parser.js

var utils = require('./utils'),
  lexer = require('./lexer');

var _t = lexer.types,
  _reserved = ['break', 'case', 'catch', 'continue', 'debugger', 'default', 'delete', 'do', 'else', 'finally', 'for', 'function', 'if', 'in', 'instanceof', 'new', 'return', 'switch', 'this', 'throw', 'try', 'typeof', 'var', 'void', 'while', 'with'];


/**
 * Filters are simply functions that perform transformations on their first input argument.
 * Filters are run at render time, so they may not directly modify the compiled template structure in any way.
 * All of Swig's built-in filters are written in this same way. For more examples, reference the `filters.js` file in Swig's source.
 *
 * To disable auto-escaping on a custom filter, simply add a property to the filter method `safe = true;` and the output from this will not be escaped, no matter what the global settings are for Swig.
 *
 * @typedef {function} Filter
 *
 * @example
 * // This filter will return 'bazbop' if the idx on the input is not 'foobar'
 * swig.setFilter('foobar', function (input, idx) {
 *   return input[idx] === 'foobar' ? input[idx] : 'bazbop';
 * });
 * // myvar = ['foo', 'bar', 'baz', 'bop'];
 * // => {{ myvar|foobar(3) }}
 * // Since myvar[3] !== 'foobar', we render:
 * // => bazbop
 *
 * @example
 * // This filter will disable auto-escaping on its output:
 * function bazbop (input) { return input; }
 * bazbop.safe = true;
 * swig.setFilter('bazbop', bazbop);
 * // => {{ "<p>"|bazbop }}
 * // => <p>
 *
 * @param {*} input Input argument, automatically sent from Swig's built-in parser.
 * @param {...*} [args] All other arguments are defined by the Filter author.
 * @return {*}
 */

/*!
 * Makes a string safe for a regular expression.
 * @param  {string} str
 * @return {string}
 * @private
 */
function escapeRegExp(str) {
  return str.replace(/[\-\/\\\^$*+?.()|\[\]{}]/g, '\\$&');
}

/**
 * Parse strings of variables and tags into tokens for future compilation.
 * @class
 * @param {array}   tokens     Pre-split tokens read by the Lexer.
 * @param {object}  filters    Keyed object of filters that may be applied to variables.
 * @param {boolean} autoescape Whether or not this should be autoescaped.
 * @param {number}  line       Beginning line number for the first token.
 * @param {string}  [filename] Name of the file being parsed.
 * @private
 */
function TokenParser(tokens, filters, autoescape, line, filename) {
  this.out = [];
  this.state = [];
  this.filterApplyIdx = [];
  this._parsers = {};
  this.line = line;
  this.filename = filename;
  this.filters = filters;
  this.escape = autoescape;

  this.parse = function () {
    var self = this;

    if (self._parsers.start) {
      self._parsers.start.call(self);
    }
    utils.each(tokens, function (token, i) {
      var prevToken = tokens[i - 1];
      self.isLast = (i === tokens.length - 1);
      if (prevToken) {
        while (prevToken.type === _t.WHITESPACE) {
          i -= 1;
          prevToken = tokens[i - 1];
        }
      }
      self.prevToken = prevToken;
      self.parseToken(token);
    });
    if (self._parsers.end) {
      self._parsers.end.call(self);
    }

    if (self.escape) {
      self.filterApplyIdx = [0];
      if (typeof self.escape === 'string') {
        self.parseToken({ type: _t.FILTER, match: 'e' });
        self.parseToken({ type: _t.COMMA, match: ',' });
        self.parseToken({ type: _t.STRING, match: String(autoescape) });
        self.parseToken({ type: _t.PARENCLOSE, match: ')'});
      } else {
        self.parseToken({ type: _t.FILTEREMPTY, match: 'e' });
      }
    }

    return self.out;
  };
}

TokenParser.prototype = {
  /**
   * Set a custom method to be called when a token type is found.
   *
   * @example
   * parser.on(types.STRING, function (token) {
   *   this.out.push(token.match);
   * });
   * @example
   * parser.on('start', function () {
   *   this.out.push('something at the beginning of your args')
   * });
   * parser.on('end', function () {
   *   this.out.push('something at the end of your args');
   * });
   *
   * @param  {number}   type Token type ID. Found in the Lexer.
   * @param  {Function} fn   Callback function. Return true to continue executing the default parsing function.
   * @return {undefined}
   */
  on: function (type, fn) {
    this._parsers[type] = fn;
  },

