import contextlib
import os
import platform
import psutil
import shlex
import subprocess
import sys
import time
import yaml

from datetime import datetime
from glob import glob
from slugify import slugify


def term():
    """Get the Terminal reference to make output pretty

    Returns:
        (blessings.Terminal): Returns
        a `blessings <https://blessings.readthedocs.io/en/latest>`_ terminal
        instance. If running in windows and not cygwin it will return an
        `intercessions <https://pypi.org/project/intercessions>`_ terminal
        instance instead
    """
    if not hasattr(term, '_handle'):
        if sys.platform != "cygwin" and platform.system() == 'Windows':
            from intercessions import Terminal

        else:
            from blessings import Terminal

        term._handle = Terminal()

    return term._handle


@contextlib.contextmanager
def pushd(newDir):
    previousDir = os.getcwd()
    os.chdir(newDir)
    try:
        yield

    finally:
        os.chdir(previousDir)


class StateException(Exception):
    pass


class BackupException(Exception):
    pass


class Job(object):
    pool = []
    maxthreads = 4
    verbosity = 3
    logTransitions = False
    READY = 0
    QUEUED = 1
    STARTING = 2
    RUNNING = 3
    ENDING = 4
    FAILED = 5
    SUCCESSFUL = 6

    @staticmethod
    def initPool():
        if Job.pool:
            maxthreads = Job.maxthreads
            running = len(Job.running())
            if maxthreads > running:
                queued = Job.queued()
                if len(queued) < maxthreads - running:
                    maxthreads = len(queued)

                if maxthreads:
                    for i in range(0, maxthreads):
                        if len(queued) > i:
                            queued[i].start()

    @staticmethod
    def finished():
        return [x for x in Job.pool if x.state in (Job.FAILED, Job.SUCCESSFUL)]

    @staticmethod
    def pending():
        return [x for x in Job.pool
                if x.state not in (Job.FAILED, Job.SUCCESSFUL)]

    @staticmethod
    def running():
        return [x for x in Job.pool
                if x.state in (Job.STARTING, Job.RUNNING, Job.ENDING)]

    @staticmethod
    def queued():
        return [x for x in Job.pending() if x.state is Job.QUEUED]

    def __init__(self, backup, config):
        self._config = config
        self._backup = backup
        self._state = Job.READY

    def __str__(self):
        return 'Backup {0} Job #{1} ({2})'.format(
                self._backup.name, self.index, self.getState())

    @property
    def config(self):
        return self._config

    @property
    def state(self):
        if self._state is Job.READY and self in Job.pool:
            self.setState(Job.QUEUED)

        elif self._state in (Job.STARTING, Job.RUNNING, Job.ENDING):
            code = self._process.poll() or self._process.returncode
            if code is None and not psutil.pid_exists(self._process.pid):
                code = -1

            if code is not None:
                if code:
                    self.setState(Job.FAILED)
                    Job.initPool()

                elif self._state is Job.ENDING:
                    self.setState(Job.SUCCESSFUL)
                    Job.initPool()

                else:
                    self.start()

        return self._state

    def queue(self):
        if self.state is not Job.READY:
            raise StateException('{} not in state to queue'.format(self))

        if self in Job.pool:
            raise StateException('{} already in queued pool'.format(self))

        self.setState(Job.QUEUED)
        Job.pool.append(self)

    @property
    def args(self):
        if self._state is Job.STARTING:
            return shlex.split(self.pre)

        elif self._state is Job.RUNNING:
            if Backup.engine == "rdiff-backup":
                args = ['rdiff-backup', '-v{}'.format(Backup.verbosity)]
                if 'filters' in self.config:
                    for item in self.config['filters']:
                        if 'include' in item:
                            args += ['--include', item['include']]

                        elif 'exclude' in item:
                            args += ['--exclude', item['exclude']]

