'use strict';

var Lexer = require('./lexer');
var nodes = require('./nodes');
var utils = require('./utils');
var filters = require('./filters');
var path = require('path');
var constantinople = require('constantinople');
var parseJSExpression = require('character-parser').parseMax;
var extname = path.extname;

/**
 * Initialize `Parser` with the given input `str` and `filename`.
 *
 * @param {String} str
 * @param {String} filename
 * @param {Object} options
 * @api public
 */

var Parser = exports = module.exports = function Parser(str, filename, options){
  //Strip any UTF-8 BOM off of the start of `str`, if it exists.
  this.input = str.replace(/^\uFEFF/, '');
  this.lexer = new Lexer(this.input, filename);
  this.filename = filename;
  this.blocks = {};
  this.mixins = {};
  this.options = options;
  this.contexts = [this];
  this.inMixin = false;
};

/**
 * Parser prototype.
 */

Parser.prototype = {

  /**
   * Save original constructor
   */

  constructor: Parser,

  /**
   * Push `parser` onto the context stack,
   * or pop and return a `Parser`.
   */

  context: function(parser){
    if (parser) {
      this.contexts.push(parser);
    } else {
      return this.contexts.pop();
    }
  },

  /**
   * Return the next token object.
   *
   * @return {Object}
   * @api private
   */

  advance: function(){
    return this.lexer.advance();
  },

  /**
   * Skip `n` tokens.
   *
   * @param {Number} n
   * @api private
   */

  skip: function(n){
    while (n--) this.advance();
  },

  /**
   * Single token lookahead.
   *
   * @return {Object}
   * @api private
   */

  peek: function() {
    return this.lookahead(1);
  },

  /**
   * Return lexer lineno.
   *
   * @return {Number}
   * @api private
   */

  line: function() {
    return this.lexer.lineno;
  },

  /**
   * `n` token lookahead.
   *
   * @param {Number} n
   * @return {Object}
   * @api private
   */

  lookahead: function(n){
    return this.lexer.lookahead(n);
  },

  /**
   * Parse input returning a string of js for evaluation.
   *
   * @return {String}
   * @api public
   */

  parse: function(){
    var block = new nodes.Block, parser;
    block.line = 0;
    block.filename = this.filename;

    while ('eos' != this.peek().type) {
      if ('newline' == this.peek().type) {
        this.advance();
      } else {
        var next = this.peek();
        var expr = this.parseExpr();
        expr.filename = expr.filename || this.filename;
        expr.line = next.line;
        block.push(expr);
      }
    }

    if (parser = this.extending) {
      this.context(parser);
      var ast = parser.parse();
      this.context();

      // hoist mixins
      for (var name in this.mixins)
        ast.unshift(this.mixins[name]);
      return ast;
    }

    return block;
  },

  /**
   * Expect the given type, or throw an exception.
   *
   * @param {String} type
   * @api private
   */

  expect: function(type){
    if (this.peek().type === type) {
      return this.advance();
    } else {
      throw new Error('expected "' + type + '", but got "' + this.peek().type + '"');
    }
  },

  /**
   * Accept the given `type`.
   *
   * @param {String} type
   * @api private
   */

  accept: function(type){
    if (this.peek().type === type) {
      return this.advance();
    }
  },

  /**
   *   tag
   * | doctype
   * | mixin
   * | include
   * | filter
   * | comment
   * | text
   * | each
   * | code
   * | yield
   * | id
   * | class
   * | interpolation
   */

  parseExpr: function(){
    switch (this.peek().type) {
      case 'tag':
        return this.parseTag();
      case 'mixin':
        return this.parseMixin();
      case 'block':
        return this.parseBlock();
      case 'mixin-block':
        return this.parseMixinBlock();
      case 'case':
        return this.parseCase();
      case 'when':
        return this.parseWhen();
      case 'default':
        return this.parseDefault();
      case 'extends':
        return this.parseExtends();
      case 'include':
        return this.parseInclude();
      case 'doctype':
        return this.parseDoctype();
      case 'filter':
        return this.parseFilter();
      case 'comment':
        return this.parseComment();
      case 'text':
        return this.parseText();
      case 'each':
        return this.parseEach();
      case 'code':
        return this.parseCode();
      case 'call':
        return this.parseCall();
      case 'interpolation':
        return this.parseInterpolation();
      case 'yield':
        this.advance();
        var block = new nodes.Block;
        block.yield = true;
        return block;
      case 'id':
      case 'class':
        var tok = this.advance();
        this.lexer.defer(this.lexer.tok('tag', 'div'));
        this.lexer.defer(tok);
        return this.parseExpr();
      default:
        throw new Error('unexpected token "' + this.peek().type + '"');
    }
  },

