"""Functions dealing with chunking of files."""
from pathlib import Path
from typing import Iterator

from flask import current_app as app
from werkzeug.utils import secure_filename


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 chunk_name(uploadfilename: str, chunkno: int) -> str:
    """Generate chunk name from original filename and chunk number"""
    if uploadfilename == "":
        raise ValueError("Name cannot be empty!")
    if chunkno < 1:
        raise ValueError("Chunk number must be greater than zero")
    return f"{secure_filename(uploadfilename)}_part_{chunkno:05d}"


def chunks_directory(uniqueidentifier: str) -> Path:
    """Compute the directory where chunks are temporarily stored."""
    if uniqueidentifier == "":
        raise ValueError("Unique identifier cannot be empty!")
    return Path(app.config["UPLOAD_FOLDER"], f"tempdir_{uniqueidentifier}")