Add support for appcast generation

src/app/FakeLib/Appcast.fs

@@ -0,0 +1,155 @@
+/// Contains code to configure FAKE for Appcast handling
+module Fake.Appcast
+open System.Xml
+open System.Xml.Linq
+
+
+//private XMLHelper inspired by https://nbevans.wordpress.com/2015/04/15/super-skinny-xml-document-generation-with-f/
+let private XDeclaration version encoding standalone = XDeclaration(version, encoding, standalone)
+let private XName expandedName = XName.Get(expandedName)
+let private XDocument xdecl content = XDocument(xdecl, content |> Seq.map (fun v -> v :> obj) |> Seq.toArray)
+let private XElement expandedName content = XElement(XName expandedName, content |> Seq.map (fun v -> v :> obj) |> Seq.toArray) :> obj
+let private XAttribute expandedName value = XAttribute(XName expandedName, value) :> obj
+let private XAttributeXName expandedName value = Linq.XAttribute(expandedName, value) :> obj
+
+/// Sparkel namespace used for RSS extension
+let private sparkle = XNamespace.Get("http://www.andymatuschak.org/xml-namespaces/sparkle")
+
+/// Mime type of the download file
+type MimeType =
+    /// Octetstream use for exe or zip files
+    | OctetStream
+    /// Custom mimetype
+    | Custom of string
+
+/// Download details for the appcast
+type AppcastItem = {
+    /// The name of the update
+    title : string;
+    /// Date when update is published
+    pubdate : System.DateTime;
+    /// URI where the update files are found
+    url : System.Uri;
+    /// Machine readable version number used to determine if an update is available by the client (should follow semver)
+    version : string;
+    /// Optional human readable version number. This will be shown to the user if present otherwise
+    /// the technical version number will be used
+    shortVersion : string option;
+    /// Mime type of the update file, usualy octetstream
+    mimetype : MimeType
+    /// Optional DSA signature for the archive. It is recommended to use this if the app itself is not signed
+    dsaSignature : string option;
+    /// Optional miminal system version for the update
+    minimumSystemVersion : string option;
+    /// Length of the file in bytes
+    length : int64;
+}
+
+/// Configuration data for the appcast
+type Appcast = {
+    /// A titel, usually the app name
+    title : string;
+    /// Short description
+    description : string;
+    /// Language of your app
+    language : string;
+    /// Updates published to client, can habe multiple updates e.g. for different OS versions
+    items : AppcastItem list;
+}
+
+/// writes an appcast to a file
+/// ##Parameters
+///
+///  - `path` - The file where the appcast should be written
+///  - `cast` - The appcast to write
+/// ##Sample
+///  // This target creates the app cast for our app. I contains two version 1.X and 2.X while 2.X requires at least OS X 10.10 Yosemite.
+///  Target "CreateAppcast" (fun _ ->
+///      let server = "https://example.com/files/"
+///      let fileLength file =
+///           let info = new System.IO.FileInfo(file)
+///           info.Length
+///           
+///      let latestSize = fileLength "build/download-2.0.1.zip"
+///      let legacySize = fileLength "build/download-1.1.4.zip"
+///      
+///      { 
+///          title = "My Awesome App"
+///          description = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. Donec a diam lectus."
+///          language = "en"
+///          items = [
+///                      {
+///                          title = "Hawk Nickel Greyhound"
+///                          pubdate = System.DateTime.Now
+///                          url = new System.Uri(server + "download-2.0.1.zip")
+///                          version = "2014" // This our internal build number
+///                          shortVersion = Some("2.0.1") //This is what we show to the user
+///                          mimetype = OctetStream
+///                          minimumSystemVersion = Some("10.10")
+///                          length = latestSize
+///                          dsaSignature = None
+///                      };
+///                      {
+///                          title = "Sparrow Platinum Beagle"
+///                          pubdate = System.DateTime.Now
+///                          url = new System.Uri(server + "download-1.1.4.zip")
+///                          version = "1142" // This our internal build number
+///                          shortVersion = Some("1.1.4") //This is what we show to the user
+///                          mimetype = OctetStream
+///                          length = legacySize
+///                          minimumSystemVersion = None
+///                          dsaSignature = None
+///                      }
+///          ]
+///      } |> writeAppcast "build/updates.xml"
+///  )
+let writeAppcast (path : string) (cast : Appcast) = 
+    let toXml (cast : Appcast) =
+        let mtToString mimetype = 
+            match mimetype with 
+                | OctetStream -> "application/octet-stream"
+                | Custom(s) -> s
+        let choose a b =
+            match a with 
+                | Some(c) -> c
+                | None -> b
+        let appendSome option consequence content =
+            match option with
+                | Some(data) -> (consequence data) :: content
+                | None -> content
+
+
+        let item (e : AppcastItem) = 
+            let appendMinimumVersion = appendSome e.minimumSystemVersion (fun d ->  XAttributeXName (sparkle + "minimumSystemVersion") d)
+            let appendSig = appendSome e.dsaSignature (fun d ->  XAttributeXName (sparkle + "dsaSignature") d)
+
+            XElement "item" [
+                XElement "title" e.title
+                XElement "pubDate" (e.pubdate.ToString("r"))
+                XElement "enclosure" ([
+                    XAttribute "url" e.url
+                    XAttributeXName (sparkle + "version") e.version
+                    XAttribute "type" (mtToString e.mimetype)
+                    XAttribute "length" e.length
+                    XAttributeXName (sparkle + "shortVersionString") (choose e.shortVersion e.version)
+                ] 
+                |> appendMinimumVersion
+                |> appendSig)
+            ]
+
+        let doc = XDocument (XDeclaration "1.0" "UTF-8" "no") [
+                    XElement "rss" [
+                        XAttribute "version" "2.0"
+                        XAttributeXName (XNamespace.Xmlns + "sparkle") "http://www.andymatuschak.org/xml-namespaces/sparkle"
+                        XAttributeXName (XNamespace.Xmlns + "dc") "http://purl.org/dc/elements/1.1/"
+                        XElement "channel" ([
+                                                XElement "title" cast.title
+                                                XElement "description" cast.description
+                                                XElement "language" cast.language] 
+                        @ List.map item cast.items)
+                    ]
+        ]
+        doc
+    let xml = toXml cast
+    use writer = XmlWriter.Create(path)
+    xml.Save(writer)

src/app/FakeLib/FakeLib.fsproj

@@ -166,6 +166,7 @@
     <Compile Include="SquirrelHelper.fs" />
     <Compile Include="XCopyHelper.fs" />
     <Compile Include="DynamicsCRMHelper.fs" />
+    <Compile Include="Appcast.fs" />
   </ItemGroup>
   <ItemGroup>
     <Reference Include="ICSharpCode.SharpZipLib">