import type { ServerChannel } from "ssh2";

const pullRate = process.env.KEYBOARD_PULLING_RATE
  ? parseInt(process.env.KEYBOARD_PULLING_RATE)
  : 5;

const leftEscape = "\x1B[D";
const rightEscape = "\x1B[C";

const ourBackspace = "\u0008";
const clientBackspace = "\x7F";

export async function readFromKeyboard(
  stream: ServerChannel,
  disableEcho: boolean = false,
): Promise<string> {
  let promise: (value: string | PromiseLike<string>) => void;

  let line = "";
  let lineIndex = 0;

  async function eventLoop(): Promise<any> {
    const readStreamDataBuf = stream.read();
    if (readStreamDataBuf == null) return setTimeout(eventLoop, pullRate);

    const readStreamData = readStreamDataBuf.toString();

    // Fixes several bugs (incl. potential social eng. exploits, ssh-copy-id being broken, etc)
    for (const character of readStreamData.split("")) {
      if (character == "\x03") {
        stream.write("^C");
        return promise("");
      } else if (character == "\r" || character == "\n") {
        return promise(line.replace("\r", ""));
      } else if (character == clientBackspace) {
        if (line.length == 0) return setTimeout(eventLoop, pullRate); // Here because if we do it in the parent if statement, shit breaks
        line = line.substring(0, lineIndex - 1) + line.substring(lineIndex);

        if (!disableEcho) {
          const deltaCursor = line.length - lineIndex;

          if (deltaCursor == line.length)
            return setTimeout(eventLoop, pullRate);

          if (deltaCursor < 0) {
            // Use old technique if the delta is < 0, as the new one is tailored to the start + 1 to end - 1
            stream.write(ourBackspace + " " + ourBackspace);
          } else {
            // Jump forward to the front, and remove the last character
            stream.write(rightEscape.repeat(deltaCursor) + " " + ourBackspace);

            // Go backwards & rerender text & go backwards again (wtf?)
            stream.write(
              leftEscape.repeat(deltaCursor + 1) +
                line.substring(lineIndex - 1) +
                leftEscape.repeat(deltaCursor + 1),
            );
          }

          lineIndex -= 1;
        }
      } else if (character == "\x1B") {
        if (character == rightEscape) {
          if (lineIndex + 1 > line.length)
            return setTimeout(eventLoop, pullRate);
          lineIndex += 1;
        } else if (character == leftEscape) {
          if (lineIndex - 1 < 0) return setTimeout(eventLoop, pullRate);
          lineIndex -= 1;
        } else {
          return setTimeout(eventLoop, pullRate);
        }

        if (!disableEcho) stream.write(character);
      } else {
        lineIndex += 1;

        // There isn't a splice method for String prototypes. So, ugh:
        line =
          line.substring(0, lineIndex - 1) +
          character +
          line.substring(lineIndex - 1);

        if (!disableEcho) {
          let deltaCursor = line.length - lineIndex;

          // wtf?
          if (deltaCursor < 0) {
            console.log(
              "FIXME: somehow, our deltaCursor value is negative! please investigate me",
            );
            deltaCursor = 0;
          }

          stream.write(
            line.substring(lineIndex - 1) + leftEscape.repeat(deltaCursor),
          );
        }
      }
    }

    setTimeout(eventLoop, pullRate);
  }

  return new Promise(resolve => {
    setTimeout(eventLoop, pullRate);
    promise = resolve;
  });
}