"""
Storage Service — Presigned URL Generation for Cloud Object Storage

Architecture Reference: insights/architecture_rule.md
    "Direct Upload (Pemisahan Beban): FastAPI tidak menerima file binary gambar.
     API hanya memberikan Presigned URL, lalu Flutter mengunggah foto langsung
     ke S3/MinIO."

This service generates short-lived presigned URLs so that the Flutter client
can upload photo evidence directly to cloud storage (S3 / GCS / MinIO)
without routing binary payloads through FastAPI.

Flow:
    1. Flutter requests  → POST /api/v1/photos/presigned-url
    2. This service generates a presigned PUT URL (expires in 5 min)
    3. Flutter uploads binary directly to the presigned URL
    4. Flutter confirms  → POST /api/v1/photos/confirm  (saves URL to DB)

Environment Variables:
    STORAGE_BACKEND   = "minio" | "s3" | "gcs"
    STORAGE_ENDPOINT  = http://localhost:9000       (MinIO only)
    STORAGE_BUCKET    = apl-gs-photos
    STORAGE_ACCESS_KEY = minioadmin
    STORAGE_SECRET_KEY = minioadmin
    STORAGE_REGION     = us-east-1                  (S3 only)
"""

import os
import uuid
import logging
from datetime import timedelta

logger = logging.getLogger(__name__)

# ── Configuration ────────────────────────────────────────────
STORAGE_BACKEND = os.getenv("STORAGE_BACKEND", "minio")
STORAGE_ENDPOINT = os.getenv("STORAGE_ENDPOINT", "http://localhost:9000")
STORAGE_BUCKET = os.getenv("STORAGE_BUCKET", "apl-gs-photos")
STORAGE_ACCESS_KEY = os.getenv("STORAGE_ACCESS_KEY", "minioadmin")
STORAGE_SECRET_KEY = os.getenv("STORAGE_SECRET_KEY", "minioadmin")
STORAGE_REGION = os.getenv("STORAGE_REGION", "us-east-1")

# Presigned URL expiry (5 minutes — matches architecture spec)
PRESIGN_EXPIRY = timedelta(minutes=5)


class StorageService:
    """
    Generates presigned URLs for direct client-to-storage uploads.

    Supports three backends:
        - MinIO (local development via docker-compose)
        - AWS S3 (production)
        - Google Cloud Storage (production alternative)
    """

    def __init__(self):
        self._client = None
        self._backend = STORAGE_BACKEND
        logger.info(f"StorageService initialized — backend: {self._backend}")

    # ── Lazy Client Init ─────────────────────────────────────
    def _get_s3_client(self):
        """Create boto3 S3 client (works for both S3 and MinIO)."""
        if self._client is None:
            try:
                import boto3
                from botocore.config import Config

                kwargs = {
                    "aws_access_key_id": STORAGE_ACCESS_KEY,
                    "aws_secret_access_key": STORAGE_SECRET_KEY,
                    "region_name": STORAGE_REGION,
                    "config": Config(signature_version="s3v4"),
                }

                # MinIO requires explicit endpoint_url
                if self._backend == "minio":
                    kwargs["endpoint_url"] = STORAGE_ENDPOINT

                self._client = boto3.client("s3", **kwargs)
                logger.info(f"S3 client created — endpoint: {kwargs.get('endpoint_url', 'AWS default')}")

            except ImportError:
                logger.error(
                    "boto3 not installed. Add 'boto3' to requirements.txt "
                    "to enable S3/MinIO storage."
                )
                raise

        return self._client

    # ── Generate Presigned URL ───────────────────────────────
    async def generate_presigned_upload_url(
        self,
        file_extension: str = "jpg",
        visit_id: str | None = None,
        assessment_id: str | None = None,
    ) -> dict:
        """
        Generate a presigned PUT URL for direct upload.

        Returns:
            {
                "upload_url": "https://...",
                "object_key": "visits/<visit_id>/<uuid>.jpg",
                "expires_in_seconds": 300,
                "storage_url": "https://<bucket>/<key>"
            }
        """
        # Build a meaningful object key
        prefix = "photos"
        if visit_id:
            prefix = f"visits/{visit_id}"
        if assessment_id:
            prefix = f"assessments/{assessment_id}"

        object_key = f"{prefix}/{uuid.uuid4().hex}.{file_extension}"

        if self._backend in ("s3", "minio"):
            client = self._get_s3_client()
            upload_url = client.generate_presigned_url(
                "put_object",
                Params={
                    "Bucket": STORAGE_BUCKET,
                    "Key": object_key,
                    "ContentType": f"image/{file_extension}",
                },
                ExpiresIn=int(PRESIGN_EXPIRY.total_seconds()),
            )

            # The permanent storage URL after upload completes
            if self._backend == "minio":
                storage_url = f"{STORAGE_ENDPOINT}/{STORAGE_BUCKET}/{object_key}"
            else:
                storage_url = f"https://{STORAGE_BUCKET}.s3.{STORAGE_REGION}.amazonaws.com/{object_key}"

        elif self._backend == "gcs":
            # Google Cloud Storage presigned URL
            # Requires: google-cloud-storage package
            try:
                from google.cloud import storage as gcs

                gcs_client = gcs.Client()
                bucket = gcs_client.bucket(STORAGE_BUCKET)
                blob = bucket.blob(object_key)

                upload_url = blob.generate_signed_url(
                    version="v4",
                    expiration=PRESIGN_EXPIRY,
                    method="PUT",
                    content_type=f"image/{file_extension}",
                )
                storage_url = f"https://storage.googleapis.com/{STORAGE_BUCKET}/{object_key}"

            except ImportError:
                logger.error(
                    "google-cloud-storage not installed. Add it to requirements.txt."
                )
                raise
        else:
            raise ValueError(f"Unsupported storage backend: {self._backend}")

        logger.info(f"Presigned URL generated — key: {object_key}")

        return {
            "upload_url": upload_url,
            "object_key": object_key,
            "expires_in_seconds": int(PRESIGN_EXPIRY.total_seconds()),
            "storage_url": storage_url,
        }

    # ── Ensure Bucket Exists (for local dev) ─────────────────
    async def ensure_bucket(self):
        """Create the storage bucket if it doesn't exist (MinIO/S3)."""
        if self._backend in ("s3", "minio"):
            client = self._get_s3_client()
            try:
                client.head_bucket(Bucket=STORAGE_BUCKET)
                logger.info(f"Bucket '{STORAGE_BUCKET}' exists")
            except Exception:
                client.create_bucket(Bucket=STORAGE_BUCKET)
                logger.info(f"Bucket '{STORAGE_BUCKET}' created")


# Singleton instance
storage_service = StorageService()