from __future__ import annotations

import json
import os
import sys
from http import HTTPStatus
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer

from packages.hub_observability import build_telemetry, trace_from_headers, valid_trace_id
from packages.hub_runtime.secret_files import SecretFileError, validate_required_secret_paths
from services.observability.health import DependencyHealth, aggregate_health


def _validate_startup() -> None:
    try:
        validate_required_secret_paths(os.environ.get("REQUIRED_SECRET_FILES", ""))
    except (SecretFileError, ValueError):
        sys.stderr.write("required runtime secret validation failed\n")
        raise SystemExit(78) from None


_validate_startup()

_telemetry = build_telemetry(os.environ.get("SERVICE_NAME", "unknown"))


def _trace_id(handler: BaseHTTPRequestHandler) -> str:
    candidate = handler.headers.get("X-Trace-Id", "")
    if valid_trace_id(candidate):
        return candidate.lower()
    return trace_from_headers({"traceparent": handler.headers.get("traceparent", "")}).trace_id


def _dependencies() -> list[DependencyHealth]:
    raw = os.environ.get("DEPENDENCY_HEALTH_JSON", "")
    if not raw:
        return [DependencyHealth(os.environ.get("SERVICE_NAME", "unknown"), "healthy")]
    try:
        document = json.loads(raw)
    except ValueError:
        return [
            DependencyHealth(
                "configuration", "unhealthy", detail="invalid dependency health configuration"
            )
        ]
    if not isinstance(document, dict):
        return [
            DependencyHealth(
                "configuration", "unhealthy", detail="dependency health must be an object"
            )
        ]
    values = []
    for name, value in document.items():
        if not isinstance(value, dict):
            continue
        values.append(
            DependencyHealth(
                str(name)[:64],
                str(value.get("status", "unknown")),
                bool(value.get("required", True)),
                bool(value.get("authoritative", True)),
                str(value.get("detail", "")),
            )
        )
    return values or [
        DependencyHealth("configuration", "unhealthy", detail="no dependencies configured")
    ]


class HealthHandler(BaseHTTPRequestHandler):
    server_version = "ITWorxHealth/0.2"

    def do_GET(self) -> None:  # noqa: N802
        trace_id = _trace_id(self)
        if self.path == "/metrics":
            body = _telemetry.metrics.render_prometheus().encode("utf-8")
            self._write(HTTPStatus.OK, body, "text/plain; version=0.0.4", trace_id)
            return
        if self.path == "/health/aggregate":
            aggregate = aggregate_health(_dependencies())
            status = (
                HTTPStatus.OK if aggregate.status != "unhealthy" else HTTPStatus.SERVICE_UNAVAILABLE
            )
            self._write_json(
                status,
                aggregate.payload(
                    service=os.environ.get("SERVICE_NAME", "unknown"), trace_id=trace_id
                ),
                trace_id,
            )
            return
        if self.path not in {"/health", "/healthz", "/ready"}:
            self.send_error(HTTPStatus.NOT_FOUND)
            return
        _telemetry.metrics.inc("itworx_health_requests_total", labels={"path": self.path})
        _telemetry.logger.emit("HEALTH_REQUEST", trace_id, fields={"path": self.path})
        self._write_json(
            HTTPStatus.OK,
            {
                "status": "ok",
                "service": os.environ.get("SERVICE_NAME", "unknown"),
                "traceId": trace_id,
            },
            trace_id,
        )

    def _write_json(self, status: HTTPStatus, payload: dict[str, object], trace_id: str) -> None:
        self._write(
            status,
            json.dumps(payload, separators=(",", ":")).encode("utf-8"),
            "application/json",
            trace_id,
        )

    def _write(self, status: HTTPStatus, body: bytes, content_type: str, trace_id: str) -> None:
        self.send_response(status)
        self.send_header("Content-Type", content_type)
        self.send_header("Content-Length", str(len(body)))
        self.send_header("X-Trace-Id", trace_id)
        self.end_headers()
        if body:
            self.wfile.write(body)

    def log_message(self, _format: str, *_args: object) -> None:
        return


if __name__ == "__main__":
    ThreadingHTTPServer(("0.0.0.0", 8080), HealthHandler).serve_forever()  # noqa: S104