module Json =

(* A generic lens for Json files                                           *)

(* Based on the following grammar from http://www.json.org/                *)

(* Object ::= '{'Members ? '}'                                             *)

(* Members ::= Pair+                                                       *)

(* Pair ::= String ':' Value                                               *)

(* Array ::= '[' Elements ']'                                              *)

(* Elements ::= Value ( "," Value )*                                       *)

(* Value ::= String | Number | Object | Array | "true" | "false" | "null"  *)

(* String ::= "\"" Char* "\""                                              *)

(* Number ::= /-?[0-9]+(\.[0-9]+)?([eE][+-]?[0-9]+)?/                      *)

let ws = del /[ \t\n]*/ ""

let comment = Util.empty_c_style | Util.comment_c_style | Util.comment_multiline

let comments = comment* . Sep.opt_space

let comma = Util.del_str "," . comments

let colon = Util.del_str ":" . comments

let lbrace = Util.del_str "{" . comments

let rbrace = Util.del_str "}"

let lbrack = Util.del_str "[" . comments

let rbrack = Util.del_str "]"

(* This follows the definition of 'string' at https://www.json.org/

   It's a little wider than what's allowed there as it would accept

   nonsensical \u escapes *)

let str_store = Quote.dquote . store /([^\\"]|\\\\["\/bfnrtu\\])*/ . Quote.dquote

let number = [ label "number" . store /-?[0-9]+(\.[0-9]+)?([eE][+-]?[0-9]+)?/

             . comments ]

let str = [ label "string" . str_store . comments ]

let const (r:regexp) = [ label "const" . store r . comments ]

let fix_value (value:lens) =

     let array = [ label "array" . lbrack

               . ( ( Build.opt_list value comma . rbrack . comments )

                   | (rbrack . ws) ) ]

  in let pair = [ label "entry" . str_store . ws . colon . value ]

  in let obj = [ label "dict" . lbrace

             . ( ( Build.opt_list pair comma. rbrace . comments )

                 | (rbrace . ws ) ) ]

  in (str | number | obj | array | const /true|false|null/)

(* Process arbitrarily deeply nested JSON objects *)

let rec rlns = fix_value rlns

let lns = comments . rlns