                        else:
                            raise BackupException(
                                '{0} has an invalid filter {1}'.format(self, item))

                return args + [self.fromPath, self.toPath]

            else:
                raise StateException(
                    'Invalid backup engine {}'.format(Backup.engine))

        elif self._state is Job.ENDING:
            return shlex.split(self.post)

        else:
            raise StateException('Invalid state {}'.format(self.getState()))

    @property
    def logfile(self):
        if not hasattr(self, '_logfile'):
            path = os.path.dirname(self.logpath)
            if not os.path.exists(path):
                os.makedirs(path, exist_ok=True)

            self._logfile = open(self.logpath, 'w' if Backup.truncateLogs else 'a')

        return self._logfile

    @property
    def logpath(self):
        if not hasattr(self, '_logpath'):
            self._logpath = os.path.join(os.path.dirname(
                self._backup.logpath), 'job{}.log'.format(self.index))

        return self._logpath

    @property
    def fromPath(self):
        if not hasattr(self, '_fromPath'):
            fromPath = self.config['from']
            if 'roots' in self._backup.config:
                roots = self._backup.config['roots']
                if 'from' in roots:
                    if '::' in roots['from']:
                        if roots['from'].endswith('::'):
                            fromPath = roots['from'] + fromPath

                        else:
                            fromPath = roots['from'] + os.sep + fromPath

                    else:
                        fromPath = os.path.join(roots['from'], fromPath)

            self._fromPath = fromPath

        return self._fromPath

    @property
    def toPath(self):
        if not hasattr(self, '_toPath'):
            toPath = self.config['to']
            if 'roots' in self._backup.config:
                roots = self._backup.config['roots']
                if 'to' in roots:
                    if '::' in roots['to']:
                        if roots['to'].endswith('::'):
                            toPath = roots['to'] + toPath

                        else:
                            toPath = roots['to'] + os.sep + toPath

                    else:
                        toPath = os.path.join(roots['to'], toPath)

            self._toPath = toPath

        return self._toPath

    @property
    def process(self):
        return self._process

    @property
    def index(self):
        if not hasattr(self, '_index'):
            self._index = self._backup.jobs.index(self)

        return self._index

    @property
    def pre(self):
        if not hasattr(self, '_pre'):
            self._pre = self.config['pre'] if 'pre' in self.config else None

        return self._pre

    @property
    def post(self):
        if not hasattr(self, '_post'):
            self._post = self.config['post'] if 'post' in self.config else None

        return self._post

    def log(self, text):
        text = '[{0}] (Backup {1} Job #{2}) {3}\n'.format(
                datetime.now().isoformat(), self._backup.name, self.index, text)
        print(text, end='')
        self._backup.logfile.write(text)
        self._backup.logfile.flush()

    def start(self):
        if self._state is self.QUEUED:
            self._backup.setStatus(Backup.RUNNING)
            self.setState(Job.STARTING)
            if self.pre is None:
                self.setState(Job.RUNNING)

        elif self._state is self.STARTING:
            self.setState(Job.RUNNING)

        elif self._state is self.RUNNING:
            self.setState(Job.ENDING)
            if self.post is None:
                self.setState(Job.SUCCESSFUL)
                Job.initPool()
                return

        else:
            raise StateException('Invalid state to start {}'.format(self))

        args = self.args
        self.logfile.write(
            "[{0}] {1} &\n".format(
                datetime.now().isoformat(),
                ' '.join([shlex.quote(x) for x in args])))
        self.logfile.flush()
        self._process = subprocess.Popen(
                args, stdout=self.logfile, stderr=subprocess.STDOUT,
                stdin=subprocess.DEVNULL, universal_newlines=True, bufsize=1)

    def setState(self, state):
        if self._state != state:
            self.log('{0} -> {1}'.format(
                    self.getState(self._state), self.getState(state)))
            self._state = state
            if state in (Job.SUCCESSFUL, Job.FAILED):
                self.logfile.close()

    def getState(self, state=None):
        return {
            Job.READY: 'ready',
            Job.QUEUED: 'queued',
            Job.STARTING: 'starting',
            Job.RUNNING: 'running',
            Job.ENDING: 'ending',
            Job.FAILED: 'failed',
            Job.SUCCESSFUL: 'successful',
        }[self.state if state is None else state]


class Backup(object):
    instances = {}
    _queue = []
    logTransitions = False
    truncateLogs = True
    engine = 'rdiff-backup'
    logdir = '/var/log/backup.d'
    BLOCKED = 0
    READY = 1
    QUEUED = 2
    RUNNING = 3
    FAILED = 4
    SUCCESSFUL = 5

