Mount OWIN implementation at the owin path.

Author: tachyus-ryan

README.md

@@ -3,9 +3,9 @@ TodoBackendFSharp
 
 Todo-Backend implementation in [F#](http://fsharp.org/) using [Dyfrig](https://github.com/fsprojects/dyfrig) and [OWIN](http://owin.org/).
 
-Run the [specs](http://todo-backend.thepete.net/specs/index.html?http://todomvcfsharp.azurewebsites.net/).
+Run the [specs](http://todo-backend.thepete.net/specs/index.html?http://todo-backend-fsharp.azurewebsites.net/owin).
 
-Try the [client](http://todo-backend.thepete.net/client/index.html?http://todomvcfsharp.azurewebsites.net/).
+Try the [client](http://todo-backend.thepete.net/client/index.html?http://todo-backend-fsharp.azurewebsites.net/owin).
 
 Read the [docs](https://github.com/panesofglass/TodoBackendFSharp/blob/master/docs/index.md).
 

TodoBackendFSharp/Startup.fs

@@ -17,23 +17,44 @@
 
 namespace TodoBackend
 
+open System
+open System.Threading.Tasks
 open Owin
 open Microsoft.Owin
+open Dyfrig
 
 module Cors =
     /// Cross Origin Resource Sharing (CORS) middleware wrapper for the `Microsoft.Owin.Cors.CorsMiddleware`.
     let middleware next env =
         Cors.CorsMiddleware(Dyfrig.OwinAppFunc next, Cors.CorsOptions.AllowAll).Invoke env
 
 module Link =
-    open Dyfrig
-
     /// Middleware that inserts an HTTP `Link` header pointing to the TodoBackendFSharp source code repository on GitHub.
     let middleware next (env: OwinEnv) =
         let headers : OwinHeaders = unbox env.[Constants.responseHeaders]
         headers.Add("Link", [|"<https://github.com/panesofglass/TodoBackendFSharp>; rel=meta"|])
         next env
 
+module Implementations =
+    /// Helper that selects an `app` mounted at the first path `segment`.
+    let choose selector (env: OwinEnv) =
+        let path : string = unbox env.[Constants.requestPath]
+        // Split the path into its segments
+        let pathSegments = path.Split([|'/'|], StringSplitOptions.RemoveEmptyEntries)
+        // Take the first segment for the purpose of matching sub-paths
+        if pathSegments.Length = 0 then
+            TodoBackend.notFound env |> Async.StartAsTask :> Task
+        else
+        let firstSegment = pathSegments.[0]
+        // Set the segment in the owin.RequestPathBase environment variable.
+        let pathBase : string = unbox env.[Constants.requestPathBase]
+        env.[Constants.requestPathBase] <- pathBase + "/" + firstSegment
+        // Update the owin.RequestPath environment variable.
+        env.[Constants.requestPath] <- String.Join("/", pathSegments.[1..])
+        match selector (firstSegment.ToLowerInvariant()) with
+        | Some app -> app env
+        | None -> TodoBackend.notFound env |> Async.StartAsTask :> Task
+
 (*
 Microsoft's Katana components make use of a `Startup` class with a single member conventionally named
 `Configuration`. `Configuration` takes an `IAppBuilder` into which you mount middleware components.
@@ -48,12 +69,16 @@ and then into the `Cors.middleware`. By doing this, Katana will pass all request
 /// Todo-backend startup used by Katana.
 [<Sealed>]
 type Startup() =
+        
     /// Configures the Katana `IAppBuilder` to run the todo-backend application and
     /// add the Link header. The `Cors.middleware` wraps every request and will respond
     /// immediately to CORS preflight requests.
     member __.Configuration(builder: IAppBuilder) =
+        // Wire up middleware
         builder.Use(fun _ ->
-            TodoBackend.app
+            Implementations.choose (function
+            | "owin" -> Some TodoBackend.app 
+            | _ -> None)
             |> Link.middleware
             |> Cors.middleware)
         |> ignore

TodoBackendFSharp/TodoBackend.fsproj

@@ -23,7 +23,7 @@
     <IISExpressAnonymousAuthentication>enabled</IISExpressAnonymousAuthentication>
     <IISExpressWindowsAuthentication>disabled</IISExpressWindowsAuthentication>
     <IISExpressUseClassicPipelineMode>false</IISExpressUseClassicPipelineMode>
-    <NameOfLastUsedPublishProfile>todomvcfsharp - Web Deploy</NameOfLastUsedPublishProfile>
+    <NameOfLastUsedPublishProfile>todo-backend-fsharp</NameOfLastUsedPublishProfile>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Debug|AnyCPU' ">
     <DebugSymbols>true</DebugSymbols>

docs/index.md

@@ -2,16 +2,16 @@
 
 TodoBackendFSharp is a Todo-Backend implementation in [F#](http://fsharp.org/)
 following the guidelines provided at http://todo-backend.thepete.net/.
-You can [run the specs](http://todo-backend.thepete.net/specs/index.html?http://todo-backend-fsharp.azurewebsites.net/) or
-[try the client](http://todo-backend.thepete.net/client/index.html?http://todo-backend-fsharp.azurewebsites.net/).
+You can [run the specs](http://todo-backend.thepete.net/specs/index.html?http://todo-backend-fsharp.azurewebsites.net/owin) or
+[try the client](http://todo-backend.thepete.net/client/index.html?http://todo-backend-fsharp.azurewebsites.net/owin).
 
 ## Why Raw OWIN?
 
 The first implementation was written as directly upon the [OWIN](http://owin.org/) spec as possible in order
 to demonstrate the ease with which you can build web applications in F#. Specific features of F# demonstrated
 in this implementation include:
 
-* [Function composition for composing applications](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Startup.fs#L56-58)
+* [Function composition for composing applications](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Startup.fs#L78-83)
 * [Active Patterns for routing](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Owin.fs#L177-205)
 * [MailboxProcessor for in-memory storage](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/TodoStorage.fs)
 * [Simple, Async functions as HTTP handlers](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Owin.fs#L64-163)
@@ -24,8 +24,8 @@ These libraries are [Katana](https://katanaproject.codeplex.com/) and [Dyfrig](h
 ### Katana
 
 Microsoft's Katana components provide a number of hosts and many, reusable middlewares to ease the burden of
-building web applications. Katana hosts make use of a [`Startup` class](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Startup.fs#L50)
-with a single member conventionally named [`Configuration`](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Startup.fs#L54).
+building web applications. Katana hosts make use of a [`Startup` class](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Startup.fs#L71)
+with a single member conventionally named [`Configuration`](https://github.com/panesofglass/TodoBackendFSharp/blob/master/TodoBackend/Startup.fs#L76).
 `Configuration` takes an `IAppBuilder` into which you mount middleware components.
 In F#, you can write middleware components as simple functions taking the next `OwinAppFunc` handler
 and an `OwinEnv` environment dictionary. F# allows you to chain these together naturally using the