from Feed import Feed
from FeedEntry import FeedEntry
from Preference import Preference
from sqlalchemy import Boolean
from sqlalchemy import Column
from sqlalchemy import DateTime
from sqlalchemy import ForeignKey
from sqlalchemy import Integer
from sqlalchemy import MetaData
from sqlalchemy import String
from sqlalchemy import Table
from sqlalchemy import Text
from sqlalchemy.orm import mapper
from sqlalchemy.orm import relation

mappingDefined = False
feedEntryTable = None

def createMapping(engine):
    """ Make sure the mapping is defined only once. This is not really needed for the feed updater
        or the GUI app but comes in handy when working interactively with the system. """
    global mappingDefined
    if not mappingDefined:
        _createMapping(engine)
        mappingDefined = True

def _createMapping(engine):
    metadata = MetaData(engine)
    metadata.bind = engine
    
    feedTable = Table("feed", metadata,
        Column("pk", Integer, primary_key=True),
        Column("title", String(255), nullable=False),
        Column("rss_url", String(255), nullable=False),
        # update interval is specified in minutes
        Column("update_interval", Integer, nullable=False),
        Column("next_update", DateTime, nullable=False),
        # when displaying an entry of this feed, do not display the summary but rather load 
        # the link directly
        Column("auto_load_entry_link", Boolean, nullable=False),
        # this is actually a hack: when opening some sites in the QWebView it just crashes.
        # This setting forces to open an entry's link in the external browser
        Column("always_open_in_browser", Boolean, nullable=False)
    )
    
    global feedEntryTable
    feedEntryTable = Table("feed_entry", metadata,
        Column("pk", Integer, primary_key=True),
        Column("create_timestamp", DateTime, nullable=False),
        Column("read", Integer, nullable=False),

        Column("id", String(512), nullable=False),
        Column("link", String(512), nullable=False),
        Column("title", Text, nullable=False),
        Column("summary", Text, nullable=False),
        Column("updated", DateTime),
        Column("feed_id", Integer, ForeignKey("feed.pk"))
    )
    
    preferencesTable = Table("preference", metadata,
        Column("pk", Integer, primary_key=True),
        Column("key", String(255), nullable=False),
        Column("value", String(255), nullable=False)
    )

    metadata.create_all()

    mapper(FeedEntry, feedEntryTable)
    mapper(Feed, feedTable,
        properties = {
            "entries" : relation(FeedEntry, backref="feed", lazy=True)
        }
    )
    mapper(Preference, preferencesTable)