/* <copyright>
Copyright (c) 2012, Motorola Mobility LLC.
All Rights Reserved.

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modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

* Neither the name of Motorola Mobility LLC nor the names of its
  contributors may be used to endorse or promote products derived from this
  software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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</copyright> */

// Consider proposal at https://rniwa.com/editing/undomanager.html

var Montage = require("montage").Montage;

var UndoManager = exports.UndoManager = Montage.create(Montage, {

    enabled: {
        value: true
    },

    _maxUndoCount: {
        enumerable: false,
        value: null
    },

    maxUndoCount: {
        get: function() {
            return this._maxUndoCount;
        },
        set: function(value) {
            if (value === this._maxUndoCount) {
                return;
            }

            this._maxUndoCount = value;

            if (this._maxUndoCount != null) {
                this._trimStacks();
            }
        }

    },

    _trimStacks: {
        enumerable: false,
        value: function() {

            var undoRemoveCount = this._maxUndoCount - this.undoStack.length,
                redoRemoveCount = this._maxUndoCount - this.redoStack.length;

            if (undoRemoveCount > 0) {
                this.undoStack.splice(0, undoRemoveCount);
            }

            if (redoRemoveCount > 0) {
                this.redoStack.splice(0, redoRemoveCount);
            }
        }
    },

    _undoStack: {
        enumerable: false,
        value: null
    },

    undoStack: {
        get: function() {
            if (!this._undoStack) {
                this._undoStack = [];
            }
            return this._undoStack
        }
    },

    redoStack: {
        value: [],
        distinct: true
    },

    add: {
        value: function(label, undoFunction, context) {

            if (0 === this._maxUndoCount) {
                return;
            }

            var undoEntry = {
                label: label,
                undoFunction: undoFunction,
                context: context,
                args: Array.prototype.slice.call(arguments, 3)
            };

            // seeing as you can only ever add one entry at a time to either stack, we should never need to make room
            // for more than a single entry at this point; there's no need for an expensive trim
            if (this.isUndoing) {

                // preserve the label of the current action being undone to be the name of the redo
                undoEntry.label = this.undoEntry.label;

                if (this.redoStack.length === this._maxUndoCount) {
                    this.redoStack.shift();
                }

                this.redoStack.push(undoEntry);
            } else {

                if (this.undoStack.length === this._maxUndoCount) {
                    this.undoStack.shift();
                }

                this.undoStack.push(undoEntry);

                if (!this.isRedoing && this.redoStack.length > 0) {
                    this.clearRedo();
                }
            }
        }
    },

    clearUndo: {
        value: function() {
            this.undoStack.splice(0, this.undoStack.length);
        }
    },

    clearRedo: {
        value: function() {
            this.redoStack.splice(0, this.redoStack.length);
        }
    },

    isUndoing: {
        dependencies: ["undoEntry"],
        get: function() {
            return !!this.undoEntry;
        }
    },

    isRedoing: {
        dependencies: ["redoEntry"],
        get: function() {
            return !!this.redoEntry;
        }
    },

    undoEntry: {
        enumerable: false,
        value: null
    },

    redoEntry: {
        enumerable: false,
        value: null
    },

    undo: {
        value: function() {

            if (this.isUndoing || this.isRedoing) {
                throw "UndoManager cannot initiate an undo or redo while undoing.";
            }

            if (this.undoStack.length === 0) {
                return;
            }

            var entry = this.undoEntry = this.undoStack.pop();
            entry.undoFunction.apply(entry.context, entry.args);
            this.undoEntry = null;
        }
    },

    redo: {
        value: function() {
            if (this.isUndoing || this.isRedoing) {
                throw "UndoManager cannot initiate an undo or redo while redoing.";
            }

            if (this.redoStack.length === 0) {
                return;
            }

            var entry = this.redoEntry = this.redoStack.pop();
            entry.undoFunction.apply(entry.context, entry.args);
            this.redoEntry = null;
        }
    },

    canUndo: {
        dependencies: ["undoStack.count()"],
        get: function() {
            return !!this.undoStack.length;
        }
    },

    canRedo: {
        dependencies: ["redoStack.count()"],
        get: function() {
            return !!this.redoStack.length;
        }
    },

    undoLabel: {
        dependencies: ["undoStack.count()"],
        get: function() {
            var undoCount = this.undoStack.length,
                label;

            if (undoCount) {
                label = this.undoStack[undoCount - 1].label;
            }

            return label ? "Undo " + label : "Undo";
        },
        set: function(value) {
            var undoCount = this.redoStack.length;
            if (undoCount) {
                this.undoStack[undoCount - 1].label = value;
            }
        }
    },

    redoLabel: {
        dependencies: ["redoStack.count()"],
        get: function() {
            var redoCount = this.redoStack.length,
                label;

            if (redoCount) {
                label = this.redoStack[redoCount - 1].label
            }

            return label ? "Redo " + label : "Redo";
        },
        set: function(value) {
            var redoCount = this.redoStack.length;
            if (redoCount) {
                this.redoStack[redoCount - 1].label = value;
            }
        }
    }

});

var _defaultUndoManager = null;
Montage.defineProperty(exports, "defaultUndoManager", {
    get: function() {
        if (!_defaultUndoManager) {
            _defaultUndoManager = UndoManager.create();
        }
        return _defaultUndoManager;
    }
});