  /**
   * Parse a single token.
   * @param  {{match: string, type: number, line: number}} token Lexer token object.
   * @return {undefined}
   * @private
   */
  parseToken: function (token) {
    var self = this,
      fn = self._parsers[token.type] || self._parsers['*'],
      match = token.match,
      prevToken = self.prevToken,
      lastState = (self.state.length) ? self.state[self.state.length - 1] : null,
      temp;

    if (fn && typeof fn === 'function') {
      if (!fn.call(this, token)) {
        return;
      }
    }

    if (lastState && prevToken &&
        lastState === _t.FILTER &&
        prevToken.type === _t.FILTER &&
        token.type !== _t.PARENCLOSE &&
        token.type !== _t.COMMA &&
        token.type !== _t.OPERATOR &&
        token.type !== _t.FILTER &&
        token.type !== _t.FILTEREMPTY) {
      self.out.push(', ');
    }

    if (lastState && lastState === _t.METHODOPEN) {
      self.state.pop();
      if (token.type !== _t.PARENCLOSE) {
        self.out.push(', ');
      }
    }

    switch (token.type) {
    case _t.WHITESPACE:
      break;

    case _t.STRING:
      self.filterApplyIdx.push(self.out.length);
      self.out.push(match.replace(/\\/g, '\\\\'));
      break;

    case _t.NUMBER:
    case _t.BOOL:
      self.filterApplyIdx.push(self.out.length);
      self.out.push(match);
      break;

    case _t.FILTER:
      if (!self.filters.hasOwnProperty(match) || typeof self.filters[match] !== "function") {
        utils.throwError('Invalid filter "' + match + '"', self.line, self.filename);
      }
      self.escape = self.filters[match].safe ? false : self.escape;
      temp = self.filterApplyIdx.pop();
      self.out.splice(temp, 0, '_filters["' + match + '"](');
      self.state.push(token.type);
      self.filterApplyIdx.push(temp);
      break;

    case _t.FILTEREMPTY:
      if (!self.filters.hasOwnProperty(match) || typeof self.filters[match] !== "function") {
        utils.throwError('Invalid filter "' + match + '"', self.line, self.filename);
      }
      self.escape = self.filters[match].safe ? false : self.escape;
      self.out.splice(self.filterApplyIdx[self.filterApplyIdx.length - 1], 0, '_filters["' + match + '"](');
      self.out.push(')');
      break;

    case _t.FUNCTION:
    case _t.FUNCTIONEMPTY:
      self.out.push('((typeof ' + match + ' !== "undefined") ? ' + match +
        ' : ((typeof _ctx.' + match + ' !== "undefined") ? _ctx.' + match +
        ' : _fn))(');
      self.escape = false;
      if (token.type === _t.FUNCTIONEMPTY) {
        self.out[self.out.length - 1] = self.out[self.out.length - 1] + ')';
      } else {
        self.state.push(token.type);
      }
      self.filterApplyIdx.push(self.out.length - 1);
      break;

    case _t.PARENOPEN:
      self.state.push(token.type);
      if (self.filterApplyIdx.length) {
        self.out.splice(self.filterApplyIdx[self.filterApplyIdx.length - 1], 0, '(');
        if (prevToken && prevToken.type === _t.VAR) {
          temp = prevToken.match.split('.').slice(0, -1);
          self.out.push(' || _fn).call(' + self.checkMatch(temp));
          self.state.push(_t.METHODOPEN);
          self.escape = false;
        } else {
          self.out.push(' || _fn)(');
        }
      } else {
        self.out.push('(');
      }
      self.filterApplyIdx.push(self.out.length - 1);
      break;

