// Copyright 2014 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.cpp;

import static java.nio.charset.StandardCharsets.UTF_8;

import com.google.common.base.Preconditions;
import com.google.devtools.build.lib.actions.ActionExecutionContext;
import com.google.devtools.build.lib.actions.ActionKeyContext;
import com.google.devtools.build.lib.actions.ActionOwner;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.EnvironmentalExecException;
import com.google.devtools.build.lib.actions.ExecException;
import com.google.devtools.build.lib.analysis.WorkspaceStatusAction;
import com.google.devtools.build.lib.analysis.actions.AbstractFileWriteAction;
import com.google.devtools.build.lib.analysis.actions.DeterministicWriter;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable;
import com.google.devtools.build.lib.server.FailureDetails.FailureDetail;
import com.google.devtools.build.lib.server.FailureDetails.WorkspaceStatus;
import com.google.devtools.build.lib.server.FailureDetails.WorkspaceStatus.Code;
import com.google.devtools.build.lib.util.Fingerprint;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import java.util.TreeMap;
import javax.annotation.Nullable;

/**
 * An action that creates a C++ header containing the build information in the form of #define
 * directives.
 */
@Immutable
public final class WriteBuildInfoHeaderAction extends AbstractFileWriteAction {
  private static final String GUID = "7243b846-b2f2-4057-97a4-00e2da6c6ffd";

  private final boolean writeVolatileInfo;
  private final boolean writeStableInfo;

  /**
   * Creates an action that writes a C++ header with the build information.
   *
   * <p>It reads the set of build info keys from an action context that is usually contributed to
   * Bazel by the workspace status module, and the value associated with said keys from the
   * workspace status files (stable and volatile) written by the workspace status action.
   *
   * <p>Without input artifacts this action uses redacted build information.
   *
   * @param inputs Artifacts that contain build information, or an empty collection to use redacted
   *     build information
   * @param primaryOutput the C++ header Artifact created by this action
   * @param writeVolatileInfo whether to write the volatile part of the build information to the
   *     generated header
   * @param writeStableInfo whether to write the non-volatile part of the build information to the
   *     generated header
   */
  public WriteBuildInfoHeaderAction(
      NestedSet<Artifact> inputs,
      Artifact primaryOutput,
      boolean writeVolatileInfo,
      boolean writeStableInfo) {
    super(ActionOwner.SYSTEM_ACTION_OWNER, inputs, primaryOutput, /*makeExecutable=*/ false);
    if (!inputs.isEmpty()) {
      // With non-empty inputs we should not generate both volatile and non-volatile data
      // in the same header file.
      Preconditions.checkState(writeVolatileInfo ^ writeStableInfo);
    }
    Preconditions.checkState(
        primaryOutput.isConstantMetadata() == (writeVolatileInfo && !inputs.isEmpty()));

    this.writeVolatileInfo = writeVolatileInfo;
    this.writeStableInfo = writeStableInfo;
  }

  @Override
  public DeterministicWriter newDeterministicWriter(ActionExecutionContext ctx)
      throws ExecException {
    WorkspaceStatusAction.Context context = ctx.getContext(WorkspaceStatusAction.Context.class);

    Map<String, WorkspaceStatusAction.Key> keys = new TreeMap<>();
    if (writeVolatileInfo) {
      keys.putAll(context.getVolatileKeys());
    }

    if (writeStableInfo) {
      keys.putAll(context.getStableKeys());
    }

    Map<String, String> values = new HashMap<>();
    for (Artifact valueFile : getInputs().toList()) {
      try {
        values.putAll(WorkspaceStatusAction.parseValues(ctx.getInputPath(valueFile)));
      } catch (IOException e) {
        throw new EnvironmentalExecException(
            e,
            FailureDetail.newBuilder()
                .setMessage("Failed to parse workspace status: " + e.getMessage())
                .setWorkspaceStatus(WorkspaceStatus.newBuilder().setCode(Code.PARSE_FAILURE))
                .build());
      }
    }

    final boolean redacted = getInputs().isEmpty();

    return out -> {
      Writer writer = new OutputStreamWriter(out, UTF_8);

      for (Map.Entry<String, WorkspaceStatusAction.Key> key : keys.entrySet()) {
        String value =
            redacted
                ? key.getValue().getRedactedValue()
                : values.containsKey(key.getKey())
                    ? values.get(key.getKey())
                    : key.getValue().getDefaultValue();

        switch (key.getValue().getType()) {
          case INTEGER:
            break;

          case STRING:
            value = quote(value);
            break;
        }
        define(writer, key.getKey(), value);
      }
      writer.flush();
    };
  }

  @Override
  protected void computeKey(
      ActionKeyContext actionKeyContext,
      @Nullable Artifact.ArtifactExpander artifactExpander,
      Fingerprint fp) {
    fp.addString(GUID);
    fp.addBoolean(writeStableInfo);
    fp.addBoolean(writeVolatileInfo);
  }

  @Override
  public boolean executeUnconditionally() {
    // Note: isVolatile must return true if executeUnconditionally can ever return true
    // for this instance.
    return isUnconditional();
  }

  @Override
  public boolean isVolatile() {
    return isUnconditional();
  }

  private boolean isUnconditional() {
    // Because of special handling in the action cache, changed volatile build
    // information does not trigger relinking of all libraries that have
    // linkstamps. But we do want to regenerate the header in case libraries are
    // relinked because of other reasons.
    // Without inputs the contents of the header do not change, so there is no
    // point in executing the action again in that case.
    return writeVolatileInfo && !getInputs().isEmpty();
  }

  /**
   * Quote a string with double quotes.
   */
  private String quote(String string) {
    // TODO(bazel-team): This is doesn't really work if the string contains quotes. Or a newline.
    // Or a backslash. Or anything unusual, really.
    return "\"" + string + "\"";
  }

  /**
   * Write a preprocessor define directive to a Writer.
   */
  private void define(Writer writer, String name, String value) throws IOException {
    writer.write("#define ");
    writer.write(name);
    writer.write(' ');
    writer.write(value);
    writer.write('\n');
  }

  @Nullable
  @Override
  protected String getRawProgressMessage() {
    return null;
  }
}