GsonJsonRpcUnmarshaller.java

/*******************************************************************************
 * Copyright (c) 2012-2017 Codenvy, S.A.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *   Codenvy, S.A. - initial API and implementation
 *******************************************************************************/
package org.eclipse.che.api.core.jsonrpc.impl;

import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import com.google.gson.JsonPrimitive;
import com.google.inject.Inject;
import com.google.inject.Singleton;

import org.eclipse.che.api.core.jsonrpc.commons.JsonRpcError;
import org.eclipse.che.api.core.jsonrpc.commons.JsonRpcParams;
import org.eclipse.che.api.core.jsonrpc.commons.JsonRpcRequest;
import org.eclipse.che.api.core.jsonrpc.commons.JsonRpcResponse;
import org.eclipse.che.api.core.jsonrpc.commons.JsonRpcResult;
import org.eclipse.che.api.core.jsonrpc.commons.JsonRpcUnmarshaller;

import java.util.ArrayList;
import java.util.List;

import static com.google.common.base.Preconditions.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static java.util.Collections.singletonList;

@Singleton
public class GsonJsonRpcUnmarshaller implements JsonRpcUnmarshaller {
    private final JsonParser jsonParser;

    @Inject
    public GsonJsonRpcUnmarshaller(JsonParser jsonParser) {
        this.jsonParser = jsonParser;
    }

    @Override
    public List<String> unmarshalArray(String message) {
        return getArray(message, jsonParser.parse(message).isJsonArray());
    }

    @Override
    public JsonRpcRequest unmarshalRequest(String message) {
        checkNotNull(message, "Message must not be null");
        checkArgument(!message.isEmpty(), "Message must not be empty");

        JsonObject request = jsonParser.parse(message).getAsJsonObject();

        String method = getMethod(request);
        String id = getId(request);
        JsonRpcParams params = getParams(request);

        return new JsonRpcRequest(id, method, params);
    }

    @Override
    public JsonRpcResponse unmarshalResponse(String message) {
        checkNotNull(message, "Message must not be null");
        checkArgument(!message.isEmpty(), "Message must not be empty");

        JsonObject response = jsonParser.parse(message).getAsJsonObject();

        String id = getId(response);
        JsonRpcResult result = getResult(response);
        JsonRpcError error = getError(response);

        return new JsonRpcResponse(id, result, error);
    }

    private JsonRpcError getError(JsonObject response) {
        if (!response.has("error")) {
            return null;
        }

        int code = response.get("error").getAsJsonObject().get("code").getAsInt();
        String errorMessage = response.get("error").getAsJsonObject().get("message").getAsString();
        return new JsonRpcError(code, errorMessage);
    }

    private JsonRpcResult getResult(JsonObject response) {
        if (!response.has("result")) {
            return null;
        }

        JsonElement jsonElement = response.get("result");
        if (!jsonElement.isJsonArray()) {
            return new JsonRpcResult(getInnerItem(jsonElement));
        }

        JsonArray jsonArray = jsonElement.getAsJsonArray();
        int size = jsonArray.size();
        List<Object> innerResults = new ArrayList<>(size);
        for (int i = 0; i < size; i++) {
            JsonElement innerJsonElement = jsonArray.get(i);
            innerResults.add(getInnerItem(innerJsonElement));
        }

        return new JsonRpcResult(innerResults);
    }

    private JsonRpcParams getParams(JsonObject jsonObject) {
        if (!jsonObject.has("params")) {
            return null;
        }

        JsonElement jsonElement = jsonObject.get("params");
        if (!jsonElement.isJsonArray()) {
            return new JsonRpcParams(getInnerItem(jsonElement));
        }

        JsonArray jsonArray = jsonElement.getAsJsonArray();
        int size = jsonArray.size();
        List<Object> innerParameters = new ArrayList<>(size);
        for (int i = 0; i < size; i++) {
            JsonElement innerJsonElement = jsonArray.get(i);
            innerParameters.add(getInnerItem(innerJsonElement));
        }

        return new JsonRpcParams(innerParameters);
    }

    private String getId(JsonObject jsonObject) {
        return jsonObject.has("id") ? jsonObject.get("id").getAsString() : null;
    }

    private String getMethod(JsonObject jsonObject) {
        return jsonObject.get("method").getAsString();
    }

    private List<String> getArray(String message, boolean isArray) {
        if (!isArray) {
            return singletonList(message);
        }

        JsonArray jsonArray = jsonParser.parse(message).getAsJsonArray();
        int size = jsonArray.size();
        List<String> result = new ArrayList<>(size);
        for (int i = 0; i < size; i++) {
            JsonElement jsonElement = jsonArray.get(i);
            result.add(jsonElement.toString());
        }
        return result;
    }

    private Object getInnerItem(JsonElement jsonElement) {
        if (jsonElement.isJsonNull()) {
            return null;
        }

        if (jsonElement.isJsonObject()) {
            return jsonElement.getAsJsonObject();
        }

        if (jsonElement.isJsonPrimitive()) {
            JsonPrimitive jsonPrimitive = jsonElement.getAsJsonPrimitive();
            if (jsonPrimitive.isNumber()) {
                return jsonPrimitive.getAsDouble();
            } else if (jsonPrimitive.isString()) {
                return jsonPrimitive.getAsString();
            } else {
                return jsonPrimitive.getAsBoolean();
            }
        }

        throw new IllegalStateException("Unexpected json element type");
    }
}