import hashlib
import json
import os
import pathlib
import shutil
import subprocess
##
import psutil
import requests


class BaseUpdater(object):
    _tpl_dir = os.path.join(os.path.dirname(os.path.abspath(os.path.expanduser(__file__))), 'tpl')
    _tpl_file = None
    _date_fmt = '%a, %d %b %Y %H:%M:%S %z'

    def __init__(self,
                 dest_dir,
                 dest_file,
                 ver_file,
                 lock_path,
                 do_grub_cfg,
                 boot_dir,
                 grub_cfg,
                 hash_type
                 # check_gpg = True,  # TODO: GPG sig checking
                 ):
        self.dest_dir = os.path.abspath(os.path.expanduser(dest_dir))
        self.dest_file = dest_file
        self.ver_file = ver_file
        self.do_grub = bool(do_grub_cfg)
        self.boot_dir = os.path.abspath(os.path.expanduser(boot_dir))
        self.grub_cfg = os.path.abspath(os.path.expanduser(grub_cfg))
        self.lckfile = os.path.abspath(os.path.expanduser(lock_path))
        p_dest = pathlib.Path(self.dest_dir)
        p_boot = pathlib.Path(self.boot_dir)
        self.grub_iso_dir = '/{0}'.format(str(p_dest.relative_to(p_boot)))
        self.old_date = None
        self.old_ver = None
        self.old_hash = None
        self.new_date = None
        self.new_ver = None
        self.new_hash = None
        self.do_update = False
        self.force_update = False
        self.iso_url = None
        self.boot_uuid = None
        self.hash_type = hash_type
        self.dest_iso = os.path.join(self.dest_dir, self.dest_file)
        self.dest_ver = os.path.join(self.dest_dir, self.ver_file)

    def main(self):
        if self.getRunning():
            return(None)
        self.lock()
        if self.do_update or \
                self.force_update or not \
                all((self.old_date,
                     self.old_ver,
                     self.old_hash)):
            self.do_update = True
            self.download()
            if self.do_grub:
                self.grub()
        self.touchVer()
        self.unlock()
        return(None)

    def download(self):
        if self.getRunning():
            return(None)
        if not any((self.do_update, self.force_update)):
            return(None)
        if not self.iso_url:
            raise RuntimeError('iso_url attribute must be set first')
        req = requests.get(self.iso_url, stream = True, headers = {'User-Agent': 'curl/7.74.0'})
        if not req.ok:
            raise RuntimeError('Received non-200/30x {0} for {1}'.format(req.status_code, self.iso_url))
        os.makedirs(os.path.dirname(self.dest_iso), exist_ok = True)
        with req as uri:
            with open(self.dest_iso, 'wb') as fh:
                shutil.copyfileobj(uri.raw, fh)
        hasher = hashlib.new(self.hash_type)
        with open(self.dest_iso, 'rb') as fh:
            hasher.update(fh.read())
        realhash = hasher.hexdigest().lower()
        if realhash != self.new_hash:
            raise RuntimeError('Hash mismatch: {0} (LOCAL), {1} (REMOTE)'.format(realhash, self.new_hash))
        self.updateVer()
        return(None)

    def getCurVer(self):
        raise RuntimeError('BaseUpdater should be subclassed and its updateVer, getCurVer, and getNewVer methods '
                           'should be replaced.')

    def getNewVer(self):
        raise RuntimeError('BaseUpdater should be subclassed and its updateVer, getCurVer, and getNewVer methods '
                           'should be replaced.')

    def getRunning(self):
        if not os.path.isfile(self.lckfile):
            return(False)
        my_pid = os.getpid()
        with open(self.lckfile, 'r') as fh:
            pid = int(fh.read().strip())
        if not psutil.pid_exists(pid):
            os.remove(self.lckfile)
            return(False)
        if pid == my_pid:
            return(False)
        return(True)

    def getUUID(self):
        disk_cmd = subprocess.run(['findmnt',
                                   '-T', '/boot',
                                   '--json'],
                                  stdout = subprocess.PIPE,
                                  stderr = subprocess.PIPE)
        if (disk_cmd.returncode != 0) or disk_cmd.stderr.decode('utf-8').strip() != '':
            raise RuntimeError('Could not get disk UUID: {0}'.format(disk_cmd.stderr.decode('utf-8')))
        disk_dict = json.loads(disk_cmd.stdout.decode('utf-8'))
        disk_dev = disk_dict['filesystems'][0]['source']
        info_cmd = subprocess.run(['blkid',
                                   '-o', 'export',
                                   disk_dev],
                                  stdout = subprocess.PIPE,
                                  stderr = subprocess.PIPE)
        if (info_cmd.returncode != 0) or info_cmd.stderr.decode('utf-8').strip() != '':
            raise RuntimeError('Could not get disk UUID: {0}'.format(info_cmd.stderr.decode('utf-8')))
        info_dict = {i.split('=', 1)[0].lower():i.split('=', 1)[1]
                     for i in info_cmd.stdout.decode('utf-8').splitlines()}
        self.boot_uuid = info_dict.get('uuid')
        return(None)

    def grub(self):
        self.getUUID()
        import jinja2
        loader = jinja2.FileSystemLoader(searchpath = self._tpl_dir)
        tplenv = jinja2.Environment(loader = loader)
        tpl = tplenv.get_template(self._tpl_file)
        with open(self.grub_cfg, 'w') as fh:
            fh.write(tpl.render(iso_path = os.path.abspath(
                                    os.path.expanduser(
                                        os.path.join(self.grub_iso_dir,
                                                     self.dest_file))),
                                disk_uuid = self.boot_uuid))
        os.chmod(self.grub_cfg, 0o0755)
        cmd = subprocess.run(['grub-mkconfig',
                              '-o', '{0}/grub/grub.cfg'.format(self.boot_dir)],
                             stdout = subprocess.PIPE,
                             stderr = subprocess.PIPE)
        if cmd.returncode != 0:
            stderr = cmd.stderr.decode('utf-8')
            if stderr.strip() != '':
                print(stderr)
            raise RuntimeError('grub-mkconfig returned a non-zero exit status ({0})'.format(cmd.returncode))
        return(None)

    def lock(self):
        with open(self.lckfile, 'w') as fh:
            fh.write(str(os.getpid()))
        return(None)

    def touchVer(self):
        if self.getRunning():
            return(None)
        ver_path = pathlib.Path(self.dest_ver)
        ver_path.touch(exist_ok = True)
        return(None)

    def unlock(self):
        if os.path.isfile(self.lckfile):
            os.remove(self.lckfile)
        return(None)

    def updateVer(self):
        raise RuntimeError('BaseUpdater should be subclassed and its updateVer, getCurVer, and getNewVer methods '
                           'should be replaced.')