#!/usr/bin/python3

import hashlib
import json
import os
import subprocess
import sys

from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.serialization import load_pem_private_key

PKG_ROOT = '/srv/build/lxc'
PRIVATE_KEY = '/srv/build/packages.key'
LXC_ROOT = '/var/lib/lxc'

def pack(path):
    # Determine correct metadata file and package name
    path = os.path.realpath(path)
    if os.path.isdir(path):
        meta_dir = path
        meta_file = os.path.join(meta_dir, 'meta')
    else:
        meta_dir = os.path.dirname(path)
        meta_file = path
    pkg_name = os.path.basename(meta_dir)

    # Load metadata
    with open(meta_file) as f:
        meta = json.load(f)

    # Prepare package file names
    os.makedirs(PKG_ROOT, 0o755, True)
    tar_path = os.path.join(PKG_ROOT, '{}_{}-{}.tar'.format(pkg_name, meta['version'], meta['release']))
    xz_path = '{}.xz'.format(tar_path)

    # Remove old package
    if os.path.exists(tar_path):
        os.unlink(tar_path)
    if os.path.exists(xz_path):
        os.unlink(xz_path)

    # Create archive
    print('Archiving', meta['lxcpath'])
    subprocess.run(['tar', '--xattrs', '-cpf', tar_path, os.path.join(LXC_ROOT, meta['lxcpath'])], cwd='/')
    # Add install/upgrade/uninstall scripts
    scripts = ('install', 'install.sh', 'upgrade', 'upgrade.sh', 'uninstall', 'uninstall.sh')
    scripts = [s for s in scripts if os.path.exists(os.path.join(meta_dir, s))]
    subprocess.run(['tar', '--transform', 's|^|srv/{}/|'.format(pkg_name), '-rpf', tar_path] + scripts, cwd=meta_dir)
    # Compress the tarball with xz (LZMA2)
    print('Compressing', tar_path, '({:.2f} MB)'.format(os.path.getsize(tar_path)/1048576))
    subprocess.run(['xz', '-9', tar_path])
    print('Compressed ', xz_path, '({:.2f} MB)'.format(os.path.getsize(xz_path)/1048576))

    # Register package
    print('Registering package')
    packages = {}
    packages_file = os.path.join(PKG_ROOT, 'packages')
    if os.path.exists(packages_file):
        with open(packages_file, 'r') as f:
            packages = json.load(f)
    packages[pkg_name] = meta
    packages[pkg_name]['size'] = os.path.getsize(xz_path)
    packages[pkg_name]['sha512'] = hash_file(xz_path)
    with open(packages_file, 'w') as f:
        json.dump(packages, f, sort_keys=True, indent=4)

    # Sign packages file
    print('Signing packages')
    with open(PRIVATE_KEY, 'rb') as f:
        priv_key = load_pem_private_key(f.read(), None, default_backend())
    with open(os.path.join(PKG_ROOT, 'packages'), 'rb') as f:
        data = f.read()
    with open(os.path.join(PKG_ROOT, 'packages.sig'), 'wb') as f:
        f.write(priv_key.sign(data, ec.ECDSA(hashes.SHA512())))

def hash_file(file_path):
    sha512 = hashlib.sha512()
    with open(file_path, 'rb') as f:
        while True:
            data = f.read(65536)
            if not data:
                break
            sha512.update(data)
    return sha512.hexdigest()

if __name__ == '__main__':
    if len(sys.argv) != 2 or sys.argv[1] in ('-h', '--help'):
        print('Usage: lxc-pack <buildpath>\n  where the buildpath can be either specific meta file or a directory containing one')
    else:
        pack(sys.argv[1])