// Copyright 2023 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.skyframe;

import com.google.devtools.build.lib.analysis.PlatformOptions;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.CoreOptions;
import com.google.devtools.build.lib.analysis.config.ExecutionTransitionFactory;
import com.google.devtools.build.lib.analysis.config.transitions.BaselineOptionsValue;
import com.google.devtools.build.lib.analysis.config.transitions.PatchTransition;
import com.google.devtools.build.lib.analysis.config.transitions.TransitionUtil;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.skyframe.SkyFunction;
import com.google.devtools.build.skyframe.SkyFunctionException;
import com.google.devtools.build.skyframe.SkyKey;
import com.google.devtools.build.skyframe.SkyValue;
import com.google.devtools.common.options.OptionsParsingException;
import javax.annotation.Nullable;

/** A builder for {@link BaselineOptionsValue} instances. */
public final class BaselineOptionsFunction implements SkyFunction {
  @Override
  @Nullable
  public SkyValue compute(SkyKey skyKey, Environment env)
      throws InterruptedException, BaselineOptionsFunctionException {
    BaselineOptionsValue.Key key = (BaselineOptionsValue.Key) skyKey.argument();

    BuildOptions rawBaselineOptions = PrecomputedValue.BASELINE_CONFIGURATION.get(env);

    // Some test infrastructure only creates mock or partial top-level BuildOptions such that
    // PlatformOptions or even CoreOptions might not be included.
    // In that case, is not worth doing any special processing of the baseline.
    if (!rawBaselineOptions.getFragmentClasses().contains(PlatformOptions.class)
        || !rawBaselineOptions.getFragmentClasses().contains(CoreOptions.class)) {
      return BaselineOptionsValue.create(rawBaselineOptions);
    }

    // Herein lies a hack to apply platform mappings to the baseline options.
    // TODO(blaze-configurability-team): this should become unnecessary once --platforms is marked
    //   as EXPLICIT_IN_OUTPUT_PATH
    PlatformMappingValue platformMappingValue =
        (PlatformMappingValue)
            env.getValue(
                PlatformMappingValue.Key.create(
                    rawBaselineOptions.get(PlatformOptions.class).platformMappings));
    if (platformMappingValue == null) {
      return null;
    }
    try {
      BuildOptions mappedBaselineOptions =
          BuildConfigurationKey.withPlatformMapping(platformMappingValue, rawBaselineOptions)
              .getOptions();

      if (key.afterExecTransition()) {
        // A null executionPlatform actually skips transition application so need some value here.
        // It is safe to supply some fake value here (as long as it is constant) since the baseline
        // should never be used to actually construct an action or do toolchain resolution
        // TODO(twigg): This can eventually be replaced by the actual exec platform once
        //   platforms is explicitly in the output path (with the garbage value as a fallback).
        PatchTransition execTransition =
            ExecutionTransitionFactory.createTransition(
                Label.parseCanonicalUnchecked(
                    "//this_is_a_faked_exec_platform_for_blaze_internals"));
        BuildOptions toOptions =
            execTransition.patch(
                TransitionUtil.restrict(execTransition, mappedBaselineOptions), env.getListener());
        return BaselineOptionsValue.create(toOptions);
      } else {
        return BaselineOptionsValue.create(mappedBaselineOptions);
      }
    } catch (OptionsParsingException e) {
      throw new BaselineOptionsFunctionException(e);
    }
  }

  private static final class BaselineOptionsFunctionException extends SkyFunctionException {
    BaselineOptionsFunctionException(Exception e) {
      super(e, Transience.PERSISTENT);
    }
  }
}