# Euneus
A JSON parser and generator in pure Erlang.
Euneus is a rewrite of [Thoas](thoas).
Like Thoas, both the parser and generator fully conform to
[RFC 8259](https://tools.ietf.org/html/rfc8259) and
[ECMA 404](http://www.ecma-international.org/publications/standards/Ecma-404.htm).
## Table of Contents
- [Installation](#installation)
- [Erlang](#erlang)
- [Elixir](#elixir)
- [Basic Usage](#basic-usage)
- [Data Mapping](#data-mapping)
- [Why not more built-in types?](#why-not-more-built-in-types)
- [Differences to Thoas](#differences-to-thoas)
- [Encode](#encode)
- [Decode](#decode)
- [Why Euneus over Thoas?](#why-euneus-over-thoas)
- [Benchmarks](#benchmarks)
- [Encode](#encode-1)
- [Decode](#decode-1)
- [Credits](#credits)
- [Why the name Euneus?](#why-the-name-euneus)
- [TODO](#todo)
- [Sponsors](#sponsors)
- [Contributing](#contributing)
- [Issues](#issues)
- [Installation](#installation-1)
- [License](#license)
## Installation
### Erlang
```
% rebar.config
{deps, [euneus]}
```
### Elixir
```
# mix.exs
def deps do
[{:euneus, "~> 0.1"}]
end
```
## Basic Usage
```erlang
1> JSON = euneus:encode_to_binary(#{name => #{english => <<"Charmander">>, japanese => <<"ヒトカゲ"/utf8>>}, caught_at => erlang:timestamp(), type => [fire], profile => #{height => 0.6, weight => 8}, ability => #{0 => <<"Blaze">>, 1 => undefined}}).
<<"{\"name\":{\"english\":\"Charmander\",\"japanese\":\"ヒトカゲ\"},\"profile\":{\"height\":0.6,\"weight\":8},\"type\":[\"fire\"],\"caught_at\":\"2023-10-24T05:47:04.939Z\",\"ability\":{\"0\":\"Blaze\",\"1\":null}}">>
2> euneus:decode(JSON).
{ok,#{<<"ability">> =>
#{<<"0">> => <<"Blaze">>,<<"1">> => undefined},
<<"caught_at">> => {1698,126333,753000},
<<"name">> =>
#{<<"english">> => <<"Charmander">>,
<<"japanese">> =>
<<227,131,146,227,131,136,227,130,171,227,130,178>>},
<<"profile">> => #{<<"height">> => 0.6,<<"weight">> => 8},
<<"type">> => [<<"fire">>]}}
3> euneus:decode(JSON, #{
normalize_key => fun
(<<Char>> = Key, _Opts) when Char >= $0, Char =< $9 ->
binary_to_integer(Key);
(Key, _Opts) ->
binary_to_existing_atom(Key)
end
}).
{ok,#{name =>
#{english => <<"Charmander">>,
japanese =>
<<227,131,146,227,131,136,227,130,171,227,130,178>>},
profile => #{height => 0.6,weight => 8},
type => [<<"fire">>],
caught_at => {1698,126333,753000},
ability => #{0 => <<"Blaze">>,1 => undefined}}}
```
## Data Mapping
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| Erlang -> | Encode Options -> | JSON -> | Decode Options -> | Erlang |
|---------------------- |---------------------------------------------------------------------------------------------------------------------------------------------------------- |----------------------------- |-------------------------------------------------------------------------------------------------------------------------- |---------------------- |
| undefined | #{} | null | #{null_term => undefined} | undefined |
| null | #{} | null | #{null_term => undefined} | undefined |
| nil | #{} | null | #{null_term => undefined} | undefined |
| true | #{} | true | #{} | true |
| false | #{} | false | #{} | false |
| abc | #{} | "abc" | #{} | <<"abc">> |
| "abc" | #{} | [97,98,99] | #{} | <<"abc">> |
| <<"abc">> | #{} | "abc" | #{} | <<"abc">> |
| {{1970,1,1},{0,0,0}} | #{} | "1970-01-01T00:00:00Z" | #{} | {{1970,1,1},{0,0,0}} |
| {0,0,0} | #{} | "1970-01-01T00:00:00.000Z" | #{} | {0,0,0} |
| 123 | #{} | 123 | #{} | 123 |
| 123.45600 | #{} | 123.456 | #{} | 123.456 |
| [true,0,undefined] | #{} | [true,0,null] | #{null_term => undefined} | [true,0,undefined] |
| #{foo => bar} | #{} | {"foo":"bar"} | #{normalize_key => fun(Key, _Opts) -> binary_to_atom(Key) end} | #{foo => <<"bar">>} |
| {myrecord, val} | #{encode_unhandled => fun({myrecord, Val}, Opts) -><br> Encode = maps:get(encode_list, Opts),<br> Encode([myrecord, #{key => Val}], Opts)<br>end}) | ["myrecord", {"key":"val"}] | #{normalize_array => fun([<<"myrecord">>, #{<<"key">> := Val}], _Opts) -><br> {myrecord, binary_to_atom(Val)}<br>end} | {myrecord, val} |
### Why not more built-in types?
The goal of `Euneus` is to have built-in types that can be encoded and then decoded to the original value. If you have any type that can be encoded and rolled back, feel free to open an issue to discuss it :)
## Differences to Thoas
Euneus is based on [Thoas](thoas), so let's discuss the differences.
