module Main
  
%default total

data Matcher =
    Directory String Matcher
  | Capture Matcher
  | End
  
HandlerType : Matcher -> Type
HandlerType (Directory s m) = HandlerType m
HandlerType (Capture m) = String -> HandlerType m
HandlerType End = String

Handler : Type
Handler = (m : Matcher ** HandlerType m)

dispatch : (handlers : List Handler) -> String -> Maybe String
dispatch [] _ = Nothing
dispatch handlers path = go handlers components where
  components : List String
  components = filter (/="") (split (=='/') path)
  
  go : List Handler -> List String -> Maybe String
  go [] cs = Nothing
  go ((m ** f) :: hs) cs = 
    let next = go hs cs in
    case m of 
      Directory dir matcher => case cs of
        (c :: cs') => if c == dir then go ((matcher ** f) :: hs) cs' else next
        _ => next
      Capture matcher => case cs of
        (c :: cs') => go ((matcher ** f c) :: hs) cs'
        _ => next
      End => Just f

helloHandler : String -> String -> String
helloHandler firstName lastName = "Hello, " ++ firstName ++ " " ++ lastName
  
weatherHandler : String -> String
weatherHandler place = "The weather in " ++ place ++ " is cold."

handlers : List Handler
handlers = [
    (Directory "hello" (Capture (Capture End)) ** helloHandler)
  , (Directory "weather" (Capture End) ** weatherHandler)
  ]

main : IO ()
main = do
  putStrLn (fromMaybe "failed" $ dispatch handlers "hello/Bob/Sunshine")
  putStrLn (fromMaybe "failed" $ dispatch handlers "weather/New York")