#!/usr/bin/python3.8
#
# Check the library for new DVD releases.
#

import http.client
import urllib.parse
import xml.etree.ElementTree as ET
import email.message
import subprocess

APL_HOST = 'gateway.bibliocommons.com'
PATH_RSS = '/v2/libraries/austin/rss/search'

SEEN_FNAME = '/var/lib/homesvr/library-seen.txt'

# The command-line to send an email based on STDIN.
SENDMAIL_CMD = ('/usr/sbin/sendmail', '-t', '-oi')


def check():
    # Every DVD that we've seen lately.
    seen = load_seen()

    # What will we send email about.
    new_items = set()

    conn = http.client.HTTPSConnection(APL_HOST)

    page = 1
    while True:
        items = get_items(conn, page)

        n_seen = 0
        for item in items:
            title = item.findtext('title')
            subtitle = item.findtext('subtitle')
            if subtitle:
                title = f'{title} / {subtitle}'
            link = item.findtext('link')
            #print('TITLE:', title)
            #print('LINK:', link)
            if link not in seen:
                #print('NEW:', link)
                seen[link] = title
                new_items.add(link)
            else:
                n_seen += 1

        # Sometimes, "seen" DVDs will reappear because a new version comes
        # out, or whatnot. If we have seen (10) items in this fetch, then
        # we're likely at the end of new acquisitions.
        if n_seen > 10:
            #print('SEEN:', n_seen, '... stopping')
            break

        page += 1

    # Send email before saving SEEN, so if a failure occurs, we will start
    # over where we began.
    if new_items:
        send_email(new_items, seen)

    save_seen(seen)


def get_items(conn, page):
    params = {
        'custom_edit': 'false',
        'query': 'formatcode:(DVD )',
        'searchType': 'bl',
        'sort': 'newly_acquired',
        'suppress': 'true',
        'title': 'recent acquisitions',
        'view': 'medium',
        }
    if page == 1:
        params['initialSearch'] = 'true'
    else:
        params['pagination_page'] = str(page)

    encode = urllib.parse.urlencode(params, quote_via=urllib.parse.quote)
    path = f'{PATH_RSS}?{encode}'
    #print('PATH:', path)
    conn.request('GET', path)
    r = conn.getresponse()
    #print('RESULT:', r.status, r.reason)
    body = r.read().decode('latin-1')
    # We have seen some problem characters. Replace them.
    for c in '\x1b\x19':
        body = body.replace(c, '*')
    #print('LEN:', len(body))

    tree = ET.fromstring(body)
    return tree.find('channel').findall('item')


def load_seen():
    "Return dict of URL:TITLE of seen titles."
    return dict(l.strip().split(maxsplit=1)
                for l in open(SEEN_FNAME).readlines())


def save_seen(seen):
    open(SEEN_FNAME, 'w').write(
        '\n'.join('%s %s'%i for i in seen.items())
        + '\n')


def send_email(new_items, seen):
    text = '\n'.join(f'* {seen[link]} ({link})' for link in new_items)
    #print('TEXT:\n', text)

    msg = email.message.EmailMessage()
    msg.set_content(text)
    msg['Subject'] = 'New items at the Library'
    msg['From'] = 'gstein@gmail.com'
    msg['To'] = 'gstein@gmail.com'
    subprocess.run(SENDMAIL_CMD, input=msg.as_bytes(), check=True)


if __name__ == '__main__':
    check()