// Copyright (C) 2015 Ericsson
//
// 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 com.ericsson.gerrit.plugins.highavailability.forwarder.rest;

import com.google.common.base.Joiner;
import com.google.common.base.Supplier;
import com.google.gerrit.extensions.annotations.PluginName;
import com.google.gerrit.server.events.Event;
import com.google.gerrit.server.events.SupplierSerializer;
import com.google.gson.GsonBuilder;
import com.google.inject.Inject;

import com.ericsson.gerrit.plugins.highavailability.forwarder.Forwarder;
import com.ericsson.gerrit.plugins.highavailability.forwarder.rest.HttpResponseHandler.HttpResult;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.IOException;

class RestForwarder implements Forwarder {
  private static final Logger log =
      LoggerFactory.getLogger(RestForwarder.class);

  private final HttpSession httpSession;
  private final String pluginRelativePath;

  @Inject
  RestForwarder(HttpSession httpClient,
      @PluginName String pluginName) {
    this.httpSession = httpClient;
    this.pluginRelativePath = Joiner.on("/").join("/plugins", pluginName);
  }

  @Override
  public boolean indexChange(final int changeId) {
    return new Request("index change " + changeId) {
      @Override
      HttpResult send() throws IOException {
        return httpSession.post(buildIndexEndpoint(changeId));
      }
    }.execute();
  }

  @Override
  public boolean deleteChangeFromIndex(final int changeId) {
    return new Request("delete change " + changeId + " from index") {
      @Override
      HttpResult send() throws IOException {
        return httpSession.delete(buildIndexEndpoint(changeId));
      }
    }.execute();
  }

  private String buildIndexEndpoint(int changeId) {
    return Joiner.on("/").join(pluginRelativePath, "index/change", changeId);
  }

  @Override
  public boolean send(final Event event) {
    return new Request("send event " + event.type) {
      @Override
      HttpResult send() throws IOException {
        String serializedEvent = new GsonBuilder()
            .registerTypeAdapter(Supplier.class, new SupplierSerializer()).create()
            .toJson(event);
      return httpSession.post(
          Joiner.on("/").join(pluginRelativePath, "event"), serializedEvent);
      }
    }.execute();
  }

  @Override
  public boolean evict(final String cacheName, final Object key) {
    return new Request("evict for cache " + cacheName + "[" + key + "]") {
      @Override
      HttpResult send() throws IOException {
        String json = GsonParser.toJson(cacheName, key);
        return httpSession
            .post(Joiner.on("/").join(pluginRelativePath, "cache", cacheName),
                json);
      }
    }.execute();
  }

  private abstract class Request {
    private String name;

    Request(String name) {
      this.name = name;
    }

    boolean execute() {
      try {
        HttpResult result = send();
        if (result.isSuccessful()) {
          return true;
        }
        log.error("Unable to {}: {}", name, result.getMessage());
      } catch (IOException e) {
        log.error("Error trying to {}", name, e);
      }
      return false;
    }

    abstract HttpResult send() throws IOException;
  }
}