first commit

backend/app/utils/storage.py

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+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