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/*
 * Copyright 2018 Azilet B.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package kg.net.bazi.gsb4j.http;

import com.google.gson.Gson;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import kg.net.bazi.gsb4j.api.SafeBrowsingApi;
import kg.net.bazi.gsb4j.data.ThreatMatch;
import org.apache.http.entity.ContentType;
import org.slf4j.Logger;

abstract class ServletBase extends HttpServlet {

    public static final String URL_PARAM = "url";

    final Gson gson;

    /**
     * Injection to this and extending servlet classes are done though constructors to conform to Sonar rule: Servlets
     * should not have mutable instance fields
     *
     * @param gson JSON serializer
     */
    ServletBase(Gson gson) {
        this.gson = gson;
    }

    abstract Logger getLogger();

    abstract SafeBrowsingApi getSafeBrowsingApi();

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String url = req.getParameter(LookupApiServlet.URL_PARAM);
        if (url == null || url.trim().isEmpty()) {
            writeResponse(HttpServletResponse.SC_BAD_REQUEST, "No URL to check", resp);
            return;
        }
        getLogger().info("Checking URL: {}", url);

        SafeBrowsingApi api = getSafeBrowsingApi();
        ThreatMatch threat = api.check(url);

        ResponsePayload payload = new ResponsePayload();
        if (threat != null) {
            payload.add(threat);
        }
        String json = gson.toJson(payload);
        writeResponseJson(HttpServletResponse.SC_OK, json, resp);
    }

    void writeResponse(int status, String data, HttpServletResponse resp) {
        try (PrintWriter writer = resp.getWriter()) {
            writer.print(data);
        } catch (IOException ex) {
            getLogger().error("Failed to write response", ex);
        }
        resp.setStatus(status);
    }

    void writeResponseJson(int status, String data, HttpServletResponse resp) {
        resp.setContentType(ContentType.APPLICATION_JSON.getMimeType());
        writeResponse(status, data, resp);
    }

    static class ResponsePayload {

        List matches = new ArrayList<>();

        public void add(ThreatMatch threat) {
            // copy only useful fields for users; DO NOT send whole object
            ThreatMatch stripped = new ThreatMatch();
            stripped.setThreatType(threat.getThreatType());
            stripped.setPlatformType(threat.getPlatformType());

            matches.add(stripped);
        }
    }

}