  /**
   * Text
   */

  parseText: function(){
    var tok = this.expect('text');
    var tokens = this.parseTextWithInlineTags(tok.val);
    if (tokens.length === 1) return tokens[0];
    var node = new nodes.Block;
    for (var i = 0; i < tokens.length; i++) {
      node.push(tokens[i]);
    };
    return node;
  },

  /**
   *   ':' expr
   * | block
   */

  parseBlockExpansion: function(){
    if (':' == this.peek().type) {
      this.advance();
      return new nodes.Block(this.parseExpr());
    } else {
      return this.block();
    }
  },

  /**
   * case
   */

  parseCase: function(){
    var val = this.expect('case').val;
    var node = new nodes.Case(val);
    node.line = this.line();
    node.block = this.block();
    return node;
  },

  /**
   * when
   */

  parseWhen: function(){
    var val = this.expect('when').val
    return new nodes.Case.When(val, this.parseBlockExpansion());
  },

  /**
   * default
   */

  parseDefault: function(){
    this.expect('default');
    return new nodes.Case.When('default', this.parseBlockExpansion());
  },

  /**
   * code
   */

  parseCode: function(){
    var tok = this.expect('code');
    var node = new nodes.Code(tok.val, tok.buffer, tok.escape);
    var block;
    var i = 1;
    node.line = this.line();
    while (this.lookahead(i) && 'newline' == this.lookahead(i).type) ++i;
    block = 'indent' == this.lookahead(i).type;
    if (block) {
      this.skip(i-1);
      node.block = this.block();
    }
    return node;
  },

  /**
   * comment
   */

  parseComment: function(){
    var tok = this.expect('comment');
    var node;

    if ('indent' == this.peek().type) {
      this.lexer.pipeless = true;
      node = new nodes.BlockComment(tok.val, this.parseTextBlock(), tok.buffer);
      this.lexer.pipeless = false;
    } else {
      node = new nodes.Comment(tok.val, tok.buffer);
    }

    node.line = this.line();
    return node;
  },

  /**
   * doctype
   */

  parseDoctype: function(){
    var tok = this.expect('doctype');
    var node = new nodes.Doctype(tok.val);
    node.line = this.line();
    return node;
  },

  /**
   * filter attrs? text-block
   */

  parseFilter: function(){
    var tok = this.expect('filter');
    var attrs = this.accept('attrs');
    var block;

    if ('indent' == this.peek().type) {
      this.lexer.pipeless = true;
      block = this.parseTextBlock();
      this.lexer.pipeless = false;
    } else {
      block = new nodes.Block;
    }

    var options = {};
    if (attrs) {
      attrs.attrs.forEach(function (attribute) {
        options[attribute.name] = constantinople.toConstant(attribute.val);
      });
    }

    var node = new nodes.Filter(tok.val, block, options);
    node.line = this.line();
    return node;
  },

  /**
   * each block
   */

  parseEach: function(){
    var tok = this.expect('each');
    var node = new nodes.Each(tok.code, tok.val, tok.key);
    node.line = this.line();
    node.block = this.block();
    if (this.peek().type == 'code' && this.peek().val == 'else') {
      this.advance();
      node.alternative = this.block();
    }
    return node;
  },

  /**
   * Resolves a path relative to the template for use in
   * includes and extends
   *
   * @param {String}  path
   * @param {String}  purpose  Used in error messages.
   * @return {String}
   * @api private
   */

  resolvePath: function (path, purpose) {
    var p = require('path');
    var dirname = p.dirname;
    var basename = p.basename;
    var join = p.join;

    if (path[0] !== '/' && !this.filename)
      throw new Error('the "filename" option is required to use "' + purpose + '" with "relative" paths');

    if (path[0] === '/' && !this.options.basedir)
      throw new Error('the "basedir" option is required to use "' + purpose + '" with "absolute" paths');

    path = join(path[0] === '/' ? this.options.basedir : dirname(this.filename), path);

    if (basename(path).indexOf('.') === -1) path += '.jade';

    return path;
  },

  /**
   * 'extends' name
   */

  parseExtends: function(){
    var fs = require('fs');

    var path = this.resolvePath(this.expect('extends').val.trim(), 'extends');
    if ('.jade' != path.substr(-5)) path += '.jade';

    var str = fs.readFileSync(path, 'utf8');
    var parser = new this.constructor(str, path, this.options);

    parser.blocks = this.blocks;
    parser.contexts = this.contexts;
    this.extending = parser;

