uccser/cs-field-guide

// Based off the work of douglasduteil
// https://gist.github.com/douglasduteil/5089187

const CodeMirror = require('codemirror');

CodeMirror.defineMode("regex", function() {
    var otherChar = /^[\^\$\.\+\?\*]/;
    var g= 0;

    var tokenBase = function(stream) {
      var ch = stream.next();

      if (ch == "\\" && stream.match(/./, false)) {
        if (stream.match(/u\w{4}/)) return "a";
        if (stream.match(/u/)) return "err";

        if (stream.match(/x\w{2}/)) return "a";
        if (stream.match(/x/)) return "err";

        if (stream.match(/./)) return "a";

        return "a";
      }


      if (ch == "{"){
        if (stream.match(/(\d|\d,\d?)\}/))  return "a";
      }

      if (ch == "[" && stream.match(/[^\]]+\]/)){
        return "b";
      }

      if (ch == "|") {
        return "g" + g;
      }

      if (ch == "(") {
        stream.match(/[\?\!\:]+/);
        return "g" + (++g % 5);
      }

      if (ch == ")") {
        if(g-1 < 0) return "err";
        return "g" + (g-- % 5);
      }

      if (otherChar.test(ch)) {
        return "a";
      }
    };

    return {
      startState: function(base) {
        g= 0;
      },
      token: tokenBase
    };
  });

  CodeMirror.defineMIME("text/x-regex", "regex");