// Copyright 2017 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.analysis;

import com.google.auto.value.AutoValue;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableMap;
import com.google.devtools.build.lib.analysis.platform.PlatformProviderUtils;
import com.google.devtools.build.lib.analysis.platform.ToolchainInfo;
import com.google.devtools.build.lib.analysis.platform.ToolchainTypeInfo;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe;
import com.google.devtools.build.lib.server.FailureDetails.Toolchain.Code;
import com.google.devtools.build.lib.skyframe.ConfiguredTargetAndData;
import com.google.devtools.build.lib.skyframe.ToolchainException;
import com.google.devtools.build.lib.skyframe.UnloadedToolchainContext;
import javax.annotation.Nullable;

/**
 * Represents the data needed for a specific target's use of toolchains and platforms, including
 * specific {@link ToolchainInfo} providers for each required toolchain type.
 */
@AutoValue
@Immutable
@ThreadSafe
public abstract class ResolvedToolchainContext implements ToolchainContext {

  /**
   * Finishes preparing the {@link ResolvedToolchainContext} by finding the specific toolchain
   * providers to be used for each toolchain type.
   */
  public static ResolvedToolchainContext load(
      UnloadedToolchainContext unloadedToolchainContext,
      String targetDescription,
      Iterable<ConfiguredTargetAndData> toolchainTargets)
      throws ToolchainException {

    ImmutableMap.Builder<ToolchainTypeInfo, ToolchainInfo> toolchains =
        new ImmutableMap.Builder<>();
    ImmutableList.Builder<TemplateVariableInfo> templateVariableProviders =
        new ImmutableList.Builder<>();
    for (ConfiguredTargetAndData target : toolchainTargets) {
      // Aliases are in toolchainTypeToResolved by the original alias label, not via the final
      // target's label.
      Label discoveredLabel = target.getConfiguredTarget().getOriginalLabel();

      for (ToolchainTypeInfo toolchainType :
          unloadedToolchainContext.toolchainTypeToResolved().inverse().get(discoveredLabel)) {
        ToolchainInfo toolchainInfo = PlatformProviderUtils.toolchain(target.getConfiguredTarget());

        // If the toolchainType hadn't been resolved to an actual target, resolution would have
        // failed with an error much earlier. However, the target might still not be an actual
        // toolchain.
        if (toolchainType != null) {
          if (toolchainInfo != null) {
            toolchains.put(toolchainType, toolchainInfo);
          } else {
            throw new TargetNotToolchainException(toolchainType, discoveredLabel);
          }
        }

        // Find any template variables present for this toolchain.
        TemplateVariableInfo templateVariableInfo =
            target.getConfiguredTarget().get(TemplateVariableInfo.PROVIDER);
        if (templateVariableInfo != null) {
          templateVariableProviders.add(templateVariableInfo);
        }
      }
    }

    return new AutoValue_ResolvedToolchainContext(
        // super:
        unloadedToolchainContext.key(),
        unloadedToolchainContext.executionPlatform(),
        unloadedToolchainContext.targetPlatform(),
        unloadedToolchainContext.requiredToolchainTypes(),
        unloadedToolchainContext.resolvedToolchainLabels(),
        // this:
        targetDescription,
        unloadedToolchainContext.requestedLabelToToolchainType(),
        toolchains.build(),
        templateVariableProviders.build());
  }

  /** Returns a description of the target being used, for error messaging. */
  public abstract String targetDescription();

  /** Sets the map from requested {@link Label} to toolchain type provider. */
  public abstract ImmutableMap<Label, ToolchainTypeInfo> requestedToolchainTypeLabels();

  public abstract ImmutableMap<ToolchainTypeInfo, ToolchainInfo> toolchains();

  /** Returns the template variables that these toolchains provide. */
  public abstract ImmutableList<TemplateVariableInfo> templateVariableProviders();

  /**
   * Returns the toolchain for the given type, or {@code null} if the toolchain type was not
   * required in this context.
   */
  @Nullable
  public ToolchainInfo forToolchainType(Label toolchainTypeLabel) {
    ToolchainTypeInfo toolchainTypeInfo = requestedToolchainTypeLabels().get(toolchainTypeLabel);
    if (toolchainTypeInfo == null) {
      return null;
    }
    return toolchains().get(toolchainTypeInfo);
  }

  @Nullable
  public ToolchainInfo forToolchainType(ToolchainTypeInfo toolchainType) {
    return toolchains().get(toolchainType);
  }

  /**
   * Exception used when a toolchain type is required but the resolved target does not have
   * ToolchainInfo.
   */
  static final class TargetNotToolchainException extends ToolchainException {
    TargetNotToolchainException(ToolchainTypeInfo toolchainType, Label resolvedTargetLabel) {
      super(
          String.format(
              "toolchain type %s resolved to target %s, but that target does not provide "
                  + ToolchainInfo.STARLARK_NAME,
              toolchainType.typeLabel(),
              resolvedTargetLabel));
    }

    @Override
    protected Code getDetailedCode() {
      return Code.MISSING_PROVIDER;
    }
  }
}