gym.d

/// based on https://github.com/openai/gym-http-api/blob/master/binding-rust/src/lib.rs

module gym;
import std.exception : enforce;
import std.json : JSONValue, parseJSON;
import std.conv : to;
import std.stdio : writeln;

enum bool isSpace(T) = is(typeof({ T.from(JSONValue.init); }));

/// Discrete Space
struct Discrete {
    long n;
    alias n this;

    static from(T: JSONValue)(scope auto ref T info) {
        enforce(info["name"].str == "Discrete");
        return Discrete(info["n"].integer);
    }
}

///
unittest {
    static assert(isSpace!Discrete);

    auto s = `{
   "name": "Discrete",
   "n": 123
}`;
    auto j = s.parseJSON;
    assert(Discrete.from(j) == Discrete(123));
}

/// Box Space
struct Box {
    long[] shape;
    double[] high;
    double[] low;

    static from(T: JSONValue)(scope auto ref T info) {
        import std.algorithm : map;
        import std.array : array;
        enforce(info["name"].str == "Box");
        return Box(
            info["shape"].array.map!(a => a.integer).array.dup,
            info["high"].array.map!(a => a.floating).array.dup,
            info["low"].array.map!(a => a.floating).array.dup
            );
    }
}

///
unittest {
    static assert(isSpace!Box);

    auto s = `{
   "name": "Box",
   "shape": [2],
   "high": [1.0, 2.0],
   "low": [0.0, 0.0]
}`;
    auto j = s.parseJSON;
    assert(Box.from(j) == Box([2], [1.0, 2.0], [0.0, 0.0]));
}


struct State {
    double[] observation;
    double reward;
    bool done;
    JSONValue info;
}

struct Environment(ActionSpace, ObservationSpace) {
    GymClient client;
    string instanceId;
    ActionSpace action;
    ObservationSpace observation;
}


struct GymClient {
    import std.net.curl;

    string address;

    this(string address) {
        this.address = address;
    }

    auto env(string name) {
        auto http = HTTP();
        http.addRequestHeader("Content-Type", "application/json");
        JSONValue req = ["env_id": name];
        auto instanceId = post(this.address ~ "/v1/envs/", req.toString, http)
            .parseJSON["instance_id"].str;
        instanceId.writeln;

        auto obs = get(this.address ~ "/v1/envs/" ~ instanceId ~ "/observation_space/");
        obs.writeln;
        auto act = get(this.address ~ "/v1/envs/" ~ instanceId ~ "/action_space/");
        act.writeln;
        // char[] d;
        // http.onReceive = (ubyte[] data) { d ~= cast(char[])(data); return data.length; };
        // writeln(req.toString);
        // http.setPostData(req.toString, "application/json");
        // http.perform();
        // writeln(d);
    }
}

///
unittest {
    GymClient("127.0.0.1:5000").env("CartPole-v0");
}