The main difference between `Euneus` to `Thoas` is that Euneus gives more control to encoding or decoding data. All encode functions can be overridden and extended and all decoded data can be overridden and transformed.
### Encode
Available encode options:
```erlang
#{
%% null_terms defines what terms will be replaced with the null literal (default: ['undefined']).
null_terms => nonempty_list(),
%% encode_binary allow override the binary() encoding.
encode_binary => function((binary(), Opts :: map()) -> iolist()),
%% encode_atom allow override the atom() encoding.
encode_atom => function((atom(), Opts :: map()) -> iolist()),
%% encode_integer allow override the integer() encoding.
encode_integer => function((integer(), Opts :: map()) -> iolist()),
%% encode_float allow override the float() encoding.
encode_float => function((float(), Opts :: map()) -> iolist()),
%% encode_list allow override the list() encoding.
encode_list => function((list(), Opts :: map()) -> iolist()),
%% encode_map allow override the map() encoding.
encode_map => function((map(), Opts :: map()) -> iolist()),
%% encode_datetime allow override the calendar:datetime() encoding.
encode_datetime => function((calendar:datetime(), Opts :: map()) -> iolist()),
%% encode_timestamp allow override the erlang:timestamp() encoding.
encode_timestamp => function((erlang:timestamp(), Opts :: map()) -> iolist()),
%% encode_unhandled allow encode any custom term (default: raise unsupported_type error).
encode_unhandled => function((term(), Opts :: map()) -> iolist()),
%% escape_binary allow override the binary escaping (default: escape_json/1)
%% There are 4 built-in functions to escape binaries:
%% - escape_json/1;
%% - escape_html/1;
%% - escape_js/1;
%% - escape_unicode/1.
escape_binary => function((binary(), Opts :: map()) -> iolist())
}
```
For example:
```erlang
EncodeOpts = #{
encode_binary => fun
(<<"foo">>, Opts) ->
euneus_encoder:escape_binary(<<"bar">>, Opts);
(Bin, Opts) ->
euneus_encoder:escape_binary(Bin, Opts)
end,
encode_unhandled => fun
({_, _, _, _} = Ip, Opts) ->
case inet:ntoa(Ip) of
{error, einval} ->
error(invalid_ip);
IpStr ->
IpBin = list_to_binary(IpStr),
euneus_encoder:escape_binary(IpBin, Opts)
end;
(Term, Opts) ->
euneus_encoder:unsupported_type_error(Term, Opts)
end
},
Data = #{<<"foo">> => bar, ipv4 => {127, 0, 0, 1}, none => undefined},
euneus:encode_to_binary(Data, EncodeOpts).
%% <<"{\"bar\":\"bar\",\"ipv4\":\"127.0.0.1\",\"none\":null}">>
```
### Decode
Available decode options:
```erlang
#{
%% null_term is the null literal override (default: 'undefined').
null_term => term(),
%% normalize_array allow override any array/list().
normalize_array => function((list(), Opts :: map()) -> term()),
%% normalize_object allow override any object/map().
normalize_object => function((map(), Opts :: map()) -> term()),
%% normalize_key allow override the keys from JSON objects.
normalize_key => function((binary(), Opts :: map()) -> term()),
%% normalize_value allow override any other term, like array item or object value.
normalize_value => function((binary(), Opts :: map()) -> term())
}
```
For example:
```erlang
DecodeOpts = #{
null_term => nil,
normalize_key => fun
(<<"bar">>, _Opts) ->
foo;
(Key, _Opts) ->
binary_to_atom(Key)
end,
normalize_value => fun
(<<"127.0.0.1">>, _Opts) ->
{127, 0, 0, 1};
(Value, _Opts) ->
Value
end
},
JSON = <<"{\"bar\":\"bar\",\"ipv4\":\"127.0.0.1\",\"none\":null}">>,
euneus:decode(JSON, DecodeOpts).
%% {ok,#{foo"=> <<"bar">>,
%% ipv4 => {127,0,0,1},
%% none => nil}}
```
### Why Euneus over Thoas?
`Thoas` is incredible, works performant and perfectly fine, but `Euneus` is more flexible, permitting more customizations, and is more performant than Thoas. See the [benchmarks](#benchmarks).