    @staticmethod
    def _log():
        print('Backup status:')
        for backup in Backup.instances.values():
            print(' {}'.format(backup))
            for job in backup.pending:
                print('  {}'.format(job))

    @staticmethod
    def load(paths):
        for path in paths:
            Backup.get(path)

    @staticmethod
    def blocked():
        return [x for x in Backup.instances.values()
                if x.status is Backup.BLOCKED]

    @staticmethod
    def get(path):
        if path not in Backup.instances:
            Backup(sources()[path])

        return Backup.instances[path]

    @staticmethod
    def start():
        for backup in Backup.instances.values():
            backup.queue()

        Job.initPool()

    @staticmethod
    def wait(log=False):
        while Backup._queue:
            for backup in Backup._queue:
                if backup.status is Backup.BLOCKED:
                    for dependency in backup.blocking:
                        if dependency.status is Backup.READY:
                            dependency.queue()

            if log:
                Backup._log()

            time.sleep(1)

    def __init__(self, config):
        self._config = config
        self._path = self._config['path']
        self._name = slugify(self._path, max_length=255)
        self._logpath = os.path.realpath(os.path.join(
                Backup.logdir, self.name, 'backup.log'))
        self._status = Backup.READY
        if self.blocking:
            self.setStatus(Backup.BLOCKED)

        Backup.instances[self._path] = self

    def __str__(self):
        return 'Backup {0} ({1}, {2} jobs)'.format(
                self.name, self.getStatus(), len([x for x in self.jobs
                    if x.state not in (Job.FAILED, Job.SUCCESSFUL)]))

    @property
    def config(self):
        return self._config

    @property
    def name(self):
        return self._name

    @property
    def path(self):
        return self._path

    @property
    def logpath(self):
        return self._logpath

    @property
    def logfile(self):
        if not hasattr(self, '_logfile'):
            path = os.path.dirname(self.logpath)
            if not os.path.exists(path):
                os.makedirs(path, exist_ok=True)

            self._logfile = open(self.logpath, 'w' if Backup.truncateLogs else 'a')

        return self._logfile

    def log(self, text):
        text = '[{0}] (Backup {1}) {2}\n'.format(
            datetime.now().isoformat(), self.name, text)
        print(text, end='')
        self.logfile.write(text)
        self.logfile.flush()

    @property
    def status(self):
        if self.blocking:
            if [x for x in self.blocking if x.status is Backup.FAILED]:
                self.setStatus(Backup.FAILED)

            elif self._status is not Backup.BLOCKED:
                self.setStatus(Backup.BLOCKED)

        elif self._status is Backup.BLOCKED:
            if self not in Backup._queue:
                self.setStatus(Backup.READY)

            else:
                self.setStatus(Backup.QUEUED)
                for job in self.ready:
                    job.queue()

                Job.initPool()

        elif self._status is Backup.QUEUED and self not in Backup._queue:
            self.setStatus(Backup.READY)

        if self._status in (Backup.RUNNING, Backup.QUEUED) and not self.pending:
            self.setStatus(Backup.FAILED if self.failed else Backup.SUCCESSFUL)

        if self._status in (Backup.FAILED, Backup.SUCCESSFUL) \
                and self in Backup._queue:
            Backup._queue.remove(self)

        return self._status

    @property
    def blocking(self):
        return [x for x in self.depends
                if x.status is not Backup.SUCCESSFUL]

