#!/bin/env/python3
import os
import email
from datetime import datetime, timezone

from imapclient import IMAPClient
from smtplib import SMTP_SSL

from dateutil.parser import parse as d_parse
from cron_descriptor import get_description
from croniter import croniter


help_text = """
A very comprehensive help text
"""
service_address = "remindme@friedersdorff.com"


def empty_reply(msg):
    reply = email.message.EmailMessage()
    reply["Subject"] = f"RE: {msg['Subject']}"
    reply["Message-ID"] = email.utils.make_msgid()
    reply["In-Reply-To"] = msg["Message-ID"]
    reply["References"] = msg["Message-ID"]
    reply["To"] = msg["Reply-To"] or msg["From"]
    reply["From"] = service_address
    return reply


def list_reminders(person, client):
    persons_messages = client.fetch(
        client.search(["FROM", person]), "BODY.PEEK[]"
    )
    reminders = []
    for uid, reminder in persons_messages.items():
        reminder = email.message_from_bytes(reminder[b"BODY[]"])
        reminders.append(
            f"({uid}) {reminder['Subject']}: {reminder.get_payload().strip()}"
        )
    return "\n".join(reminders)


def ack_message(uid, message, client):
    msg = email.message_from_bytes(message[b"BODY[]"])
    if msg.is_multipart():
        return None, True
        client.delete_messages([uid])

    payload = msg.get_payload().strip()
    if payload.startswith("help"):
        reply = empty_reply(msg)
        reply.set_content(help_text)
        return reply, True

    reply = empty_reply(msg)
    reply.set_content(list_reminders(msg["From"], client))

    if payload.startswith("list"):
        reply["Subject"] = f"List of active reminders (was: {reply['Subject']})"
        return reply, True
    else:
        msg.replace_header("Subject", f"Set reminder: {reply['Subject']}")
        prefix = (
            f"Successfully set reminder: {payload}.\n\n" "Your reminders are:"
        )
        reply.set_content(f"{prefix}\n{reply.get_content()}")
        return reply, False


def remind(uid, message, client):
    msg = email.message_from_bytes(message[b"BODY[]"])

    payload = msg.get_payload().strip()
    if payload.startswith("repeat"):
        try:
            croniter(payload, datetime.now())
        except Exception as e:
            print("An error occured", e)
        return None, False

    remind_time = d_parse(payload.splitlines()[0])
    if not remind_time.tzinfo:
        sender_timezone = d_parse(msg["Date"]).tzinfo
        remind_time = remind_time.replace(tzinfo=sender_timezone)

    now = datetime.now(timezone.utc)
    if now > remind_time:
        reply = empty_reply(msg)
        reply.replace_header("Subject", f"Reminder: {msg['Subject']}")
        reply.set_content(f"This is a reminder:\n{msg['Subject']}")
        return reply, True
    else:
        return None, False


def main():
    mhost = "mail.friedersdorff.com"
    user = os.environ["REMINDME_USERNAME"]
    passwd = os.environ["REMINDME_PASS"]
    with IMAPClient(host=mhost) as iclient, SMTP_SSL(mhost) as sclient:
        iclient.login(user, passwd)
        sclient.login(user, passwd)
        iclient.select_folder("INBOX")

        unseen_msgs = iclient.fetch(iclient.search(["UNSEEN"]), "BODY.PEEK[]")
        for uid, message in unseen_msgs.items():
            reply, delete = ack_message(uid, message, iclient)
            try:
                if reply:
                    sclient.send_message(reply)
                if delete:
                    pass
                    # iclient.delete_messages([uid])
                else:
                    pass
                    # iclient.set_flags([uid], [r"\SEEN"])
            except Exception as e:
                print("An error occured", e)

        all_msgs = iclient.fetch(iclient.search(["NOT", "DELETED"]), "BODY[]")
        for uid, message in all_msgs.items():
            reply, delete = remind(uid, message, iclient)
            try:
                if reply:
                    sclient.send_message(reply)
                if delete:
                    pass
                    # iclient.delete_messages([uid])
                else:
                    pass
                    # iclient.set_flags([uid], [r"\SEEN"])
            except Exception as e:
                print("An error occured", e)


if __name__ == "__main__":
    main()