// luma.gl
// SPDX-License-Identifier: MIT
// Copyright (c) vis.gl contributors

const IFDEF_REGEXP = /^\s*\#\s*ifdef\s*([a-zA-Z_]+)\s*$/;
const ENDIF_REGEXP = /^\s*\#\s*endif\s*$/;

export type PreprocessorOptions = {
  defines?: Record<string, boolean>;
};

export function preprocess(source: string, options?: PreprocessorOptions): string {
  const lines = source.split('\n');
  const output: string[] = [];

  let conditional = true;
  let currentDefine: string | null = null;
  for (const line of lines) {
    const matchIf = line.match(IFDEF_REGEXP);
    const matchEnd = line.match(ENDIF_REGEXP);
    if (matchIf) {
      currentDefine = matchIf[1];
      conditional = Boolean(options?.defines?.[currentDefine]);
    } else if (matchEnd) {
      conditional = true;
    } else if (conditional) {
      output.push(line);
    }
  }
  return output.join('\n');
}