    // TODO: null node
    return new nodes.Literal('');
  },

  /**
   * 'block' name block
   */

  parseBlock: function(){
    var block = this.expect('block');
    var mode = block.mode;
    var name = block.val.trim();

    block = 'indent' == this.peek().type
      ? this.block()
      : new nodes.Block(new nodes.Literal(''));

    var prev = this.blocks[name] || {prepended: [], appended: []}
    if (prev.mode === 'replace') return this.blocks[name] = prev;

    var allNodes = prev.prepended.concat(block.nodes).concat(prev.appended);

    switch (mode) {
      case 'append':
        prev.appended = prev.parser === this ?
                        prev.appended.concat(block.nodes) :
                        block.nodes.concat(prev.appended);
        break;
      case 'prepend':
        prev.prepended = prev.parser === this ?
                         block.nodes.concat(prev.prepended) :
                         prev.prepended.concat(block.nodes);
        break;
    }
    block.nodes = allNodes;
    block.appended = prev.appended;
    block.prepended = prev.prepended;
    block.mode = mode;
    block.parser = this;

    return this.blocks[name] = block;
  },

  parseMixinBlock: function () {
    var block = this.expect('mixin-block');
    if (!this.inMixin) {
      throw new Error('Anonymous blocks are not allowed unless they are part of a mixin.');
    }
    return new nodes.MixinBlock();
  },

  /**
   * include block?
   */

  parseInclude: function(){
    var fs = require('fs');
    var tok = this.expect('include');

    var path = this.resolvePath(tok.val.trim(), 'include');

    // has-filter
    if (tok.filter) {
      var str = fs.readFileSync(path, 'utf8').replace(/\r/g, '');
      str = filters(tok.filter, str, { filename: path });
      return new nodes.Literal(str);
    }

    // non-jade
    if ('.jade' != path.substr(-5)) {
      var str = fs.readFileSync(path, 'utf8').replace(/\r/g, '');
      return new nodes.Literal(str);
    }

    var str = fs.readFileSync(path, 'utf8');
    var parser = new this.constructor(str, path, this.options);
    parser.blocks = utils.merge({}, this.blocks);

    parser.mixins = this.mixins;

    this.context(parser);
    var ast = parser.parse();
    this.context();
    ast.filename = path;

    if ('indent' == this.peek().type) {
      ast.includeBlock().push(this.block());
    }

    return ast;
  },

  /**
   * call ident block
   */

  parseCall: function(){
    var tok = this.expect('call');
    var name = tok.val;
    var args = tok.args;
    var mixin = new nodes.Mixin(name, args, new nodes.Block, true);

    this.tag(mixin);
    if (mixin.code) {
      mixin.block.push(mixin.code);
      mixin.code = null;
    }
    if (mixin.block.isEmpty()) mixin.block = null;
    return mixin;
  },

  /**
   * mixin block
   */

  parseMixin: function(){
    var tok = this.expect('mixin');
    var name = tok.val;
    var args = tok.args;
    var mixin;

    // definition
    if ('indent' == this.peek().type) {
      this.inMixin = true;
      mixin = new nodes.Mixin(name, args, this.block(), false);
      this.mixins[name] = mixin;
      this.inMixin = false;
      return mixin;
    // call
    } else {
      return new nodes.Mixin(name, args, null, true);
    }
  },

  parseTextWithInlineTags: function (str) {
    var line = this.line();

    var match = /(\\)?#\[((?:.|\n)*)$/.exec(str);
    if (match) {
      if (match[1]) { // escape
        var text = new nodes.Text(str.substr(0, match.index) + '#[');
        text.line = line;
        var rest = this.parseTextWithInlineTags(match[2]);
        if (rest[0].type === 'Text') {
          text.val += rest[0].val;
          rest.shift();
        }
        return [text].concat(rest);
      } else {
        var text = new nodes.Text(str.substr(0, match.index));
        text.line = line;
        var buffer = [text];
        var rest = match[2];
        var range = parseJSExpression(rest);
        var inner = new Parser(range.src, this.filename, this.options);
        buffer.push(inner.parse());
        return buffer.concat(this.parseTextWithInlineTags(rest.substr(range.end + 1)));
      }
    } else {
      var text = new nodes.Text(str);
      text.line = line;
      return [text];
    }
  },

