/*
 * Copyright 2012-present Facebook, Inc.
 *
 * 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.facebook.buck.android;

import static com.facebook.buck.rules.BuildableProperties.Kind.ANDROID;
import static com.facebook.buck.rules.BuildableProperties.Kind.LIBRARY;

import com.facebook.buck.model.BuildTarget;
import com.facebook.buck.model.BuildTargetPattern;
import com.facebook.buck.rules.AbstractBuildRuleBuilderParams;
import com.facebook.buck.rules.AbstractBuildable;
import com.facebook.buck.rules.BuildContext;
import com.facebook.buck.rules.BuildRuleParams;
import com.facebook.buck.rules.BuildRuleResolver;
import com.facebook.buck.rules.BuildRuleType;
import com.facebook.buck.rules.BuildableContext;
import com.facebook.buck.rules.BuildableProperties;
import com.facebook.buck.rules.RecordArtifactsInDirectoryStep;
import com.facebook.buck.rules.RuleKey;
import com.facebook.buck.rules.SrcsAttributeBuilder;
import com.facebook.buck.step.Step;
import com.facebook.buck.util.BuckConstant;
import com.google.common.base.Function;
import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSortedSet;
import com.google.common.collect.Sets;

import java.io.IOException;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.List;
import java.util.Set;

import javax.annotation.Nullable;

/**
 * An object that represents a collection of Android NDK source code.
 * <p>
 * Suppose this were a rule defined in <code>src/com/facebook/feed/jni/BUCK</code>:
 * <pre>
 * ndk_library(
 *   name = 'feed-jni',
 *   deps = [],
 *   flags = ["NDK_DEBUG=1", "V=1"],
 * )
 * </pre>
 */
public class NdkLibrary extends AbstractBuildable implements NativeLibraryBuildable {

  private final static BuildableProperties PROPERTIES = new BuildableProperties(ANDROID, LIBRARY);

  /** @see NativeLibraryBuildable#isAsset() */
  private final boolean isAsset;

  /** The directory containing the Android.mk file to use. This value includes a trailing slash. */
  private final String makefileDirectory;
  private final String lastPathComponent;
  private final String buildArtifactsDirectory;
  private final String genDirectory;

  private final ImmutableSortedSet<String> sources;
  private final ImmutableList<String> flags;

  protected NdkLibrary(
      BuildTarget buildTarget,
      Set<String> sources,
      List<String> flags,
      boolean isAsset) {
    this.isAsset = isAsset;

    this.makefileDirectory = buildTarget.getBasePathWithSlash();
    this.lastPathComponent = "__lib" + buildTarget.getShortName();
    this.buildArtifactsDirectory = getBuildArtifactsDirectory(buildTarget, true /* isScratchDir */);
    this.genDirectory = getBuildArtifactsDirectory(buildTarget, false /* isScratchDir */);

    Preconditions.checkArgument(!sources.isEmpty(),
        "Must include at least one file (Android.mk?) in ndk_library rule");
    this.sources = ImmutableSortedSet.copyOf(sources);
    this.flags = ImmutableList.copyOf(flags);
  }

  @Override
  public boolean isAsset() {
    return isAsset;
  }

  @Override
  public String getLibraryPath() {
    return genDirectory;
  }

  @Override
  @Nullable
  public String getPathToOutputFile() {
    // An ndk_library() does not have a "primary output" at this time.
    return null;
  }

  @Override
  public List<Step> getBuildSteps(BuildContext context, BuildableContext buildableContext)
      throws IOException {
    // .so files are written to the libs/ subdirectory of the output directory.
    // All of them should be recorded via the BuildableContext.
    Path binDirectory = Paths.get(buildArtifactsDirectory, "libs");
    Step nkdBuildStep = new NdkBuildStep(makefileDirectory,
        buildArtifactsDirectory + "/",
        binDirectory,
        flags);

    Function<String, Path> artifactPathTransform = new Function<String, Path>() {
      @Override
      public Path apply(String pathRelativeTo) {
        return Paths.get(lastPathComponent, pathRelativeTo);
      }
    };
    Step recordStep = new RecordArtifactsInDirectoryStep(
        buildableContext,
        binDirectory,
        genDirectory,
        artifactPathTransform);
    return ImmutableList.of(nkdBuildStep, recordStep);
  }

  /**
   * @param isScratchDir true if this should be the "working directory" where a build rule may write
   *     intermediate files when computing its output. false if this should be the gen/ directory
   *     where the "official" outputs of the build rule should be written. Files of the latter type
   *     can be referenced via the genfile() function.
   */
  private String getBuildArtifactsDirectory(BuildTarget target, boolean isScratchDir) {
    return String.format("%s/%s%s",
        isScratchDir ? BuckConstant.BIN_DIR : BuckConstant.GEN_DIR,
        target.getBasePathWithSlash(),
        lastPathComponent);
  }

  @Override
  public BuildableProperties getProperties() {
    return PROPERTIES;
  }

  @Override
  public RuleKey.Builder appendDetailsToRuleKey(RuleKey.Builder builder) throws IOException {
    // TODO(#2493457): This rule uses the ndk-build script (part of the Android NDK), so the RuleKey
    // should incorporate which version of the NDK is used.
    return builder
        .set("sources", sources)
        .set("flags", flags)
        .set("is_asset", isAsset());
  }

  @Override
  public Iterable<String> getInputsToCompareToOutput() {
    return this.sources;
  }

  public static Builder newNdkLibraryRuleBuilder(AbstractBuildRuleBuilderParams params) {
    return new Builder(params);
  }

  public static class Builder extends AbstractBuildable.Builder implements SrcsAttributeBuilder {

    private boolean isAsset = false;
    private Set<String> sources = Sets.newHashSet();
    private ImmutableList.Builder<String> flags = ImmutableList.builder();

    private Builder(AbstractBuildRuleBuilderParams params) {
      super(params);
    }

    @Override
    public BuildRuleType getType() {
      return BuildRuleType.NDK_LIBRARY;
    }

    @Override
    protected NdkLibrary newBuildable(BuildRuleParams params, BuildRuleResolver resolver) {
      return new NdkLibrary(params.getBuildTarget(), sources, flags.build(), isAsset);
    }

    public Builder setIsAsset(boolean isAsset) {
      this.isAsset = isAsset;
      return this;
    }

    @Override
    public Builder setBuildTarget(BuildTarget buildTarget) {
      super.setBuildTarget(buildTarget);
      return this;
    }

    @Override
    public Builder addVisibilityPattern(BuildTargetPattern visibilityPattern) {
      super.addVisibilityPattern(visibilityPattern);
      return this;
    }

    @Override
    public Builder addSrc(String source) {
      this.sources.add(source);
      return this;
    }

    public Builder addFlag(String flag) {
      this.flags.add(flag);
      return this;
    }

  }
}