import json
import os
import shutil
from pathlib import Path
from threading import Thread
from typing import Any, Dict, List

import requests
from tqdm import tqdm


class BaseModelDownloader:
    """
    A utility for fast download of base model from S3 or any CDN served storage.
    Works by downloading multiple files in parallel and dividing large files
    into smaller chunks and combining them at the end.

    Currently it uses multithreading (not multiprocessing) assuming GIL won't
    interfere with network/disk IO.

    Created by: KP
    """

    def __init__(self, urls: List[str], url_paths: List[str], out_dir: Path):
        self.urls = urls
        self.url_paths = url_paths
        shutil.rmtree(out_dir, ignore_errors=True)
        out_dir.mkdir(parents=True, exist_ok=True)
        self.out_dir = out_dir

    def download(self):
        threads = []
        batch_urls = {}

        for url, url_path in zip(self.urls, self.url_paths):
            out_dir = self.out_dir / url_path
            self.out_dir.parent.mkdir(parents=True, exist_ok=True)
            if url.endswith(".bin"):
                if "unet/" in url_path:
                    thread = Thread(
                        target=self.__download_parallel, args=(url, out_dir, 6)
                    )
                    thread.start()
                    threads.append(thread)
                else:
                    thread = Thread(
                        target=self.__download_files, args=([url], [out_dir])
                    )
                    thread.start()
                    threads.append(thread)
                    pass
            else:
                batch_urls[url] = out_dir

        if batch_urls:
            thread = Thread(
                target=self.__download_files,
                args=(list(batch_urls.keys()), list(batch_urls.values())),
            )
            thread.start()
            threads.append(thread)
            pass

        for thread in threads:
            thread.join()

    def __download_parallel(self, url, output_filename, num_parts=4):
        response = requests.head(url)
        total_size = int(response.headers.get("content-length", 0))
        print("total_size", total_size)

        chunk_size = total_size // num_parts
        ranges = [
            (i * chunk_size, (i + 1) * chunk_size - 1) for i in range(num_parts - 1)
        ]
        ranges.append((ranges[-1][1] + 1, total_size))

        print(ranges)

        save_dir = Path.home() / ".cache" / "download_parts"
        os.makedirs(save_dir, exist_ok=True)

        threads = []
        for i, (start, end) in enumerate(ranges):
            thread = Thread(
                target=self.__download_part, args=(url, start, end, i, save_dir)
            )
            thread.start()
            threads.append(thread)

        for thread in threads:
            thread.join()

        self.__combine_parts(save_dir, output_filename, num_parts)
        os.rmdir(save_dir)

    def __combine_parts(self, save_dir, output_filename, num_parts):
        part_files = [os.path.join(save_dir, f"part_{i}.tmp") for i in range(num_parts)]

        output_filename.parent.mkdir(parents=True, exist_ok=True)
        with open(output_filename, "wb") as output_file:
            for part_file in part_files:
                print("combining: ", part_file)
                with open(part_file, "rb") as part:
                    output_file.write(part.read())

            out_file_size = output_file.tell()
            print("out_file_size", out_file_size)

        for part_file in part_files:
            os.remove(part_file)

    def __download_part(self, url, start_byte, end_byte, part_num, save_dir):
        headers = {"Range": f"bytes={start_byte}-{end_byte}"}
        response = requests.get(url, headers=headers, stream=True)

        part_filename = os.path.join(save_dir, f"part_{part_num}.tmp")
        print("Downloading part: ", url, part_filename, end_byte - start_byte)

        with open(part_filename, "wb") as part_file, tqdm(
            desc=str(part_filename),
            total=end_byte - start_byte,
            unit="B",
            unit_scale=True,
            unit_divisor=1024,
        ) as bar:
            for chunk in response.iter_content(chunk_size=8192):
                if chunk:
                    size = part_file.write(chunk)
                    bar.update(size)

        return part_filename

    def __download_files(self, urls, out_paths: List[Path]):
        for url, out_path in zip(urls, out_paths):
            out_path.parent.mkdir(parents=True, exist_ok=True)
            with requests.get(url, stream=True) as r:
                print("Downloading: ", url)
                total_size = int(r.headers.get("content-length", 0))
                chunk_size = 8192
                r.raise_for_status()
                with open(out_path, "wb") as f, tqdm(
                    desc=str(out_path),
                    total=total_size,
                    unit="B",
                    unit_scale=True,
                    unit_divisor=1024,
                ) as bar:
                    for data in r.iter_content(chunk_size=chunk_size):
                        size = f.write(data)
                        bar.update(size)