    case _t.PARENCLOSE:
      temp = self.state.pop();
      if (temp !== _t.PARENOPEN && temp !== _t.FUNCTION && temp !== _t.FILTER) {
        utils.throwError('Mismatched nesting state', self.line, self.filename);
      }
      self.out.push(')');
      self.filterApplyIdx.pop();
      break;

    case _t.COMMA:
      if (lastState !== _t.FUNCTION &&
          lastState !== _t.FILTER &&
          lastState !== _t.ARRAYOPEN &&
          lastState !== _t.CURLYOPEN &&
          lastState !== _t.PARENOPEN &&
          lastState !== _t.COLON) {
        utils.throwError('Unexpected comma', self.line, self.filename);
      }
      if (lastState === _t.COLON) {
        self.state.pop();
      }
      self.out.push(', ');
      self.filterApplyIdx.pop();
      break;

    case _t.LOGIC:
    case _t.COMPARATOR:
      if (!prevToken ||
          prevToken.type === _t.COMMA ||
          prevToken.type === token.type ||
          prevToken.type === _t.BRACKETOPEN ||
          prevToken.type === _t.CURLYOPEN ||
          prevToken.type === _t.PARENOPEN ||
          prevToken.type === _t.FUNCTION) {
        utils.throwError('Unexpected logic', self.line, self.filename);
      }
      self.out.push(token.match);
      break;

    case _t.NOT:
      self.out.push(token.match);
      break;

    case _t.VAR:
      self.parseVar(token, match, lastState);
      break;

    case _t.BRACKETOPEN:
      if (!prevToken ||
          (prevToken.type !== _t.VAR &&
            prevToken.type !== _t.BRACKETCLOSE &&
            prevToken.type !== _t.PARENCLOSE)) {
        self.state.push(_t.ARRAYOPEN);
        self.filterApplyIdx.push(self.out.length);
      } else {
        self.state.push(token.type);
      }
      self.out.push('[');
      break;

    case _t.BRACKETCLOSE:
      temp = self.state.pop();
      if (temp !== _t.BRACKETOPEN && temp !== _t.ARRAYOPEN) {
        utils.throwError('Unexpected closing square bracket', self.line, self.filename);
      }
      self.out.push(']');
      self.filterApplyIdx.pop();
      break;

    case _t.CURLYOPEN:
      self.state.push(token.type);
      self.out.push('{');
      self.filterApplyIdx.push(self.out.length - 1);
      break;

    case _t.COLON:
      if (lastState !== _t.CURLYOPEN) {
        utils.throwError('Unexpected colon', self.line, self.filename);
      }
      self.state.push(token.type);
      self.out.push(':');
      self.filterApplyIdx.pop();
      break;

    case _t.CURLYCLOSE:
      if (lastState === _t.COLON) {
        self.state.pop();
      }
      if (self.state.pop() !== _t.CURLYOPEN) {
        utils.throwError('Unexpected closing curly brace', self.line, self.filename);
      }
      self.out.push('}');

      self.filterApplyIdx.pop();
      break;

    case _t.DOTKEY:
      if (!prevToken || (prevToken.type !== _t.VAR && prevToken.type !== _t.BRACKETCLOSE && prevToken.type !== _t.DOTKEY)) {
        utils.throwError('Unexpected key "' + match + '"', self.line, self.filename);
      }
      self.out.push('.' + match);
      break;

    case _t.OPERATOR:
      self.out.push(' ' + match + ' ');
      self.filterApplyIdx.pop();
      break;
    }
  },

