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define(function(require, exports, module) {
"use strict";

var oop = require("./lib/oop");
var EventEmitter = require("./lib/event_emitter").EventEmitter;

/**
 * 
 * Defines the floating pointer in the document. Whenever text is inserted or deleted before the cursor, the position of the cursor is updated.
 *
 * @class Anchor
 **/

/**
 * Creates a new `Anchor` and associates it with a document.
 *
 * @param {Document} doc The document to associate with the anchor
 * @param {Number} row The starting row position
 * @param {Number} column The starting column position
 *
 * @constructor
 **/

var Anchor = exports.Anchor = function(doc, row, column) {
    this.document = doc;
    
    if (typeof column == "undefined")
        this.setPosition(row.row, row.column);
    else
        this.setPosition(row, column);

    this.$onChange = this.onChange.bind(this);
    doc.on("change", this.$onChange);
};

(function() {

    oop.implement(this, EventEmitter);
    
    /**
     * Returns an object identifying the `row` and `column` position of the current anchor.
     * @returns {Object}
     **/

    this.getPosition = function() {
        return this.$clipPositionToDocument(this.row, this.column);
    };
 
     /**
     * 
     * Returns the current document.
     * @returns {Document}
     **/
        
    this.getDocument = function() {
        return this.document;
    };
    
     /**
     * Fires whenever the anchor position changes.
     *
     * Both of these objects have a `row` and `column` property corresponding to the position.
     *
     * Events that can trigger this function include [[Anchor.setPosition `setPosition()`]].
     * 
     * @event change 
     * @param {Object} e  An object containing information about the anchor position. It has two properties:  
     *  - `old`: An object describing the old Anchor position
     *  - `value`: An object describing the new Anchor position  
     *
     *
     **/

    this.onChange = function(e) {
        var delta = e.data;
        var range = delta.range;
            
        if (range.start.row == range.end.row && range.start.row != this.row)
            return;
            
        if (range.start.row > this.row)
            return;
            
        if (range.start.row == this.row && range.start.column > this.column)
            return;
    
        var row = this.row;
        var column = this.column;
        
        if (delta.action === "insertText") {
            if (range.start.row === row && range.start.column <= column) {
                if (range.start.row === range.end.row) {
                    column += range.end.column - range.start.column;
                }
                else {
                    column -= range.start.column;
                    row += range.end.row - range.start.row;
                }
            }
            else if (range.start.row !== range.end.row && range.start.row < row) {
                row += range.end.row - range.start.row;
            }
        } else if (delta.action === "insertLines") {
            if (range.start.row <= row) {
                row += range.end.row - range.start.row;
            }
        }
        else if (delta.action == "removeText") {
            if (range.start.row == row && range.start.column < column) {
                if (range.end.column >= column)
                    column = range.start.column;
                else
                    column = Math.max(0, column - (range.end.column - range.start.column));
                
            } else if (range.start.row !== range.end.row && range.start.row < row) {
                if (range.end.row == row) {
                    column = Math.max(0, column - range.end.column) + range.start.column;
                }
                row -= (range.end.row - range.start.row);
            }
            else if (range.end.row == row) {
                row -= range.end.row - range.start.row;
                column = Math.max(0, column - range.end.column) + range.start.column;
            }
        } else if (delta.action == "removeLines") {
            if (range.start.row <= row) {
                if (range.end.row <= row)
                    row -= range.end.row - range.start.row;
                else {
                    row = range.start.row;
                    column = 0;
                }
            }
        }

        this.setPosition(row, column, true);
    };

     /**
     * Sets the anchor position to the specified row and column. If `noClip` is `true`, the position is not clipped.
     * @param {Number} row The row index to move the anchor to
     * @param {Number} column The column index to move the anchor to
     * @param {Boolean} noClip Identifies if you want the position to be clipped
     *
     * 
     *
     **/

    this.setPosition = function(row, column, noClip) {
        var pos;
        if (noClip) {
            pos = {
                row: row,
                column: column
            };
        }
        else {
            pos = this.$clipPositionToDocument(row, column);
        }
        
        if (this.row == pos.row && this.column == pos.column)
            return;
            
        var old = {
            row: this.row,
            column: this.column
        };
        
        this.row = pos.row;
        this.column = pos.column;
        this._emit("change", {
            old: old,
            value: pos
        });
    };
    
    /**
     * When called, the `'change'` event listener is removed.
     *
     **/

    this.detach = function() {
        this.document.removeEventListener("change", this.$onChange);
    };
    
    /** 
     * Clips the anchor position to the specified row and column.
     * @param {Number} row The row index to clip the anchor to
     * @param {Number} column The column index to clip the anchor to
     *
     *
     *
     **/
    this.$clipPositionToDocument = function(row, column) {
        var pos = {};
    
        if (row >= this.document.getLength()) {
            pos.row = Math.max(0, this.document.getLength() - 1);
            pos.column = this.document.getLine(pos.row).length;
        }
        else if (row < 0) {
            pos.row = 0;
            pos.column = 0;
        }
        else {
            pos.row = row;
            pos.column = Math.min(this.document.getLine(pos.row).length, Math.max(0, column));
        }
        
        if (column < 0)
            pos.column = 0;
            
        return pos;
    };
    
}).call(Anchor.prototype);

});