/*
Language: Handlebars
Requires: xml.js
Author: Robin Ward <robin.ward@gmail.com>
Description: Matcher for Handlebars as well as EmberJS additions.
Website: https://handlebarsjs.com
Category: template
*/

export default function(hljs) {
  const regex = hljs.regex;
  const BUILT_INS = {
    $pattern: /[\w.\/]+/,
    built_in: [
      'action',
      'bindattr',
      'collection',
      'component',
      'concat',
      'debugger',
      'each',
      'each-in',
      'get',
      'hash',
      'if',
      'in',
      'input',
      'link-to',
      'loc',
      'log',
      'lookup',
      'mut',
      'outlet',
      'partial',
      'query-params',
      'render',
      'template',
      'textarea',
      'unbound',
      'unless',
      'view',
      'with',
      'yield'
    ]
  };

  const LITERALS = {
    $pattern: /[\w.\/]+/,
    literal: [
      'true',
      'false',
      'undefined',
      'null'
    ]
  };

  // as defined in https://handlebarsjs.com/guide/expressions.html#literal-segments
  // this regex matches literal segments like ' abc ' or [ abc ] as well as helpers and paths
  // like a/b, ./abc/cde, and abc.bcd

  const DOUBLE_QUOTED_ID_REGEX = /""|"[^"]+"/;
  const SINGLE_QUOTED_ID_REGEX = /''|'[^']+'/;
  const BRACKET_QUOTED_ID_REGEX = /\[\]|\[[^\]]+\]/;
  const PLAIN_ID_REGEX = /[^\s!"#%&'()*+,.\/;<=>@\[\\\]^`{|}~]+/;
  const PATH_DELIMITER_REGEX = /(\.|\/)/;
  const ANY_ID = regex.either(
    DOUBLE_QUOTED_ID_REGEX,
    SINGLE_QUOTED_ID_REGEX,
    BRACKET_QUOTED_ID_REGEX,
    PLAIN_ID_REGEX
  );

  const IDENTIFIER_REGEX = regex.concat(
    regex.optional(/\.|\.\/|\//), // relative or absolute path
    ANY_ID,
    regex.anyNumberOfTimes(regex.concat(
      PATH_DELIMITER_REGEX,
      ANY_ID
    ))
  );

  // identifier followed by a equal-sign (without the equal sign)
  const HASH_PARAM_REGEX = regex.concat(
    '(',
    BRACKET_QUOTED_ID_REGEX, '|',
    PLAIN_ID_REGEX,
    ')(?==)'
  );

  const HELPER_NAME_OR_PATH_EXPRESSION = { begin: IDENTIFIER_REGEX };

  const HELPER_PARAMETER = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, { keywords: LITERALS });

  const SUB_EXPRESSION = {
    begin: /\(/,
    end: /\)/
    // the "contains" is added below when all necessary sub-modes are defined
  };

  const HASH = {
    // fka "attribute-assignment", parameters of the form 'key=value'
    className: 'attr',
    begin: HASH_PARAM_REGEX,
    relevance: 0,
    starts: {
      begin: /=/,
      end: /=/,
      starts: { contains: [
        hljs.NUMBER_MODE,
        hljs.QUOTE_STRING_MODE,
        hljs.APOS_STRING_MODE,
        HELPER_PARAMETER,
        SUB_EXPRESSION
      ] }
    }
  };

  const BLOCK_PARAMS = {
    // parameters of the form '{{#with x as | y |}}...{{/with}}'
    begin: /as\s+\|/,
    keywords: { keyword: 'as' },
    end: /\|/,
    contains: [
      {
        // define sub-mode in order to prevent highlighting of block-parameter named "as"
        begin: /\w+/ }
    ]
  };

  const HELPER_PARAMETERS = {
    contains: [
      hljs.NUMBER_MODE,
      hljs.QUOTE_STRING_MODE,
      hljs.APOS_STRING_MODE,
      BLOCK_PARAMS,
      HASH,
      HELPER_PARAMETER,
      SUB_EXPRESSION
    ],
    returnEnd: true
    // the property "end" is defined through inheritance when the mode is used. If depends
    // on the surrounding mode, but "endsWithParent" does not work here (i.e. it includes the
    // end-token of the surrounding mode)
  };

  const SUB_EXPRESSION_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
    className: 'name',
    keywords: BUILT_INS,
    starts: hljs.inherit(HELPER_PARAMETERS, { end: /\)/ })
  });

