"""File storage utilities for persistence, retrieval, and checksum calculation."""

import hashlib
import uuid
from datetime import UTC, datetime
from pathlib import Path

from app.core.config import get_settings


settings = get_settings()


def ensure_storage() -> None:
    """Ensures required storage directories exist at service startup."""

    for relative in ["originals", "derived/previews", "tmp"]:
        (settings.storage_root / relative).mkdir(parents=True, exist_ok=True)


def compute_sha256(data: bytes) -> str:
    """Computes a SHA-256 hex digest for raw file bytes."""

    return hashlib.sha256(data).hexdigest()


def store_bytes(filename: str, data: bytes) -> str:
    """Stores file content under a unique path and returns its storage-relative location."""

    stamp = datetime.now(UTC).strftime("%Y/%m/%d")
    safe_ext = Path(filename).suffix.lower()
    target_dir = settings.storage_root / "originals" / stamp
    target_dir.mkdir(parents=True, exist_ok=True)
    target_name = f"{uuid.uuid4()}{safe_ext}"
    target_path = target_dir / target_name
    target_path.write_bytes(data)
    return str(target_path.relative_to(settings.storage_root))


def read_bytes(relative_path: str) -> bytes:
    """Reads and returns bytes from a storage-relative path."""

    return (settings.storage_root / relative_path).read_bytes()


def absolute_path(relative_path: str) -> Path:
    """Returns the absolute filesystem path for a storage-relative location."""

    return settings.storage_root / relative_path


def write_preview(document_id: str, data: bytes, suffix: str = ".jpg") -> str:
    """Writes preview bytes and returns the preview path relative to storage root."""

    target_dir = settings.storage_root / "derived" / "previews"
    target_dir.mkdir(parents=True, exist_ok=True)
    target_path = target_dir / f"{document_id}{suffix}"
    target_path.write_bytes(data)
    return str(target_path.relative_to(settings.storage_root))