// Copyright (C) 2013 The Android Open Source Project
//
// 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.googlesource.gerrit.plugins.javamelody;

import com.google.common.base.Strings;
import com.google.common.flogger.FluentLogger;
import com.google.gerrit.extensions.annotations.PluginData;
import com.google.gerrit.extensions.annotations.PluginName;
import com.google.gerrit.httpd.AllRequestFilter;
import com.google.gerrit.server.config.PluginConfig;
import com.google.gerrit.server.config.PluginConfigFactory;
import com.google.inject.Inject;
import com.google.inject.Singleton;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.Optional;
import java.util.StringJoiner;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import net.bull.javamelody.MonitoringFilter;
import net.bull.javamelody.Parameter;
import net.bull.javamelody.internal.common.HttpParameter;
import net.bull.javamelody.internal.common.Parameters;

@Singleton
class GerritMonitoringFilter extends AllRequestFilter {
  private static final FluentLogger log = FluentLogger.forEnclosingClass();
  private final JavamelodyFilter monitoring;

  @Inject
  GerritMonitoringFilter(JavamelodyFilter monitoring) {
    this.monitoring = monitoring;
  }

  @Override
  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException {
    if (!(request instanceof HttpServletRequest) || !(response instanceof HttpServletResponse)) {
      chain.doFilter(request, response);
      return;
    }

    HttpServletResponse httpResponse = (HttpServletResponse) response;
    HttpServletRequest httpRequest = (HttpServletRequest) request;

    if (monitoring.canMonitor(httpRequest)) {
      monitoring.doFilter(request, response, chain);
    } else {
      httpResponse.sendError(HttpServletResponse.SC_FORBIDDEN, "Forbidden access");
    }
  }

  @Override
  public void init(FilterConfig config) throws ServletException {
    monitoring.init(config);
  }

  @Override
  public void destroy() {
    monitoring.destroy();
  }

  static class JavamelodyFilter extends MonitoringFilter {
    private static final String JAVAMELODY_PREFIX = "javamelody";
    private static final String HTTP_TRANSFORM_PATTERN = Parameter.HTTP_TRANSFORM_PATTERN.getCode();
    private static final String GLOBAL_HTTP_TRANSFORM_PATTERN =
        String.format("%s.%s", JAVAMELODY_PREFIX, HTTP_TRANSFORM_PATTERN);
    private static final String STORAGE_DIR = Parameter.STORAGE_DIRECTORY.getCode();
    private static final String GLOBAL_STORAGE_DIR =
        String.format("%s.%s", JAVAMELODY_PREFIX, STORAGE_DIR);
    private static final String PROMETHEUS_BEARER_TOKEN = "prometheusBearerToken";
    private static final String FORMAT_PROMETHEUS = "prometheus";
    private static final String AUTHORIZATION_HEADER = "Authorization";
    private final CapabilityChecker capabilityChecker;
    private final boolean useBearerTokenForPrometheus;

    static final String GERRIT_GROUPING =
        new StringJoiner("|")
            .add("[0-9a-f]{64}") // Long SHA for LFS
            .add("[0-9a-f]{40}") // SHA-1
            .add("[0-9A-F]{32}") // GWT cache ID
            .add("(?<=files/)[^/]+") // review files part
            .add("(?<=/projects/)[^/]+") // project name
            .add("(?<=/accounts/)[^/]+") // account id
            .add("(.+)(?=/git-upload-pack)") // Git fetch/clone
            .add("(.+)(?=/git-receive-pack)") // Git push
            .add("(.+)(?=/info/)") // Git and LFS operations
            .add("\\d+") // various ids e.g. change id
            .toString();

    private final PluginConfig cfg;
    private final Path defaultDataDir;
    private String authenticatedMonitoringUrl;

    @Inject
    JavamelodyFilter(
        PluginConfigFactory cfgFactory,
        @PluginName String pluginName,
        @PluginData Path defaultDataDir,
        CapabilityChecker capabilityChecker) {
      this.defaultDataDir = defaultDataDir;
      this.cfg = cfgFactory.getFromGerritConfig(pluginName);
      this.capabilityChecker = capabilityChecker;
      this.useBearerTokenForPrometheus = isPropertyInPluginConfig(PROMETHEUS_BEARER_TOKEN);
    }

