#!/bin/env python
import argparse
import email
import json
import smtplib
import ssl
import sys
from datetime import datetime, timezone, timedelta
from email.mime.base import MIMEBase
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText
from os import getenv
from textwrap import dedent

import humanize
import pgsql


class Config:
    """
    Get config from environment variables
    """

    def __init__(self):
        self.postgres_hostname = getenv('POSTGRES_HOSTNAME', 'localhost')
        self.postgres_username = getenv('POSTGRES_USERNAME', 'hedgedoc')
        self.postgres_password = getenv('POSTGRES_PASSWORD', 'geheim')
        self.postgres_database = getenv('POSTGRES_DATABASE', 'hedgedoc')
        self.postgres_port = int(getenv('POSTGRES_PORT', '5432'))

        self.smtp_hostname = getenv('SMTP_HOSTNAME', 'localhost')
        self.smtp_port = int(getenv('SMTP_PORT', '587'))
        self.smtp_username = getenv('SMTP_USERNAME', '')
        self.smtp_password = getenv('SMTP_PASSWORD', '')
        self.smtp_from = getenv('SMTP_FROM', '')
        self.url = getenv('URL', 'http://localhost:3000')


class EmailSender:
    """
    Send email message through SMTP
    """

    def __init__(self, hostname: str, port: int, username: str, password: str, mail_from: str):
        self.hostname = hostname
        self.port = port
        self.username = username
        self.password = password
        self.mail_from = mail_from

    def send(self, message: email.message.Message) -> None:
        """
        Using the configured SMTP coordinates, send the message out. The code assumes the submission protocol with
        StartTLS enabled, and authentication required.
        :param message: to be sent
        :return:
        """
        smtp_server = smtplib.SMTP(self.hostname, port=self.port)
        context = ssl.create_default_context()
        smtp_server.starttls(context=context)
        smtp_server.login(self.username, self.password)
        smtp_server.send_message(message)


def email_from_email_or_profile(row) -> str:
    """
    Get the email address of the creator from a database row. If the email column is populated, use that, otherwise
    try to extract it from the login profile. The profile is a JSON object that has an emails array. We're using the
    first address from there.
    :param row: database row as a dict with email and profile columns
    :return: email address
    """
    if row['email'] is not None:
        return row['email']
    profile = json.loads(row['profile'])
    return profile['emails'][0]


def notes_to_be_expired(cutoff: datetime) -> list[any]:
    """
    Get a list of all notes to be expired.
    :param cutoff: notes that have last beed updated before this date are designated to be expired.
    :return:
    """
    notes = []
    with db.prepare('''SELECT
                        "Notes"."alias",
                        "Notes"."content",
                        "Notes"."createdAt",
                        "Notes"."ownerId",
                        "Notes"."shortid",
                        "Notes"."id",
                        "Notes"."title",
                        "Notes"."updatedAt",
                        "Users"."email",
                        "Users"."profile"
                    FROM "Notes", "Users"
                    WHERE "Notes"."updatedAt" < $1
                      AND "Notes"."ownerId" = "Users"."id"
                    ORDER BY "Notes"."updatedAt"
                    ''') as notes_older_than:
        for row in notes_older_than(cutoff):
            notes.append({
                'alias': row.alias if row.alias is not None else row.shortid,
                'content': row.content,
                'createdAt': row.createdAt,
                'email': row.email,
                "id": row.id,
                'ownerId': row.ownerId,
                'profile': row.profile,
                'shortid': row.shortid,
                'title': row.title,
                'updatedAt': row.updatedAt
            })
    return notes


def revisions_to_be_expired(cutoff: datetime) -> list[any]:
    """
    Obtain a list of revisions to be expired.
    :param cutoff:
    :return:
    """
    revisions = []
    with db.prepare('''SELECT
                        "Notes"."alias",
                        "Revisions"."createdAt",
                        "Users"."email",
                        "Users"."profile",
                        "Revisions"."id" as "revisionId",
                        "Notes"."id" as "noteId", 
                        "Notes"."shortid" as "shortid",
                        "Notes"."title"
                    FROM "Revisions", "Notes", "Users" 
                    WHERE "Revisions"."createdAt" < $1 
                      AND "Revisions"."noteId" = "Notes"."id"
                      AND "Notes"."ownerId" = "Users"."id"
                    ORDER BY "Notes"."createdAt", "Revisions"."createdAt"
                ''') as revs_older_than:
        for row in revs_older_than(cutoff):
            revisions.append({
                'alias': row.alias,
                'createdAt': row.createdAt,
                'email': row.email,
                'noteId': row.noteId,
                'profile': row.profile,
                'revisionId': row.revisionId,
                'shortid': row.shortid,
                'title': row.title
            })
    return revisions


