import logging
import json
import time

from datetime import timedelta, datetime
from itertools import chain

import features
from app import app, storage
from data.database import UseThenDisconnect
from data.model import db_transaction
from data.model.log import (get_stale_logs, get_stale_logs_start_id,
                            get_stale_logs_end_id, delete_stale_logs)
from util.registry.gzipwrap import GzipWrap
from workers.globalworkerbase import GlobalWorker

logger = logging.getLogger(__name__)

WORKER_FREQUENCY = 3600
STALE_AFTER = timedelta(days=30)
MIN_LOGS_PER_ROTATION = 10000
BATCH_SIZE = 500
SAVE_PATH = app.config.get('ACTION_LOG_ARCHIVE_PATH')
SAVE_LOCATION = app.config.get('ACTION_LOG_ARCHIVE_LOCATION')

class LogRotateWorker(GlobalWorker):
  """ Worker used to rotate old logs out the database and into storage. """
  def __init__(self):
    super(LogRotateWorker, self).__init__(app, sleep_period_seconds=WORKER_FREQUENCY)

  def perform_global_work(self):
    logger.debug('Attempting to rotate log entries')
    with UseThenDisconnect(app.config):
      with db_transaction():
        cutoff = datetime.now() - STALE_AFTER
        start_id = get_stale_logs_start_id()
        end_id = get_stale_logs_end_id(cutoff)

        if start_id is None or end_id is None:
          logger.warning('No logs to be archived.')
          return

        logger.debug('Found starting ID %s and ending ID %s', start_id, end_id)

        approx_count = end_id - start_id
        if approx_count < MIN_LOGS_PER_ROTATION:
          logger.debug('Not enough stale logs to warrant rotation (approx %d)', approx_count)
          return

        # Build a generator of all the logs we want to archive in batches of 500.
        log_generator = (_ for _ in ())
        logs_to_fetch = range(start_id, end_id+1)
        while len(logs_to_fetch) != 0:
          (batch, logs_to_fetch) = _take(BATCH_SIZE, logs_to_fetch)
          logger.debug('Reading archived logs from IDs %s to %s', batch[0], batch[-1])
          batch_generator = (pretty_print_in_json(log) + '\n'
                             for log in get_stale_logs(batch[0], batch[-1]))
          log_generator = chain(log_generator, batch_generator)

        logger.debug('Archiving logs from IDs %s to %s', start_id, end_id)
        filename = '%s%d-%d.txt.gz' % (SAVE_PATH, start_id, end_id)
        storage.stream_write(SAVE_LOCATION, filename, GzipWrap(log_generator))

        logs_to_delete = range(start_id, end_id+1)
        while len(logs_to_delete) != 0:
          (batch, logs_to_delete) = _take(BATCH_SIZE, logs_to_delete)
          logger.debug('Deleting archived logs from IDs %s to %s', batch[0], batch[-1])
          delete_stale_logs(batch[0], batch[-1])


def _take(count, lst):
  return lst[:count], lst[count:]

def pretty_print_in_json(log):
  """ Pretty prints a LogEntry in JSON. """
  return json.dumps({'kind_id': log.kind_id,
                     'account_id': log.account_id,
                     'performer_id': log.performer_id,
                     'repository_id': log.repository_id,
                     'datetime': str(log.datetime),
                     'ip': str(log.ip),
                     'metadata_json': json.loads(str(log.metadata_json))})


def main():
  if not features.ACTION_LOG_ROTATION or None in [SAVE_PATH, SAVE_LOCATION]:
    while True:
      time.sleep(100000)

  worker = LogRotateWorker()
  worker.start()


if __name__ == "__main__":
  main()