var assert = require("assert")
var UndoStack = require("./undo.js")
UndoStack.debug = false

describe('undo', function(){
  
  var state = "zero"
  
  describe('#register()', function(){
  
    UndoStack.register({
      type: "demo",
      undo: function(myState){
        state = myState
      },
      redo: function(myState){
        state = myState
      },
    })

    it('registers undoable actions', function(){
      assert( UndoStack.types.hasOwnProperty("demo") )
    })
  })
  
  describe('#push()', function(){
    
    it('starts empty', function(){
      assert.equal(0, UndoStack.stack.length)
      assert.equal(-1, UndoStack.pointer)
    })
    
    it('pushes some actions', function(){

      UndoStack.push({
        type: "demo",
        undo: state,
        redo: "one"
      })
      state = "one"

      UndoStack.push({
        type: "demo",
        undo: state,
        redo: "two"
      })
      state = "two"

      UndoStack.push({
        type: "demo",
        undo: state,
        redo: "three"
      })
      state = "three"
    
      assert.equal(3, UndoStack.stack.length)
      assert.equal(2, UndoStack.pointer)
    })
  })
  
  describe('#undo()', function(){
  
    it('retrieves old state', function(){
      assert.equal("three", state)
      UndoStack.undo()
      assert.equal("two", state)
      assert.equal(1, UndoStack.pointer)
    })
    
    it('can only undo so far', function(){
      var canUndo

      canUndo = UndoStack.undo()
      assert.equal("one", state)
      assert.equal(0, UndoStack.pointer)
      assert.equal(true, canUndo)

      canUndo = UndoStack.undo()
      assert.equal("zero", state)
      assert.equal(-1, UndoStack.pointer)
      assert.equal(false, canUndo)
      
      canUndo = UndoStack.undo()
      assert.equal("zero", state)
      assert.equal(-1, UndoStack.pointer)
      assert.equal(false, canUndo)
    })
  
  })

  describe('#redo()', function(){

    it('reassigns new state', function(){
      UndoStack.redo()
      assert.equal("one", state)
    })
    
    it('can only redo so far', function(){
      var canRedo
      
      canRedo = UndoStack.redo()
      assert.equal("two", state)
      assert.equal(true, canRedo)

      canRedo = UndoStack.redo()
      assert.equal("three", state)
      assert.equal(false, canRedo)

      canRedo = UndoStack.redo()
      assert.equal("three", state)
      assert.equal(false, canRedo)
    })

    it('clobbers old state if we undo then do something else', function(){
      UndoStack.undo()
      assert.equal("two", state)
      assert.equal(1, UndoStack.pointer)

      UndoStack.undo()
      assert.equal("one", state)
      assert.equal(0, UndoStack.pointer)
      assert.equal(3, UndoStack.stack.length)

      UndoStack.push({
        type: "demo",
        undo: state,
        redo: "four"
      })
      state = "four"

      assert.equal(1, UndoStack.pointer)
      assert.equal(2, UndoStack.stack.length)

      UndoStack.undo()
      assert.equal("one", state)
      assert.equal(0, UndoStack.pointer)
      assert.equal(2, UndoStack.stack.length)

      UndoStack.redo()
      assert.equal("four", state)
      assert.equal(1, UndoStack.pointer)
      assert.equal(2, UndoStack.stack.length)
    })
  })
  
})

// 1) push action
// 2) push action
// 3) push action
// undo 3
// undo 2
// undo 1
// undo * can't undo anymore
// redo 1
// redo 2
// redo 3
// redo * can't redo anymore
// undo 3
// 4) push action (clobbers action 3)
// undo 4
// undo 2
// redo 2
// redo 4