function makeSticky( re: RegExp ): RegExp
{
  if ( re.sticky ) return re;
  const flags = re.flags.includes( 'y' ) ? re.flags : re.flags + 'y';
  return new RegExp( re.source, flags );
}

export class BrowserMatcher
{
  readonly type: string;
  private _re: RegExp;

  constructor( type: string, re: RegExp )
  {
    this.type = type;
    this._re  = makeSticky( re );
  }

  matchLength( source: string, offset: number ): number
  {
    this._re.lastIndex = offset;
    const result = this._re.exec( source );
    if ( result && result.index === offset ) return result[ 0 ].length;
    return -1;
  }
}

export class BrowserLexer
{
  readonly modes = new Map<string, BrowserMatcher[]>();

  addMatchers( ...matchers: BrowserMatcher[] ): void
  {
    const list = this.modes.get( 'default' ) ?? [];
    list.push( ...matchers );
    this.modes.set( 'default', list );
  }
}

export function cLikeLexer(): BrowserLexer
{
  const l = new BrowserLexer();
  l.addMatchers(
    new BrowserMatcher( 'SINGLE_LINE_COMMENT',  /\/\/.*/                                          ),
    new BrowserMatcher( 'MULTI_LINE_COMMENT',   /\/\*[\s\S]*?\*\//                                ),
    new BrowserMatcher( 'DOUBLE_QUOTED_STRING', /"(?:[^"\\]|\\.)*"/                               ),
    new BrowserMatcher( 'SINGLE_QUOTED_STRING', /'(?:[^'\\]|\\.)*'/                               ),
    new BrowserMatcher( 'C_INSTRUCTION',        /\#.*/                                            ),
    new BrowserMatcher( 'NUMBER',               /(?=\.\d|\d)(?:\d+)?(?:\.?\d*)(?:[eE][+-]?\d+)?/ ),
    new BrowserMatcher( 'NULL',                 /\bnull\b/                                        ),
    new BrowserMatcher( 'BOOL',                 /\b(?:true|false)\b/                              ),
    new BrowserMatcher( 'BREAK',                /\r\n|\r|\n/                                      ),
    new BrowserMatcher( 'WHITESPACE',           /\s+/                                             ),
    new BrowserMatcher( 'LOGIC',                /\b(?:if|else|switch|do|while|for|break|continue|return|case)\b/ ),
    new BrowserMatcher( 'BRACKET',              /[()[\]{}]/                                       ),
    new BrowserMatcher( 'ACCESS_MODIFIER',      /\b(?:public|protected|private)\b/               ),
    new BrowserMatcher( 'CLASS',                /\bclass\b/                                       ),
    new BrowserMatcher( 'OPERATOR',             /==|\+\+|--|[+\-*\/^|~&%<>=!.:,;]/               ),
    new BrowserMatcher( 'CFUNCTION',            /[a-zA-Z_]\w*(?=\s*\()/                          ),
    new BrowserMatcher( 'CWORD',                /[a-zA-Z_]\w*/                                   ),
    new BrowserMatcher( 'ANY_SYMBOL',           /./                                               ),
  );
  return l;
}