Add part4

part4/src/Data/Article/Author.elm

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+module Data.Article.Author exposing (Author, decoder)
+
+import Data.User as User exposing (Username)
+import Data.UserPhoto as UserPhoto exposing (UserPhoto)
+import Json.Decode as Decode exposing (Decoder)
+import Json.Decode.Pipeline exposing (custom, decode, required)
+
+
+decoder : Decoder Author
+decoder =
+    decode Author
+        |> required "username" User.usernameDecoder
+        |> required "bio" (Decode.nullable Decode.string)
+        |> required "image" UserPhoto.decoder
+        |> required "following" Decode.bool
+
+
+type alias Author =
+    { username : Username
+    , bio : Maybe String
+    , image : UserPhoto
+    , following : Bool
+    }

part4/src/Data/Article/Comment.elm

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+module Data.Article.Comment exposing (Comment, CommentId, commentIdDecoder, decoder, idToString)
+
+import Data.Article.Author as Author exposing (Author)
+import Date exposing (Date)
+import Json.Decode as Decode exposing (Decoder)
+import Json.Decode.Extra
+import Json.Decode.Pipeline exposing (custom, decode, required)
+
+
+type alias Comment =
+    { id : CommentId
+    , body : String
+    , createdAt : Date
+    , updatedAt : Date
+    , author : Author
+    }
+
+
+
+-- SERIALIZATION --
+
+
+decoder : Decoder Comment
+decoder =
+    decode Comment
+        |> required "id" commentIdDecoder
+        |> required "body" Decode.string
+        |> required "createdAt" Json.Decode.Extra.date
+        |> required "updatedAt" Json.Decode.Extra.date
+        |> required "author" Author.decoder
+
+
+
+-- IDENTIFIERS --
+
+
+type CommentId
+    = CommentId Int
+
+
+idToString : CommentId -> String
+idToString (CommentId id) =
+    toString id
+
+
+commentIdDecoder : Decoder CommentId
+commentIdDecoder =
+    Decode.map CommentId Decode.int

part4/src/Data/Article/Feed.elm

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+module Data.Article.Feed exposing (Feed, decoder)
+
+import Data.Article as Article exposing (Article)
+import Json.Decode as Decode exposing (Decoder)
+import Json.Decode.Pipeline exposing (decode, required)
+
+
+type alias Feed =
+    { articles : List (Article ())
+    , articlesCount : Int
+    }
+
+
+
+-- SERIALIZATION --
+
+
+decoder : Decoder Feed
+decoder =
+    decode Feed
+        |> required "articles" (Decode.list Article.decoder)
+        |> required "articlesCount" Decode.int