  /**
   * Parse variable token
   * @param  {{match: string, type: number, line: number}} token      Lexer token object.
   * @param  {string} match       Shortcut for token.match
   * @param  {number} lastState   Lexer token type state.
   * @return {undefined}
   * @private
   */
  parseVar: function (token, match, lastState) {
    var self = this;

    match = match.split('.');

    if (_reserved.indexOf(match[0]) !== -1) {
      utils.throwError('Reserved keyword "' + match[0] + '" attempted to be used as a variable', self.line, self.filename);
    }

    self.filterApplyIdx.push(self.out.length);
    if (lastState === _t.CURLYOPEN) {
      if (match.length > 1) {
        utils.throwError('Unexpected dot', self.line, self.filename);
      }
      self.out.push(match[0]);
      return;
    }

    self.out.push(self.checkMatch(match));
  },

  /**
   * Return contextual dot-check string for a match
   * @param  {string} match       Shortcut for token.match
   * @private
   */
  checkMatch: function (match) {
    var temp = match[0];

    function checkDot(ctx) {
      var c = ctx + temp,
        m = match,
        build = '';

      build = '(typeof ' + c + ' !== "undefined"';
      utils.each(m, function (v, i) {
        if (i === 0) {
          return;
        }
        build += ' && ' + c + '.' + v + ' !== undefined';
        c += '.' + v;
      });
      build += ')';

      return build;
    }

    function buildDot(ctx) {
      return '(' + checkDot(ctx) + ' ? ' + ctx + match.join('.') + ' : "")';
    }

    return '(' + checkDot('') + ' ? ' + buildDot('') + ' : ' + buildDot('_ctx.') + ')';
  }
};

/**
 * Parse a source string into tokens that are ready for compilation.
 *
 * @example
 * exports.parse('{{ tacos }}', {}, tags, filters);
 * // => [{ compile: [Function], ... }]
 *
 * @param  {string} source  Swig template source.
 * @param  {object} opts    Swig options object.
 * @param  {object} tags    Keyed object of tags that can be parsed and compiled.
 * @param  {object} filters Keyed object of filters that may be applied to variables.
 * @return {array}          List of tokens ready for compilation.
 */
exports.parse = function (source, opts, tags, filters) {
  source = source.replace(/\r\n/g, '\n');
  var escape = opts.autoescape,
    tagOpen = opts.tagControls[0],
    tagClose = opts.tagControls[1],
    varOpen = opts.varControls[0],
    varClose = opts.varControls[1],
    escapedTagOpen = escapeRegExp(tagOpen),
    escapedTagClose = escapeRegExp(tagClose),
    escapedVarOpen = escapeRegExp(varOpen),
    escapedVarClose = escapeRegExp(varClose),
    tagStrip = new RegExp('^' + escapedTagOpen + '-?\\s*-?|-?\\s*-?' + escapedTagClose + '$', 'g'),
    tagStripBefore = new RegExp('^' + escapedTagOpen + '-'),
    tagStripAfter = new RegExp('-' + escapedTagClose + '$'),
    varStrip = new RegExp('^' + escapedVarOpen + '-?\\s*-?|-?\\s*-?' + escapedVarClose + '$', 'g'),
    varStripBefore = new RegExp('^' + escapedVarOpen + '-'),
    varStripAfter = new RegExp('-' + escapedVarClose + '$'),
    cmtOpen = opts.cmtControls[0],
    cmtClose = opts.cmtControls[1],
    anyChar = '[\\s\\S]*?',
    // Split the template source based on variable, tag, and comment blocks
    // /(\{%[\s\S]*?%\}|\{\{[\s\S]*?\}\}|\{#[\s\S]*?#\})/
    splitter = new RegExp(
      '(' +
        escapedTagOpen + anyChar + escapedTagClose + '|' +
        escapedVarOpen + anyChar + escapedVarClose + '|' +
        escapeRegExp(cmtOpen) + anyChar + escapeRegExp(cmtClose) +
        ')'
    ),
    line = 1,
    stack = [],
    parent = null,
    tokens = [],
    blocks = {},
    inRaw = false,
    stripNext;

  /**
   * Parse a variable.
   * @param  {string} str  String contents of the variable, between <i>{{</i> and <i>}}</i>
   * @param  {number} line The line number that this variable starts on.
   * @return {VarToken}      Parsed variable token object.
   * @private
   */
  function parseVariable(str, line) {
    var tokens = lexer.read(utils.strip(str)),
      parser,
      out;

    parser = new TokenParser(tokens, filters, escape, line, opts.filename);
    out = parser.parse().join('');

    if (parser.state.length) {
      utils.throwError('Unable to parse "' + str + '"', line, opts.filename);
    }

