#!/usr/bin/env python3
#
# Simple script to download StackExchange archive XML files with posts (threaded version)
#
# Note: you probably want to download stackoverflow.com-Posts.7z manually, as it is 18GB
# and takes a long time to download. You can try using torrent:
#
# webtorrent https://archive.org/download/stackexchange/stackexchange_archive.torrent --select 658
#

import requests
import concurrent.futures
import os
from bs4 import BeautifulSoup as bs
import pandas as pd
import re

base_url = "https://ia600107.us.archive.org/view_archive.php?archive=/27/items/stackexchange/{0}&file=Posts.xml"
DOWNLOAD_DIR = "xml/"
NUM_PARALLEL = 20
RE_IGNORE = r"_meta|stackoverflow\.com\-"


def get_all_filenames():
    """
    Retrieve all urls from stackexchange archive.
    This needs quite some mangling because of special cases.
    """
    response = requests.get("https://archive.org/download/stackexchange")
    if response.ok:
        soup = bs(response.content, "html.parser")
        table = soup.find("table")
        link_tags = table.find_all("a")
        urls = {
            "stackoverflow": "https://archive.org/download/stackexchange/stackoverflow.com-Posts.7z"
        }
        for link in link_tags:
            url = link["href"]
            name = url.split(".stackexchange")[0].replace(".", "_").replace("-", "_")
            name = name.replace("_com_7z", "")
            if url.endswith("7z") and not re.search(RE_IGNORE, url):
                urls[name] = base_url.format(url)
        return urls


urls = get_all_filenames()


def download_url(dataset_name: str, url: str):
    if not os.path.exists(DOWNLOAD_DIR):
        os.mkdir(DOWNLOAD_DIR)
    cache_path = os.path.join(DOWNLOAD_DIR, dataset_name + ".xml")
    if os.path.exists(cache_path):
        print("Using cached: ", cache_path)
        return cache_path
    else:
        print("Downloading xml: ", dataset_name)
        response = requests.get(url)
        print("Finished downloading: ", dataset_name)
        with open(cache_path, "wb") as f:
            f.write(response.content)
        return cache_path


with concurrent.futures.ThreadPoolExecutor(max_workers=NUM_PARALLEL) as executor:
    futures = [
        executor.submit(download_url, dataset, url) for dataset, url in urls.items()
    ]

# Wait for all downloads to complete
concurrent.futures.wait(futures)

print("All downloads complete")