from abc import ABC, abstractmethod
from pathlib import Path

from app.core.config import get_settings

settings = get_settings()


class StorageBackend(ABC):
    @abstractmethod
    def save(self, key: str, data: bytes) -> str:
        raise NotImplementedError

    @abstractmethod
    def public_url(self, key: str) -> str:
        raise NotImplementedError


class LocalStorage(StorageBackend):
    def __init__(self, root: str) -> None:
        self.root = Path(root)
        self.root.mkdir(parents=True, exist_ok=True)

    def save(self, key: str, data: bytes) -> str:
        path = self.root / key.replace("\\", "/").lstrip("/")
        path.parent.mkdir(parents=True, exist_ok=True)
        path.write_bytes(data)
        return key.replace("\\", "/").lstrip("/")

    def public_url(self, key: str) -> str:
        normalized = key.replace("\\", "/").lstrip("/")
        return f"/media/{normalized}"


class S3Storage(StorageBackend):
    def __init__(self) -> None:
        import boto3

        if not settings.s3_bucket:
            raise RuntimeError("S3_BUCKET is required when STORAGE_BACKEND=s3")
        self.bucket = settings.s3_bucket
        self.client = boto3.client(
            "s3",
            region_name=settings.aws_region,
            aws_access_key_id=settings.aws_access_key_id,
            aws_secret_access_key=settings.aws_secret_access_key,
        )
        base = settings.s3_public_base_url
        self.public_base = (
            base.rstrip("/") if base else f"https://{self.bucket}.s3.{settings.aws_region}.amazonaws.com"
        )

    def save(self, key: str, data: bytes) -> str:
        normalized = key.replace("\\", "/").lstrip("/")
        self.client.put_object(Bucket=self.bucket, Key=normalized, Body=data)
        return normalized

    def public_url(self, key: str) -> str:
        normalized = key.replace("\\", "/").lstrip("/")
        return f"{self.public_base}/{normalized}"


_storage: StorageBackend | None = None


def get_storage() -> StorageBackend:
    global _storage
    if _storage is None:
        backend = settings.storage_backend.lower()
        if backend == "s3":
            _storage = S3Storage()
        else:
            _storage = LocalStorage(settings.upload_dir)
    return _storage