"""
TG Storage API \u2014 Store & retrieve files via Telegram as a backend.

Endpoints:
  GET    /                        \u2014 Frontend UI
  POST   /upload                  \u2014 Upload a file (optional custom_path)
  GET    /cdn/<path>              \u2014 Public CDN URL \u2014 works with:
                                      /cdn/<file_id>
                                      /cdn/<custom_path>        e.g. /cdn/logo.png
                                      /cdn/<folder/name.ext>   e.g. /cdn/images/avatar.jpg
  GET    /file/<file_id>          \u2014 Download (auth required, forces attachment)
  GET    /files                   \u2014 List all stored files
  DELETE /file/<file_id>          \u2014 Delete a file record
  GET    /health                  \u2014 Health check
"""

import os
import re
import uuid
from dotenv import load_dotenv

load_dotenv()  # load .env before importing app so env vars are available

import logging
import mimetypes
import atexit
from datetime import datetime, timezone
from pathlib import Path
from typing import Optional

logger = logging.getLogger(__name__)

from flask import Flask, request, jsonify, Response, abort, send_file
from flask_cors import CORS

from db import (
    init_db, save_file_record,
    get_file_record, get_file_by_custom_path,
    list_file_records, delete_file_record, count_files,
)
from tg import upload_to_telegram, download_from_telegram, init_bot_pool, close_http

# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
#  App
# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
app = Flask(__name__)
CORS(app)

ADMIN_API_KEY = os.getenv("ADMIN_API_KEY", "changeme")
BASE_URL      = os.getenv("BASE_URL", "http://localhost:8082").rstrip("/")

_HERE         = Path(__file__).parent
FRONTEND_PATH = _HERE / "frontend.html"

# Allowed characters in a custom path segment
_CUSTOM_PATH_RE = re.compile(r'^[a-zA-Z0-9._\-/]+$')

# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
#  Startup / Shutdown
# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
_initialized   = False
_startup_error: Optional[str] = None   # FIX: track last startup failure message


def _startup():
    """
    FIX: Idempotent startup with proper error tracking.

    - If already initialized \u2192 return immediately (no-op).
    - If previously failed \u2192 retry (allows recovery when Supabase was
      temporarily unreachable, e.g. cold-start DNS not yet ready).
    - On failure \u2192 reset _initialized=False so next request retries,
      and store the error message for clean logging.
    - Raises RuntimeError so callers can return 503 instead of crashing.
    """
    global _initialized, _startup_error

    if _initialized:
        return

    _startup_error = None
    try:
        init_db()          # connect Supabase + verify table exists
        init_bot_pool()    # verify tokens.txt & build bot pool
        _initialized = True
        logger.info("Startup complete \u2014 Supabase + Telegram bot pool ready.")
    except Exception as exc:
        _initialized   = False          # allow retry on next request
        _startup_error = str(exc)
        logger.error(f"Startup failed: {exc}")
        raise RuntimeError(f"Service not ready: {exc}") from exc


atexit.register(close_http)  # drain httpx connection pool on exit


# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
#  Helpers
# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
def require_api_key():
    key = request.headers.get("X-API-Key", "")
    if key != ADMIN_API_KEY:
        abort(401, description="Invalid or missing API key")


def _sanitize_custom_path(raw: str) -> str:
    path = raw.strip().strip("/")
    if not path:
        abort(400, description="custom_path cannot be empty after stripping slashes.")
    if ".." in path:
        abort(400, description="custom_path must not contain '..'")
    if not _CUSTOM_PATH_RE.match(path):
        abort(400, description="custom_path may only contain letters, digits, hyphens, underscores, dots, and slashes.")
    return path


def _build_public_url(identifier: str) -> str:
    return f"{BASE_URL}/cdn/{identifier}"


def _make_stream_response(record: dict, disposition: str = "inline") -> Response:
    """Download from Telegram and return to client."""
    try:
        data: bytes = download_from_telegram(record["tg_message_id"], record["tg_file_id"])
    except Exception as exc:
        logger.exception("Telegram download error")
        abort(502, description=str(exc))

    return Response(
        data,
        mimetype=record["mime_type"],
        headers={
            "Content-Disposition": f'{disposition}; filename="{record["filename"]}"',
            "Content-Length":      str(len(data)),
            "Cache-Control":       "public, max-age=31536000, immutable",
        },
    )


# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
#  Routes
# \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500

@app.route("/")
def frontend():
    if FRONTEND_PATH.exists():
        return Response(FRONTEND_PATH.read_text(encoding="utf-8"), mimetype="text/html")
    return Response("<h2>frontend.html not found</h2>", status=404, mimetype="text/html")


@app.route("/health")
def health():
    # FIX: wrap _startup() so a Supabase/network error returns 503 instead of 500 crash
    try:
        _startup()
    except Exception as exc:
        return jsonify({
            "status":    "error",
            "error":     str(exc),
            "timestamp": datetime.now(timezone.utc).isoformat(),
            "base_url":  BASE_URL,
        }), 503

    try:
        total = count_files()
    except Exception as exc:
        logger.exception("count_files failed during health check")
        return jsonify({
            "status":    "degraded",
            "error":     str(exc),
            "timestamp": datetime.now(timezone.utc).isoformat(),
            "base_url":  BASE_URL,
        }), 503

    return jsonify({
        "status":      "ok",
        "timestamp":   datetime.now(timezone.utc).isoformat(),
        "total_files": total,
        "base_url":    BASE_URL,
    })


