From 5fa235a556d384117840b7088575012dcd1787dd Mon Sep 17 00:00:00 2001
From: Jules Laplace <jules@okfoc.us>
Date: Mon, 17 Nov 2014 15:46:39 -0500
Subject: polygonal lasso

---
 assets/javascripts/util/undostack.js | 54 ++++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 assets/javascripts/util/undostack.js

(limited to 'assets/javascripts/util/undostack.js')

diff --git a/assets/javascripts/util/undostack.js b/assets/javascripts/util/undostack.js
new file mode 100644
index 0000000..040a4eb
--- /dev/null
+++ b/assets/javascripts/util/undostack.js
@@ -0,0 +1,54 @@
+(function(){
+
+  var UndoStack = function(){
+    this.debug = true
+    this.stack = []
+    this.types = {}
+    this.pointer = -1
+  }
+  UndoStack.prototype.push = function(action){
+    this.pointer++
+    this.stack[this.pointer] = action
+    this.purge()
+    this.debug && console.log("push", action.type)
+  }
+  UndoStack.prototype.purge = function(){
+    if (this.stack.length-1 == this.pointer) return
+    this.stack.length = this.pointer+1
+  }
+  UndoStack.prototype.undo = function(){
+    if (this.pointer == -1) return false
+    var action = this.stack[this.pointer]
+    this.debug && console.log("undo", action.type)
+    this.types[ action.type ].undo(action.undo)
+    this.pointer--
+    return this.pointer > -1
+  }
+  UndoStack.prototype.redo = function(){
+    if (this.pointer == this.stack.length-1) return false
+    this.pointer++
+    var action = this.stack[this.pointer]
+    this.debug && console.log("redo", action.type)
+    this.types[ action.type ].redo(action.redo)
+    return this.pointer < this.stack.length-1
+  }
+  UndoStack.prototype.register = function(actions){
+  	if (actions.length) {
+  		actions.forEach(this.registerOne.bind(this))
+  	}
+  	else {
+  		this.registerOne(actions)
+		}
+  }
+  UndoStack.prototype.registerOne = function(action){
+		if (! action.redo) { action.redo = action.undo }
+		this.types[ action.type ] = action
+	}  
+  if ('window' in this) {
+    window.UndoStack = new UndoStack
+  }
+  else {
+    module.exports = new UndoStack
+  }
+
+})()
-- 
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