// Copyright (C) 2018 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.google.gerrit.server.config;

import com.google.common.base.Strings;
import com.google.gerrit.common.Nullable;
import com.google.gerrit.entities.Change;
import com.google.gerrit.entities.Project;
import java.util.Optional;

/**
 * Formats URLs to different parts of the Gerrit API and UI.
 *
 * <p>By default, these gerrit URLs are formed by adding suffixes to the web URL. The interface
 * centralizes these conventions, and also allows introducing different, custom URL schemes.
 *
 * <p>Unfortunately, Gerrit operates in modes for which there is no canonical URL. This can be in
 * standalone utilities that have no HTTP server (eg. index upgrade commands), in servers that run
 * SSH only, or in a HTTP/SSH server that is accessed over SSH without canonical web URL configured.
 */
public interface UrlFormatter {

  /**
   * The canonical base URL where this Gerrit installation can be reached.
   *
   * <p>For the default implementations below to work, it must end in "/".
   */
  Optional<String> getWebUrl();

  /** Returns the URL for viewing a change. */
  default Optional<String> getChangeViewUrl(Project.NameKey project, Change.Id id) {

    // In the PolyGerrit URL (contrary to REST URLs) there is no need to URL-escape strings, since
    // the /+/ separator unambiguously defines how to parse the path.
    return getWebUrl().map(url -> url + "c/" + project.get() + "/+/" + id.get());
  }

  /** Returns the URL for viewing a file in a given patch set of a change. */
  default Optional<String> getPatchFileView(Change change, int patchsetId, String filename) {
    return getChangeViewUrl(change.getProject(), change.getId())
        .map(url -> url + "/" + patchsetId + "/" + filename);
  }

  /** Returns the URL for viewing a comment in a file in a given patch set of a change. */
  default Optional<String> getInlineCommentView(
      Change change, int patchsetId, String filename, short side, int startLine) {
    return getPatchFileView(change, patchsetId, filename)
        .map(url -> url + String.format("@%s%d", side == 0 ? "a" : "", startLine));
  }

  /** Returns a URL pointing to a section of the settings page. */
  default Optional<String> getSettingsUrl() {
    return getWebUrl().map(url -> url + "settings");
  }

  /**
   * Returns a URL pointing to a section of the settings page, or the settings page if {@code
   * section} is null.
   */
  default Optional<String> getSettingsUrl(@Nullable String section) {
    return Strings.isNullOrEmpty(section)
        ? getSettingsUrl()
        : getSettingsUrl().map(url -> url + "#" + section);
  }

  /** Returns a URL pointing to a documentation page, at a given named anchor. */
  default Optional<String> getDocUrl(String page, String anchor) {
    return getWebUrl().map(url -> url + "Documentation/" + page + "#" + anchor);
  }

  /** Returns a REST API URL for a given suffix (eg. "accounts/self/details") */
  default Optional<String> getRestUrl(String suffix) {
    return getWebUrl().map(url -> url + suffix);
  }
}