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

/**
 * Module dependencies.
 */

var Token = require('./token')
  , nodes = require('./nodes')
  , errors = require('./errors')
  , units = require('./units');

/**
 * Expose `Lexer`.
 */

exports = module.exports = Lexer;

/**
 * Operator aliases.
 */

var alias = {
    'and': '&&'
  , 'or': '||'
  , 'is': '=='
  , 'isnt': '!='
  , 'is not': '!='
  , ':=': '?='
};

/**
 * Units.
 */

units = units.join('|');

/**
 * Unit RegExp.
 */

var unit = new RegExp('^(-)?(\\d+\\.\\d+|\\d+|\\.\\d+)(' + units + ')?[ \\t]*');

/**
 * Initialize a new `Lexer` with the given `str` and `options`.
 *
 * @param {String} str
 * @param {Object} options
 * @api private
 */

function Lexer(str, options) {
  options = options || {};
  this.stash = [];
  this.indentStack = [];
  this.indentRe = null;
  this.lineno = 1;

  function comment(str, val, offset, s) {
    return s.lastIndexOf('/*', offset) > s.lastIndexOf('*/', offset)
      ? str
      : val;
  };

  this.str = str
    .replace(/\s+$/, '\n')
    .replace(/\r\n?/g, '\n')
    .replace(/\\ *\n/g, ' ')
    .replace(/([,:(]) *\n\s*/g, comment)
    .replace(/\s*\n *([,)])/g, comment);
};

/**
 * Lexer prototype.
 */

Lexer.prototype = {
  
  /**
   * Custom inspect.
   */
  
  inspect: function(){
    var tok
      , tmp = this.str
      , buf = [];
    while ('eos' != (tok = this.next()).type) {
      buf.push(tok.inspect());
    }
    this.str = tmp;
    this.prevIndents = 0;
    return buf.concat(tok.inspect()).join('\n');
  },

  /**
   * Lookahead `n` tokens.
   *
   * @param {Number} n
   * @return {Object}
   * @api private
   */
  
  lookahead: function(n){
    var fetch = n - this.stash.length;
    while (fetch-- > 0) this.stash.push(this.advance());
    return this.stash[--n];
  },
  
  /**
   * Consume the given `len`.
   *
   * @param {Number|Array} len
   * @api private
   */

  skip: function(len){
    this.str = this.str.substr(Array.isArray(len)
      ? len[0].length
      : len);
  },

  /**
   * Fetch next token including those stashed by peek.
   *
   * @return {Token}
   * @api private
   */

  next: function() {
    var tok = this.stashed() || this.advance();
    switch (tok.type) {
      case 'newline':
      case 'indent':
        ++this.lineno;
        break;
      case 'outdent':
        if ('outdent' != this.prev.type) ++this.lineno;
    }
    this.prev = tok;
    tok.lineno = this.lineno;
    return tok;
  },

  /**
   * Fetch next token.
   *
   * @return {Token}
   * @api private
   */

  advance: function() {
    return this.eos()
      || this.null()
      || this.sep()
      || this.keyword()
      || this.urlchars()
      || this.atrule()
      || this.scope()
      || this.extends()
      || this.media()
      || this.comment()
      || this.newline()
      || this.escaped()
      || this.important()
      || this.literal()
      || this.function()
      || this.brace()
      || this.paren()
      || this.color()
      || this.string()
      || this.unit()
      || this.namedop()
      || this.boolean()
      || this.ident()
      || this.op()
      || this.space()
      || this.selector();
  },

  /**
   * Lookahead a single token.
   *
   * @return {Token}
   * @api private
   */
  
  peek: function() {
    return this.lookahead(1);
  },
  
  /**
   * Return the next possibly stashed token.
   *
   * @return {Token}
   * @api private
   */

  stashed: function() {
    return this.stash.shift();
  },

  /**
   * EOS | trailing outdents.
   */

  eos: function() {
    if (this.str.length) return;
    if (this.indentStack.length) {
      this.indentStack.shift();
      return new Token('outdent');
    } else {
      return new Token('eos');
    }
  },

  /**
   * url char
   */

  urlchars: function() {
    var captures;
    if (!this.isURL) return;
    if (captures = /^[\/:@.;?&=*!,<>#%0-9]+/.exec(this.str)) {
      this.skip(captures);
      return new Token('literal', new nodes.Literal(captures[0]));
    }
  },