    @property
    def depends(self):
        if not hasattr(self, '_depends'):
            self._depends = []
            for path in self.config["depends"]:
                if path not in Backup.instances:
                    Backup(sources()[path])

                self._depends.append(Backup.instances[path])

        return self._depends

    @property
    def jobs(self):
        if not hasattr(self, '_jobs'):
            self._jobs = []
            if 'jobs' in self.config:
                for job in self.config['jobs']:
                    self._jobs.append(Job(self, job))

        return self._jobs

    @property
    def pending(self):
        return [x for x in self.jobs if x.state not in (Job.FAILED, Job.SUCCESSFUL)]

    @property
    def ready(self):
        return [x for x in self.jobs if x.state is Job.READY]

    @property
    def failed(self):
        return [x for x in self.jobs if x.state is Job.FAILED]

    def setStatus(self, status):
        if self._status != status:
            self.log('{0} -> {1}'.format(
                self.getStatus(self._status), self.getStatus(status)))
            self._status = status
            if status in (Backup.SUCCESSFUL, Backup.FAILED):
                self.logfile.close()

    def getStatus(self, status=None):
        return {
            Backup.BLOCKED: 'blocked',
            Backup.READY: 'ready',
            Backup.QUEUED: 'queued',
            Backup.RUNNING: 'running',
            Backup.FAILED: 'failed',
            Backup.SUCCESSFUL: 'successful'
        }[self.status if status is None else status]

    def queue(self):
        if self in Backup._queue:
            raise StateException('Backup already queued')

        Backup._queue.append(self)
        self.setStatus(Backup.QUEUED)
        if self.status is not Backup.BLOCKED:
            for job in self.ready:
                job.queue()

            Job.initPool()


def config():
    if hasattr(config, '_handle'):
        return config._handle

    with pushd(config._root):
        with open("backup.yml") as f:
            config._handle = yaml.load(f, Loader=yaml.SafeLoader)

    return config._handle


def sources():
    if hasattr(sources, '_handle'):
        return sources._handle

    sources._handle = {}
    with pushd(config._root):
        for source in config()['sources']:
            source = os.path.realpath(source)
            for path in glob('{}/*.yml'.format(source)) + \
                    glob('{}/*.yaml'.format(source)):
                path = os.path.realpath(path)
                with pushd(os.path.dirname(path)), open(path) as f:
                    data = yaml.load(f, Loader=yaml.SafeLoader)
                    if "active" in data and data["active"]:
                        data['path'] = path
                        if "depends" not in data:
                            data["depends"] = []

                        for i in range(0, len(data["depends"])):
                            data["depends"][i] = os.path.realpath(
                                    '{}.yml'.format(data["depends"][i]))

                        sources._handle[path] = data

    return sources._handle


def main(args):
    try:
        config._root = args[0] if len(args) else '/etc/backup.d'
        if not os.path.exists(config._root):
            raise BackupException(
                'Configuration files missing from {}'.format(config._root))

        if 'engine' in config():
            engine = config()["engine"]
            if engine not in ("rdiff-backup"):
                raise BackupException('Unknown backup engine: {}'.format(engine))

            Backup.engine = engine

        if 'logdir' in config():
            logdir = config()['logdir']
            os.makedirs(logdir, exist_ok=True)
            if not os.path.exists(logdir):
                raise BackupException(
                    'Unable to create logging directory: {}'.format(logdir))

            Backup.logdir = logdir

        if 'maxthreads' in config():
            Job.maxthreads = config()['maxthreads']

        if 'verbosity' in config():
            Backup.verbosity = config()['verbosity']

        Backup.logTransitions = Job.logTransitions = True
        Backup.truncateLogs = "truncateLogs" in config() and config["truncateLogs"]
        Backup.load(sources().keys())
        Backup.start()
        Backup.wait()
    except BackupException as ex:
        print(ex)
        sys.exit(1)

    except Exception:
        from traceback import format_exc
        msg = "Error encountered:\n" + format_exc().strip()
        print(msg)
        sys.exit(1)


if __name__ == '__main__':
    main(sys.argv[1:])