import json
import threading
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from typing import Optional

from app.common.config import config
from app.common.logging import setup_logger
from app.worker.metrics import worker_metrics

logger = setup_logger("processing-worker")


class WorkerHTTPRequestHandler(BaseHTTPRequestHandler):
    """
    Lightweight HTTP request handler for worker internal metrics and stats.
    """
    error_content_type = "application/json"

    def log_message(self, format: str, *args) -> None:
        # Suppress default noisy stderr logging
        pass

    def send_error(self, code: int, message: Optional[str] = None, explain: Optional[str] = None) -> None:
        from http import HTTPStatus
        try:
            if hasattr(self, "headers") and self.headers:
                content_length = int(self.headers.get("Content-Length", 0))
                if content_length > 0:
                    self.rfile.read(min(content_length, 65536))
        except Exception:
            pass
        try:
            status = HTTPStatus(code)
            short_msg = status.phrase
        except ValueError:
            short_msg = "error"
        err_msg = message or short_msg
        detail = explain or err_msg
        body = json.dumps({"error": err_msg, "detail": detail}).encode("utf-8")
        self.send_response(code)
        self.send_header("Content-Type", "application/json")
        self.send_header("Content-Length", str(len(body)))
        self.send_header("Connection", "close")
        self.end_headers()
        self.wfile.write(body)

    def do_GET(self) -> None:
        if self.path == "/internal/stats":
            stats = worker_metrics.get_internal_stats()
            body = json.dumps(stats, indent=2).encode("utf-8")
            self.send_response(200)
            self.send_header("Content-Type", "application/json")
            self.send_header("Content-Length", str(len(body)))
            self.end_headers()
            self.wfile.write(body)
            return

        if self.path == "/metrics":
            metrics_text = worker_metrics.get_prometheus_metrics()
            body = metrics_text.encode("utf-8")
            self.send_response(200)
            self.send_header(
                "Content-Type", "text/plain; version=0.0.4; charset=utf-8"
            )
            self.send_header("Content-Length", str(len(body)))
            self.end_headers()
            self.wfile.write(body)
            return

        if self.path in ("/health", "/healthz", "/live"):
            body = b'{"status": "ok"}'
            self.send_response(200)
            self.send_header("Content-Type", "application/json")
            self.send_header("Content-Length", str(len(body)))
            self.end_headers()
            self.wfile.write(body)
            return

        self.send_error(404, "not_found", f"Cannot GET {self.path}")


class WorkerInternalServer:
    """
    Background HTTP server serving /internal/stats and /metrics on worker port (8001).
    """

    def __init__(self, host: Optional[str] = None, port: Optional[int] = None):
        self.host = host or config.worker.stats_host
        self.port = port or config.worker.stats_port
        self._server: Optional[ThreadingHTTPServer] = None
        self._thread: Optional[threading.Thread] = None

    def start(self) -> None:
        self._server = ThreadingHTTPServer(
            (self.host, self.port), WorkerHTTPRequestHandler
        )
        self._thread = threading.Thread(
            target=self._server.serve_forever, daemon=True, name="WorkerInternalHTTP"
        )
        self._thread.start()
        logger.info(
            f"Worker internal HTTP server started on http://{self.host}:{self.port}",
            extra={"event": "worker_http_started"},
        )

    def stop(self) -> None:
        if self._server:
            self._server.shutdown()
            self._server.server_close()
            if self._thread:
                self._thread.join(timeout=2.0)
            logger.info(
                "Worker internal HTTP server stopped cleanly",
                extra={"event": "worker_http_stopped"},
            )