import os

RESOLVED_STATUSES = ('UP', 'OK', 'resolved')


def create_file(file_path):
    if not os.path.exists(file_path):
        with open(file_path, 'w+'):
            return file_path


def _format_subject(alert, add_links=False):
    if add_links:
        severity = alert['labels']['severity'].upper()
        name = alert['labels']['alertname']
        return '[{}] {}'.format(severity, name)

    subject = alert['annotations']['summary']
    host = alert['labels'].get('host')
    if host is not None:
        return '[{}] {}'.format(host, subject)
    return subject


def _remove_advice(description):
    return description.split(' Modify the')[0]


def _get_prometheus_link(alert):
    # switch from Console to Graph tab to show trends
    condition_url = alert['generatorURL'].replace('g0.tab=1', 'g0.tab=0')

    # list alert firing instances in the cluster
    # via query: ALERTS{alertname="<alertname>",alertstate="firing"}
    alert_query = ('g1.range_input=1h&'
                   'g1.expr=ALERTS%7Balertname%3D%22'
                   '{}'
                   '%22%2Calertstate%3D%22firing%22%7D&'
                   'g1.tab=0').format(alert['labels']['alertname'])
    return '{}&{}'.format(condition_url, alert_query)


def _format_description(alert, add_links=False):
    description_old = _remove_advice(alert['annotations']['description'])

    if not add_links:
        return description_old

    msg = ('To check trends of the alert underlying condition metric '
           ' and alert occurrence click on Prometheus UI link')

    prometheus_url = _get_prometheus_link(alert)
    return '{}\n\n{}:\n{}'.format(description_old, msg, prometheus_url)


def alert_fields_and_action(alert, add_links=False):
    fields = []

    if alert['status'] in RESOLVED_STATUSES:
        action = 'close_case'
        fields.append(alert['labels'])
    else:
        action = 'create_case'
        # Order of keys matters
        fields.append(_format_subject(alert, add_links))
        fields.append(_format_description(alert, add_links))
        fields.append(alert['labels'])
    return fields, action