// High-performance JSON parsing with System.Text.Json and F#
// Example translated to F# from 
// https://learn.microsoft.com/en-us/dotnet/standard/serialization/system-text-json/use-utf8jsonreader
#r "nuget:System.Text.Json"

open System
open System.Text
open System.Text.Json

let options = JsonReaderOptions(
                AllowTrailingCommas = true, 
                CommentHandling = JsonCommentHandling.Skip)

let readJson (jsonUtf8Bytes:ReadOnlySpan<byte>) =
    let reader = Utf8JsonReader(jsonUtf8Bytes, options)

    while reader.Read() do
        Console.WriteLine reader.TokenType
        match reader.TokenType with
        | JsonTokenType.PropertyName
        | JsonTokenType.String ->
            let text = reader.GetString()
            Console.Write " "
            Console.Write text
        | JsonTokenType.Number ->
            let intValue = reader.GetInt32()
            Console.Write " "
            Console.Write intValue
        | JsonTokenType.None | JsonTokenType.Null | JsonTokenType.Comment 
        | JsonTokenType.True | JsonTokenType.False
        | JsonTokenType.StartObject | JsonTokenType.EndObject
        | JsonTokenType.StartArray  | JsonTokenType.EndArray 
        | _ -> () // Other token types elided for brevity

    Console.WriteLine()

let sampleJson = 
    let jsonBytes = 
        """{ "x": 3 }""" 
        |> Encoding.UTF8.GetBytes
    readJson (System.ReadOnlySpan jsonBytes)