app/services/file_validator.py

from __future__ import annotations

import hashlib
import mimetypes
from pathlib import Path
from typing import Any
from uuid import uuid4

from fastapi import HTTPException, UploadFile
from PIL import Image, ImageOps

from app.config import settings


EXTENSION_TO_FORMAT = {
    "jpg": "JPEG",
    "jpeg": "JPEG",
    "png": "PNG",
    "webp": "WEBP",
}


def new_verification_id() -> str:
    return str(uuid4())


def validate_upload_metadata(file: UploadFile) -> str:
    if not file.filename:
        raise HTTPException(status_code=400, detail="Uploaded file must have a filename.")
    suffix = Path(file.filename).suffix.lower().lstrip(".")
    if suffix not in settings.allowed_extensions:
        raise HTTPException(status_code=415, detail=f"Unsupported image type: {suffix or 'unknown'}")
    return suffix


def save_upload(file: UploadFile, verification_id: str, suffix: str) -> Path:
    target = settings.uploads_dir / f"{verification_id}.{suffix}"
    size = 0
    with target.open("wb") as out:
        while chunk := file.file.read(1024 * 1024):
            size += len(chunk)
            if size > settings.max_upload_bytes:
                target.unlink(missing_ok=True)
                raise HTTPException(status_code=413, detail="Uploaded image exceeds size limit.")
            out.write(chunk)
    file.file.seek(0)
    return target


def sha256_file(path: Path) -> str:
    digest = hashlib.sha256()
    with path.open("rb") as f:
        for chunk in iter(lambda: f.read(1024 * 1024), b""):
            digest.update(chunk)
    return digest.hexdigest()


def validate_image_file(path: Path, original_filename: str, suffix: str) -> dict[str, Any]:
    try:
        with Image.open(path) as img:
            img.verify()
        with Image.open(path) as img:
            transposed = ImageOps.exif_transpose(img)
            width, height = transposed.size
            mode = transposed.mode
            fmt = img.format
    except Exception as exc:
        path.unlink(missing_ok=True)
        raise HTTPException(status_code=400, detail=f"Invalid or unreadable image: {exc}") from exc

    expected = EXTENSION_TO_FORMAT.get(suffix)
    if fmt not in set(EXTENSION_TO_FORMAT.values()) or (expected and fmt != expected):
        raise HTTPException(status_code=400, detail=f"Uploaded file content is not a valid {suffix} image.")

    mime_type = mimetypes.guess_type(original_filename)[0] or Image.MIME.get(fmt) or "application/octet-stream"
    return {
        "filename": original_filename,
        "sha256": sha256_file(path),
        "width": int(width),
        "height": int(height),
        "format": fmt,
        "mode": mode,
        "mime_type": mime_type,
        "file_size_bytes": path.stat().st_size,
    }