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open System
open System.Globalization
open FParsec

type Token =
  | KeyGroup of string list
  | KeyValue of string * obj

let (<||>) p1 p2 = attempt (p1 |>> box) <|> attempt (p2 |>> box)
let spc      = many (anyOf [' '; '\t']) 
let lexeme s = pstring s .>> spc
let lexemel s= pstring s .>> spaces
let comment  = pchar '#' .>>. restOfLine false
let blanks   = skipMany ((comment <||> spc) .>> newline .>> spc) .>> spc
let brace p  = between (lexemel "[") (lexemel "]") p
let pbool    = (lexeme "true" >>% true) <|> (lexeme "false" >>% false)
let pstr     = between (lexeme "\"") (lexeme "\"") (manySatisfy ((<>)'"'))
//let pdate' s = try preturn (Instant.FromDateTimeUtc (DateTime.Parse (s, null, DateTimeStyles.RoundtripKind))) with _ -> fail ""
//let pdate    = between spc spc (anyString 20) >>= pdate'
let ary elem = brace (sepBy (elem .>> spaces) (lexemel ","))
let pary     = ary pbool <||> ary pint64 <||> ary pstr <||> ary pfloat
let value    = pbool <||> pstr <||> pint64 <||> pfloat <||> pary <||> ary pary
let kvKey    = many1Chars (noneOf " \t\n=")
let keyvalue = (kvKey .>> spc) .>>. (lexeme "=" >>. value) |>> KeyValue
let kgKey    = (many1Chars (noneOf " \t\n].")) .>> spc
let keygroup = blanks >>. brace (sepBy kgKey (lexeme ".")) |>> KeyGroup
let document = blanks >>. many (keygroup <|> keyvalue .>> blanks)

let parse text : Map<string, obj> =
  match run document text with
  | Success(tokens, _, _) ->
    tokens
    |> List.fold
        (fun (currentKg, m) t ->
         match t with
         | KeyGroup kg -> (kg, m)
         | KeyValue (key, value) ->
           let key = String.concat "." [ yield! currentKg; yield key]
           currentKg, m |> Map.add key value)
        ([], Map.empty)
    |> snd
  | __ -> Map.empty