add frontend (boilerplate)

frontend/LICENSE

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+Copyright (c) 2024, Alexander Foremny
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Alexander Foremny nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

frontend/app/Main.hs

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+module Main where
+
+#ifndef ghcjs_HOST_OS
+import Language.Javascript.JSaddle.Warp as JSaddle
+#endif
+
+import Data.ByteString.UTF8 qualified as B
+import Data.Maybe
+import Miso
+import Miso.String
+
+#ifndef ghcjs_HOST_OS
+import Network.HTTP.Simple
+import Data.String
+#else
+import JavaScript.Web.XMLHttpRequest
+#endif
+
+type Model = Maybe Schema
+
+type Schema = String
+
+data Action
+  = FetchSchema
+  | SetSchema Schema
+  deriving (Show, Eq)
+
+#ifndef ghcjs_HOST_OS
+runApp :: JSM () -> IO ()
+runApp f = JSaddle.debugOr 8080 (f >> syncPoint) JSaddle.jsaddleApp
+#else
+runApp :: IO () -> IO ()
+runApp app = app
+#endif
+
+main :: IO ()
+main = runApp $ startApp App {..}
+  where
+    initialAction = FetchSchema
+    model = Nothing
+    update = updateModel
+    view = viewModel
+    events = defaultEvents
+    subs = []
+    mountPoint = Nothing
+    logLevel = Off
+
+updateModel :: Action -> Model -> Effect Action Model
+updateModel action m =
+  case action of
+    FetchSchema -> m <# do SetSchema <$> fetchSchema
+    SetSchema schema -> noEff (Just schema)
+
+fetchSchema :: JSM String
+fetchSchema = fetch "http://localhost:8081/posts.schema.json"
+
+#ifndef ghcjs_HOST_OS
+fetch :: String -> JSM String
+fetch url = B.toString . getResponseBody <$> httpBS (fromString url)
+#else
+fetch :: String -> JSM String
+fetch url = maybe "" B.toString . contents <$> xhrByteString req
+  where
+    req =
+      Request
+        { reqMethod = GET,
+          reqURI = pack url,
+          reqLogin = Nothing,
+          reqHeaders = [],
+          reqWithCredentials = False,
+          reqData = NoData
+        }
+#endif
+
+viewModel :: Model -> View Action
+viewModel schema =
+  div_ [] [text (toMisoString (fromMaybe ".." schema))]

frontend/frontend.cabal

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+cabal-version:   3.4
+name:            frontend
+version:         0.1.0.0
+license:         BSD-3-Clause
+license-file:    LICENSE
+maintainer:      aforemny@posteo.de
+author:          Alexander Foremny
+build-type:      Simple
+extra-doc-files: CHANGELOG.md
+
+executable frontend
+    main-is:            Main.hs
+    hs-source-dirs:     app
+    default-language:   GHC2021
+    default-extensions: CPP OverloadedStrings RecordWildCards
+    ghc-options:        -Wall
+    build-depends:
+        base,
+        bytestring,
+        containers,
+        miso,
+        text,
+        utf8-string
+
+    if !arch(javascript)
+        build-depends: jsaddle-warp
+
+    if arch(javascript)
+        build-depends: ghcjs-base
+    else
+        build-depends: http-conduit