
/*!
 * Stylus - Expression
 * Copyright(c) 2010 LearnBoost <dev@learnboost.com>
 * MIT Licensed
 */

/**
 * Module dependencies.
 */

var Node = require('./node')
  , nodes = require('../nodes')
  , utils = require('../utils');

/**
 * Initialize a new `Expression`.
 *
 * @param {Boolean} isList
 * @api public
 */

var Expression = module.exports = function Expression(isList){
  Node.call(this);
  this.nodes = [];
  this.isList = isList;
};

/**
 * Check if the variable has a value.
 *
 * @return {Boolean}
 * @api public
 */

Expression.prototype.__defineGetter__('isEmpty', function(){
  return !this.nodes.length;
});

/**
 * Return the first node in this expression.
 *
 * @return {Node}
 * @api public
 */

Expression.prototype.__defineGetter__('first', function(){
  return this.nodes[0]
    ? this.nodes[0].first
    : nodes.null;
});

/**
 * Hash all the nodes in order.
 *
 * @return {String}
 * @api public
 */

Expression.prototype.__defineGetter__('hash', function(){
  return this.nodes.map(function(node){
    return node.hash;
  }).join('::');
});

/**
 * Inherit from `Node.prototype`.
 */

Expression.prototype.__proto__ = Node.prototype;

/**
 * Return a clone of this node.
 * 
 * @return {Node}
 * @api public
 */

Expression.prototype.clone = function(){
  var clone = new this.constructor(this.isList);
  clone.preserve = this.preserve;
  clone.lineno = this.lineno;
  clone.filename = this.filename;
  for (var i = 0; i < this.nodes.length; ++i) {
    clone.push(this.nodes[i].clone());
  }
  return clone;
};

/**
 * Push the given `node`.
 *
 * @param {Node} node
 * @api public
 */

Expression.prototype.push = function(node){
  this.nodes.push(node);
};

/**
 * Operate on `right` with the given `op`.
 *
 * @param {String} op
 * @param {Node} right
 * @return {Node}
 * @api public
 */

Expression.prototype.operate = function(op, right, val){
  switch (op) {
    case '[]=':
      var self = this
        , range = utils.unwrap(right).nodes
        , val = utils.unwrap(val)
        , len;
      range.forEach(function(unit){
        len = self.nodes.length;
        if ('unit' == unit.nodeName) {
          var i = unit.val;
          while (i-- > len) self.nodes[i] = nodes.null;
          self.nodes[unit.val] = val;
        }
      });
      return val;
    case '[]':
      var expr = new nodes.Expression
        , vals = utils.unwrap(this).nodes
        , range = utils.unwrap(right).nodes;
      range.forEach(function(unit){
        if ('unit' == unit.nodeName) {
          var node = vals[unit.val];
          if (node) expr.push(node);
        }
      });
      return expr.isEmpty
        ? nodes.null
        : utils.unwrap(expr);
    case '||':
      return this.toBoolean().isTrue
        ? this
        : right;
    case 'in':
      return Node.prototype.operate.call(this, op, right);
    case '!=':
      return this.operate('==', right, val).negate();
    case '==':
      var len = this.nodes.length
        , right = right.toExpression()
        , a
        , b;
      if (len != right.nodes.length) return nodes.false;
      for (var i = 0; i < len; ++i) {
        a = this.nodes[i];
        b = right.nodes[i];
        if (a.operate(op, b).isTrue) continue;
        return nodes.false;
      }
      return nodes.true;
      break;
    default:
      return this.first.operate(op, right, val);
  }
};

/**
 * Expressions with length > 1 are truthy,
 * otherwise the first value's toBoolean()
 * method is invoked.
 *
 * @return {Boolean}
 * @api public
 */

Expression.prototype.toBoolean = function(){
  if (this.nodes.length > 1) return nodes.true;
  return this.first.toBoolean();
};

/**
 * Return "<a> <b> <c>" or "<a>, <b>, <c>" if
 * the expression represents a list.
 *
 * @return {String}
 * @api public
 */

Expression.prototype.toString = function(){
  return '(' + this.nodes.map(function(node){
    return node.toString();
  }).join(this.isList ? ', ' : ' ') + ')';
};