The motivation for Euneus is [this PR](https://github.com/lpil/thoas/pull/28).
## Benchmarks
All the benchmarks compare `Euneus` and `Thoas` using [Benchee](https://github.com/bencheeorg/benchee) through a Thoas fork. (There is a todo to embed benchmarks into Euneus)
> **Note**
>
> - Results:
>
> Values in `IPS` (iterations per second), aka how often can the given function be executed within one second (the higher the better - good for graphing), only for run times.
> - `Bold`: best IPS;
>
> - System info:
> - Erlang: 26.1
> - Elixir: 1.16.0-dev
> - Operating system: Linux
> - Available memory: 15.54 GB
> - CPU Information: Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
> - Number of Available Cores: 8
>
> - Benchmark setup:
> - warmup: 5
> - time: 30
### Encode
> `Thoas` does not permit any customization.
<!-- Generated via https://www.tablesgenerator.com/markdown_tables -->
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| **File** | **Euneus** | **Thoas** | **Comparison** |
|---------------------------- |------------: |-----------: |---------------: |
| blockchain.json | **9.73 K** | 7.86 K | 1.24x |
| giphy.json | **897.47** | 853.31 | 1.05x |
| github.json | **3.14 K** | 2.54 K | 1.24x |
| govtrack.json | **12.72** | 12.27 | 1.04x |
| issue-90.json | **28.92** | 17.50 | 1.65x |
| json-generator-pretty.json | **1.16 K** | 1.08 K | 1.08x |
| json-generator.json | **1.17 K** | 1.08 K | 1.08x |
| pokedex.json | 1.63 K | **1.73 K** | 1.07x |
| utf-8-escaped.json | **11.88 K** | 10.57 K | 1.12x |
| utf-8-unescaped.json | **12.19 K** | 10.83 K | 1.13x |
### Decode
> **Note**:
>
> `Thoas` does not permit any customization and does not decode `ISO 8601` dates to erlang term, but Euneus decodes out of the box, for example, `"1970-01-01T00:00:00Z"` to `{{1970,01,01},{0,0,0}}` :: [calendar:datetime()](https://www.erlang.org/doc/man/calendar.html#data-types) and `"1970-01-01T00:00:00.000Z"` to `{0,0,0}` :: [erlang:timestamp()](https://www.erlang.org/doc/man/os#timestamp-0).
<!-- Generated via https://www.tablesgenerator.com/markdown_tables -->
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| **File** | **Euneus** | **Thoas** | **Comparison** |
|---------------------------- |------------: |----------: |---------------: |
| blockchain.json | **7.18 K** | 5.78 K | 1.24x |
| giphy.json | **474.91** | 474.75 | 1.00x |
| github.json | **2.33 K** | 2.02 K | 1.16x |
| govtrack.json | **16.35** | 15.65 | 1.04x |
| issue-90.json | **25.35** | 17.70 | 1.43x |
| json-generator-pretty.json | **617.33** | 542.99 | 1.14x |
| json-generator.json | **728.01** | 655.15 | 1.11x |
| pokedex.json | **1.37 K** | 1.33 K | 1.03x |
| utf-8-escaped.json | **1.88 K** | 1.66 K | 1.13x |
| utf-8-unescaped.json | **10.87 K** | 10.47 K | 1.04x |
## Credits
Euneus is a rewrite of Thoas, so all credits go to [Michał Muskała](https://github.com/michalmuskala), [Louis Pilfold](https://github.com/lpil), also both [Jason](jason) and [Thoas](thoas) contributors. Thanks for the hard work!
## Why the name Euneus?
Euneus is the twin brother of [Thoas](https://en.wikipedia.org/wiki/Thoas_(son_of_Jason)).
## TODO
- [] Improve docs
- [] All specs
- [] Embed benchmarks
- [] Test suites
## Sponsors
If you like this tool, please consider [sponsoring me](https://github.com/sponsors/williamthome).\
I'm thankful for your never-ending support :heart:
I also accept coffees :coffee:
[](https://www.buymeacoffee.com/williamthome)
## Contributing
### Issues
Feel free to [submit an issue on Github](https://github.com/williamthome/euneus/issues/new).
### Installation
```shell
# Clone this repo
git clone git@github.com:williamthome/euneus.git
# Navigate to the project root
cd euneus
# Compile (ensure you have rebar3 installed)
rebar3 compile
```
## License
Euneus is released under the [Apache License 2.0](LICENSE.md).
Euneus is based off of [Thoas][thoas], which is also Apache 2.0 licensed.
Some elements have their origins in the [Poison library](poison) and were initially licensed under [CC0-1.0](https://creativecommons.org/publicdomain/zero/1.0/).
[jason]: https://github.com/michalmuskala/jason
[thoas]: https://github.com/lpil/thoas
[poison]: https://github.com/devinus/poison
