type TripId    = Integer
data Transport = Plane | Train | Bus | Ship deriving (Eq, Show)
type Place     = String
type Price     = Integer
type Trip      = (TripId, Transport, Place, Place, Price)

type TicketId = Integer
type PersonId = Integer
data Tarif    = Adult | Child | Student | Senior deriving (Eq, Show)
type Ticket   = (TicketId, PersonId, TripId, Tarif)

type Database = ([Ticket], [Trip])


-- Gettery
getTripId :: Trip -> TripId
getTripId = undefined

getTransport :: Trip -> Transport
getTransport = undefined

getPlaceFrom :: Trip -> Place
getPlaceFrom = undefined

getPlaceTo :: Trip -> Place
getPlaceTo = undefined

getPrice :: Trip -> Price
getPrice = undefined

getTicketId :: Ticket -> TicketId
getTicketId = undefined

getPersonId :: Ticket -> PersonId
getPersonId = undefined

getTicketTripId :: Ticket -> TripId
getTicketTripId = undefined

getTarif :: Ticket -> Tarif
getTarif = undefined

-- Funkce pracující s databází
lookupTarif :: TicketId -> [Ticket] -> Tarif
lookupTarif = undefined

tripsFrom :: Place -> [Trip] -> [Trip]
tripsFrom = undefined

tripsTo :: Place -> [Trip] -> [Trip]
tripsTo = undefined

transports :: Place -> Place -> [Trip] -> [Transport]
transports = undefined

updatePrice :: TripId -> Price -> [Trip] -> [Trip]
updatePrice = undefined

tripCountByTransport :: Transport -> [Trip] -> Int
tripCountByTransport = undefined

travelsBy :: PersonId -> TripId -> [Ticket] -> Bool
travelsBy = undefined

peopleByTarif :: Tarif -> [Ticket] -> [PersonId]
peopleByTarif = undefined

travellersFrom :: Place -> Database -> [PersonId]
travellersFrom = undefined

ticketPrice :: (Tarif -> Price -> Price) -> TripId -> Tarif -> [Trip] -> Price
ticketPrice = undefined

spent :: (Tarif -> Price -> Price) -> PersonId -> Database -> Price
spent = undefined


-------------------------------------------------------------------------------
--                     S A M P L E    D A T A B A S E                        --
-------------------------------------------------------------------------------

testDB :: Database
testDB = (tickets, trips)
  where
    tickets = [ (0, 42, 0, Student), (1, 42, 4, Student)
              , (5, 4, 2, Adult), (42, 142, 5, Child)
              ]
    trips = [ (0, Plane, "Brno", "Praha", 1000), (1, Plane, "Praha", "Brno", 1050)
            , (2, Train, "Brno", "Praha", 400), (3, Train, "Praha", "Brno", 450)
            , (4, Bus, "Bratislava", "Kosice", 351), (5, Ship, "Bergen", "Stavanger", 5000)
            ]

tarifSR :: Tarif -> Price -> Price
tarifSR Adult price = price
tarifSR _     _     = 0

tarifCR :: Tarif -> Price -> Price
tarifCR Adult price = price
tarifCR Child _     = 0
tarifCR _     price = div (price * 3) 4

tarifNoDiscount :: Tarif -> Price -> Price
tarifNoDiscount _ p = p