7,100 +7,144 @@ module.exports = async function * trickleReduceToRoot (source, reduce, options)
 }
 
 async function trickleStream (source, reduce, options) {
-  let root = {
-    children: []
-  }
-  let node = root
+  let root
+  let iteration = 0
   let maxDepth = 1
-  let currentDepth = 1
-  let layerSize = 0
+  let subTree = root = new Root(options.layerRepeat)
 
   for await (const layer of batch(source, options.maxChildrenPerNode)) {
-    node.data = layer
-
-    let parent = node.parent || root
-    const nextNode = {
-      children: []
-    }
+    if (subTree.isFull()) {
+      if (subTree !== root) {
+        root.addChild(await subTree.reduce(reduce))
+      }
 
-    if (currentDepth < maxDepth) {
-      // the current layer can't have more children
-      // but we can descend a layer
-      node.children.push(nextNode)
-      nextNode.parent = node
-      node = nextNode
-      currentDepth++
-    } else if (parent.children.length < options.layerRepeat) {
-      // the current layer can have more children
-      parent.children.push(nextNode)
-      nextNode.parent = parent
-      node = nextNode
-    } else if (currentDepth === maxDepth) {
-      // hit the bottom of the current iteration, can we find a sibling?
-      parent = findNext(root, 0, maxDepth, options)
-
-      if (parent) {
-        nextNode.parent = parent
-        parent.children.push(nextNode)
-        node = nextNode
-      } else {
-        if (layerSize === 0) {
-          maxDepth++
-        }
-
-        layerSize++
-
-        if (layerSize === options.layerRepeat) {
-          layerSize = 0
-        }
-
-        nextNode.parent = root
-        root.children.push(nextNode)
-        node = nextNode
-
-        currentDepth = 1
+      if (iteration && iteration % options.layerRepeat === 0) {
+        maxDepth++
       }
+
+      subTree = new SubTree(maxDepth, options.layerRepeat, iteration)
+
+      iteration++
     }
+
+    subTree.append(layer)
   }
 
-  // reduce to root
-  return walk(root, reduce)
+  if (subTree && subTree !== root) {
+    root.addChild(await subTree.reduce(reduce))
+  }
+
+  return root.reduce(reduce)
 }
 
-const walk = async (node, reduce) => {
-  let children = []
+class SubTree {
+  constructor (maxDepth, layerRepeat, iteration) {
+    this.maxDepth = maxDepth
+    this.layerRepeat = layerRepeat
+    this.currentDepth = 1
+    this.iteration = iteration
+
+    this.root = this.node = this.parent = {
+      children: [],
+      depth: this.currentDepth,
+      maxDepth,
+      maxChildren: (this.maxDepth - this.currentDepth) * this.layerRepeat
+    }
+  }
+
+  isFull () {
+    if (!this.root.data) {
+      return false
+    }
+
+    if (this.currentDepth < this.maxDepth && this.node.maxChildren) {
+      // can descend
+      this._addNextNodeToParent(this.node)
+
+      return false
+    }
+
+    // try to find new node from node.parent
+    const distantRelative = this._findParent(this.node, this.currentDepth)
+
+    if (distantRelative) {
+      this._addNextNodeToParent(distantRelative)
+
+      return false
+    }
 
-  if (node.children.length) {
-    children = await Promise.all(
-      node.children
-        .filter(child => child.data)
-        .map(child => walk(child, reduce))
-    )
+    return true
   }
 
-  return reduce(node.data.concat(children))
-}
+  _addNextNodeToParent (parent) {
+    this.parent = parent
+
+    // find site for new node
+    const nextNode = {
+      children: [],
+      depth: parent.depth + 1,
+      parent,
+      maxDepth: this.maxDepth,
+      maxChildren: Math.floor(parent.children.length / this.layerRepeat) * this.layerRepeat
+    }
+
+    parent.children.push(nextNode)
 
-const findNext = (node, depth, maxDepth, options) => {
-  if (depth === maxDepth) {
-    return
+    this.currentDepth = nextNode.depth
+    this.node = nextNode
   }
 
-  let nodeMatches = false
+  append (layer) {
+    this.node.data = layer
+  }
+
+  reduce (reduce) {
+    return this._reduce(this.root, reduce)
+  }
+
+  async _reduce (node, reduce) {
+    let children = []
+
+    if (node.children.length) {
+      children = await Promise.all(
+        node.children
+          .filter(child => child.data)
+          .map(child => this._reduce(child, reduce))
+      )
+    }
 
-  if (node.children.length < options.layerRepeat) {
-    nodeMatches = true
+    return reduce(node.data.concat(children))
   }
 
-  if (node.children.length) {
-    const childMatches = findNext(node.children[node.children.length - 1], depth + 1, maxDepth, options)
+  _findParent (node, depth) {
+    const parent = node.parent
+
+    if (!parent || parent.depth === 0) {
+      return
+    }
 
-    if (childMatches) {
-      return childMatches
+    if (parent.children.length === parent.maxChildren || !parent.maxChildren) {
+      // this layer is full, may be able to traverse to a different branch
+      return this._findParent(parent, depth)
     }
+
+    return parent
+  }
+}
+
+class Root extends SubTree {
+  constructor (layerRepeat) {
+    super(0, layerRepeat)
+
+    this.root.depth = 0
+    this.currentDepth = 1
+  }
+
+  addChild (child) {
+    this.root.children.push(child)
   }
 
-  if (nodeMatches) {
-    return node
+  reduce (reduce) {
+    return reduce(this.root.data.concat(this.root.children))
   }
 }