import json
import asyncio
from uuid import UUID
from datetime import datetime
import aio_pika
from sqlalchemy import update, select
from app.db import SessionLocal
from app.models import Task, TaskStatus
from app.services import refresh_job_status, release_dependent_tasks
from app.config import settings

class BaseWorker:
    def __init__(self, routing_key: str, worker_id: str):
        self.routing_key = routing_key
        self.worker_id = worker_id

    async def run(self):
        connection = await aio_pika.connect_robust(settings.RABBITMQ_URL)
        async with connection:
            channel = await connection.channel()
            await channel.set_qos(prefetch_count=1)
            exchange = await channel.declare_exchange(
                settings.RABBITMQ_EXCHANGE, aio_pika.ExchangeType.TOPIC, durable=True
            )
            queue = await channel.declare_queue(
                name=f"q.{self.routing_key}",
                durable=True,
                arguments={
                    "x-dead-letter-exchange": f"{settings.RABBITMQ_EXCHANGE}.dlx"
                },
            )
            await queue.bind(exchange, routing_key=self.routing_key)
            print(f"[{self.worker_id}] listening on {self.routing_key} ...")
            await queue.consume(self._on_message, no_ack=False)
            await asyncio.Future()

    async def _on_message(self, message: aio_pika.IncomingMessage):
        async with message.process(requeue=False):
            data = json.loads(message.body.decode("utf-8"))
            task_id = UUID(data["task_id"])
            job_id = UUID(data["job_id"])
            payload = data.get("payload", {})
            try:
                await self._set_status(task_id, TaskStatus.RUNNING, started_at=datetime.utcnow())
                result = await self.process(payload, job_id=job_id, task_id=task_id)
                await self._set_status(task_id, TaskStatus.SUCCESS, result=result, finished_at=datetime.utcnow())
                async with SessionLocal() as session:
                    await release_dependent_tasks(session, task_id)
                    await refresh_job_status(session, job_id)
                    await session.commit()
                print(f"[{self.worker_id}] SUCCESS {task_id}")
            except Exception as e:
                print(f"[{self.worker_id}] ERROR: {e}")
                await self._handle_failure(message, str(e), job_id)

    async def _handle_failure(self, message: aio_pika.IncomingMessage, err: str, job_id):
        data = json.loads(message.body.decode("utf-8"))
        task_id = UUID(data["task_id"])
        async with SessionLocal() as session:
            res = await session.execute(select(Task).where(Task.id == task_id))
            task = res.scalar_one_or_none()
            if task is None:
                return
            new_retries = (task.retries or 0) + 1
            if new_retries <= (task.max_retries or settings.MAX_RETRIES):
                await session.execute(
                    update(Task)
                    .where(Task.id == task_id)
                    .values(status=TaskStatus.QUEUED, retries=new_retries, error=f"Retry {new_retries}: {err}")
                )
                await session.commit()
                await asyncio.sleep(min(2 ** new_retries, 30))
                connection = await aio_pika.connect_robust(settings.RABBITMQ_URL)
                async with connection:
                    ch = await connection.channel()
                    ex = await ch.declare_exchange(settings.RABBITMQ_EXCHANGE, aio_pika.ExchangeType.TOPIC, durable=True)
                    await ex.publish(aio_pika.Message(body=message.body), routing_key=message.routing_key)
            else:
                await session.execute(
                    update(Task)
                    .where(Task.id == task_id)
                    .values(status=TaskStatus.FAILED, error=f"Max retries exceeded: {err}", finished_at=datetime.utcnow())
                )
                await refresh_job_status(session, job_id)
                await session.commit()

    async def _set_status(self, task_id: UUID, status: TaskStatus, **extra):
        async with SessionLocal() as session:
            await session.execute(
                update(Task).where(Task.id == task_id).values(status=status, worker_id=self.worker_id, **extra)
            )
            await session.commit()

    async def process(self, payload: dict, **meta) -> dict:
        raise NotImplementedError