// Copyright (C) 2016 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.oauth;

import com.google.common.base.CharMatcher;
import com.google.gerrit.extensions.annotations.PluginName;
import com.google.gerrit.extensions.auth.oauth.OAuthServiceProvider;
import com.google.gerrit.extensions.auth.oauth.OAuthToken;
import com.google.gerrit.extensions.auth.oauth.OAuthUserInfo;
import com.google.gerrit.extensions.auth.oauth.OAuthVerifier;
import com.google.gerrit.server.OutputFormat;
import com.google.gerrit.server.config.CanonicalWebUrl;
import com.google.gerrit.server.config.PluginConfig;
import com.google.gerrit.server.config.PluginConfigFactory;
import com.google.gson.JsonArray;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.inject.Inject;
import com.google.inject.Provider;
import com.google.inject.Singleton;
import java.io.IOException;
import javax.servlet.http.HttpServletResponse;
import org.scribe.builder.ServiceBuilder;
import org.scribe.model.OAuthRequest;
import org.scribe.model.Response;
import org.scribe.model.Token;
import org.scribe.model.Verb;
import org.scribe.model.Verifier;
import org.scribe.oauth.OAuthService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

@Singleton
class CasOAuthService implements OAuthServiceProvider {
  private static final Logger log = LoggerFactory.getLogger(CasOAuthService.class);
  static final String CONFIG_SUFFIX = "-cas-oauth";
  private static final String CAS_PROVIDER_PREFIX = "cas-oauth:";
  private static final String PROTECTED_RESOURCE_URL = "%s/oauth2.0/profile";

  private final String rootUrl;
  private final boolean fixLegacyUserId;
  private final OAuthService service;

  @Inject
  CasOAuthService(
      PluginConfigFactory cfgFactory,
      @PluginName String pluginName,
      @CanonicalWebUrl Provider<String> urlProvider) {
    PluginConfig cfg = cfgFactory.getFromGerritConfig(pluginName + CONFIG_SUFFIX);
    rootUrl = cfg.getString(InitOAuth.ROOT_URL);
    String canonicalWebUrl = CharMatcher.is('/').trimTrailingFrom(urlProvider.get()) + "/";
    fixLegacyUserId = cfg.getBoolean(InitOAuth.FIX_LEGACY_USER_ID, false);
    service =
        new ServiceBuilder()
            .provider(new CasApi(rootUrl))
            .apiKey(cfg.getString(InitOAuth.CLIENT_ID))
            .apiSecret(cfg.getString(InitOAuth.CLIENT_SECRET))
            .callback(canonicalWebUrl + "oauth")
            .build();
  }

  @Override
  public OAuthUserInfo getUserInfo(OAuthToken token) throws IOException {
    final String protectedResourceUrl = String.format(PROTECTED_RESOURCE_URL, rootUrl);
    OAuthRequest request = new OAuthRequest(Verb.GET, protectedResourceUrl);
    Token t = new Token(token.getToken(), token.getSecret(), token.getRaw());
    service.signRequest(t, request);

    Response response = request.send();
    if (response.getCode() != HttpServletResponse.SC_OK) {
      throw new IOException(
          String.format(
              "Status %s (%s) for request %s",
              response.getCode(), response.getBody(), request.getUrl()));
    }

    if (log.isDebugEnabled()) {
      log.debug("User info response: {}", response.getBody());
    }

    JsonElement userJson =
        OutputFormat.JSON.newGson().fromJson(response.getBody(), JsonElement.class);
    if (!userJson.isJsonObject()) {
      throw new IOException(String.format("Invalid JSON '%s': not a JSON Object", userJson));
    }
    JsonObject jsonObject = userJson.getAsJsonObject();

    JsonElement id = jsonObject.get("id");
    if (id == null || id.isJsonNull()) {
      throw new IOException(String.format("CAS response missing id: %s", response.getBody()));
    }

    JsonElement attrListJson = jsonObject.get("attributes");
    if (attrListJson == null) {
      throw new IOException(
          String.format("CAS response missing attributes: %s", response.getBody()));
    }

    String email = null, name = null, login = null;

    if (attrListJson.isJsonArray()) {
      // It is possible for CAS to be configured to not return any attributes (email, name, login),
      // in which case,
      // CAS returns an empty JSON object "attributes":{}, rather than "null" or an empty JSON array
      // "attributes": []

      JsonArray attrJson = attrListJson.getAsJsonArray();
      for (JsonElement elem : attrJson) {
        if (elem == null || !elem.isJsonObject()) {
          throw new IOException(String.format("Invalid JSON '%s': not a JSON Object", elem));
        }
        JsonObject obj = elem.getAsJsonObject();

        String property = getStringElement(obj, "email");
        if (property != null) email = property;
        property = getStringElement(obj, "name");
        if (property != null) name = property;
        property = getStringElement(obj, "login");
        if (property != null) login = property;
      }
    }

    return new OAuthUserInfo(
        CAS_PROVIDER_PREFIX + id.getAsString(),
        login,
        email,
        name,
        fixLegacyUserId ? id.getAsString() : null);
  }

  private String getStringElement(JsonObject o, String name) {
    JsonElement elem = o.get(name);
    if (elem == null || elem.isJsonNull()) return null;

    return elem.getAsString();
  }

  @Override
  public OAuthToken getAccessToken(OAuthVerifier rv) {
    Verifier vi = new Verifier(rv.getValue());
    Token to = service.getAccessToken(null, vi);
    return new OAuthToken(to.getToken(), to.getSecret(), to.getRawResponse());
  }

  @Override
  public String getAuthorizationUrl() {
    return service.getAuthorizationUrl(null);
  }

  @Override
  public String getVersion() {
    return service.getVersion();
  }

  @Override
  public String getName() {
    return "Generic CAS OAuth2";
  }
}