wrote a pretty printer as an example

examples/pretty_printer.erl

@@ -0,0 +1,64 @@
+-module(pretty_printer).
+
+-export([print/2, jsx_event/2]).
+
+-record(opts, {
+    indent = 4
+}).
+
+print(JSON, Opts) ->
+    Init = init(parse_opts(Opts, #opts{})),
+    {{pretty_printer, Result}, _} = (jsx:decoder({pretty_printer, Init}, []))(JSON),
+    Result.
+    
+parse_opts([{indent, Val}|Rest], Opts) ->
+    parse_opts(Rest, Opts#opts{indent = Val});
+parse_opts([], Opts) ->
+    Opts.
+    
+init(Opts) ->
+    {[], Opts#opts.indent, 0, false}.
+    
+
+jsx_event(start_object, {Acc, Indent, Level, _}) ->
+    {Acc ++ "{", Indent, Level + 1, false};
+jsx_event(start_array, {Acc, Indent, Level, _}) ->
+    {Acc ++ "[", Indent, Level + 1, false};
+
+jsx_event({key, Key}, {Acc, Indent, Level, true}) ->
+    {Acc ++ ",\n" ++ indent(Indent, Level) ++ "\"" ++ Key ++ "\": ", Indent, Level, false};
+jsx_event({key, Key}, {Acc, Indent, Level, false}) ->
+    {Acc ++ "\n" ++ indent(Indent, Level) ++ "\"" ++ Key ++ "\": ", Indent, Level, false};
+
+jsx_event({number, Number}, {Acc, Indent, Level, true})  ->
+    {Acc ++ ",\n" ++ indent(Indent, Level) ++ Number, Indent, Level, true};
+jsx_event({number, Number}, {Acc, Indent, Level, false})  ->
+    {Acc ++ "\n" ++ indent(Indent, Level) ++ Number, Indent, Level, true};
+
+jsx_event({string, String}, {Acc, Indent, Level, true})  ->
+    {Acc ++ ",\n" ++ indent(Indent, Level) ++ "\"" ++ String ++ "\"", Indent, Level, true};
+jsx_event({string, String}, {Acc, Indent, Level, false})  ->
+    {Acc ++ "\n" ++ indent(Indent, Level) ++ "\"" ++ String ++ "\"", Indent, Level, true};
+
+jsx_event({literal, Literal}, {Acc, Indent, Level, true})  ->
+    {Acc ++ ",\n" ++ indent(Indent, Level) ++ atom_to_list(Literal), Indent, Level, true};
+jsx_event({literal, Literal}, {Acc, Indent, Level, false})  ->
+    {Acc ++ "\n" ++ indent(Indent, Level) ++ atom_to_list(Literal), Indent, Level, true};
+
+jsx_event(end_object, {Acc, Indent, Level, true}) ->
+    {Acc ++ "\n" ++ indent(Indent, Level - 1) ++ "}", Indent, Level - 1, true};
+jsx_event(end_object, {Acc, Indent, Level, false}) ->
+    {Acc ++ "}", Indent, Level - 1, true};
+    
+jsx_event(end_array, {Acc, Indent, Level, true}) ->
+    {Acc ++ "\n" ++ indent(Indent, Level - 1) ++ "]", Indent, Level - 1, true};
+jsx_event(end_array, {Acc, Indent, Level, false}) ->
+    {Acc ++ "]", Indent, Level - 1, true};
+    
+jsx_event(eof, {Acc, _, _, _}) ->
+    Acc.
+    
+
+indent(Indent, Level) ->
+    [ 16#20 || _ <- lists:seq(1, Indent * Level) ].
+