src/TSN/Location.hs

   1 {-# LANGUAGE FlexibleInstances #-}
   2 {-# LANGUAGE GADTs #-}
   3 {-# LANGUAGE QuasiQuotes #-}
   4 {-# LANGUAGE TemplateHaskell #-}
   5 {-# LANGUAGE TypeFamilies #-}
   6
   7 -- | (At least) two different XML types have a notion of locations:
   8 --   "TSN.XML.News" and "TSN.XML.Scores". And in fact those two types
   9 --   agree on the city, state, and country -- at least for the
  10 --   database representation.
  11 --
  12 --   This module contains a data type for the common database
  13 --   representation.
  14 --
  15 module TSN.Location (
  16   Location(..),
  17   LocationConstructor(..) )
  18 where
  19
  20 -- System imports
  21 import Database.Groundhog () -- Required for some String instance
  22 import Database.Groundhog.TH (
  23   defaultCodegenConfig,
  24   groundhog,
  25   mkPersist )
  26
  27
  28 -- | Database representation of a location.
  29 --
  30 --   The country has always been present in the XML that we've
  31 --   seen. The city/state however have been observed missing in some
  32 --   cases. The Scores are better about always having a city/state,
  33 --   but in the interest of consolidation, we've made them optional so
  34 --   that they can be mushed together into this one type.
  35 --
  36 data Location =
  37   Location {
  38     city :: Maybe String,
  39     state :: Maybe String,
  40     country :: String }
  41   deriving (Eq, Show)
  42
  43
  44 -- Generate the Groundhog code for 'Location'.
  45 mkPersist defaultCodegenConfig [groundhog|
  46 - entity: Location
  47   dbName: locations
  48   constructors:
  49     - name: Location
  50       uniques:
  51         - name: unique_location
  52           type: constraint
  53           fields: [city, state, country]
  54 |]