Script to download CurseForge modpacks

cfpackdl.py

from urllib import request
import io
import json
import os
import sys
import zipfile

def main():
	if len(sys.argv) < 2:
		print(f"Usage: {sys.argv[0]} <pack zip URL>")
		raise SystemExit(1)
	
	packZipUrl = sys.argv[1]
	if "curseforge.com/api/v1/mods" not in packZipUrl:
		print('Pack zip URL should look like "https://www.curseforge.com/api/v1/mods/..."')
		print('(copy the manual download link, labeled "try again")')
		raise SystemExit(1)
	
	os.makedirs("mods", exist_ok = True)
	print("Downloading pack zip")
	with fetch(packZipUrl) as rawZip:
		rawZip = io.BytesIO(rawZip.read())
		with zipfile.ZipFile(rawZip) as zip:
			print("Parsing manifest")
			manifest = None
			with zip.open("manifest.json", "r") as f:
				manifest = json.load(f)
			
			print("Downloading mods")
			for file in manifest["files"]:
				project = file["projectID"]
				file = file["fileID"]
				filename = downloadJar(project, file)
				print(f"=> downloaded {filename}")
			
			print("Unzipping config")
			configs = (f for f in zip.namelist() if f.startswith("overrides/"))
			for file in configs:
				path = file.split("/", 1)[1]
				os.makedirs(os.path.dirname(path), exist_ok = True)
				with zip.open(file, "r") as src:
					with open(path, "wb") as dst:
						pipeFile(src, dst)
				print(f"=> unzipped {path}")
			
			mcInfo = manifest["minecraft"]
			print(f"\nMinecraft version {mcInfo['version']}")
			print("Recommended modloader version(s):")
			for loader in mcInfo["modLoaders"]:
				print(f"* {loader['id']}")
			
			print("\nDone!")

headers = {
	"User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; rv:117.0) Gecko/20100101 Firefox/117.0"
}
def fetch(url):
	req = request.Request(url, headers = headers)
	return request.urlopen(req)

def downloadJar(project, file):
	url = f"https://www.curseforge.com/api/v1/mods/{project}/files/{file}/download"
	with fetch(url) as resp:
		(_, filename) = resp.url.rsplit("/", 1)
		with open(f"mods/{filename}", "wb") as f:
			pipeFile(resp, f)
		return filename

pipeBuf = bytearray(64 * 1024)
def pipeFile(src, dst):
	while True:
		len = src.readinto(pipeBuf)
		if len > 0:
			dst.write(pipeBuf[:len])
		else:
			break

if __name__ == "__main__":
	main()