import json
import dateutil
from datetime import datetime, timezone

from flask import Flask, request, abort
from feedgen.feed import FeedGenerator

from pony import orm
from pony.orm import Required, Optional, Set

app = Flask(__name__)

SITE_URL = 'http://localhost:5000/feeds/'

db = orm.Database()

class Feed(db.Entity):
    slug = Required(str, unique=True)
    admin_token = Required(str)
    title = Required(str)
    atom_id = Required(str) # also link
    description = Required(str)
    login = Optional(str)
    password = Optional(str)
    items = Set('Item')

class Item(db.Entity):
    feed = Required(Feed)
    atom_id = Required(str)
    title = Required(str)
    content = Required(str)
    date = Required(datetime)

db.bind(provider='sqlite', filename='db.sqlite', create_db=True)
db.generate_mapping(create_tables=True)
orm.set_sql_debug(True)

def does_slug_exist(slug):
    with orm.db_session:
        return len(orm.select(f for f in Feed if f.slug == slug)[:1])

@app.route('/feeds', methods=['POST'])
def add_feed():
    data = request.get_json(silent=True)

    if 'slug' not in data:
        abort(400, 'missing slug')

    slug = data['slug']

    if does_slug_exist(slug):
        abort(400, "feed with this slug already exists")

    if 'title' not in data or 'description' not in data or 'admin_token' not in data:
        abort(400, "missing title or description or admin_token")

    url = SITE_URL + slug

    with orm.db_session:
        feed = Feed(slug=slug,
                    admin_token=data['admin_token'],
                    title=data['title'],
                    atom_id=url,
                    description=data['description'])

        if 'login' in data and 'password' in data:
            feed.login = data['login']
            feed.password = data['password']

    return "OK"

@app.route('/feeds/<slug>', methods=['GET', 'POST'])
@orm.db_session
def by_feed_name(slug):
    if not does_slug_exist(slug):
        abort(404, "unknown slug")

    feed = orm.select(f for f in Feed if f.slug == slug)[:1][0]

    if feed.password is not '':
        auth = request.authorization
        if not auth or auth.username != feed.login or auth.password != feed.password:
            abort(401, "missing or incorrect password")

    if request.method == 'POST':
        data = request.get_json(silent=True)

        if 'title' not in data or 'content' not in data or 'admin_token' not in data:
            abort(400, "missing title or content")

        if data['admin_token'] != feed.admin_token:
            abort(401, "incorrect admin_token")

        item_id = feed.atom_id + '/' + str(len(feed.items))
        date = datetime.now(dateutil.tz.tzutc())

        with orm.db_session:
            item = Item(feed=feed,
                        atom_id=item_id,
                        title=data['title'],
                        content=data['content'],
                        date=date)

        return "OK"

    gen = FeedGenerator()
    gen.title(feed.title)
    gen.id(feed.atom_id)
    gen.link(href=feed.atom_id)
    gen.description(feed.description)

    for item in feed.items:
        fe = gen.add_entry()
        fe.id(item.atom_id)
        fe.title(item.title)
        fe.content(item.content)

        date = item.date.replace(tzinfo=timezone.utc)
        fe.updated(date)

    return gen.atom_str(pretty=True).decode('utf8')