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/*
 *  Copyright 2011 Twitter, Inc.
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

(function (Hogan) {
  // Setup regex  assignments
  // remove whitespace according to Mustache spec
  var rIsWhitespace = /\S/,
      rQuot = /\"/g,
      rNewline =  /\n/g,
      rCr = /\r/g,
      rSlash = /\\/g,
      tagTypes = {
        '#': 1, '^': 2, '/': 3,  '!': 4, '>': 5,
        '<': 6, '=': 7, '_v': 8, '{': 9, '&': 10
      };

  Hogan.scan = function scan(text, delimiters) {
    var len = text.length,
        IN_TEXT = 0,
        IN_TAG_TYPE = 1,
        IN_TAG = 2,
        state = IN_TEXT,
        tagType = null,
        tag = null,
        buf = '',
        tokens = [],
        seenTag = false,
        i = 0,
        lineStart = 0,
        otag = '{{',
        ctag = '}}';

    function addBuf() {
      if (buf.length > 0) {
        tokens.push(new String(buf));
        buf = '';
      }
    }

    function lineIsWhitespace() {
      var isAllWhitespace = true;
      for (var j = lineStart; j < tokens.length; j++) {
        isAllWhitespace =
          (tokens[j].tag && tagTypes[tokens[j].tag] < tagTypes['_v']) ||
          (!tokens[j].tag && tokens[j].match(rIsWhitespace) === null);
        if (!isAllWhitespace) {
          return false;
        }
      }

      return isAllWhitespace;
    }

    function filterLine(haveSeenTag, noNewLine) {
      addBuf();

      if (haveSeenTag && lineIsWhitespace()) {
        for (var j = lineStart, next; j < tokens.length; j++) {
          if (!tokens[j].tag) {
            if ((next = tokens[j+1]) && next.tag == '>') {
              // set indent to token value
              next.indent = tokens[j].toString()
            }
            tokens.splice(j, 1);
          }
        }
      } else if (!noNewLine) {
        tokens.push({tag:'\n'});
      }

      seenTag = false;
      lineStart = tokens.length;
    }

    function changeDelimiters(text, index) {
      var close = '=' + ctag,
          closeIndex = text.indexOf(close, index),
          delimiters = trim(
            text.substring(text.indexOf('=', index) + 1, closeIndex)
          ).split(' ');

      otag = delimiters[0];
      ctag = delimiters[1];

      return closeIndex + close.length - 1;
    }

    if (delimiters) {
      delimiters = delimiters.split(' ');
      otag = delimiters[0];
      ctag = delimiters[1];
    }

    for (i = 0; i < len; i++) {
      if (state == IN_TEXT) {
        if (tagChange(otag, text, i)) {
          --i;
          addBuf();
          state = IN_TAG_TYPE;
        } else {
          if (text.charAt(i) == '\n') {
            filterLine(seenTag);
          } else {
            buf += text.charAt(i);
          }
        }
      } else if (state == IN_TAG_TYPE) {
        i += otag.length - 1;
        tag = tagTypes[text.charAt(i + 1)];
        tagType = tag ? text.charAt(i + 1) : '_v';
        if (tagType == '=') {
          i = changeDelimiters(text, i);
          state = IN_TEXT;
        } else {
          if (tag) {
            i++;
          }
          state = IN_TAG;
        }
        seenTag = i;
      } else {
        if (tagChange(ctag, text, i)) {
          tokens.push({tag: tagType, n: trim(buf), otag: otag, ctag: ctag,
                       i: (tagType == '/') ? seenTag - ctag.length : i + otag.length});
          buf = '';
          i += ctag.length - 1;
          state = IN_TEXT;
          if (tagType == '{') {
            if (ctag == '}}') {
              i++;
            } else {
              cleanTripleStache(tokens[tokens.length - 1]);
            }
          }
        } else {
          buf += text.charAt(i);
        }
      }
    }

    filterLine(seenTag, true);

    return tokens;
  }

  function cleanTripleStache(token) {
    if (token.n.substr(token.n.length - 1) === '}') {
      token.n = token.n.substring(0, token.n.length - 1);
    }
  }

  function trim(s) {
    if (s.trim) {
      return s.trim();
    }

    return s.replace(/^\s*|\s*$/g, '');
  }

  function tagChange(tag, text, index) {
    if (text.charAt(index) != tag.charAt(0)) {
      return false;
    }

    for (var i = 1, l = tag.length; i < l; i++) {
      if (text.charAt(index + i) != tag.charAt(i)) {
        return false;
      }
    }

    return true;
  }

  function buildTree(tokens, kind, stack, customTags) {
    var instructions = [],
        opener = null,
        token = null;

