Decoding a JSON multi-track tree to a F # multi-faceted tree

Question

I have the following JSON data in documentdb, and I would like to parse this in a F # tree tree join

"commentTree": {
    "commentModel": {
        "commentId": "",
        "userId": "",
        "message": ""
      },
      "forest": []
    }

Multi-user demarcated union F #

type public CommentMultiTreeDatabaseModel = 
| CommentDatabaseModelNode of CommentDatabaseModel * list<CommentMultiTreeDatabaseModel>

where CommentMultiTreeDatabaseModel is defined as

type public CommentDatabaseModel =
{ commentId : string
  userId : string
  message : string
}

I refer to Fold / Recursion over a multi-track tree in f # . I'm not sure where to start parsing such a JSON structure into a F # multi-track tree. Any suggestions would be highly appreciated. Thanks

Answer 1

- , , CommentMultiTreeDatabaseModel. CommentDatabaseModel CommentMultiTreeDatabaseModel. :

let parseComment (input : JSON) : CommentDatabaseModel =
    ...

let parseTree (input : JSON) : CommentMultiTreeDatabaseModel =
    ...

, parseTree - , ! rec , .

, . , , parseTree, . JSON DU. , Chiron, - .

, JSON . , , , .

[<RequireQualifiedAccess>]
type JSON =
    | String of string
    | Object of (string * JSON) list
    | Array of JSON list

type public CommentDatabaseModel = {
    commentId : string
    userId : string
    message : string
}

type public CommentMultiTreeDatabaseModel = 
    | CommentDatabaseModelNode of CommentDatabaseModel * list<CommentMultiTreeDatabaseModel>


let parseComment = function
    | JSON.Object [ "commentId", JSON.String commentId; "userId", JSON.String userId; "message", JSON.String message ] ->
        {
            commentId = commentId
            userId = userId
            message = message
        }
    | _ -> failwith "Bad data"

let rec parseTree (input : JSON) : CommentMultiTreeDatabaseModel =
    match input with
    | JSON.Object [ "commentModel", commentModel; "forest", JSON.Array forest ] ->
        CommentDatabaseModelNode (parseComment commentModel, List.map parseTree forest)
    | _ -> failwith "Bad data"

let parse (input : JSON) : CommentMultiTreeDatabaseModel =
    match input with
    | JSON.Object [ "commentTree", commentTree ] ->
        parseTree commentTree
    | _ -> failwith "Bad data"


let comment text =    
    JSON.Object [
        "commentId", JSON.String ""
        "userId", JSON.String ""
        "message", JSON.String text
    ]

let sampleData =
    JSON.Object [
        "commentTree", JSON.Object [
            "commentModel", comment "one"
            "forest", JSON.Array [
                JSON.Object [
                    "commentModel", comment "two"
                    "forest", JSON.Array []
                ]

                JSON.Object [
                    "commentModel", comment "three"
                    "forest", JSON.Array []
                ]
            ]
        ]
    ]

parse sampleData

(*
val it : CommentMultiTreeDatabaseModel =
  CommentDatabaseModelNode
    ({commentId = "";
      userId = "";
      message = "one";},
     [CommentDatabaseModelNode ({commentId = "";
                                 userId = "";
                                 message = "two";},[]);
      CommentDatabaseModelNode ({commentId = "";
                                 userId = "";
                                 message = "three";},[])])
*)