# -*- coding: utf-8 -*-

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_STORAGE = '/var/lib/lxc/storage'

class LXCPacker:
    def __init__(self, image):
        self.image = image
        self.tar_path = None
        self.xz_path = None

    def pack(self):
        # Prepare package file names
        self.tar_path = os.path.join(PKG_ROOT, '{}.tar'.format(self.image.upper_layer))
        self.xz_path = '{}.xz'.format(self.tar_path)
        if os.path.exists(self.xz_path):
            print('Package {} already exists, skipping packaging tasks'.format(self.xz_path))
            return
        os.makedirs(PKG_ROOT, 0o755, True)
        self.create_archive()
        self.register_package()
        self.sign_packages()

    def create_archive(self):
        # Create archive
        print('Archiving', self.image.upper_layer)
        subprocess.run(['tar', '--xattrs', '-cpf', self.tar_path, os.path.join(LXC_STORAGE, self.image.upper_layer)], 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(self.image.build_dir, s))]
        subprocess.run(['tar', '--transform', 's|^|srv/{}/|'.format(self.image.upper_layer), '-rpf', self.tar_path] + scripts, cwd=self.image.build_dir)
        # Compress the tarball with xz (LZMA2)
        print('Compressing', self.tar_path, '({:.2f} MB)'.format(os.path.getsize(self.tar_path)/1048576))
        subprocess.run(['xz', '-9', self.tar_path])
        print('Compressed ', self.xz_path, '({:.2f} MB)'.format(os.path.getsize(self.xz_path)/1048576))

    def register_package(self):
        # Prepare metadata
        meta = self.image.meta.copy()
        meta['lxc'] = {}
        for key in ('layers', 'mounts', 'env', 'cmd', 'cwd', 'uid', 'gid', 'halt'):
            value = getattr(self.image, key)
            if value:
                meta['lxc'][key] = value

        # 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[self.image.name] = meta
        packages[self.image.name]['size'] = os.path.getsize(self.xz_path)
        packages[self.image.name]['sha512'] = hash_file(self.xz_path)
        with open(packages_file, 'w') as f:
            json.dump(packages, f, sort_keys=True, indent=4)

    def sign_packages(self):
        # 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()