from __future__ import annotations

import importlib
import os
import time
import uuid
from pathlib import Path

from django.core.cache import cache
from django.db import connection

BACKUP_MAX_AGE_SECONDS = 48 * 60 * 60


def check_db() -> dict[str, float | str]:
    started = time.perf_counter()
    try:
        with connection.cursor() as cursor:
            cursor.execute("SELECT 1")
    except Exception as exc:
        return {"status": "fail", "detail": str(exc)}
    return {"status": "ok", "latency_ms": (time.perf_counter() - started) * 1000}


def check_cache() -> dict[str, float | str]:
    cache_key = f"health:{uuid.uuid4().hex}"
    probe_value = uuid.uuid4().hex
    started = time.perf_counter()
    try:
        cache.set(cache_key, probe_value, timeout=5)
        cached_value = cache.get(cache_key)
        if cached_value != probe_value:
            return {"status": "fail", "detail": "Cache probe returned unexpected value"}
        cache.delete(cache_key)
    except Exception as exc:
        return {"status": "fail", "detail": str(exc)}
    return {"status": "ok", "latency_ms": (time.perf_counter() - started) * 1000}


def check_celery() -> dict[str, str]:
    broker_url = os.environ.get("CELERY_BROKER_URL")
    if not broker_url:
        return {"status": "ok", "detail": "Celery not configured: CELERY_BROKER_URL is unset"}

    try:
        kombu = importlib.import_module("kombu")
    except ImportError:
        return {"status": "ok", "detail": "Celery broker check skipped: kombu is not installed"}

    try:
        with kombu.Connection(broker_url, connect_timeout=3) as broker_connection:
            broker_connection.ensure_connection(max_retries=1)
    except Exception as exc:
        return {"status": "fail", "detail": str(exc)}
    return {"status": "ok"}


def check_backup() -> dict[str, str]:
    backup_status_file = os.environ.get("BACKUP_STATUS_FILE")
    if not backup_status_file:
        return {"status": "fail", "detail": "Backup monitoring not configured: BACKUP_STATUS_FILE is unset"}

    try:
        raw_timestamp = Path(backup_status_file).read_text(encoding="utf-8").strip()
    except FileNotFoundError:
        return {"status": "fail", "detail": f"Backup status file not found: {backup_status_file}"}
    except OSError as exc:
        return {"status": "fail", "detail": str(exc)}

    try:
        last_backup_at = float(raw_timestamp)
    except ValueError:
        return {"status": "fail", "detail": "Invalid backup status file"}

    age_seconds = time.time() - last_backup_at
    if age_seconds > BACKUP_MAX_AGE_SECONDS:
        age_hours = age_seconds / 3600
        return {"status": "fail", "detail": f"Last backup is {age_hours:.1f} hours old (> 48 h)"}

    return {"status": "ok"}