    /**
     * A parsed variable token.
     * @typedef {object} VarToken
     * @property {function} compile Method for compiling this token.
     */
    return {
      compile: function () {
        return '_output += ' + out + ';\n';
      }
    };
  }
  exports.parseVariable = parseVariable;

  /**
   * Parse a tag.
   * @param  {string} str  String contents of the tag, between <i>{%</i> and <i>%}</i>
   * @param  {number} line The line number that this tag starts on.
   * @return {TagToken}      Parsed token object.
   * @private
   */
  function parseTag(str, line) {
    var tokens, parser, chunks, tagName, tag, args, last;

    if (utils.startsWith(str, 'end')) {
      last = stack[stack.length - 1];
      if (last && last.name === str.split(/\s+/)[0].replace(/^end/, '') && last.ends) {
        switch (last.name) {
        case 'autoescape':
          escape = opts.autoescape;
          break;
        case 'raw':
          inRaw = false;
          break;
        }
        stack.pop();
        return;
      }

      if (!inRaw) {
        utils.throwError('Unexpected end of tag "' + str.replace(/^end/, '') + '"', line, opts.filename);
      }
    }

    if (inRaw) {
      return;
    }

    chunks = str.split(/\s+(.+)?/);
    tagName = chunks.shift();

    if (!tags.hasOwnProperty(tagName)) {
      utils.throwError('Unexpected tag "' + str + '"', line, opts.filename);
    }

    tokens = lexer.read(utils.strip(chunks.join(' ')));
    parser = new TokenParser(tokens, filters, false, line, opts.filename);
    tag = tags[tagName];

    /**
     * Define custom parsing methods for your tag.
     * @callback parse
     *
     * @example
     * exports.parse = function (str, line, parser, types, options) {
     *   parser.on('start', function () {
     *     // ...
     *   });
     *   parser.on(types.STRING, function (token) {
     *     // ...
     *   });
     * };
     *
     * @param {string} str The full token string of the tag.
     * @param {number} line The line number that this tag appears on.
     * @param {TokenParser} parser A TokenParser instance.
     * @param {TYPES} types Lexer token type enum.
     * @param {TagToken[]} stack The current stack of open tags.
     * @param {SwigOpts} options Swig Options Object.
     */
    if (!tag.parse(chunks[1], line, parser, _t, stack, opts)) {
      utils.throwError('Unexpected tag "' + tagName + '"', line, opts.filename);
    }

    parser.parse();
    args = parser.out;

    switch (tagName) {
    case 'autoescape':
      escape = (args[0] !== 'false') ? args[0] : false;
      break;
    case 'raw':
      inRaw = true;
      break;
    }

    /**
     * A parsed tag token.
     * @typedef {Object} TagToken
     * @property {compile} [compile] Method for compiling this token.
     * @property {array} [args] Array of arguments for the tag.
     * @property {Token[]} [content=[]] An array of tokens that are children of this Token.
     * @property {boolean} [ends] Whether or not this tag requires an end tag.
     * @property {string} name The name of this tag.
     */
    return {
      block: !!tags[tagName].block,
      compile: tag.compile,
      args: args,
      content: [],
      ends: tag.ends,
      name: tagName
    };
  }

  /**
   * Strip the whitespace from the previous token, if it is a string.
   * @param  {object} token Parsed token.
   * @return {object}       If the token was a string, trailing whitespace will be stripped.
   */
  function stripPrevToken(token) {
    if (typeof token === 'string') {
      token = token.replace(/\s*$/, '');
    }
    return token;
  }

