Add gametree.getHash()

README.md

@@ -42,12 +42,12 @@ A node is represented by an object of the following form:
 
 ```js
 {
-    id: <Primitive>,
-    data: {
-        [property: <String>]: <Array<Primitive>>
-    },
-    parentId: <Primitive> | null,
-    children: <Array<NodeObject>>
+  id: <Primitive>,
+  data: {
+    [property: <String>]: <Array<Primitive>>
+  },
+  parentId: <Primitive> | null,
+  children: <Array<NodeObject>>
 }
 ```
 
@@ -58,7 +58,7 @@ children of nodes with an object of the following form:
 
 ```js
 {
-    [id: <Primitive>]: <Primitive>
+  [id: <Primitive>]: <Primitive>
 }
 ```
 
@@ -200,6 +200,11 @@ Equivalent to `[...tree.listCurrentNodes(currents)].length`.
 Calculates and returns the height of the tree as an integer. This value will be
 cached across mutations when possible.
 
+#### `tree.getHash()`
+
+Calculates and returns a hash of the whole tree as a string. This value will
+be cached.
+
 #### `tree.getStructureHash()`
 
 Calculates and returns a hash of the tree structure as a string. This value will

src/GameTree.js

@@ -1,4 +1,5 @@
 const Draft = require('./Draft')
+const hasher = require('./hasher')
 
 class GameTree {
   constructor({getId = null, merger = null, root = null} = {}) {
@@ -17,6 +18,7 @@ class GameTree {
     this._nodeCache = {}
     this._idAliases = {}
     this._heightCache = null
+    this._hashCache = null
     this._structureHashCache = null
   }
 
@@ -214,20 +216,7 @@ class GameTree {
 
   getStructureHash() {
     if (this._structureHashCache == null) {
-      // Simple hash function adapted from
-      // https://github.com/darkskyapp/string-hash
-
-      let hash = (() => {
-        let result = 5381
-
-        return str => {
-          for (let i = 0; i < str.length; i++) {
-            result = (result * 33) ^ str.charCodeAt(i)
-          }
-
-          return result
-        }
-      })()
+      let hash = hasher.new()
 
       let inner = node => {
         hash('[' + JSON.stringify(node.id) + ',')
@@ -241,6 +230,22 @@ class GameTree {
     return (this._structureHashCache >>> 0) + ''
   }
 
+  getHash() {
+    if (this._hashCache == null) {
+      let hash = hasher.new()
+
+      let inner = node => {
+        hash('[' + JSON.stringify(node.data) + ',')
+        node.children.forEach(inner)
+        return hash(']')
+      }
+
+      this._hashCache = inner(this.root)
+    }
+
+    return (this._hashCache >>> 0) + ''
+  }
+
   onCurrentLine(id, currents) {
     let node = this.get(id)
     let {parentId} = node

src/hasher.js

@@ -0,0 +1,14 @@
+exports.new = function() {
+  // Simple hash function adapted from
+  // https://github.com/darkskyapp/string-hash
+
+  let result = 5381
+
+  return str => {
+    for (let i = 0; i < str.length; i++) {
+      result = (result * 33) ^ str.charCodeAt(i)
+    }
+
+    return result
+  }
+}

tests/GameTree.test.js

@@ -198,3 +198,21 @@ t.test('getStructureHash method', t => {
 
   t.end()
 })
+
+t.test('getHash method', t => {
+  let hash = tree.getHash()
+
+  let tree2 = tree.mutate(draft => {
+    draft.addToProperty(draft.root.id, 'MA', 'aa')
+    draft.removeProperty(childId1, 'MA')
+  })
+
+  let tree3 = tree2.mutate(draft => {
+    draft.appendNode(draft.root.id, {})
+  })
+
+  t.notEqual(hash, tree2.getStructureHash())
+  t.notEqual(hash, tree3.getStructureHash())
+
+  t.end()
+})