# most of the code here comes from https://github.com/dbader/schedule

from .job import ALIASES, Job
import logging
import time

logger = logging.getLogger('schedule')


def std_launch_func(cmd_splitted):
    """
    Default way of executing commands is to invoke subprocess.run()
    """
    def f():
        import subprocess
        subprocess.run(cmd_splitted)
        # not returning anything here
    return f


class Scheduler(object):
    """
    Objects instantiated by the :class:`Scheduler <Scheduler>` are
    factories to create jobs, keep record of scheduled jobs and
    handle their execution.
    """
    def __init__(self):
        self.delay = 60         # in seconds
        self.jobs = []

    def run_pending(self):
        """
        Run all jobs that are scheduled to run.
        Please note that it is *intended behavior that run_pending()
        does not run missed jobs*. For example, if you've registered a job
        that should run every minute and you only call run_pending()
        in one hour increments then your job won't be run 60 times in
        between but only once.
        """
        runnable_jobs = (job for job in self.jobs if job.should_run)
        for job in runnable_jobs:
            self._run_job(job)

    def run_all(self, delay_seconds=0):
        """
        Run all jobs regardless if they are scheduled to run or not.
        A delay of `delay` seconds is added between each job. This helps
        distribute system load generated by the jobs more evenly
        over time.
        :param delay_seconds: A delay added between every executed job
        """
        logger.info('Running *all* %i jobs with %is delay inbetween',
                    len(self.jobs), delay_seconds)
        for job in self.jobs[:]:
            self._run_job(job)
            time.sleep(delay_seconds)

    def clear(self):
        """
        Deletes scheduled jobs
        """
        del self.jobs[:]

    def cancel_job(self, job):
        """
        Delete a scheduled job.
        If the job is running it won't be stopped.
        :param job: The job to be unscheduled
        """
        try:
            self.jobs.remove(job)
        except ValueError:
            pass

    def cron(self, crontab, job_func):
        """
        Schedule a new periodic job.
        :param crontab: A crontab-like time specification
        :param job_func_or_command: the function to be executed
        :return: A configured :class:`Job <Job>`
        """
        job = Job(crontab, job_func)
        return job

    def _run_job(self, job):
        ret = job.job_func()
        return ret

    def add_job(self, crontab, job_func):
        """
        Create a job and add it to this Scheduler
        :param crontab:
            string containing crontab pattern
            Its tokens may be either: 1 (if alias), 5 (without year token),
            6 (with year token)
        :param job_func:
            the job 0-ary function to run
        :return: a Job
        """
        job = Job(crontab, job_func, self)
        self.jobs.append(job)
        return job

    def _load_crontab_line(self, rownum, crontab_line, job_func_func=std_launch_func):
        """
        create a Job from a single crontab entry, and add it to this Scheduler
        :param crontab_line:
            a line from crontab
            PRE: not empty and it not a comment
        :param job_func_func:
            function to be executed, @see load_crontab_file
        :return: a Job
        """
        pieces = crontab_line.split()

        # is pattern using aliases?
        if pieces[0] in ALIASES.keys():
            try:
                # pattern using alias
                job = self.add_job(pieces[0:1], job_func_func(pieces[1:]))
                return job
            except ValueError:
                # shouldn't happen
                print("Error at line %d, cannot parse pattern" % rownum)
                return None
        elif len(pieces) < 6:
            print("Error at line %d, expected at least 6 tokens" % rownum)
            return None
            if len(pieces) >= 7:
                try:
                    # pattern including year
                    job = self.add_job(" ".join(pieces[0:6]), job_func_func(
                                                                pieces[6:]))
                    return job
                except ValueError:
                    pass
            try:
                # pattern not including  year
                job = self.add_job(" ".join(pieces[0:5]), job_func_func(
                                                                pieces[5:]))
                return job
            except ValueError:
                print("Error at line %d, cannot parse pattern" % rownum)
                return None

    def load_crontab_file(self, crontab_file, clear=True, job_func_func=std_launch_func):
        """
        Read crontab file, create corresponding jobs in this scheduler
        :param crontab_file:
            crontab file path
        :param job_func_func:
            a function that takes a list of tokens (from crontab file) and
            returns a 0-args function
        :param clear:
            should the new schedule override the previous ones?
        """
        if clear:
            self.clear()
        with open(crontab_file) as fp:
            for rownum, line in enumerate(fp):
                if line is not None:                  # not sure if this can happen
                    line = line.strip()
                    if line != "" and line[0] != "#":
                        # skip empty lines and comments
                        self._load_crontab_line(rownum, line, job_func_func)

    def main_loop(self):
        """
        Perform main run-and-wait loop.
        """
        import time
        while True:
            self.run_pending()
            time.sleep(self.delay)