const PRELUDE = `
  define('STDIN', fopen('php://stdin', 'r'));
  define('STDOUT', fopen('php://stdout', 'r'));
  define('STDERR', fopen('php://stderr', 'r'));

  error_reporting(E_ALL & ~E_WARNING & ~E_NOTICE & ~E_DEPRECATED);

  `;

const BUFFER_MAX = 10 * 1024;

export function preprocessCode(originalCode) {
  if (originalCode.startsWith("<?php")) {
    return PRELUDE + originalCode.slice(5);
  }
  if (originalCode.startsWith("<?")) {
    return PRELUDE + originalCode.slice(2);
  }
  return PRELUDE + originalCode;
}

export function createIOCallbacks(input) {
  let stdinPos = 0;
  const stdinBuf = Buffer.from(input);
  let stdoutPos = 0;
  const stdoutBuf = Buffer.alloc(BUFFER_MAX);
  let stderrPos = 0;
  const stderrBuf = Buffer.alloc(BUFFER_MAX);

  return {
    stdin: () => {
      if (stdinBuf.length <= stdinPos) {
        return null;
      }
      return stdinBuf.readUInt8(stdinPos++);
    },
    stdout: (asciiCode) => {
      if (asciiCode === null) {
        return;
      }
      if (BUFFER_MAX <= stdoutPos) {
        return;
      }
      stdoutBuf.writeUInt8(
        asciiCode < 0 ? asciiCode + 256 : asciiCode,
        stdoutPos++,
      );
    },
    stderr: (asciiCode) => {
      if (asciiCode === null) {
        return;
      }
      if (BUFFER_MAX <= stderrPos) {
        return;
      }
      stderrBuf.writeUInt8(
        asciiCode < 0 ? asciiCode + 256 : asciiCode,
        stderrPos++,
      );
    },
    getStdout: () => stdoutBuf.subarray(0, stdoutPos).toString(),
    getStderr: () => stderrBuf.subarray(0, stderrPos).toString(),
  };
}

export function buildResult(err, ccallResult, getStdout, getStderr) {
  if (err) {
    return {
      status: "runtime_error",
      stdout: getStdout(),
      stderr: `${getStderr()}\n${err.toString()}`,
    };
  }
  return {
    status: ccallResult === 0 ? "success" : "runtime_error",
    stdout: getStdout(),
    stderr: getStderr(),
  };
}