  SUB_EXPRESSION.contains = [ SUB_EXPRESSION_CONTENTS ];

  const OPENING_BLOCK_MUSTACHE_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
    keywords: BUILT_INS,
    className: 'name',
    starts: hljs.inherit(HELPER_PARAMETERS, { end: /\}\}/ })
  });

  const CLOSING_BLOCK_MUSTACHE_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
    keywords: BUILT_INS,
    className: 'name'
  });

  const BASIC_MUSTACHE_CONTENTS = hljs.inherit(HELPER_NAME_OR_PATH_EXPRESSION, {
    className: 'name',
    keywords: BUILT_INS,
    starts: hljs.inherit(HELPER_PARAMETERS, { end: /\}\}/ })
  });

  const ESCAPE_MUSTACHE_WITH_PRECEEDING_BACKSLASH = {
    begin: /\\\{\{/,
    skip: true
  };
  const PREVENT_ESCAPE_WITH_ANOTHER_PRECEEDING_BACKSLASH = {
    begin: /\\\\(?=\{\{)/,
    skip: true
  };

  return {
    name: 'Handlebars',
    aliases: [
      'hbs',
      'html.hbs',
      'html.handlebars',
      'htmlbars'
    ],
    case_insensitive: true,
    subLanguage: 'xml',
    contains: [
      ESCAPE_MUSTACHE_WITH_PRECEEDING_BACKSLASH,
      PREVENT_ESCAPE_WITH_ANOTHER_PRECEEDING_BACKSLASH,
      hljs.COMMENT(/\{\{!--/, /--\}\}/),
      hljs.COMMENT(/\{\{!/, /\}\}/),
      {
        // open raw block "{{{{raw}}}} content not evaluated {{{{/raw}}}}"
        className: 'template-tag',
        begin: /\{\{\{\{(?!\/)/,
        end: /\}\}\}\}/,
        contains: [ OPENING_BLOCK_MUSTACHE_CONTENTS ],
        starts: {
          end: /\{\{\{\{\//,
          returnEnd: true,
          subLanguage: 'xml'
        }
      },
      {
        // close raw block
        className: 'template-tag',
        begin: /\{\{\{\{\//,
        end: /\}\}\}\}/,
        contains: [ CLOSING_BLOCK_MUSTACHE_CONTENTS ]
      },
      {
        // open block statement
        className: 'template-tag',
        begin: /\{\{#/,
        end: /\}\}/,
        contains: [ OPENING_BLOCK_MUSTACHE_CONTENTS ]
      },
      {
        className: 'template-tag',
        begin: /\{\{(?=else\}\})/,
        end: /\}\}/,
        keywords: 'else'
      },
      {
        className: 'template-tag',
        begin: /\{\{(?=else if)/,
        end: /\}\}/,
        keywords: 'else if'
      },
      {
        // closing block statement
        className: 'template-tag',
        begin: /\{\{\//,
        end: /\}\}/,
        contains: [ CLOSING_BLOCK_MUSTACHE_CONTENTS ]
      },
      {
        // template variable or helper-call that is NOT html-escaped
        className: 'template-variable',
        begin: /\{\{\{/,
        end: /\}\}\}/,
        contains: [ BASIC_MUSTACHE_CONTENTS ]
      },
      {
        // template variable or helper-call that is html-escaped
        className: 'template-variable',
        begin: /\{\{/,
        end: /\}\}/,
        contains: [ BASIC_MUSTACHE_CONTENTS ]
      }
    ]
  };
}