from __future__ import annotations

from datetime import timedelta
from functools import lru_cache
from io import BytesIO
from collections.abc import Iterator
from typing import Any

from minio import Minio
from minio.error import S3Error

from app.core.config import get_settings


class ObjectStorageError(RuntimeError):
    pass


class MinioObjectStorage:
    def __init__(self) -> None:
        settings = get_settings()
        endpoint = settings.minio_endpoint.replace("http://", "").replace("https://", "").rstrip("/")
        self.client = Minio(endpoint, access_key=settings.minio_access_key, secret_key=settings.minio_secret_key, secure=settings.minio_secure)
        self.bucket = settings.minio_bucket

    def _ensure_enabled(self) -> None:
        if not get_settings().minio_enabled:
            raise ObjectStorageError("MinIO object storage is disabled")

    def ensure_bucket(self) -> None:
        self._ensure_enabled()
        try:
            if not self.client.bucket_exists(self.bucket):
                self.client.make_bucket(self.bucket)
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc

    def presigned_put(self, object_key: str, expires_seconds: int = 3600) -> str:
        self._ensure_enabled()
        self.ensure_bucket()
        return self.client.presigned_put_object(self.bucket, object_key, expires=timedelta(seconds=expires_seconds))

    def presigned_get(self, object_key: str, expires_seconds: int = 3600) -> str:
        self._ensure_enabled()
        self.ensure_bucket()
        return self.client.presigned_get_object(self.bucket, object_key, expires=timedelta(seconds=expires_seconds))

    def stat(self, object_key: str) -> dict[str, Any]:
        self._ensure_enabled()
        self.ensure_bucket()
        try:
            result = self.client.stat_object(self.bucket, object_key)
            return {"object_key": object_key, "byte_size": result.size, "etag": result.etag, "last_modified": result.last_modified.isoformat() if result.last_modified else None}
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc

    def get_bytes(self, object_key: str) -> bytes:
        """Read an object through the backend for small API responses and workers."""
        self._ensure_enabled()
        self.ensure_bucket()
        response = None
        try:
            response = self.client.get_object(self.bucket, object_key)
            return response.read()
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc
        finally:
            if response is not None:
                response.close()
                response.release_conn()

    def iter_bytes(self, object_key: str, chunk_size: int = 256 * 1024) -> Iterator[bytes]:
        """Stream an object without loading the complete file into memory."""
        self._ensure_enabled()
        self.ensure_bucket()
        response = None
        try:
            response = self.client.get_object(self.bucket, object_key)
            while True:
                chunk = response.read(chunk_size)
                if not chunk:
                    break
                yield chunk
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc
        finally:
            if response is not None:
                response.close()
                response.release_conn()

    def list_objects(self, prefix: str) -> list[dict[str, Any]]:
        self._ensure_enabled()
        self.ensure_bucket()
        try:
            return [
                {
                    "object_key": item.object_name,
                    "byte_size": item.size or 0,
                    "etag": item.etag,
                    "last_modified": item.last_modified.isoformat() if item.last_modified else None,
                }
                for item in self.client.list_objects(self.bucket, prefix=prefix, recursive=True)
            ]
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc

    def delete(self, object_key: str) -> None:
        self._ensure_enabled()
        self.ensure_bucket()
        try:
            self.client.remove_object(self.bucket, object_key)
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc

    def put_bytes(self, object_key: str, content: bytes, content_type: str = "application/octet-stream") -> dict[str, Any]:
        self._ensure_enabled()
        self.ensure_bucket()
        try:
            result = self.client.put_object(self.bucket, object_key, BytesIO(content), len(content), content_type=content_type)
            return {"bucket": self.bucket, "object_key": object_key, "etag": result.etag, "byte_size": len(content)}
        except S3Error as exc:
            raise ObjectStorageError(str(exc)) from exc


@lru_cache
def get_object_storage() -> MinioObjectStorage:
    return MinioObjectStorage()