#!/usr/bin/env python3

import argparse
import os
import sys
import hashlib
import shutil

import requests

parser = argparse.ArgumentParser(
    description="A Simple Git-Based Modpack Manager",
    formatter_class=argparse.RawDescriptionHelpFormatter,
    epilog='''\
Available commands:
    install          : Downloads mods listed in version.txt and populates the mods folder specified in pack-location.txt
    apply_updates    : Using the urls in mods.txt, repopulates version.txt to reflect the most recent mod versions
    check_updates    : Compares version.txt and mods.txt to see if any mods can be updated
''')

parser.add_argument('command',
    nargs='?',
    default='install',
    help="The action to perform (default: install)")
parser.add_argument('filename',
    nargs='?',
    default="mods.txt",
    help="Optional filename to specify latest mods (default: mods.txt)")
parser.add_argument('--version-file',
    type=str,
    default="version.txt",
    help="Optional custom version file to download mods from (default: version.txt)")
parser.add_argument('--pack-location',
    type=str,
    help="Optional custom modpack folder location (default: read from pack-location.txt)")

## loaded from version.txt
VERSION = 0

def read_file(fil):
    strings = []
    with open(fil) as f:
        for line in f:
            string = line.strip().split()
            if len(line) > 1 and line[0] != '#':
                # run strip on each element
                string = tuple(map(lambda x: x.strip(), string))
                strings.append(string)

    return strings

# Apply updates to the actual mod pack
def install(args):
    print("Updating pack with version " + str(VERSION) + "...")
    print()
    # (fname, checksum, url)
    mods = read_file(args.version_file)
    names = [mod[0] for mod in mods]

    for mod in mods:
        mod_path = os.path.join(args.pack_location, mod[0])
        if os.path.exists(mod_path) and os.path.isfile(mod_path) and \
        hashlib.sha1(open(mod_path, 'rb').read()).hexdigest() == mod[1]:
            print("Skipping {mod[0]}, already up to date".format(mod=mod))
        else:
            print('Installing {mod[0]} from {mod[2]}...'.format(mod=mod))
            download_obj = requests.get(mod[2], stream=True)
            with open(mod_path, "wb") as write_file:
                shutil.copyfileobj(download_obj.raw, write_file)
            print("Done!")

    print()
    print("Removing old mods...")
    
    for jar in os.listdir(args.pack_location):
        if jar not in names and os.path.splitext(jar)[1] == ".jar":
            os.remove(os.path.join(args.pack_location, jar))
            print("Removing '{jar}'".format(jar=jar))

    print()
    print("Finished installing mods!")


# Using the latest urls, update downloads.txt to match and have the correct sha1
def apply_updates(args):
    print("Populating version File...")
    mods = read_file(args.filename)
    print("Getting new versions of all mods...")
    with open(args.version_file, 'w') as f:
        f.write('# Format: <jarname> <hex digested sha1> <direct download url>\n')
        f.write("#VERSION " + str(VERSION + 1) + "\n")
        for mod in mods:
            print("Fetching {mod[0]}...".format(mod=mod))
            resp = requests.get(mod[1])
            hsh = hashlib.sha1(resp.content).hexdigest()
            f.write('{mod[0]} {hsh} {resp.url}\n'.format(mod=mod, hsh=hsh, resp=resp))
    print()
    print("Done!")
    print("Updates applied to {args.version_file}".format(args=args))
    print("New pack version is " + str(VERSION + 1))
    print("[!] No mods were installed. To update your mods folder, run 'update.py install'")


# Find if any updates are available
def check_updates(args):
    print("Checking for updates to version " + str(VERSION) + "...")
    latest = read_file(args.filename)
    old = read_file(args.version_file)
    old_urls = [mod[2] for mod in old]

    print("Checking updates...")
    for mod in latest:
        print("Checking for updates to {mod[0]}...".format(mod=mod), end="")
        sys.stdout.flush()  # takes care of line-buffered terminals
        resp = requests.get(mod[1])
        if resp.url in old_urls:
            print(" No updates")
        else:
            print(" Found update: {resp.url.split('/')[-1]}".format(resp=resp))
    
    print("Finished checking for updates!")

COMMAND_MAP = {
    'install': install,
    'apply_updates': apply_updates,
    'check_updates': check_updates,
}

if __name__ == "__main__":
    args = parser.parse_args()
    
    if not args.pack_location:
        # initialize from config
        with open("pack-location.txt", "r") as f:
            args.pack_location = f.read().strip()

    if not os.path.exists(args.version_file):
        print("Error: version file\"" + args.version_file + "\" does not exist.")
        parser.print_help()
        sys.exit(1)
    if not os.path.exists(args.pack_location):
        print("Error: mod folder \"" + args.pack_location + "\" does not exist.")
        parser.print_help()
        sys.exit(1)
    elif not os.path.isdir(args.pack_location):
        print("Error: mod folder \"" + args.pack_location + "\" is not actually a folder.")
        parser.print_help()
        sys.exit(1)
        
    if not (args.command in COMMAND_MAP):
        print("Error: command \"" + args.command + "\" does not exist")
        parser.print_help()
        sys.exit(1)
    
    # fetch version
    with open(args.version_file) as f:
        for line in f:
            if line.strip().split()[0] == "#VERSION":
                VERSION = int(line.strip().split()[1])
                break
    # run the command
    COMMAND_MAP[args.command](args)