"""Telegram bot — runs as a daemon thread sharing the same ledger instance."""

import os
import asyncio
import logging
import threading
from telegram import Update
from telegram.ext import (
    ApplicationBuilder, CommandHandler, MessageHandler,
    ContextTypes, filters,
)

from ledger import Ledger
from agent import batch_response, execute

logger = logging.getLogger(__name__)

MAX_HISTORY = 20  # messages (10 turns) kept per user


# ── handlers ──────────────────────────────────────────────────────────────────

async def on_start(update: Update, context: ContextTypes.DEFAULT_TYPE):
    await update.message.reply_text(
        "👋 *Finance Manager*\n\n"
        "Just tell me about your expenses naturally:\n"
        "• _Spent $12 on lunch_\n"
        "• _Paid $1200 rent yesterday_\n"
        "• _Undo_ — removes the last entry\n\n"
        "Commands:\n"
        "/summary — spending by category\n"
        "/clear — reset conversation history",
        parse_mode="Markdown",
    )


async def on_summary(update: Update, context: ContextTypes.DEFAULT_TYPE):
    ledger: Ledger = context.bot_data["ledger"]
    by_cat = ledger.by_category()
    total = ledger.total()

    if not by_cat:
        await update.message.reply_text("No entries yet. Start logging expenses!")
        return

    lines = [f"💰 *Total: ${total:.2f}*\n"]
    lines += [
        f"• {cat}: ${amt:.2f}"
        for cat, amt in sorted(by_cat.items(), key=lambda x: -x[1])
    ]
    await update.message.reply_text("\n".join(lines), parse_mode="Markdown")


async def on_clear(update: Update, context: ContextTypes.DEFAULT_TYPE):
    context.user_data["history"] = []
    await update.message.reply_text("Conversation history cleared.")


async def on_message(update: Update, context: ContextTypes.DEFAULT_TYPE):
    ledger: Ledger = context.bot_data["ledger"]
    token = os.getenv("HF_TOKEN", "")

    if not token:
        await update.message.reply_text("HF_TOKEN is not configured.")
        return

    history: list[dict] = context.user_data.get("history", [])
    text = update.message.text

    reply, action = await asyncio.to_thread(batch_response, text, history, ledger, token)

    if action:
        confirmation = execute(action, ledger, text)
        if confirmation:
            reply += f"\n\n{confirmation}"

    # Persist last N messages for context
    context.user_data["history"] = (
        history + [
            {"role": "user", "content": text},
            {"role": "assistant", "content": reply},
        ]
    )[-MAX_HISTORY:]

    await update.message.reply_text(reply, parse_mode="Markdown")


# ── entry point ───────────────────────────────────────────────────────────────

def start(ledger: Ledger):
    """Start the Telegram bot in a daemon thread. No-op if token not set."""
    bot_token = os.getenv("TELEGRAM_BOT_TOKEN")
    if not bot_token:
        logger.info("TELEGRAM_BOT_TOKEN not set — Telegram bot disabled.")
        return

    async def _run():
        app = ApplicationBuilder().token(bot_token).build()
        app.bot_data["ledger"] = ledger
        app.add_handler(CommandHandler("start", on_start))
        app.add_handler(CommandHandler("summary", on_summary))
        app.add_handler(CommandHandler("clear", on_clear))
        app.add_handler(MessageHandler(filters.TEXT & ~filters.COMMAND, on_message))

        logger.info("Telegram bot polling started.")
        async with app:
            await app.start()
            await app.updater.start_polling()
            await asyncio.Event().wait()  # run until process exits

    threading.Thread(target=lambda: asyncio.run(_run()), daemon=True).start()