"""Tiny TG bot: reacts to /start (and a couple of helper commands).

Pure stdlib \u2014 no aiogram/python-telegram-bot dependency. The panel
spawns it as a subprocess (sees run.py) and injects BOT_TOKEN.

Why stdlib only: the panel's requirements.txt does not include
aiogram, and a multi-tenant subprocess model means each bot would
otherwise need its own venv. ``urllib.request`` + json is enough
for the Bot API. Long-polling handles the event loop.
"""
import json
import os
import sys
import time
import urllib.error
import urllib.parse
import urllib.request


TOKEN = (os.environ.get("BOT_TOKEN") or "").strip()
if not TOKEN:
    sys.stderr.write("FATAL: BOT_TOKEN env var is empty\n")
    sys.exit(2)

API = "https://api.telegram.org/bot" + TOKEN


def api(method: str, **params):
    """Minimal Bot API wrapper. Returns parsed JSON dict.

    Raises on HTTP errors so the loop's except can log + back off.
    """
    data = urllib.parse.urlencode(params).encode("utf-8")
    req = urllib.request.Request(API + "/" + method, data=data,
                                  headers={"Content-Type": "application/x-www-form/x-www-form-urlencoded"})
    with urllib.request.urlopen(req, timeout=35) as resp:
        body = resp.read()
    return json.loads(body)


def reply(chat_id: int, text: str):
    try:
        return api("sendMessage", chat_id=chat_id, text=text,
                   parse_mode="HTML", disable_web_page_preview=True)
    except urllib.error.HTTPError as exc:
        # Surface 4xx / 5xx without crashing the whole loop.
        sys.stderr.write(f"sendMessage HTTP {exc.code}: {exc.read()[:200]!r}\n")
        return None


def help_text() -> str:
    return (
        "<b>MMaxAI micro bot</b>\n"
        "/start \u2014 say hi\n"
        "/help  \u2014 this list\n"
        "/ping  \u2014 pong\n"
        "/echo  \u2014 echo back what you type\n"
        "/id    \u2014 show chat id + msg id\n"
    )


def handle(text: str, chat_id: int, msg_id: int, sender: str | None) -> None:
    cmd = text.split(maxsplit=1)[0].lower() if text else ""
    if cmd == "/start":
        reply(chat_id, f"\U0001f44b Привіт, <b>{sender or 'друже'}</b>!\n" + help_text())
    elif cmd == "/help":
        reply(chat_id, help_text())
    elif cmd == "/ping":
        reply(chat_id, "pong \U0001f3d3")
    elif cmd == "/id":
        reply(chat_id, f"chat_id = <code>{chat_id}</code>\nmsg_id = <code>{msg_id}</code>")
    elif cmd == "/echo":
        body = text.split(maxsplit=1, )[1] if " " in text else ""
        reply(chat_id, body or "(empty)")
    else:
        reply(chat_id, "Unknown command. Try /help.")


def main() -> int:
    sys.stdout.write(f"micro-bot starting (chat link hidden, "
                     f"token length {len(TOKEN)})\n")
    sys.stdout.flush()
    offset = 0
    failures = 0
    while True:
        try:
            data = api("getUpdates", offset=offset, timeout=25,
                       allowed_updates="message")
            for upd in data.get("result", []):
                offset = max(offset, upd["update_id"] + 1)
                msg = upd.get("message") or {}
                chat = msg.get("chat") or {}
                sender = (msg.get("from") or {}).get("first_name")
                text = (msg.get("text") or "").strip()
                if not text.startswith("/"):
                    continue
                handle(text, chat["id"], msg["message_id"], sender)
            failures = 0
        except urllib.error.HTTPError as exc:
            failures += 1
            sys.stderr.write(f"getUpdates HTTP {exc.code} (attempt {failures})\n")
            sys.stderr.flush()
            time.sleep(min(30, 2 * failures))
        except (urllib.error.URLError, TimeoutError, OSError) as exc:
            failures += 1
            sys.stderr.write(f"getUpdates net err {exc!r} (attempt {failures})\n")
            sys.stderr.flush()
            time.sleep(min(30, 2 * failures))
        except Exception as exc:  # noqa: BLE001
            failures += 1
            sys.stderr.write(f"getUpdates unhandled {exc!r}\n")
            sys.stderr.flush()
            time.sleep(5)


if __name__ == "__main__":
    sys.exit(main())