  /**
   * ';' [ \t]*
   */

  sep: function() {
    var captures;
    if (captures = /^;[ \t]*/.exec(this.str)) {
      this.skip(captures);
      return new Token(';');
    }
  },
  
  /**
   * ' '+
   */

  space: function() {
    var captures;
    if (captures = /^([ \t]+)/.exec(this.str)) {
      this.skip(captures);
      return new Token('space');
    }
  },
  
  /**
   * '\\' . ' '*
   */
   
  escaped: function() {
    var captures;
    if (captures = /^\\(.)[ \t]*/.exec(this.str)) {
      var c = captures[1];
      this.skip(captures);
      return new Token('ident', new nodes.Literal(c));
    }
  },
  
  /**
   * '@css' ' '* '{' .* '}' ' '*
   */
  
  literal: function() {
    // HACK attack !!!
    var captures;
    if (captures = /^@css[ \t]*\{/.exec(this.str)) {
      this.skip(captures);
      var c
        , braces = 1
        , css = '';
      while (c = this.str[0]) {
        this.str = this.str.substr(1);
        switch (c) {
          case '{': ++braces; break;
          case '}': --braces; break;
        }
        css += c;
        if (!braces) break;
      }
      css = css.replace(/\s*}$/, '');
      return new Token('literal', new nodes.Literal(css));
    }
  },
  
  /**
   * '!important' ' '*
   */
  
  important: function() {
    var captures;
    if (captures = /^!important[ \t]*/.exec(this.str)) {
      this.skip(captures);
      return new Token('ident', new nodes.Literal('!important'));
    }
  },
  
  /**
   * '{' | '}'
   */
  
  brace: function() {
    var captures;
    if (captures = /^([{}])/.exec(this.str)) {
      this.skip(1);
      var brace = captures[1];
      return new Token(brace, brace);
    }
  },
  
  /**
   * '(' | ')' ' '*
   */
  
  paren: function() {
    var captures;
    if (captures = /^([()])([ \t]*)/.exec(this.str)) {
      var paren = captures[1];
      this.skip(captures);
      if (')' == paren) this.isURL = false;
      var tok = new Token(paren, paren);
      tok.space = captures[2];
      return tok;
    }
  },
  
  /**
   * 'null'
   */
  
  null: function() {
    var captures;
    if (captures = /^(null)\b[ \t]*/.exec(this.str)) {
      this.skip(captures);
      return new Token('null', nodes.null);
    }
  },
  
  /**
   *   'if'
   * | 'else'
   * | 'unless'
   * | 'return'
   * | 'for'
   * | 'in'
   */
  
  keyword: function() {
    var captures;
    if (captures = /^(return|if|else|unless|for|in)\b[ \t]*/.exec(this.str)) {
      var keyword = captures[1];
      this.skip(captures);
      return new Token(keyword, keyword);
    }
  },
  
  /**
   *   'not'
   * | 'and'
   * | 'or'
   * | 'is'
   * | 'is not'
   * | 'isnt'
   * | 'is a'
   * | 'is defined'
   */
  
  namedop: function() {
    var captures;
    if (captures = /^(not|and|or|is a|is defined|isnt|is not|is)(?!-)\b([ \t]*)/.exec(this.str)) {
      var op = captures[1];
      this.skip(captures);
      op = alias[op] || op;
      var tok = new Token(op, op);
      tok.space = captures[2];
      return tok;
    }
  },
  
  /**
   *   ','
   * | '+'
   * | '+='
   * | '-'
   * | '-='
   * | '*'
   * | '*='
   * | '/'
   * | '/='
   * | '%'
   * | '%='
   * | '**'
   * | '!'
   * | '&'
   * | '&&'
   * | '||'
   * | '>'
   * | '>='
   * | '<'
   * | '<='
   * | '='
   * | '=='
   * | '!='
   * | '!'
   * | '~'
   * | '?='
   * | ':='
   * | '?'
   * | ':'
   * | '['
   * | ']'
   * | '..'
   * | '...'
   */
  
  op: function() {
    var captures;
    if (captures = /^([.]{2,3}|&&|\|\||[!<>=?:]=|\*\*|[-+*\/%]=?|[,=?:!~<>&\[\]])([ \t]*)/.exec(this.str)) {
      var op = captures[1];
      this.skip(captures);
      op = alias[op] || op;
      var tok = new Token(op, op);
      tok.space = captures[2];
      this.isURL = false;
      return tok;
    }
  },