  /**
   * indent (text | newline)* outdent
   */

  parseTextBlock: function(){
    var block = new nodes.Block;
    block.line = this.line();
    var spaces = this.expect('indent').val;
    if (null == this._spaces) this._spaces = spaces;
    var indent = Array(spaces - this._spaces + 1).join(' ');
    while ('outdent' != this.peek().type) {
      switch (this.peek().type) {
        case 'newline':
          this.advance();
          break;
        case 'indent':
          this.parseTextBlock(true).nodes.forEach(function(node){
            block.push(node);
          });
          break;
        default:
          var texts = this.parseTextWithInlineTags(indent + this.advance().val);
          texts.forEach(function (text) {
            block.push(text);
          });
      }
    }

    if (spaces == this._spaces) this._spaces = null;
    this.expect('outdent');

    return block;
  },

  /**
   * indent expr* outdent
   */

  block: function(){
    var block = new nodes.Block;
    block.line = this.line();
    block.filename = this.filename;
    this.expect('indent');
    while ('outdent' != this.peek().type) {
      if ('newline' == this.peek().type) {
        this.advance();
      } else {
        var expr = this.parseExpr();
        expr.filename = this.filename;
        block.push(expr);
      }
    }
    this.expect('outdent');
    return block;
  },

  /**
   * interpolation (attrs | class | id)* (text | code | ':')? newline* block?
   */

  parseInterpolation: function(){
    var tok = this.advance();
    var tag = new nodes.Tag(tok.val);
    tag.buffer = true;
    return this.tag(tag);
  },

  /**
   * tag (attrs | class | id)* (text | code | ':')? newline* block?
   */

  parseTag: function(){
    var tok = this.advance();
    var tag = new nodes.Tag(tok.val);

    tag.selfClosing = tok.selfClosing;

    return this.tag(tag);
  },

  /**
   * Parse tag.
   */

  tag: function(tag){
    tag.line = this.line();

    var seenAttrs = false;
    // (attrs | class | id)*
    out:
      while (true) {
        switch (this.peek().type) {
          case 'id':
          case 'class':
            var tok = this.advance();
            tag.setAttribute(tok.type, "'" + tok.val + "'");
            continue;
          case 'attrs':
            if (seenAttrs) {
              console.warn('You should not have jade tags with multiple attributes.');
            }
            seenAttrs = true;
            var tok = this.advance();
            var attrs = tok.attrs;

            if (tok.selfClosing) tag.selfClosing = true;

            for (var i = 0; i < attrs.length; i++) {
              tag.setAttribute(attrs[i].name, attrs[i].val, attrs[i].escaped);
            }
            continue;
          case '&attributes':
            var tok = this.advance();
            tag.addAttributes(tok.val);
            break;
          default:
            break out;
        }
      }

    // check immediate '.'
    if ('dot' == this.peek().type) {
      tag.textOnly = true;
      this.advance();
    }
    
    if (tag.selfClosing
        && ['newline', 'outdent', 'eos'].indexOf(this.peek().type) === -1
        && (this.peek().type !== 'text' || /^\s*$/.text(this.peek().val))) {
      throw new Error(name + ' is self closing and should not have content.');
    }

    // (text | code | ':')?
    switch (this.peek().type) {
      case 'text':
        tag.block.push(this.parseText());
        break;
      case 'code':
        tag.code = this.parseCode();
        break;
      case ':':
        this.advance();
        tag.block = new nodes.Block;
        tag.block.push(this.parseExpr());
        break;
      case 'newline':
      case 'indent':
      case 'outdent':
      case 'eos':
        break;
      default:
        throw new Error('Unexpected token `' + this.peek().type + '` expected `text`, `code`, `:`, `newline` or `eos`')
    }

    // newline*
    while ('newline' == this.peek().type) this.advance();

    // block?
    if ('indent' == this.peek().type) {
      if (tag.textOnly) {
        this.lexer.pipeless = true;
        tag.block = this.parseTextBlock();
        this.lexer.pipeless = false;
      } else {
        var block = this.block();
        if (tag.block) {
          for (var i = 0, len = block.nodes.length; i < len; ++i) {
            tag.block.push(block.nodes[i]);
          }
        } else {
          tag.block = block;
        }
      }
    }

    return tag;
  }
};