from __future__ import annotations

from dataclasses import dataclass
from pathlib import Path
from typing import BinaryIO


@dataclass(frozen=True)
class LocalConfig:
    root_dir: Path


class LocalStorageBackend:
    def __init__(self, cfg: LocalConfig) -> None:
        self._cfg = cfg
        self._cfg.root_dir.mkdir(parents=True, exist_ok=True)

    def _full_path(self, key: str) -> Path:
        return (self._cfg.root_dir / key).resolve()

    def upload_fileobj(
        self, key: str, fileobj: BinaryIO, *, content_type: str | None
    ) -> None:
        # content_type is unused for filesystem backend.
        _ = content_type

        full_path = self._full_path(key)
        full_path.parent.mkdir(parents=True, exist_ok=True)

        with open(full_path, "wb") as out:
            while True:
                chunk = fileobj.read(1024 * 1024)
                if not chunk:
                    break
                out.write(chunk)

    def download_fileobj(self, key: str, fileobj: BinaryIO) -> None:
        full_path = self._full_path(key)
        with open(full_path, "rb") as src:
            while True:
                chunk = src.read(1024 * 1024)
                if not chunk:
                    break
                fileobj.write(chunk)

    def exists(self, key: str) -> bool:
        return self._full_path(key).exists()

    def size(self, key: str) -> int:
        return self._full_path(key).stat().st_size

    def delete(self, key: str) -> None:
        path = self._full_path(key)
        if path.exists():
            path.unlink()

    def read(self, key: str) -> bytes:
        return self._full_path(key).read_bytes()

    def generate_url(self, key: str) -> str:
        # Served by cpv3 via /api/files/local/{path}
        return f"/api/files/local/{key}"