import email
import smtplib
import socket
import subprocess

import systemd.journal

def _get_status(name):
    cmd = ['/usr/bin/systemctl', 'status', name]
    
    proc = subprocess.Popen(
	    cmd,
	    stdout=subprocess.PIPE)
    out, err = proc.communicate()
    out = out.decode('utf-8')
    return out

def _send_email(subject, message, config):
    mail = email.message.EmailMessage()
    hostname = socket.getfqdn()
    smtp_host='localhost'
    mail_from=f'sysalert <root@{hostname}>'
    mail_to=f'root <root@{hostname}>'
    if 'smtp_host' in config:
        smtp_host = config['smtp_host']
    if 'mail_from' in config:
        mail_from = config['mail_from']
    if 'mail_to' in config:
        mail_to = config['mail_to']


    mail.set_content(message)
    mail['To'] = mail_to
    mail['From'] = mail_from
    mail['Subject'] = subject

    with smtplib.SMTP(smtp_host) as smtp:
        smtp.send_message(mail)

def success(name, failures, config):
    cur_status = _get_status(name)
    nr_failures = len(failures)
    hostname = socket.getfqdn()
    subject=f'{hostname} - {name}: recovery'
    message=f"""
{name} has recovered after {nr_failures} failures.
Current status:

{cur_status}
"""
    _send_email(subject, message, config)


def failure(name, failures, config):
    cur_status = _get_status(name)
    hostname = socket.getfqdn()
    latest_inv_id = failures[-1]['invocation_id']
    nr_failures = len(failures)
    prev_failures=0
    for i,f in enumerate(reversed(failures[:-1])):
        if f['alert_method']:
            prev_failures=i+1
            break

    reader = systemd.journal.Reader()
    reader.add_match(MONITOR_INVOCATION_ID=latest_inv_id)
    reader.add_disjunction()
    reader.add_match(_SYSTEMD_INVOCATION_ID=lateset_inv_id)
    journal_txt = "\n".join([entry['MESSAGE'] for entry in reader])

    if nr_failures <= 1:
        subject=f"{hostname} - {name}: failure"
        message=f"""
New failure for {name}.
Current status:

{cur_status}


Latest journal log:

{journal_txt}
"""
    else:
        subject=f"{hostname} - {name}: {nr_failures} failures"
        message=f"""
{nr_failures} failures for {name} ({prev_failures} since last notification).
Current status:

{cur_status}


Latest journal log:

{journal_txt}
"""

    _send_email(subject, message, config)