"""
Storage abstraction for templates/documents.

MVP: Local filesystem implementation; S3-compatible interface ready.
"""
from __future__ import annotations

import os
import uuid
from typing import Optional

from app.config import settings


class StorageAdapter:
    """Abstract storage adapter."""

    def save_bytes(self, *, content: bytes, filename_hint: str, subdir: Optional[str] = None, content_type: Optional[str] = None) -> str:
        raise NotImplementedError

    def open_bytes(self, storage_path: str) -> bytes:
        raise NotImplementedError

    def delete(self, storage_path: str) -> bool:
        raise NotImplementedError

    def exists(self, storage_path: str) -> bool:
        raise NotImplementedError

    def public_url(self, storage_path: str) -> Optional[str]:
        return None


class LocalStorageAdapter(StorageAdapter):
    """Store bytes under settings.upload_dir using relative storage_path."""

    def __init__(self, base_dir: Optional[str] = None) -> None:
        self.base_dir = os.path.abspath(base_dir or settings.upload_dir)

    def _ensure_dir(self, directory: str) -> None:
        os.makedirs(directory, exist_ok=True)

    def save_bytes(self, *, content: bytes, filename_hint: str, subdir: Optional[str] = None, content_type: Optional[str] = None) -> str:
        safe_name = filename_hint.replace("/", "_").replace("\\", "_")
        if not os.path.splitext(safe_name)[1]:
            # Ensure a default extension when missing
            safe_name = f"{safe_name}.bin"
        unique = uuid.uuid4().hex
        directory = os.path.join(self.base_dir, subdir) if subdir else self.base_dir
        self._ensure_dir(directory)
        final_name = f"{unique}_{safe_name}"
        abs_path = os.path.join(directory, final_name)
        with open(abs_path, "wb") as f:
            f.write(content)
        # Return storage path relative to base_dir for portability
        rel_path = os.path.relpath(abs_path, self.base_dir)
        return rel_path

    def open_bytes(self, storage_path: str) -> bytes:
        abs_path = os.path.join(self.base_dir, storage_path)
        with open(abs_path, "rb") as f:
            return f.read()

    def delete(self, storage_path: str) -> bool:
        abs_path = os.path.join(self.base_dir, storage_path)
        try:
            os.remove(abs_path)
            return True
        except FileNotFoundError:
            return False

    def exists(self, storage_path: str) -> bool:
        abs_path = os.path.join(self.base_dir, storage_path)
        return os.path.exists(abs_path)

    def public_url(self, storage_path: str) -> Optional[str]:
        # Uploads are mounted at /uploads in FastAPI main
        # Map base_dir to /uploads; when base_dir is settings.upload_dir, this works.
        return f"/uploads/{storage_path}".replace("\\", "/")


def get_default_storage() -> StorageAdapter:
    # MVP: always local storage
    return LocalStorageAdapter()