from datetime import datetime, timedelta
import math

from flask import current_app
from notifications_utils.statsd_decorators import statsd
from requests import (
    post as requests_post,
    RequestException
)
from botocore.exceptions import ClientError as BotoClientError

from notifications_utils.s3 import s3upload

from app import notify_celery
from app.aws import s3
from app.config import QueueNames, TaskNames
from app.dao.notifications_dao import (
    get_notification_by_id,
    update_notification_status_by_id,
    dao_update_notification,
    dao_get_notifications_by_references,
)
from app.models import NOTIFICATION_CREATED

LETTERS_PDF_FILE_LOCATION_STRUCTURE = \
    '{folder}/NOTIFY.{reference}.{duplex}.{letter_class}.{colour}.{crown}.{date}.pdf'


def get_letter_pdf_filename(reference, crown):
    now = datetime.utcnow()

    print_datetime = now
    if now.time() > current_app.config.get('LETTER_PROCESSING_DEADLINE'):
        print_datetime = now + timedelta(days=1)

    upload_file_name = LETTERS_PDF_FILE_LOCATION_STRUCTURE.format(
        folder=print_datetime.date(),
        reference=reference,
        duplex="D",
        letter_class="2",
        colour="C",
        crown="C" if crown else "N",
        date=now.strftime('%Y%m%d%H%M%S')
    ).upper()

    return upload_file_name


@notify_celery.task(bind=True, name="create-letters-pdf", max_retries=15, default_retry_delay=300)
@statsd(namespace="tasks")
def create_letters_pdf(self, notification_id):
    try:
        notification = get_notification_by_id(notification_id, _raise=True)

        pdf_data, billable_units = get_letters_pdf(
            notification.template,
            contact_block=notification.reply_to_text,
            org_id=notification.service.dvla_organisation.id,
            values=notification.personalisation
        )
        current_app.logger.info("PDF Letter {} reference {} created at {}, {} bytes".format(
            notification.id, notification.reference, notification.created_at, len(pdf_data)))

        upload_file_name = get_letter_pdf_filename(
            notification.reference, notification.service.crown)

        s3upload(
            filedata=pdf_data,
            region=current_app.config['AWS_REGION'],
            bucket_name=current_app.config['LETTERS_PDF_BUCKET_NAME'],
            file_location=upload_file_name
        )

        current_app.logger.info("Uploaded letters PDF {} to {}".format(
            upload_file_name, current_app.config['LETTERS_PDF_BUCKET_NAME']))

        notification.billable_units = billable_units
        dao_update_notification(notification)

        current_app.logger.info(
            'Letter notification reference {reference}: billable units set to {billable_units}'.format(
                reference=str(notification.reference), billable_units=billable_units))

    except (RequestException, BotoClientError):
        try:
            current_app.logger.exception(
                "Letters PDF notification creation for id: {} failed".format(notification_id)
            )
            self.retry(queue=QueueNames.RETRY)
        except self.MaxRetriesExceededError:
            current_app.logger.exception(
                "RETRY FAILED: task create_letters_pdf failed for notification {}".format(notification_id),
            )
            update_notification_status_by_id(notification_id, 'technical-failure')


def get_letters_pdf(template, contact_block, org_id, values):
    template_for_letter_print = {
        "subject": template.subject,
        "content": template.content
    }

    data = {
        'letter_contact_block': contact_block,
        'template': template_for_letter_print,
        'values': values,
        'dvla_org_id': org_id,
    }
    resp = requests_post(
        '{}/print.pdf'.format(
            current_app.config['TEMPLATE_PREVIEW_API_HOST']
        ),
        json=data,
        headers={'Authorization': 'Token {}'.format(current_app.config['TEMPLATE_PREVIEW_API_KEY'])}
    )
    resp.raise_for_status()

    pages_per_sheet = 2
    billable_units = math.ceil(int(resp.headers.get("X-pdf-page-count", 0)) / pages_per_sheet)

    return resp.content, billable_units


@notify_celery.task(name='collate-letter-pdfs-for-day')
def collate_letter_pdfs_for_day(date):
    letter_pdfs = s3.get_s3_bucket_objects(
        current_app.config['LETTERS_PDF_BUCKET_NAME'],
        subfolder=date
    )
    for letters in group_letters(letter_pdfs):
        filenames = [letter['Key'] for letter in letters]
        current_app.logger.info(
            'Calling task zip-and-send-letter-pdfs for {} pdfs of total size {:,} bytes'.format(
                len(filenames),
                sum(letter['Size'] for letter in letters)
            )
        )
        notify_celery.send_task(
            name=TaskNames.ZIP_AND_SEND_LETTER_PDFS,
            kwargs={'filenames_to_zip': filenames},
            queue=QueueNames.PROCESS_FTP,
            compression='zlib'
        )


def group_letters(letter_pdfs):
    """
    Group letters in chunks of MAX_LETTER_PDF_ZIP_FILESIZE. Will add files to lists, never going over that size.
    If a single file is (somehow) larger than MAX_LETTER_PDF_ZIP_FILESIZE that'll be in a list on it's own.
    If there are no files, will just exit (rather than yielding an empty list).
    """
    running_filesize = 0
    list_of_files = []
    for letter in letter_pdfs:
        if letter['Key'].lower().endswith('.pdf') and letter_in_created_state(letter['Key']):
            if (
                running_filesize + letter['Size'] > current_app.config['MAX_LETTER_PDF_ZIP_FILESIZE'] or
                len(list_of_files) >= current_app.config['MAX_LETTER_PDF_COUNT_PER_ZIP']
            ):
                yield list_of_files
                running_filesize = 0
                list_of_files = []

            running_filesize += letter['Size']
            list_of_files.append(letter)

    if list_of_files:
        yield list_of_files


def letter_in_created_state(filename):
    # filename looks like '2018-01-13/NOTIFY.ABCDEF1234567890.D.2.C.C.20180113120000.PDF'
    subfolder = filename.split('/')[0]
    ref = filename.split('.')[1]
    notifications = dao_get_notifications_by_references([ref])
    if notifications:
        if notifications[0].status == NOTIFICATION_CREATED:
            return True
        current_app.logger.info('Collating letters for {} but notification with reference {} already in {}'.format(
            subfolder,
            ref,
            notifications[0].status
        ))
    return False