  /*!
   * Loop over the source, split via the tag/var/comment regular expression splitter.
   * Send each chunk to the appropriate parser.
   */
  utils.each(source.split(splitter), function (chunk) {
    var token, lines, stripPrev, prevToken, prevChildToken;

    if (!chunk) {
      return;
    }

    // Is a variable?
    if (!inRaw && utils.startsWith(chunk, varOpen) && utils.endsWith(chunk, varClose)) {
      stripPrev = varStripBefore.test(chunk);
      stripNext = varStripAfter.test(chunk);
      token = parseVariable(chunk.replace(varStrip, ''), line);
    // Is a tag?
    } else if (utils.startsWith(chunk, tagOpen) && utils.endsWith(chunk, tagClose)) {
      stripPrev = tagStripBefore.test(chunk);
      stripNext = tagStripAfter.test(chunk);
      token = parseTag(chunk.replace(tagStrip, ''), line);
      if (token) {
        if (token.name === 'extends') {
          parent = token.args.join('').replace(/^\'|\'$/g, '').replace(/^\"|\"$/g, '');
        }

        if (token.block && (!stack.length || token.name === 'block')) {
          blocks[token.args.join('')] = token;
        }
      }
      if (inRaw && !token) {
        token = chunk;
      }
    // Is a content string?
    } else if (inRaw || (!utils.startsWith(chunk, cmtOpen) && !utils.endsWith(chunk, cmtClose))) {
      token = (stripNext) ? chunk.replace(/^\s*/, '') : chunk;
      stripNext = false;
    } else if (utils.startsWith(chunk, cmtOpen) && utils.endsWith(chunk, cmtClose)) {
      return;
    }

    // Did this tag ask to strip previous whitespace? <code>{%- ... %}</code> or <code>{{- ... }}</code>
    if (stripPrev && tokens.length) {
      prevToken = tokens.pop();
      if (typeof prevToken === 'string') {
        prevToken = stripPrevToken(prevToken);
      } else if (prevToken.content && prevToken.content.length) {
        prevChildToken = stripPrevToken(prevToken.content.pop());
        prevToken.content.push(prevChildToken);
      }
      tokens.push(prevToken);
    }

    // This was a comment, so let's just keep going.
    if (!token) {
      return;
    }

    // If there's an open item in the stack, add this to its content.
    if (stack.length) {
      stack[stack.length - 1].content.push(token);
    } else {
      tokens.push(token);
    }

    // If the token is a tag that requires an end tag, open it on the stack.
    if (token.name && token.ends) {
      stack.push(token);
    }

    lines = chunk.match(/\n/g);
    line += (lines) ? lines.length : 0;
  });

  return {
    name: opts.filename,
    parent: parent,
    tokens: tokens,
    blocks: blocks
  };
};


/**
 * Compile an array of tokens.
 * @param  {Token[]} template     An array of template tokens.
 * @param  {Templates[]} parents  Array of parent templates.
 * @param  {SwigOpts} [options]   Swig options object.
 * @param  {string} [blockName]   Name of the current block context.
 * @return {string}               Partial for a compiled JavaScript method that will output a rendered template.
 */
exports.compile = function (template, parents, options, blockName) {
  var out = '',
    tokens = utils.isArray(template) ? template : template.tokens;

  utils.each(tokens, function (token) {
    var o;
    if (typeof token === 'string') {
      out += '_output += "' + token.replace(/\\/g, '\\\\').replace(/\n|\r/g, '\\n').replace(/"/g, '\\"') + '";\n';
      return;
    }

    /**
     * Compile callback for VarToken and TagToken objects.
     * @callback compile
     *
     * @example
     * exports.compile = function (compiler, args, content, parents, options, blockName) {
     *   if (args[0] === 'foo') {
     *     return compiler(content, parents, options, blockName) + '\n';
     *   }
     *   return '_output += "fallback";\n';
     * };
     *
     * @param {parserCompiler} compiler
     * @param {array} [args] Array of parsed arguments on the for the token.
     * @param {array} [content] Array of content within the token.
     * @param {array} [parents] Array of parent templates for the current template context.
     * @param {SwigOpts} [options] Swig Options Object
     * @param {string} [blockName] Name of the direct block parent, if any.
     */
    o = token.compile(exports.compile, token.args ? token.args.slice(0) : [], token.content ? token.content.slice(0) : [], parents, options, blockName);
    out += o || '';
  });

  return out;
};