  /**
   * '@extends' ([^{\n]+)
   */
  
  extends: function() {
    var captures;
    if (captures = /^@extends?[ \t]*([^\/{\n;]+)/.exec(this.str)) {
      this.skip(captures);
      return new Token('extend', captures[1].trim());
    }
  },

  /**
   * '@media' ([^{\n]+)
   */
  
  media: function() {
    var captures;
    if (captures = /^@media[ \t]*([^\/{\n]+)/.exec(this.str)) {
      this.skip(captures);
      return new Token('media', captures[1].trim());
    }
  },

  /**
   * '@scope' ([^{\n]+)
   */
  
  scope: function() {
    var captures;
    if (captures = /^@scope[ \t]*([^\/{\n]+)/.exec(this.str)) {
      this.skip(captures);
      return new Token('scope', captures[1].trim());
    }
  },

  /**
   * '@' ('import' | 'keyframes' | 'charset' | 'page' | 'font-face')
   */
  
  atrule: function() {
    var captures;
    if (captures = /^@(import|(?:-(\w+)-)?keyframes|charset|font-face|page)[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var vendor = captures[2]
        , type = captures[1];
      if (vendor) type = 'keyframes';
      return new Token(type, vendor);
    }
  },

  /**
   * '//' *
   */
  
  comment: function() {
    // Single line
    if ('/' == this.str[0] && '/' == this.str[1]) {
      var end = this.str.indexOf('\n');
      if (-1 == end) end = this.str.length;
      this.skip(end);
      return this.advance();
    }

    // Multi-line
    if ('/' == this.str[0] && '*' == this.str[1]) {
      var end = this.str.indexOf('*/');
      if (-1 == end) end = this.str.length;
      var str = this.str.substr(0, end + 2)
        , lines = str.split('\n').length - 1
        , suppress = true;
      this.lineno += lines;
      this.skip(end + 2);
      // output
      if ('!' == str[2]) {
        str = str.replace('*!', '*');
        suppress = false;
      }
      return new Token('comment', new nodes.Comment(str, suppress));
    }
  },

  /**
   * 'true' | 'false'
   */
  
  boolean: function() {
    var captures;
    if (captures = /^(true|false)\b([ \t]*)/.exec(this.str)) {
      var val = nodes.Boolean('true' == captures[1]);
      this.skip(captures);
      var tok = new Token('boolean', val);
      tok.space = captures[2];
      return tok;
    }
  },

  /**
   * -*[_a-zA-Z$] [-\w\d$]* '('
   */
  
  function: function() {
    var captures;
    if (captures = /^(-*[_a-zA-Z$][-\w\d$]*)\(([ \t]*)/.exec(this.str)) {
      var name = captures[1];
      this.skip(captures);
      this.isURL = 'url' == name;
      var tok = new Token('function', new nodes.Ident(name));
      tok.space = captures[2];
      return tok;
    } 
  },

  /**
   * -*[_a-zA-Z$] [-\w\d$]*
   */
  
  ident: function() {
    var captures;
    if (captures = /^(@)?(-*[_a-zA-Z$][-\w\d$]*)/.exec(this.str)) {
      var at = captures[1]
        , name = captures[2]
        , id = new nodes.Ident(name);
      this.skip(captures);
      id.property = !! at;
      return new Token('ident', id);
    }
  },
  
  /**
   * '\n' ' '+
   */

  newline: function() {
    var captures, re;

    // we have established the indentation regexp
    if (this.indentRe){
      captures = this.indentRe.exec(this.str);
    // figure out if we are using tabs or spaces
    } else {
      // try tabs
      re = /^\n([\t]*)[ \t]*/;
      captures = re.exec(this.str);

      // nope, try spaces
      if (captures && !captures[1].length) {
        re = /^\n([ \t]*)/;
        captures = re.exec(this.str);
      }

      // established
      if (captures && captures[1].length) this.indentRe = re;
    }


    if (captures) {
      var tok
        , indents = captures[1].length;

      this.skip(captures);
      if (this.str[0] === ' ' || this.str[0] === '\t') {
        throw new errors.SyntaxError('Invalid indentation. You can use tabs or spaces to indent, but not both.');
      }

      // Reset state
      this.isVariable = false;

      // Blank line
      if ('\n' == this.str[0]) {
        ++this.lineno;
        return this.advance();
      }

