from django.core.management.base import BaseCommand
from django.db import connection


def _pg(cursor):
    cursor.execute("""
    CREATE OR REPLACE FUNCTION update_alert_after()
    RETURNS trigger AS $update_alert_after$
        BEGIN
            IF NEW.last_ping IS NOT NULL THEN
                NEW.alert_after := NEW.last_ping + NEW.timeout + NEW.grace;
            END IF;
            RETURN NEW;
        END;
    $update_alert_after$ LANGUAGE plpgsql;

    DROP TRIGGER IF EXISTS update_alert_after ON api_check;

    CREATE TRIGGER update_alert_after
    BEFORE INSERT OR UPDATE OF last_ping, timeout, grace  ON api_check
    FOR EACH ROW EXECUTE PROCEDURE update_alert_after();
    """)


def _mysql(cursor):
    cursor.execute("""
    DROP TRIGGER IF EXISTS update_alert_after;

    CREATE TRIGGER update_alert_after
    BEFORE UPDATE ON api_check
    FOR EACH ROW SET NEW.alert_after = NEW.last_ping + INTERVAL (NEW.timeout + NEW.grace) MICROSECOND;
    """)


class Command(BaseCommand):
    help = 'Ensures triggers exist in database'

    def handle(self, *args, **options):
        cursor = connection.cursor()

        if connection.vendor == "postgresql":
            _pg(cursor)
            print("Created PostgreSQL trigger")
        if connection.vendor == "mysql":
            _mysql(cursor)
            print("Created MySQL trigger")