    while (tokens.length > 0) {
      token = tokens.shift();
      if (token.tag == '#' || token.tag == '^' || isOpener(token, customTags)) {
        stack.push(token);
        token.nodes = buildTree(tokens, token.tag, stack, customTags);
        instructions.push(token);
      } else if (token.tag == '/') {
        if (stack.length === 0) {
          throw new Error('Closing tag without opener: /' + token.n);
        }
        opener = stack.pop();
        if (token.n != opener.n && !isCloser(token.n, opener.n, customTags)) {
          throw new Error('Nesting error: ' + opener.n + ' vs. ' + token.n);
        }
        opener.end = token.i;
        return instructions;
      } else {
        instructions.push(token);
      }
    }

    if (stack.length > 0) {
      throw new Error('missing closing tag: ' + stack.pop().n);
    }

    return instructions;
  }

  function isOpener(token, tags) {
    for (var i = 0, l = tags.length; i < l; i++) {
      if (tags[i].o == token.n) {
        token.tag = '#';
        return true;
      }
    }
  }

  function isCloser(close, open, tags) {
    for (var i = 0, l = tags.length; i < l; i++) {
      if (tags[i].c == close && tags[i].o == open) {
        return true;
      }
    }
  }

  function writeCode(tree) {
    return 'i = i || "";var b = i + "";var _ = this;' + walk(tree) + 'return b;';
  }

  Hogan.generate = function (code, text, options) {
    if (options.asString) {
      return 'function(c,p,i){' + code + ';}';
    }

    return new Hogan.Template(new Function('c', 'p', 'i', code), text, Hogan);
  }

  function esc(s) {
    return s.replace(rSlash, '\\\\')
            .replace(rQuot, '\\\"')
            .replace(rNewline, '\\n')
            .replace(rCr, '\\r');
  }

  function chooseMethod(s) {
    return (~s.indexOf('.')) ? 'd' : 'f';
  }

  function walk(tree) {
    var code = '';
    for (var i = 0, l = tree.length; i < l; i++) {
      var tag = tree[i].tag;
      if (tag == '#') {
        code += section(tree[i].nodes, tree[i].n, chooseMethod(tree[i].n),
                        tree[i].i, tree[i].end, tree[i].otag + " " + tree[i].ctag);
      } else if (tag == '^') {
        code += invertedSection(tree[i].nodes, tree[i].n,
                                chooseMethod(tree[i].n));
      } else if (tag == '<' || tag == '>') {
        code += partial(tree[i]);
      } else if (tag == '{' || tag == '&') {
        code += tripleStache(tree[i].n, chooseMethod(tree[i].n));
      } else if (tag == '\n') {
        code += text('"\\n"' + (tree.length-1 == i ? '' : ' + i'));
      } else if (tag == '_v') {
        code += variable(tree[i].n, chooseMethod(tree[i].n));
      } else if (tag === undefined) {
        code += text('"' + esc(tree[i]) + '"');
      }
    }
    return code;
  }

  function section(nodes, id, method, start, end, tags) {
    return 'if(_.s(_.' + method + '("' + esc(id) + '",c,p,1),' +
           'c,p,0,' + start + ',' + end + ', "' + tags + '")){' +
           'b += _.rs(c,p,' +
           'function(c,p){ var b = "";' +
           walk(nodes) +
           'return b;});c.pop();}' +
           'else{b += _.b; _.b = ""};';
  }

  function invertedSection(nodes, id, method) {
    return 'if (!_.s(_.' + method + '("' + esc(id) + '",c,p,1),c,p,1,0,0,"")){' +
           walk(nodes) +
           '};';
  }

  function partial(tok) {
    return 'b += _.rp("' +  esc(tok.n) + '",c,p,"' + (tok.indent || '') + '");';
  }

  function tripleStache(id, method) {
    return 'b += (_.' + method + '("' + esc(id) + '",c,p,0));';
  }

  function variable(id, method) {
    return 'b += (_.v(_.' + method + '("' + esc(id) + '",c,p,0)));';
  }

  function text(id) {
    return 'b += ' + id + ';';
  }

  Hogan.parse = function(tokens, options) {
    options = options || {};
    return buildTree(tokens, '', [], options.sectionTags || []);
  },

  Hogan.cache = {};

  Hogan.compile = function(text, options) {
    // options
    //
    // asString: false (default)
    //
    // sectionTags: [{o: '_foo', c: 'foo'}]
    // An array of object with o and c fields that indicate names for custom
    // section tags. The example above allows parsing of {{_foo}}{{/foo}}.
    //
    // delimiters: A string that overrides the default delimiters.
    // Example: "<% %>"
    //
    options = options || {};

    var key = text + '||' + !!options.asString;

    var t = this.cache[key];

    if (t) {
      return t;
    }

    t = this.generate(writeCode(this.parse(this.scan(text, options.delimiters), options)), text, options);
    return this.cache[key] = t;
  };
})(typeof exports !== 'undefined' ? exports : Hogan);
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