ELM parse nested json

Question

I have a json array with a few comments that can be nested.

Exemple:

[
  {
    "author": "john",
    "comment" : ".....",
    "reply": "",
  },
  {
    "author": "Paul",
    "comment" : ".....",
    "reply": [  
      {
        "author": "john",
        "comment" : "nested comment",
        "reply": [
          {
            "author": "Paul",
            "comment": "second nested comment"
          }
        ]
      },
      {
        "author": "john",
        "comment" : "another nested comment",
        "reply": ""
      }
    ]
  },
  {
    "author": "Dave",
    "comment" : ".....",
    "reply": ""
  },
]

So, this is a list of comments that each comment can have an answer with an infinite number of answers. With help Json.Decode.listI can decode the first level of the comment, but how to check if there is any answer and then analyze it again?

This is a simplified version of what I'm trying to do. I am actually trying to decrypt reddit comments. example

Answer 1

Elm , Customer. , Json.map3.

json : reply - , . , (, ).

, lazy , .

import Html exposing (Html, text)
import Json.Decode as Json exposing (..)


main : Html msg
main =
    text <| toString <| decodeString (list commentDecoder) s


type Comment
    = Comment
        { author : String
        , comment : String
        , reply : List Comment
        }


newComment : String -> String -> List Comment -> Comment
newComment author comment reply =
    Comment
        { author = author
        , comment = comment
        , reply = reply
        }


emptyStringToListDecoder : Decoder (List a)
emptyStringToListDecoder =
    string
        |> andThen
            (\s ->
                case s of
                    "" ->
                        succeed []

                    _ ->
                        fail "Expected an empty string"
            )


commentDecoder : Decoder Comment
commentDecoder =
    map3 newComment
        (field "author" string)
        (field "comment" string)
        (field "reply" <|
            oneOf
                [ emptyStringToListDecoder
                , list (lazy (\_ -> commentDecoder))
                ]
        )


s =
    """
[{
  "author": "john",
  "comment": ".....",
  "reply": ""
}, {
  "author": "Dave",
  "comment": ".....",
  "reply": ""
}, {
  "author": "Paul",
  "comment": ".....",
  "reply": [{
    "author": "john",
    "comment": "nested comment",
    "reply": [{
      "author": "Paul",
      "comment": "second nested comment",
      "reply": ""
    }]
  }, {
    "author": "john",
    "comment": "another nested comment",
    "reply": ""
  }]
}]
"""

( json : , reply )