import type { Message, Part } from "../ir.ts";
import { linesOf, parseState } from "./dot.ts";

const START = /@!@!@STARTMSG (\d+):(\d+) @!@!@$/;
const END = /^@!@!@ENDMSG \d+ @!@!@$/;

const isCutMarker = (lastLine: string) => lastLine.startsWith("@!@!@");

function cutMessage(open: Message[]) {
  for (let i = open.length - 1; i > 0 && !open[i].body.length; i--) open[i - 1].body.pop();
  return open[0]?.body.length ? open[0] : undefined;
}

export function* readMessages(tlcOut: string | Iterable<string>): Generator<Part> {
  const lines = linesOf(tlcOut)[Symbol.iterator]();
  const open: Message[] = [];
  try {
    for (let next = lines.next(); !next.done;) {
      const line = next.value;
      next = lines.next();
      if (next.done && (!line || isCutMarker(line))) break;
      const start = START.exec(line);
      if (start) {
        const message: Message = { code: Number(start[1]), level: Number(start[2]), body: [] };
        if (start.index) message.beforeMarker = line.slice(0, start.index);
        open.at(-1)?.body.push(message);
        open.push(message);
      } else if (END.test(line)) {
        const done = open.pop();
        if (done && !open.length) yield done;
      } else if (open.length) open[open.length - 1].body.push(line);
      else yield line;
    }
  } finally {
    lines.return?.();
  }
  const cut = cutMessage(open);
  if (cut) yield cut;
}

export const textOf = ({ body }: Message) =>
  body.filter((part) => typeof part === "string").join("\n");

export const actionOf = (m: Message) =>
  /^\d+: (?:Back to state: )?<([^\s>]+)/.exec(textOf(m))?.[1];

export const messageState = (m: Message) => {
  const lines = textOf(m).split("\n");
  const body: string[] = [];
  for (let i = 1; i < lines.length && lines[i].trim(); i++) body.push(lines[i]);
  return parseState(body.join("\n"));
};