    @Override
    public void init(FilterConfig config) throws ServletException {
      if (isPropertyInPluginConfig(HTTP_TRANSFORM_PATTERN)
          || isPropertyUndefined(config, HTTP_TRANSFORM_PATTERN, GLOBAL_HTTP_TRANSFORM_PATTERN)) {
        System.setProperty(GLOBAL_HTTP_TRANSFORM_PATTERN, getTransformPattern());
      }

      if (isPropertyInPluginConfig(STORAGE_DIR)
          || isPropertyUndefined(config, STORAGE_DIR, GLOBAL_STORAGE_DIR)) {
        System.setProperty(GLOBAL_STORAGE_DIR, getStorageDir());
      }

      super.init(config);
    }

    public String getJavamelodyUrl(HttpServletRequest httpRequest) {
      return getMonitoringUrl(httpRequest);
    }

    @Override
    protected String getMonitoringUrl(HttpServletRequest httpRequest) {
      if (authenticatedMonitoringUrl == null) {
        authenticatedMonitoringUrl =
            httpRequest.getContextPath() + "/a" + Parameters.getMonitoringPath();
      }

      if (httpRequest.getRequestURI().equals(authenticatedMonitoringUrl)) {
        return authenticatedMonitoringUrl;
      }

      return super.getMonitoringUrl(httpRequest);
    }

    private String getTransformPattern() {
      return cfg.getString(HTTP_TRANSFORM_PATTERN, GERRIT_GROUPING);
    }

    private String getStorageDir() {
      // default to old path for javamelody storage-directory if it exists
      final Path tmp = Paths.get(System.getProperty("java.io.tmpdir")).resolve(JAVAMELODY_PREFIX);
      if (Files.isDirectory(tmp)) {
        log.atWarning().log(
            "Javamelody data exists in 'tmp' [%s]. Configuration (if any) will be ignored.", tmp);
        return tmp.toString();
      }

      // plugin config has the highest priority
      Path storageDir =
          Optional.ofNullable(cfg.getString(STORAGE_DIR)).map(Paths::get).orElse(defaultDataDir);
      if (!Files.isDirectory(storageDir)) {
        try {
          Files.createDirectories(storageDir);
        } catch (IOException e) {
          log.atSevere().withCause(e).log(
              "Creation of javamelody data dir [%s] failed.", storageDir);
          throw new RuntimeException(e);
        }
      }
      return storageDir.toString();
    }

    private boolean isPropertyInPluginConfig(String name) {
      return !Strings.isNullOrEmpty(cfg.getString(name));
    }

    private boolean isPropertyUndefined(FilterConfig config, String name, String globalName) {
      return System.getProperty(globalName) == null
          && config.getServletContext().getInitParameter(globalName) == null
          && config.getInitParameter(name) == null;
    }

    boolean canMonitor(HttpServletRequest httpRequest) {
      if (httpRequest.getRequestURI().equals(getJavamelodyUrl(httpRequest))) {
        /* Exception when access to metrics for Prometheus using Bearer Token
         * without going through any Gerrit Authentication step.
         * Enable to access the Prometheus metrics ONLY and nothing else, skipping
         * any authentication and ACL check.
         */
        if (useBearerTokenForPrometheus
            && httpRequest.getHeader(AUTHORIZATION_HEADER) != null
            && FORMAT_PROMETHEUS.equals(HttpParameter.FORMAT.getParameterFrom(httpRequest))) {
          return canMonitorFromPrometheusUsingBearerToken(httpRequest);
        }
        return capabilityChecker.canMonitor();
      }
      return true;
    }

    private boolean canMonitorFromPrometheusUsingBearerToken(HttpServletRequest httpRequest) {
      return httpRequest
          .getHeader(AUTHORIZATION_HEADER)
          .equals("Bearer " + cfg.getString(PROMETHEUS_BEARER_TOKEN));
    }
  }
}