import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;

import com.android.volley.AuthFailureError;
import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.Response.ErrorListener;
import com.android.volley.Response.Listener;
import com.android.volley.toolbox.HttpHeaderParser;

import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;

import java.io.UnsupportedEncodingException;
import java.util.Map;

/**
 * Volley adapter for JSON requests that will be parsed into Java objects by Gson.
 * From https://gist.github.com/ficusk/5474673
 * @author Ficus Kirkpatrick
 */
public class GsonRequest<T> extends Request<T> {
    private final Gson gson = new Gson();
    private final Class<T> clazz;
    @Nullable
    private final Map<String, String> headers;
    @Nullable
    private final Map<String, String> params;
    private final Listener<T> listener;
    private final int method;

    /**
     * Make a GET request and return a parsed object from JSON.
     *
     * @param url URL of the request to make
     * @param clazz Relevant class object, for Gson's reflection
     * @param data Map of request headers or parameters
     */
    public GsonRequest(int method, String url, Class<T> clazz, Map<String, String> data,
                       Listener<T> listener, ErrorListener errorListener) {
        super(method, url, errorListener);
        this.clazz = clazz;

        switch (method) {
            case Method.GET:
                this.headers = data;
                this.params = null;
                break;

            case Method.POST:
                this.headers = null;
                this.params = data;
                break;

            default:
                this.headers = null;
                this.params = null;
        }

        this.listener = listener;
        this.method = method;
    }

    @Nullable
    @Override
    public Map<String, String> getHeaders() throws AuthFailureError {
        return headers != null ? headers : super.getHeaders();
    }

    @Nullable
    @Override
    public Map<String, String> getParams() throws AuthFailureError {
        return params != null ? params : super.getParams();
    }

    @Override
    protected void deliverResponse(T response) {
        listener.onResponse(response);
    }

    @NotNull
    @Override
    public String getBodyContentType() {
        return "application/json; charset=" + getParamsEncoding();
    }

    @Override
    public byte[] getBody() throws AuthFailureError {
        if (this.method == Method.POST) {
            return new Gson().toJsonTree(this.params).toString().getBytes();
        }
        else
            return super.getBody();
    }

    @Override
    protected Response<T> parseNetworkResponse(@NotNull NetworkResponse response) {
        try {
            String json = new String(
                    response.data, HttpHeaderParser.parseCharset(response.headers));
            return Response.success(
                    gson.fromJson(json, clazz), HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));
        } catch (JsonSyntaxException e) {
            return Response.error(new ParseError(e));
        }
    }
}