from datetime import datetime

from flask import current_app
from sqlalchemy import String, and_, desc, func, literal, text

from app import db
from app.models import (
    JOB_STATUS_CANCELLED,
    JOB_STATUS_SCHEDULED,
    LETTER_TYPE,
    NOTIFICATION_CANCELLED,
    Job,
    Notification,
    ServiceDataRetention,
    Template,
)
from app.utils import midnight_n_days_ago


def _get_printing_day(created_at):
    return func.date_trunc(
        'day',
        func.timezone('Europe/London', func.timezone('UTC', created_at)) + text(
            # We add 6 hours 30 minutes to the local created_at time so that
            # any letters created after 5:30pm get shifted into the next day
            "interval '6 hours 30 minutes'"
        )
    )


def _get_printing_datetime(created_at):
    return _get_printing_day(created_at) + text(
        # Letters are printed from 5:30pm each day
        "interval '17 hours 30 minutes'"
    )


def _naive_gmt_to_utc(column):
    return func.timezone('UTC', func.timezone('Europe/London', column))


def dao_get_uploads_by_service_id(service_id, limit_days=None, page=1, page_size=50):
    # Hardcoded filter to exclude cancelled or scheduled jobs
    # for the moment, but we may want to change this method take 'statuses' as a argument in the future
    today = datetime.utcnow().date()
    jobs_query_filter = [
        Job.service_id == service_id,
        Job.original_file_name != current_app.config['TEST_MESSAGE_FILENAME'],
        Job.original_file_name != current_app.config['ONE_OFF_MESSAGE_FILENAME'],
        Job.job_status.notin_([JOB_STATUS_CANCELLED, JOB_STATUS_SCHEDULED]),
        func.coalesce(
            Job.processing_started, Job.created_at
        ) >= today - func.coalesce(ServiceDataRetention.days_of_retention, 7),
        Job.contact_list_id.is_(None),
    ]
    if limit_days is not None:
        jobs_query_filter.append(Job.created_at >= midnight_n_days_ago(limit_days))

    jobs_query = db.session.query(
        Job.id,
        Job.original_file_name,
        Job.notification_count,
        Template.template_type,
        func.coalesce(ServiceDataRetention.days_of_retention, 7).label('days_of_retention'),
        Job.created_at.label("created_at"),
        Job.scheduled_for.label("scheduled_for"),
        Job.processing_started.label('processing_started'),
        Job.job_status.label("status"),
        literal('job').label('upload_type'),
        literal(None).label('recipient'),
    ).join(
        Template, Job.template_id == Template.id
    ).outerjoin(
        ServiceDataRetention, and_(
            Template.service_id == ServiceDataRetention.service_id,
            func.cast(Template.template_type, String) == func.cast(ServiceDataRetention.notification_type, String)
        )
    ).filter(
        *jobs_query_filter
    )

    letters_query_filter = [
        Notification.service_id == service_id,
        Notification.notification_type == LETTER_TYPE,
        Notification.api_key_id == None,  # noqa
        Notification.status != NOTIFICATION_CANCELLED,
        Template.hidden == True,  # noqa
        Notification.created_at >= today - func.coalesce(ServiceDataRetention.days_of_retention, 7)
    ]
    if limit_days is not None:
        letters_query_filter.append(Notification.created_at >= midnight_n_days_ago(limit_days))

    letters_subquery = db.session.query(
        func.count().label('notification_count'),
        _naive_gmt_to_utc(_get_printing_datetime(Notification.created_at)).label('printing_at'),
    ).join(
        Template, Notification.template_id == Template.id
    ).outerjoin(
        ServiceDataRetention, and_(
            Template.service_id == ServiceDataRetention.service_id,
            func.cast(Template.template_type, String) == func.cast(ServiceDataRetention.notification_type, String)
        )
    ).filter(
        *letters_query_filter
    ).group_by(
        'printing_at'
    ).subquery()

    letters_query = db.session.query(
        literal(None).label('id'),
        literal('Uploaded letters').label('original_file_name'),
        letters_subquery.c.notification_count.label('notification_count'),
        literal('letter').label('template_type'),
        literal(None).label('days_of_retention'),
        letters_subquery.c.printing_at.label('created_at'),
        literal(None).label('scheduled_for'),
        letters_subquery.c.printing_at.label('processing_started'),
        literal(None).label('status'),
        literal('letter_day').label('upload_type'),
        literal(None).label('recipient'),
    ).group_by(
        letters_subquery.c.notification_count,
        letters_subquery.c.printing_at,
    )

    return jobs_query.union_all(
        letters_query
    ).order_by(
        desc("processing_started"), desc("created_at")
    ).paginate(page=page, per_page=page_size)


def dao_get_uploaded_letters_by_print_date(service_id, letter_print_date, page=1, page_size=50):
    return db.session.query(
        Notification,
    ).join(
        Template, Notification.template_id == Template.id
    ).filter(
        Notification.service_id == service_id,
        Notification.notification_type == LETTER_TYPE,
        Notification.api_key_id.is_(None),
        Notification.status != NOTIFICATION_CANCELLED,
        Template.hidden.is_(True),
        _get_printing_day(Notification.created_at) == letter_print_date.date(),
    ).order_by(
        desc(Notification.created_at)
    ).paginate(
        page=page,
        per_page=page_size,
    )