from __future__ import annotations

import logging
import os
import signal
import socket
import threading
import uuid
from dataclasses import dataclass
from datetime import timedelta

from supply_infra.config import InfraSettings, get_infra_settings
from supply_infra.db.repositories.pipeline_run_repo import PipelineRunRepository
from supply_infra.db.repositories.pipeline_step_run_repo import PipelineStepRunRepository
from supply_infra.db.session import dispose_engine, get_session
from supply_infra.pipeline.dates import china_now
from supply_infra.pipeline.orchestrator import complete_step
from supply_infra.pipeline.contracts import StepResult
from supply_infra.pipeline.step_runner import StepExecutionRequest, run_step_subprocess

logger = logging.getLogger(__name__)


@dataclass(frozen=True)
class ClaimedStep:
    run_id: str
    step_run_id: str
    step_key: str
    timeout_seconds: int


class PipelineWorker:
    def __init__(
        self,
        *,
        settings: InfraSettings | None = None,
        worker_id: str | None = None,
    ) -> None:
        self.settings = settings or get_infra_settings()
        self.worker_id = worker_id or (
            f"{socket.gethostname()}:{os.getpid()}:{uuid.uuid4().hex[:8]}"
        )
        self._stop = threading.Event()

    def stop(self, *_args: object) -> None:
        logger.info("Worker stop requested: worker_id=%s", self.worker_id)
        self._stop.set()

    def claim(self) -> ClaimedStep | None:
        now = china_now()
        with get_session() as session:
            step = PipelineStepRunRepository(session).claim_next_ready(
                owner=self.worker_id,
                lease_seconds=self.settings.pipeline_lease_seconds,
                max_active_steps=self.settings.pipeline_max_active_steps,
                now=now,
            )
            if step is None:
                return None
            run = PipelineRunRepository(session).get(step.run_id, for_update=True)
            if run is None:
                raise ValueError(f"pipeline run not found: {step.run_id}")
            PipelineRunRepository(session).mark_running(
                run,
                step_key=step.step_key,
                owner=self.worker_id,
                now=now,
                lease_until=now + timedelta(seconds=self.settings.pipeline_lease_seconds),
            )
            return ClaimedStep(
                run_id=step.run_id,
                step_run_id=step.step_run_id,
                step_key=step.step_key,
                timeout_seconds=step.timeout_seconds,
            )

    def _heartbeat_loop(self, claimed: ClaimedStep, stopped: threading.Event) -> None:
        while not stopped.wait(self.settings.pipeline_heartbeat_seconds):
            now = china_now()
            lease_until = now + timedelta(seconds=self.settings.pipeline_lease_seconds)
            try:
                with get_session() as session:
                    step_ok = PipelineStepRunRepository(session).heartbeat(
                        claimed.step_run_id,
                        owner=self.worker_id,
                        now=now,
                        lease_until=lease_until,
                    )
                    run_ok = PipelineRunRepository(session).heartbeat(
                        claimed.run_id,
                        owner=self.worker_id,
                        now=now,
                        lease_until=lease_until,
                    )
                    if not step_ok or not run_ok:
                        logger.error(
                            "Pipeline lease lost: worker=%s step=%s",
                            self.worker_id,
                            claimed.step_run_id,
                        )
                        stopped.set()
            except Exception:
                logger.exception("Pipeline heartbeat failed: step=%s", claimed.step_run_id)

    def run_once(self) -> bool:
        claimed = self.claim()
        if claimed is None:
            return False
        heartbeat_stop = threading.Event()
        heartbeat = threading.Thread(
            target=self._heartbeat_loop,
            args=(claimed, heartbeat_stop),
            name=f"pipeline-heartbeat-{claimed.step_run_id[:8]}",
            daemon=True,
        )
        heartbeat.start()
        try:
            try:
                result = run_step_subprocess(
                    StepExecutionRequest(
                        run_id=claimed.run_id,
                        step_run_id=claimed.step_run_id,
                        step_key=claimed.step_key,
                        timeout_seconds=claimed.timeout_seconds,
                    ),
                    settings=self.settings,
                )
            except Exception as exc:
                logger.exception("Unexpected step runner failure: %s", claimed.step_run_id)
                result = StepResult(
                    success=False,
                    payload={},
                    error_code="step_runner_exception",
                    error_message=str(exc),
                )
        finally:
            heartbeat_stop.set()
            heartbeat.join(timeout=2)
        try:
            with get_session() as session:
                state = complete_step(
                    session,
                    step_run_id=claimed.step_run_id,
                    owner=self.worker_id,
                    result=result,
                )
        except RuntimeError:
            logger.exception(
                "Discarding step result after lease loss: step=%s",
                claimed.step_run_id,
            )
            return True
        logger.info(
            "Pipeline step completed: step=%s state=%s",
            claimed.step_run_id,
            state,
        )
        return True

    def run_forever(self) -> None:
        signal.signal(signal.SIGTERM, self.stop)
        signal.signal(signal.SIGINT, self.stop)
        logger.info("Pipeline worker started: worker_id=%s", self.worker_id)
        try:
            while not self._stop.is_set():
                if not self.run_once():
                    self._stop.wait(self.settings.pipeline_worker_poll_seconds)
        finally:
            dispose_engine()
            logger.info("Pipeline worker stopped: worker_id=%s", self.worker_id)