import logging
from datetime import datetime

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker

from .workers.base_worker import RenderStatus, BaseRenderWorker, Base

logger = logging.getLogger()


class JobNotFoundError(Exception):
    def __init__(self, job_id, *args):
        super().__init__(args)
        self.job_id = job_id


class RenderQueue:
    engine = create_engine('sqlite:///database.db')
    Base.metadata.create_all(engine)
    Session = sessionmaker(bind=engine)
    session = Session()
    job_queue = []
    maximum_renderer_instances = {'blender': 1, 'aerender': 1, 'ffmpeg': 4}
    last_saved_counts = {}

    def __init__(self):
        pass

    @classmethod
    def add_to_render_queue(cls, render_job, force_start=False):
        logger.debug('Adding priority {} job to render queue: {}'.format(render_job.priority, render_job))
        cls.job_queue.append(render_job)
        if force_start:
            cls.start_job(render_job)
        cls.session.add(render_job)
        cls.save_state()

    @classmethod
    def all_jobs(cls):
        return cls.job_queue

    @classmethod
    def running_jobs(cls):
        return cls.jobs_with_status(RenderStatus.RUNNING)

    @classmethod
    def pending_jobs(cls):
        pending_jobs = cls.jobs_with_status(RenderStatus.NOT_STARTED)
        pending_jobs.extend(cls.jobs_with_status(RenderStatus.SCHEDULED))
        return pending_jobs

    @classmethod
    def jobs_with_status(cls, status, priority_sorted=False):
        found_jobs = [x for x in cls.all_jobs() if x.status == status]
        if priority_sorted:
            found_jobs = sorted(found_jobs, key=lambda a: a.priority, reverse=False)
        return found_jobs

    @classmethod
    def job_with_id(cls, job_id, none_ok=False):
        found_job = next((x for x in cls.all_jobs() if x.id == job_id), None)
        if not found_job and not none_ok:
            raise JobNotFoundError(job_id)
        return found_job

    @classmethod
    def clear_history(cls):
        to_remove = [x for x in cls.all_jobs() if x.status in [RenderStatus.CANCELLED,
                                                                        RenderStatus.COMPLETED, RenderStatus.ERROR]]
        for job_to_remove in to_remove:
            cls.delete_job(job_to_remove)
        cls.save_state()

    @classmethod
    def load_state(cls):
        cls.job_queue = cls.session.query(BaseRenderWorker).all()

    @classmethod
    def save_state(cls):
        cls.session.commit()

    @classmethod
    def evaluate_queue(cls):
        not_started = cls.jobs_with_status(RenderStatus.NOT_STARTED, priority_sorted=True)
        if not_started:
            for job in not_started:
                instances = cls.renderer_instances()
                higher_priority_jobs = [x for x in cls.running_jobs() if x.priority < job.priority]
                max_renderers = job.renderer in instances.keys() and instances[
                    job.renderer] >= cls.maximum_renderer_instances.get(job.renderer, 1)

                if not max_renderers and not higher_priority_jobs:
                    cls.start_job(job)

        scheduled = cls.jobs_with_status(RenderStatus.SCHEDULED, priority_sorted=True)
        for job in scheduled:
            if job.scheduled_start <= datetime.now():
                logger.debug(f"Starting scheduled job: {job}")
                cls.start_job(job)

        if cls.last_saved_counts != cls.job_counts():
            cls.save_state()

    @classmethod
    def start_job(cls, job):
        logger.info(f'Starting render: {job.name} - Priority {job.priority}')
        job.start()

    @classmethod
    def cancel_job(cls, job):
        logger.info(f'Cancelling job ID: {job.id}')
        job.stop()
        return job.status == RenderStatus.CANCELLED

    @classmethod
    def delete_job(cls, job):
        logger.info(f"Deleting job ID: {job.id}")
        job.stop()
        cls.job_queue.remove(job)
        cls.session.delete(job)
        cls.save_state()
        return True

    @classmethod
    def renderer_instances(cls):
        from collections import Counter
        all_instances = [x.renderer for x in cls.running_jobs()]
        return Counter(all_instances)

    @classmethod
    def job_counts(cls):
        job_counts = {}
        for job_status in RenderStatus:
            job_counts[job_status.value] = len(cls.jobs_with_status(job_status))
        return job_counts