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

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
    READY = 0
    ACTIVE = 1
    RUNNING = 2
    FAILED = 3
    SUCCESSFUL = 4

    @staticmethod
    def initPool():
        if Job.pool:
            maxthreads = Job.maxthreads
            if len(Job.pool) < maxthreads:
                maxthreads = len(Job.pool)

            for i in range(0, maxthreads):
                Job.pool.pop(0).start()

    @staticmethod
    def finished():
        return not [x.state for x in Job.pool]

    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._backup.jobs.index(self), {
                    Job.READY: 'ready',
                    Job.ACTIVE: 'active',
                    Job.RUNNING: 'running',
                    Job.FAILED: 'failed',
                    Job.SUCCESSFUL: 'successful',
                }[self.state])

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

    @property
    def state(self):
        if self._state is Job.RUNNING:
            code = self._process.poll()
            if code is not None:
                self._state = Job.FAILED if code else Job.SUCCESSFUL
                Job.initPool()

        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._state = Job.ACTIVE
        Job.pool.append(self)

    @property
    def args(self):
        return Backup.args + []

    @property
    def logfile(self):
        return self._backup.logfile

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

    def start(self):
        if self.state is not Job.ACTIVE:
            raise StateException('Invalid state to start {}'.format(self))

        self._process = subprocess.Popen(
                self.args, stdout=self.logfile, stderr=self.logfile,
                stdin=subprocess.DEVNULL, universal_newlines=True)
        self._state = Job.RUNNING
        self._backup._state = Backup.RUNNING


class Backup(object):
    instances = {}
    _queue = []
    args = ['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 = os.path.basename(self._path)
        self._logpath = os.path.realpath(os.path.join(
            Backup.logdir, '{}.log'.format(slugify(self._path))))
        self._status = Backup.BLOCKED if self.blocking else Backup.READY
        Backup.instances[self._path] = self

    def __str__(self):
        return 'Backup {0} ({1}, {2} jobs)'.format(
                self.name, {
                    Backup.BLOCKED: 'blocked',
                    Backup.READY: 'ready',
                    Backup.QUEUED: 'queued',
                    Backup.RUNNING: 'running',
                    Backup.FAILED: 'failed',
                    Backup.SUCCESSFUL: 'successful'
                }[self.status], 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'):
            self._logfile = open(self.logpath, 'w')

        return self._logfile

    def log(self, text):
        self._logfile.write(text)

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

            elif self._status is not Backup.BLOCKED:
                self._status = Backup.BLOCKED

        elif self._status is Backup.BLOCKED:
            if self not in Backup._queue:
                self._status = Backup.READY

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

        elif self._status is Backup.QUEUED and self not in Backup._queue:
            self._status = Backup.READY

        if self._status in (Backup.RUNNING, Backup.QUEUED) and not self.pending:
            self._status = 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 = []
            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, state):
        if state in (None, False, True):
            self._status = state

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

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


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

    with pushd('etc/backup.d'):
        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('etc/backup.d'):
        for source in config()['sources']:
            source = os.path.realpath(source)
            for path in glob('{}/*.yml'.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):
    if 'engine' in config():
        engine = config()["engine"]
        if engine not in ("rdiff-backup"):
            raise BackupException('Unknown backup engine: {}'.format(engine))

        Backup.args = [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']

    Backup.load(sources().keys())
    Backup._log()
    Backup.start()
    Backup._log()
    Backup.wait(True)


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

    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)