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

var oop = require("ace/lib/oop");
var EventEmitter = require("ace/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;
        var start = range.start;
        var end = range.end;

        if (delta.action === "insertText") {
            if (start.row === row && start.column <= column) {
                if (start.row === end.row) {
                    column += end.column - start.column;
                } else {
                    column -= start.column;
                    row += end.row - start.row;
                }
            } else if (start.row !== end.row && start.row < row) {
                row += end.row - start.row;
            }
        } else if (delta.action === "insertLines") {
            if (start.row <= row) {
                row += end.row - start.row;
            }
        } else if (delta.action === "removeText") {
            if (start.row === row && start.column < column) {
                if (end.column >= column)
                    column = start.column;
                else
                    column = Math.max(0, column - (end.column - start.column));

            } else if (start.row !== end.row && start.row < row) {
                if (end.row === row)
                    column = Math.max(0, column - end.column) + start.column;
                row -= (end.row - start.row);
            } else if (end.row === row) {
                row -= end.row - start.row;
                column = Math.max(0, column - end.column) + start.column;
            }
        } else if (delta.action == "removeLines") {
            if (start.row <= row) {
                if (end.row <= row)
                    row -= end.row - start.row;
                else {
                    row = 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);

});
