/**
 * Generic DataModel node.
 *
 * @class
 * @abstract
 * @constructor
 * @extends {ve.Node}
 * @param {String} type Symbolic name of node type
 * @param {Integer} [length] Length of content data in document
 * @param {Object} [attributes] Reference to map of attribute key/value pairs
 */
ve.dm.Node = function( type, length, attributes ) {
	// Inheritance
	ve.Node.call( this, type );

	// Properties
	this.length = length || 0;
	this.attributes = attributes || {};
	this.doc = undefined;
};

/* Methods */

/**
 * Gets a list of allowed child node types.
 *
 * @method
 * @returns {String[]|null} List of node types allowed as children or null if any type is allowed
 */
ve.dm.Node.prototype.getChildNodeTypes = function() {
	return ve.dm.nodeFactory.getChildNodeTypes( this.type );
};

/**
 * Gets a list of allowed parent node types.
 *
 * @method
 * @returns {String[]|null} List of node types allowed as parents or null if any type is allowed
 */
ve.dm.Node.prototype.getParentNodeTypes = function() {
	return ve.dm.nodeFactory.getParentNodeTypes( this.type );
};

/**
 * Checks if this node can have child nodes.
 *
 * @method
 * @returns {Boolean} Node can have children
 */
ve.dm.Node.prototype.canHaveChildren = function() {
	return ve.dm.nodeFactory.canNodeHaveChildren( this.type );
};

/**
 * Checks if this node can have child nodes which can also have child nodes.
 *
 * @method
 * @returns {Boolean} Node can have grandchildren
 */
ve.dm.Node.prototype.canHaveGrandchildren = function() {
	return ve.dm.nodeFactory.canNodeHaveGrandchildren( this.type );
};

/**
 * Checks if this node represents a wrapped element in the linear model.
 *
 * @method
 * @returns {Boolean} Node represents a wrapped element
 */
ve.dm.Node.prototype.isWrapped = function() {
	return ve.dm.nodeFactory.isNodeWrapped( this.type );
};

/**
 * Checks if this node can contain content.
 *
 * @method
 * @returns {Boolean} Node can contain content
 */
ve.dm.Node.prototype.canContainContent = function() {
	return ve.dm.nodeFactory.canNodeContainContent( this.type );
};

/**
 * Checks if this node is content.
 *
 * @method
 * @returns {Boolean} Node is content
 */
ve.dm.Node.prototype.isContent = function() {
	return ve.dm.nodeFactory.isNodeContent( this.type );
};

/**
 * Gets the inner length.
 *
 * @method
 * @returns {Integer} Length of the node's contents
 */
ve.dm.Node.prototype.getLength = function() {
	return this.length;
};

/**
 * Gets the outer length, including any opening/closing elements.
 *
 * @method
 * @returns {Integer} Length of the entire node
 */
ve.dm.Node.prototype.getOuterLength = function() {
	return this.length + ( this.isWrapped() ? 2 : 0 );
};

/**
 * Sets the inner length.
 *
 * @method
 * @param {Integer} length Length of content
 * @throws Invalid content length error if length is less than 0
 * @emits lengthChange (diff)
 * @emits update
 */
ve.dm.Node.prototype.setLength = function( length ) {
	if ( length < 0 ) {
		throw 'Length cannot be negative';
	}
	// Compute length adjustment from old length
	var diff = length - this.length;
	// Set new length
	this.length = length;
	// Adjust the parent's length
	if ( this.parent ) {
		this.parent.adjustLength( diff );
	}
	// Emit events
	this.emit( 'lengthChange', diff );
	this.emit( 'update' );
};

/**
 * Adjust the length.
 *
 * @method
 * @param {Integer} adjustment Amount to adjust length by
 * @throws Invalid adjustment error if resulting length is less than 0
 * @emits lengthChange (diff)
 * @emits update
 */
ve.dm.Node.prototype.adjustLength = function( adjustment ) {
	this.setLength( this.length + adjustment );
};

/**
 * Gets the offset of this node within the document.
 *
 * If this node has no parent than the result will always be 0.
 *
 * @method
 * @returns {Integer} Offset of node
 */
ve.dm.Node.prototype.getOffset = function() {
	return this.root === this ? 0 : this.root.getOffsetFromNode( this );
};

/**
 * Gets an element attribute value.
 *
 * @method
 * @returns {Mixed} Value of attribute, or undefined if no such attribute exists
 */
ve.dm.Node.prototype.getAttribute = function( key ) {
	return this.attributes[key];
};

/**
 * Gets a reference to this node's attributes object
 *
 * @method
 * @returns {Object} Attributes object (by reference)
 */
ve.dm.Node.prototype.getAttributes = function() {
	return this.attributes;
};

/**
 * Checks if this node can be merged with another.
 *
 * For two nodes to be mergeable, this node and the given node must either be the same node or:
 *  - Have the same type
 *  - Have the same depth
 *  - Have similar ancestory (each node upstream must have the same type)
 *
 * @method
 * @param {ve.dm.Node} node Node to consider merging with
 * @returns {Boolean} Nodes can be merged
 */
ve.dm.Node.prototype.canBeMergedWith = function( node ) {
	var	n1 = this,
		n2 = node;
	// Move up from n1 and n2 simultaneously until we find a common ancestor
	while ( n1 !== n2 ) {
		if (
			// Check if we have reached a root (means there's no common ancestor or unequal depth)
			( n1 === null || n2 === null ) ||
			// Ensure that types match
			n1.getType() !== n2.getType()
		) {
			return false;
		}
		// Move up
		n1 = n1.getParent();
		n2 = n2.getParent();
	}
	return true;
};

/* Inheritance */

ve.extendClass( ve.dm.Node, ve.Node );