"""
REPORT GENERATION TASKS

Celery tasks for generating an audit report.

The find() task is a periodic task (like a cron). It is meant to be run
as a single process that will spawn other asynchronous tasks in this file.
This is accomplished via cache locking method described in celery docs:
http://celery.readthedocs.org/en/latest/tutorials/
task-cookbook.html#cookbook-task-serial
"""

from celery import Celery
from kombu import Exchange, Queue

import os
from datetime import timedelta

from labelaudit.connectors import sentry
from labelaudit import config
from labelaudit.logic import audit_persistence
from labelaudit.tasks.task_lock import TaskLock
from labelaudit.logic import report_generation


sentry  # pep8

app = Celery('label_audit_cron_app')
app.config_from_object(dict(
    BROKER_URL=config.BROKER_URL,
    CELERY_DEFAULT_QUEUE=config.AUDIT_GENERATION_QUEUE,
    CELERY_ACCEPT_CONTENT=['pickle'],
    CELERY_QUEUES=(Queue(
        config.AUDIT_GENERATION_QUEUE,
        Exchange(config.AUDIT_GENERATION_QUEUE),
        routing_key='labelaudit.tasks.report_generation_tasks.#'),),
    CELERYBEAT_SCHEDULE={
        'run_every_5_minutes': {
            'task': 'labelaudit.tasks.report_generation_tasks.find',
            'schedule': timedelta(
                seconds=int(
                    os.environ.get('AUDIT_GENERATION_RUN_INTERVAL') or 300)),
        },
    },
    CELERY_TIMEZONE='UTC',
    CELERY_ENABLE_UTC=True,
    BROKER_TRANSPORT_OPTIONS=dict(
        queue_name_prefix=config.CELERY_QUEUE_PREFIX)))


@app.task(
    name='labelaudit.tasks.report_generation_tasks.find',
    queue=config.AUDIT_GENERATION_QUEUE)
def find():
    """The main workflow of the periodic audit completion job.

    Runs every few minutes to check for a new batch of audit reports
    which have all the data ready to be generated into a CSV file.
    This is a periodic task and each time it processes one batch.

    Each report generation is kicked off asynchronously and then
    the status of the report is set to 'generating'.

    Task will retry if there is an error trying to get the reports.
    """

    # Cache is not optional for this, so alert if it's off
    if not config.CACHE_ENABLED:
        raise Exception(
            'You must enable the cache (CACHE_ENABLED) '
            'to run the periodic find() task.')

    lock = TaskLock('labelaudit.tasks.report_generation_tasks.find')
    if lock.acquire_task():
        try:
            limit = config.AUDIT_GENERATION_BATCH_SIZE
            results = audit_persistence.fetch_all(
                allReleasesStatus='complete', auditStatus='in_progress',
                limit=limit, offset=0)

            reports = results.message.get('reports') or []
            for report in reports:
                generate.delay(report)
                # Update the status of reports synchronously to avoid
                # unnecessarily rerunning the reports just kicked off above.
                audit_persistence.update_report_status(
                    report.get('youtubeAuditId'), 'generating')

        # TODO add except that will use log/alert system for exceptions
        finally:
            lock.delete()
    else:
        # TODO convert to logger once we have decided on logging/alerts.
        print('Audit completion periodic task already running.')


@app.task(
    name='labelaudit.tasks.report_generation_tasks.generate',
    queue=config.AUDIT_GENERATION_QUEUE)
def generate(report):
    """Generate a CSV audit report and drop in S3 bucket.

    This will create a CSV report then call task to drop
    it on S3. This should be idempotent and replace a
    previous report if called to be run again. On
    completion of the copy to S3, the status of the report
    will be moved to 'complete'.

    Args:
        report (dict): data for a single report
            EX: {
                'auditStatus': 'in_progress',
                'initiatedById': '888',
                'reportLocation': 'some location',
                'updatedTimestamp': '2015-06-09 14:30:36',
                'vendorId': '5',
                'youtubeAuditId': '3'
            }
    """

    report_generation.generate(report)