// Copyright 2015 The Bazel Authors. All rights reserved.
//
// 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.devtools.build.lib.rules.objc;

import com.google.common.base.Joiner;
import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.Fragment;
import com.google.devtools.build.lib.analysis.config.RequiresOptions;
import com.google.devtools.build.lib.analysis.starlark.annotations.StarlarkConfigurationField;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.events.Event;
import com.google.devtools.build.lib.events.EventHandler;
import com.google.devtools.build.lib.starlarkbuildapi.apple.J2ObjcConfigurationApi;
import java.util.Collections;
import javax.annotation.Nullable;

/**
 * A J2ObjC transpiler configuration fragment containing J2ObjC translation flags. This
 * configuration fragment is used by Java rules that can be transpiled (specifically, J2ObjCAspects
 * thereof).
 */
@Immutable
@RequiresOptions(options = {J2ObjcCommandLineOptions.class})
public class J2ObjcConfiguration extends Fragment implements J2ObjcConfigurationApi {
  /**
   * Always-on flags for J2ObjC translation. These flags are always used when invoking the J2ObjC
   * transpiler, and cannot be overridden by user-specified flags in {@link
   * J2ObjcCommandLineOptions}. See https://j2objc.org/reference/j2objc.html for flag documentation.
   */
  private static final ImmutableList<String> J2OBJC_ALWAYS_ON_TRANSLATION_FLAGS =
      ImmutableList.of(
          "-encoding", "UTF-8", "--doc-comments", "-XcombineJars", "-XDinjectLogSites=true");

  /**
   * Default flags for J2ObjC translation. These flags are used by default when invoking the J2ObjC
   * transpiler, but can be overridden by user-specified flags in {@link J2ObjcCommandLineOptions}.
   * See https://j2objc.org/reference/j2objc.html for flag documentation.
   */
  private static final ImmutableList<String> J2OBJC_DEFAULT_TRANSLATION_FLAGS =
      ImmutableList.of("-g:relative"); // Java source debugging with WORKSPACE-relative paths.

  /**
   * Disallowed flags for J2ObjC translation. See https://j2objc.org/reference/j2objc.html for flag
   * documentation.
   */
  static final ImmutableList<String> J2OBJC_BLACKLISTED_TRANSLATION_FLAGS =
      ImmutableList.of("--prefixes", "--prefix", "-x");

  static final String INVALID_TRANSLATION_FLAGS_MSG_TEMPLATE =
      "J2Objc translation flags: %s not supported. Unsupported flags are: %s";

  private final ImmutableList<String> translationFlags;

  @Nullable private final Label deadCodeReport;

  public J2ObjcConfiguration(BuildOptions buildOptions) {
    J2ObjcCommandLineOptions j2ObjcOptions = buildOptions.get(J2ObjcCommandLineOptions.class);
    this.translationFlags =
        ImmutableList.<String>builder()
            .addAll(J2OBJC_DEFAULT_TRANSLATION_FLAGS)
            .addAll(j2ObjcOptions.getTranslationFlags())
            .addAll(J2OBJC_ALWAYS_ON_TRANSLATION_FLAGS)
            .build();
    this.deadCodeReport = j2ObjcOptions.getDeadCodeReport();
  }

  /**
   * Returns the translation flags used to invoke the J2ObjC transpiler. The returned flags contain
   * the default flags from {@link #J2OBJC_DEFAULT_TRANSLATION_FLAGS}, user-specified flags from
   * {@link J2ObjcCommandLineOptions}, and always-on flags from {@link
   * #J2OBJC_ALWAYS_ON_TRANSLATION_FLAGS}. The set of disallowed flags can be found at
   * {@link #J2OBJC_BLACKLISTED_TRANSLATION_FLAGS}.
   */
  @Override
  public ImmutableList<String> getTranslationFlags() {
    return translationFlags;
  }

  /**
   * Returns the label of the dead code report generated by ProGuard for J2ObjC to eliminate dead
   * code. The dead Java code in the report will not be translated to Objective-C code.
   *
   * <p>Returns null if no such report was requested.
   */
  @Nullable
  @StarlarkConfigurationField(
      name = "dead_code_report",
      doc =
          "The label of the dead code report generated by ProGuard for dead code elimination, "
              + "or <code>None</code> if no such report was requested.",
      defaultLabel = "")
  public Label deadCodeReport() {
    return deadCodeReport;
  }

  @Override
  public void reportInvalidOptions(EventHandler reporter, BuildOptions buildOptions) {
    if (!Collections.disjoint(translationFlags, J2OBJC_BLACKLISTED_TRANSLATION_FLAGS)) {
      String errorMsg = String.format(INVALID_TRANSLATION_FLAGS_MSG_TEMPLATE,
          Joiner.on(",").join(translationFlags),
          Joiner.on(",").join(J2OBJC_BLACKLISTED_TRANSLATION_FLAGS));
      reporter.handle(Event.error(errorMsg));
    }
  }
}
