/**
 * DataModel surface.
 *
 * @class
 * @constructor
 * @extends {ve.EventEmitter}
 * @param {ve.dm.Document} doc Document model to create surface for
 */
ve.dm.Surface = function( doc ) {
	// Inheritance
	ve.EventEmitter.call( this );
	// Properties
	this.documentModel = doc;
	this.selection = null;
	this.smallStack = [];
	this.bigStack = [];
	this.undoIndex = 0;
	this.historyTrackingInterval = null;
};

/* Methods */

ve.dm.Surface.prototype.startHistoryTracking = function() {
	this.historyTrackingInterval = setInterval( ve.proxy( this.breakpoint, this ), 750 );
};

ve.dm.Surface.prototype.stopHistoryTracking = function() {
	clearInterval( this.historyTrackingInterval );
};

ve.dm.Surface.prototype.purgeHistory = function() {
	this.selection = null;
	this.smallStack = [];
	this.bigStack = [];
	this.undoIndex = 0;
};

ve.dm.Surface.prototype.getHistory = function() {
	if ( this.smallStack.length > 0 ) {
		return this.bigStack.slice( 0 ).concat( [{ 'stack': this.smallStack.slice(0) }] );
	} else {
		return this.bigStack.slice( 0 );
	}
};

/**
 * Gets the document model of the surface.
 *
 * @method
 * @returns {ve.dm.DocumentNode} Document model of the surface
 */
ve.dm.Surface.prototype.getDocument = function() {
	return this.documentModel;
};

/**
 * Gets the selection
 *
 * @method
 * @returns {ve.Range} Current selection
 */
ve.dm.Surface.prototype.getSelection = function() {
	return this.selection;
};

/**
 * Applies a series of transactions to the content data and sets the selection.
 *
 * @method
 * @param {ve.dm.Transaction} transaction Transaction to apply to the document
 * @param {ve.Range} selection
 */
ve.dm.Surface.prototype.change = function( transaction, selection ) {
	if ( transaction ) {
		this.bigStack = this.bigStack.slice( 0, this.bigStack.length - this.undoIndex );
		this.undoIndex = 0;
		this.smallStack.push( transaction );
		ve.dm.TransactionProcessor.commit( this.getDocument(), transaction );
	}
	if ( selection && ( !this.selection || !this.selection.equals ( selection ) ) ) {
		selection.normalize();
		this.selection = selection;
		this.emit ('select', this.selection.clone() );
	}
	if ( transaction ) {
		this.emit( 'transact', transaction );
	}
	this.emit( 'change', transaction, selection );
};

/**
 * Applies an annotation to the current selection
 *
 * @method
 * @param {String} annotation action: toggle, clear, set
 * @param {Object} annotation object to apply.
 */
ve.dm.Surface.prototype.annotate = function( method, annotation ) {
	var selection = this.getSelection();
	if ( this.selection.getLength() ) {
		var tx = ve.dm.Transaction.newFromAnnotation(
			this.getDocument(), selection, method, annotation
		);
		this.change( tx );
	}
};

ve.dm.Surface.prototype.breakpoint = function( selection ) {
	if( this.smallStack.length > 0 ) {
		this.bigStack.push( {
			stack: this.smallStack,
			selection: selection || this.selection.clone()
		} );
		this.smallStack = [];
		this.emit ( 'history' );
	}
};

ve.dm.Surface.prototype.undo = function() {
	this.breakpoint();
	this.undoIndex++;
	if ( this.bigStack[this.bigStack.length - this.undoIndex] ) {
		var diff = 0;
		var item = this.bigStack[this.bigStack.length - this.undoIndex];
		for( var i = item.stack.length - 1; i >= 0; i-- ) {
			this.documentModel.rollback( item.stack[i] );
			diff += item.stack[i].lengthDifference;
		}
		var selection = item.selection;
		selection.end -= diff;
		this.emit ( 'history' );
		return selection;
	}
	return null;
};

ve.dm.Surface.prototype.redo = function() {
	this.breakpoint();
	if ( this.undoIndex > 0 ) {
		if ( this.bigStack[this.bigStack.length - this.undoIndex] ) {
			var diff = 0;
			var item = this.bigStack[this.bigStack.length - this.undoIndex];
			for( var i = 0; i < item.stack.length; i++ ) {
				this.documentModel.commit( item.stack[i] );
				diff += item.stack[i].lengthDifference;
			}
			var selection = item.selection;
			selection.end += diff;
		}
		this.undoIndex--;
		this.emit ( 'history' );
		return selection;
	}
	return null;
};


/* Inheritance */

ve.extendClass( ve.dm.Surface, ve.EventEmitter );