      // Outdent
      if (this.indentStack.length && indents < this.indentStack[0]) {
        while (this.indentStack.length && this.indentStack[0] > indents) {
          this.stash.push(new Token('outdent'));
          this.indentStack.shift();
        }
        tok = this.stash.pop();
      // Indent
      } else if (indents && indents != this.indentStack[0]) {
        this.indentStack.unshift(indents);
        tok = new Token('indent');
      // Newline
      } else {
        tok = new Token('newline');
      }

      return tok;
    }
  },

  /**
   * '-'? (digit+ | digit* '.' digit+) unit
   */

  unit: function() {
    var captures;
    if (captures = unit.exec(this.str)) {
      this.skip(captures);
      var n = parseFloat(captures[2]);
      if ('-' == captures[1]) n = -n;
      var node = new nodes.Unit(n, captures[3]);
      return new Token('unit', node);
    }
  },

  /**
   * '"' [^"]+ '"' | "'"" [^']+ "'"
   */

  string: function() {
    var captures;
    if (captures = /^("[^"]*"|'[^']*')[ \t]*/.exec(this.str)) {
      var str = captures[1]
        , quote = captures[0][0];
      this.skip(captures);
      str = str.slice(1,-1).replace(/\\n/g, '\n');
      return new Token('string', new nodes.String(str, quote));
    }
  },

  /**
   * #rrggbbaa | #rrggbb | #rgba | #rgb | #nn | #n
   */

  color: function() {
    return this.rrggbbaa()
      || this.rrggbb()
      || this.rgba()
      || this.rgb()
      || this.nn()
      || this.n()
  },

  /**
   * #n
   */
  
  n: function() {
    var captures;
    if (captures = /^#([a-fA-F0-9]{1})[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var n = parseInt(captures[1] + captures[1], 16)
        , color = new nodes.RGBA(n, n, n, 1);
      color.raw = captures[0];
      return new Token('color', color); 
    }
  },

  /**
   * #nn
   */
  
  nn: function() {
    var captures;
    if (captures = /^#([a-fA-F0-9]{2})[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var n = parseInt(captures[1], 16)
        , color = new nodes.RGBA(n, n, n, 1);
      color.raw = captures[0];
      return new Token('color', color); 
    }
  },

  /**
   * #rgb
   */
  
  rgb: function() {
    var captures;
    if (captures = /^#([a-fA-F0-9]{3})[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var rgb = captures[1]
        , r = parseInt(rgb[0] + rgb[0], 16)
        , g = parseInt(rgb[1] + rgb[1], 16)
        , b = parseInt(rgb[2] + rgb[2], 16)
        , color = new nodes.RGBA(r, g, b, 1);
      color.raw = captures[0];
      return new Token('color', color); 
    }
  },
  
  /**
   * #rgba
   */
  
  rgba: function() {
    var captures;
    if (captures = /^#([a-fA-F0-9]{4})[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var rgb = captures[1]
        , r = parseInt(rgb[0] + rgb[0], 16)
        , g = parseInt(rgb[1] + rgb[1], 16)
        , b = parseInt(rgb[2] + rgb[2], 16)
        , a = parseInt(rgb[3] + rgb[3], 16)
        , color = new nodes.RGBA(r, g, b, a/255);
      color.raw = captures[0];
      return new Token('color', color); 
    }
  },
  
  /**
   * #rrggbb
   */
  
  rrggbb: function() {
    var captures;
    if (captures = /^#([a-fA-F0-9]{6})[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var rgb = captures[1]
        , r = parseInt(rgb.substr(0, 2), 16)
        , g = parseInt(rgb.substr(2, 2), 16)
        , b = parseInt(rgb.substr(4, 2), 16)
        , color = new nodes.RGBA(r, g, b, 1);
      color.raw = captures[0];
      return new Token('color', color); 
    }
  },
  
  /**
   * #rrggbbaa
   */
  
  rrggbbaa: function() {
    var captures;
    if (captures = /^#([a-fA-F0-9]{8})[ \t]*/.exec(this.str)) {
      this.skip(captures);
      var rgb = captures[1]
        , r = parseInt(rgb.substr(0, 2), 16)
        , g = parseInt(rgb.substr(2, 2), 16)
        , b = parseInt(rgb.substr(4, 2), 16)
        , a = parseInt(rgb.substr(6, 2), 16)
        , color = new nodes.RGBA(r, g, b, a/255);
      color.raw = captures[0];
      return new Token('color', color); 
    }
  },
  
  /**
   * [^\n,;]+
   */
  
  selector: function() {
    var captures;
    if (captures = /^[^{\n,]+/.exec(this.str)) {
      var selector = captures[0];
      this.skip(captures);
      return new Token('selector', selector);
    }
  }
};