# \u2500\u2500 CDN \u2014 public, no auth \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
@app.route("/cdn/<path:path>")
def cdn_file(path: str):
    try:
        _startup()
    except Exception as exc:
        return jsonify({"detail": str(exc)}), 503

    # 1 \u2014 custom path lookup
    record = get_file_by_custom_path(path)

    # 2 \u2014 fall back to file_id lookup
    if not record:
        record = get_file_record(path)

    if not record:
        return jsonify({
            "detail": f"No file found for path '{path}'. "
                      f"Provide a valid file_id or a custom_path assigned at upload."
        }), 404

    return _make_stream_response(record)


# \u2500\u2500 Upload \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
@app.route("/upload", methods=["POST"])
def upload_file_route():
    try:
        _startup()
    except Exception as exc:
        return jsonify({"detail": str(exc)}), 503

    require_api_key()

    if "file" not in request.files:
        return jsonify({"detail": "No file provided."}), 400

    file = request.files["file"]
    content = file.read()
    if not content:
        return jsonify({"detail": "Empty file."}), 400

    filename  = file.filename or f"upload_{uuid.uuid4().hex}"
    mime_type = file.content_type or mimetypes.guess_type(filename)[0] or "application/octet-stream"
    size      = len(content)

    # Validate + normalise custom_path if provided
    clean_custom_path = None
    custom_path_raw = request.form.get("custom_path", "")
    if custom_path_raw and custom_path_raw.strip():
        clean_custom_path = _sanitize_custom_path(custom_path_raw)
        existing = get_file_by_custom_path(clean_custom_path)
        if existing:
            return jsonify({
                "detail": f"custom_path '{clean_custom_path}' is already taken by file_id={existing['file_id']}."
            }), 409

    # Upload bytes to Telegram
    try:
        tg_message_id, tg_file_id = upload_to_telegram(content, filename, mime_type)
    except Exception as exc:
        logger.exception("Telegram upload error")
        return jsonify({"detail": str(exc)}), 502

    # Build URLs
    file_id    = str(uuid.uuid4())
    cdn_key    = clean_custom_path if clean_custom_path else file_id
    public_url = _build_public_url(cdn_key)

    save_file_record(
        file_id=file_id,
        filename=filename,
        mime_type=mime_type,
        size=size,
        tg_message_id=tg_message_id,
        tg_file_id=tg_file_id,
        public_url=public_url,
        custom_path=clean_custom_path,
    )

    logger.info(f"Uploaded {filename!r} \u2192 {public_url}")

    return jsonify({
        "file_id":         file_id,
        "filename":        filename,
        "mime_type":       mime_type,
        "size_bytes":      size,
        "custom_path":     clean_custom_path,
        "public_url":      public_url,
        "cdn_url_by_id":   _build_public_url(file_id),
        "cdn_url_by_path": _build_public_url(clean_custom_path) if clean_custom_path else None,
        "uploaded_at":     datetime.now(timezone.utc).isoformat(),
    })


# \u2500\u2500 Authenticated download \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
@app.route("/file/<file_id>", methods=["GET"])
def download_file_route(file_id: str):
    try:
        _startup()
    except Exception as exc:
        return jsonify({"detail": str(exc)}), 503

    require_api_key()

    record = get_file_record(file_id)
    if not record:
        return jsonify({"detail": "File not found."}), 404

    try:
        data: bytes = download_from_telegram(record["tg_message_id"], record["tg_file_id"])
    except Exception as exc:
        logger.exception("Download error")
        return jsonify({"detail": str(exc)}), 502

    return Response(
        data,
        mimetype=record["mime_type"],
        headers={
            "Content-Disposition": f'attachment; filename="{record["filename"]}"',
            "Content-Length":      str(len(data)),
        },
    )


# \u2500\u2500 List \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
@app.route("/files")
def list_files_route():
    try:
        _startup()
    except Exception as exc:
        return jsonify({"detail": str(exc)}), 503

    require_api_key()

    limit  = request.args.get("limit", 50, type=int)
    offset = request.args.get("offset", 0, type=int)
    limit  = max(1, min(limit, 500))
    offset = max(0, offset)

    records = list_file_records(limit=limit, offset=offset)
    total   = count_files()
    return jsonify({"total": total, "limit": limit, "offset": offset, "files": records})


# \u2500\u2500 Delete \u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500\u2500
@app.route("/file/<file_id>", methods=["DELETE"])
def delete_file_route(file_id: str):
    try:
        _startup()
    except Exception as exc:
        return jsonify({"detail": str(exc)}), 503

    require_api_key()

    record = get_file_record(file_id)
    if not record:
        return jsonify({"detail": "File not found."}), 404
    delete_file_record(file_id)
    return jsonify({"deleted": True, "file_id": file_id})