update.py

#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p python3Packages.requests

import json
import requests
from pathlib import Path
from typing import Union, Dict


# These versions don't have servers
BLACKLIST = [
    "1.2.4",
    "1.2.3",
    "1.2.2",
    "1.2.1",
    "1.1",
    "1.0",
]


def parse_manifest() -> Dict[str, str]:
    """
    Fetches the version manifest from Mojang and processes it
    Returns its output as a dict of {id: url}
    """

    print("Fetching manifest")
    response = requests.get(
        "https://launchermeta.mojang.com/mc/game/version_manifest.json"
    )
    response.raise_for_status()

    return dict(
        map(
            lambda elem: (elem["id"], elem["url"]),
            filter(
                lambda elem: elem["type"] in ("release", "snapshot"),
                response.json()["versions"],
            ),
        )
    )


def parse_version(url) -> Union[Dict[str, Union[str, int]], None]:
    """
    Fetches the version JSON at the URl and processes it
    Returns a dict in the form:
    {
        "url": string,
        "sha1": string,
        "version": string,
        "javaVersion": int,
        "manifestUrl": string
    }
    """

    print(f"Fetching {url}")
    response = requests.get(url)
    response.raise_for_status()

    data = response.json()
    if "server" in data["downloads"]:
        return {
            "url": data["downloads"]["server"]["url"],
            "sha1": data["downloads"]["server"]["sha1"],
            "version": data["id"],
            "javaVersion": data.get("javaVersion", {"majorVersion": 8})["majorVersion"],
            "manifestUrl": url,
        }


def main(versions, lock_file):
    """
    Takes in a dict of the existing version lock, and the output file
    Fetches the version manifest and fetches any missing/changed versions
    Writes the new version lock to the output file
    """

    manifest = parse_manifest()

    try:
        for version, url in manifest.items():
            if (
                not (v := versions.get(version, None))
                or v.get("manifestUrl", None) != url
            ):  # Fetch if version isn't locked or if manifest url changes
                if version in BLACKLIST:
                    continue
                elif (parsed := parse_version(url)) is not None:
                    versions[version] = parsed
                else:
                    print(f"{version} has no server, add to blacklist")
    except KeyboardInterrupt:
        print("Cancelled fetching. Writing and exiting")

    json.dump(versions, lock_file, indent=2)
    lock_file.write("\n")


if __name__ == "__main__":
    lock_path = Path(__file__).parent / "versions.json"
    lock_path.touch()

    versions = (
        {} if lock_path.stat().st_size == 0 else json.loads(lock_path.read_text())
    )

    with lock_path.open("w") as lock_file:
        main(versions, lock_file)