Add dispatch stuff.

1 files changed, 53 insertions, 0 deletions

diff --git a/Dispatch.idr b/Dispatch.idr
new file mode 100644
index 0000000..a13fef4
--- /dev/null
+++ b/Dispatch.idr
@@ -0,0 +1,53 @@
+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)
+  ]
+
+partial
+main : IO ()
+main = do
+  putStrLn (fromMaybe "failed" $ dispatch handlers "hello/Bob/Sunshine")
+  putStrLn (fromMaybe "failed" $ dispatch handlers "weather/New York")