def check_notes_to_be_expired(age: timedelta, config: Config) -> None:
    """
    Print a list of notes that will be expired.
    :param age: expire notes not updated in this timespan
    :param config: configuration parameters used in output
    :return:
    """
    cutoff = datetime.now(timezone.utc) - age
    print(f'Notes to be deleted older than {cutoff} ({humanize.naturaldelta(age)}):')
    for note in notes_to_be_expired(cutoff):
        age = datetime.now(timezone.utc) - datetime.fromisoformat(note['updatedAt'])
        url = config.url + '/' + (note["alias"] if note["alias"] is not None else note["shortid"])
        print(f'    {email_from_email_or_profile(note)} ({humanize.naturaldelta(age)}) {url}: {note["title"]}')


def check_revisions_to_be_expired(age: timedelta, config: Config) -> None:
    """
    Print a list of revisions that will be expired.
    :param age: expire revisions created before this timespan
    :param config: configuration parameters used in output
    :return:
    """
    cutoff = datetime.now(timezone.utc) - age
    print(f'Revisions to be deleted older than {cutoff} ({humanize.naturaldelta(age)}):')
    notes = {}
    for row in revisions_to_be_expired(cutoff):
        row['age'] = datetime.now(timezone.utc) - datetime.fromisoformat(row['createdAt'])
        if row['noteId'] not in notes:
            notes[row['noteId']] = []
        notes[row['noteId']].append(row)
    for id, revisions in notes.items():
        email = email_from_email_or_profile(revisions[0])
        url = config.url + '/' + (
            revisions[0]["alias"] if revisions[0]["alias"] is not None else revisions[0]["shortid"])
        print(f'    {email} {url}: {revisions[0]["title"]}')
        for rev in revisions:
            print(f'        {humanize.naturaldelta(rev["age"])}: {rev["revisionId"]}')


def expire_old_notes(age: timedelta, config: Config, mail: EmailSender) -> None:
    """
    Email old notes to their owners, then delete them.
    :param age: expire notes not updated in this timespan
    :param config: configuration parameters used in output
    :param mail: how to send the mail
    :return:
    """
    cutoff = datetime.now(timezone.utc) - age
    with db.prepare('DELETE FROM "Notes" WHERE "id" = $1') as delete_statement:
        for note in notes_to_be_expired(cutoff):
            try:
                note_age = datetime.now(timezone.utc) - datetime.fromisoformat(note['updatedAt'])
                msg = MIMEMultipart()
                msg['From'] = mail.mail_from
                msg['To'] = email_from_email_or_profile(note)
                msg['Subject'] = f'Your HedgeDoc Note "{note["title"]}" has been expired'
                msg.attach(MIMEText(dedent(f'''\
                    You created the note titled "{note["title"]}" on {note["createdAt"]}.
                    It was lasted updated {note['updatedAt']}, {humanize.naturaldelta(note_age)} ago. We expire all notes
                    that have not been updated within {humanize.naturaldelta(age)}.
                    
                    Please find attached the contents of the latest revision of your note.
                    
                    The admin team for {config.url}
                    
                    '''
                                           )))
                md = MIMEBase('text', "markdown")
                md.add_header('Content-Disposition', f'attachment; filename={note["title"]}')
                md.set_payload(note["content"])
                msg.attach(md)
                mail.send(msg)

                # email backup of the note sent, now we can delete it
                delete_statement(note["id"])
            except Exception as e:
                print(f'Unable to send email to {note["email"]}: {e}', file=sys.stderr)


def expire_old_revisions(age: timedelta) -> None:
    """
    Removes all revision on all notes that have been modified earlier than age.
    :param age:
    :return:
    """
    cutoff = datetime.now(timezone.utc) - age
    with db.prepare('DELETE FROM "Revisions" WHERE "createdAt" < $1') as delete:
        delete(cutoff)


if __name__ == '__main__':
    parser = argparse.ArgumentParser(
        prog='hedgedoc-expire',
        description='Remove old notes and revisions from Hedgedoc',
        epilog='See https://git.hamburg.ccc.de/CCCHH/hedgedoc-expire')
    parser.add_argument('-c', '--check', action='store_true',
                        help='print what would be done, then exit')
    parser.add_argument('-n', '--notes', metavar='DAYS', type=float, default=95,
                        help='remove all notes not changed in these many days')
    parser.add_argument('-r', '--revisions', metavar='DAYS', type=float, default=14,
                        help='remove all revisions created more than these many days ago')
    args = parser.parse_args()

    revisions_delta = timedelta(days=args.revisions)
    notes_delta = timedelta(days=args.notes)

    config = Config()
    mail = EmailSender(config.smtp_hostname, config.smtp_port, config.smtp_username, config.smtp_password,
                       config.smtp_from)

    with pgsql.Connection((config.postgres_hostname, config.postgres_port), config.postgres_username,
                          config.postgres_password) as db:
        if args.check:
            check_revisions_to_be_expired(revisions_delta, config)
            check_notes_to_be_expired(notes_delta, config)
            sys.exit(0)
        expire_old_revisions(revisions_delta)
        expire_old_notes(notes_delta, config, mail)