"""Utilities to deal with uploaded files."""
import hashlib
from pathlib import Path
from typing import Iterator
from datetime import datetime

from flask import current_app

from werkzeug.utils import secure_filename
from werkzeug.datastructures import FileStorage

def save_file(fileobj: FileStorage, upload_dir: Path) -> Path:
    """Save the uploaded file and return the path."""
    assert bool(fileobj), "Invalid file object!"
    hashed_name = hashlib.sha512(
        f"{fileobj.filename}::{datetime.now().isoformat()}".encode("utf8")
    ).hexdigest()
    filename = Path(secure_filename(hashed_name)) # type: ignore[arg-type]
    if not upload_dir.exists():
        upload_dir.mkdir()

    filepath = Path(upload_dir, filename)
    fileobj.save(filepath)
    return filepath


def fullpath(filename: str):
    """Get a file's full path. This makes use of `flask.current_app`."""
    return Path(current_app.config["UPLOAD_FOLDER"], filename).absolute()


def chunked_binary_read(filepath: Path, chunksize: int = 2048) -> Iterator:
    """Read a file in binary mode in chunks."""
    with open(filepath, "rb") as inputfile:
        while True:
            data = inputfile.read(chunksize)
            if data != b"":
                yield data
                continue
            break


def sha256_digest_over_file(filepath: Path) -> str:
    """Compute the sha256 digest over a file's contents."""
    filehash = hashlib.sha256()
    for chunk in chunked_binary_read(filepath):
        filehash.update(chunk)

    return filehash.hexdigest()