import { StreamMessageWrapper } from "../CommonTypes";

export function* getParsablePartIterator<T>(
  str: string
): Generator<T, undefined, string> {
  let remainingStr = str;
  while (true) {
    const jsonRange = findParsablePart(remainingStr);
    if (jsonRange === undefined) {
      return;
    }
    const jsonStr = remainingStr.slice(jsonRange.start, jsonRange.end);
    remainingStr = remainingStr.slice(jsonRange.end);
    const result = JSON.parse(jsonStr) as T;
    yield result;
  }
}

function findParsablePart(
  str: string
): { start: number; end: number } | undefined {
  let startText = StreamMessageWrapper.startIndicator;
  let endText = StreamMessageWrapper.endIndicator;
  const startIndex = str.indexOf(startText);
  if (startIndex === -1) {
    return undefined;
  }
  const endIndex = str.indexOf(endText, startIndex + startText.length);
  if (endIndex === -1) {
    return undefined;
  }
  return { start: startIndex + startText.length, end: endIndex };
}