// 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.buildjar.javac.plugins.processing;

import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableSet;
import com.google.devtools.build.buildjar.javac.plugins.BlazeJavaCompilerPlugin;
import com.google.devtools.build.buildjar.proto.JavaCompilation.CompilationUnit;
import com.google.devtools.build.buildjar.proto.JavaCompilation.Manifest;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

/** A module for information about the compilation's annotation processing. */
public class AnnotationProcessingModule {

  /** A builder for {@link AnnotationProcessingModule}s. */
  public static class Builder {
    private Path sourceGenDir;
    private Path manifestProto;
    private final ImmutableSet.Builder<Path> sourceRoots = ImmutableSet.builder();

    private Builder() {}

    public AnnotationProcessingModule build() {
      return new AnnotationProcessingModule(
          sourceGenDir, manifestProto, validateSourceRoots(sourceRoots.build()));
    }

    /**
     * Verify that source roots do not contain other source roots.
     *
     * <p>If one source root is an ancestor of another, the source path to use in the manifest will
     * be ambiguous.
     */
    private ImmutableSet<Path> validateSourceRoots(ImmutableSet<Path> roots) {
      // It's sad that this is quadratic, but the number of source roots
      // should be <= 2.
      for (Path a : roots) {
        for (Path b : roots) {
          if (a.equals(b) || b.getNameCount() == 0) {
            continue;
          }
          if (a.startsWith(b)) {
            throw new IllegalArgumentException(
                String.format("Source root %s is a parent of %s", b, a));
          }
        }
      }
      return roots;
    }

    public void setSourceGenDir(Path sourceGenDir) {
      this.sourceGenDir = sourceGenDir;
    }

    public void setManifestProtoPath(Path manifestProto) {
      this.manifestProto = manifestProto.toAbsolutePath();
    }

    public void addAllSourceRoots(Set<String> sourceRoots) {
      for (String root : sourceRoots) {
        this.sourceRoots.add(Paths.get(root));
      }
    }
  }

  private final boolean enabled;
  private final Path sourceGenDir;
  private final Path manifestProto;
  private final ImmutableSet<Path> sourceRoots;

  public boolean isGenerated(Path path) {
    return path.startsWith(sourceGenDir);
  }

  public Path stripSourceRoot(Path path) {
    if (path.startsWith(sourceGenDir)) {
      return sourceGenDir.relativize(path);
    }
    for (Path sourceRoot : sourceRoots) {
      if (path.startsWith(sourceRoot)) {
        return sourceRoot.relativize(path);
      }
    }
    return path;
  }

  private AnnotationProcessingModule(
      Path sourceGenDir, Path manifestProto, ImmutableSet<Path> sourceRoots) {
    this.sourceGenDir = sourceGenDir;
    this.manifestProto = manifestProto;
    this.sourceRoots = sourceRoots;
    this.enabled = sourceGenDir != null && manifestProto != null;
  }

  public static Builder builder() {
    return new Builder();
  }

  public void registerPlugin(ImmutableList.Builder<BlazeJavaCompilerPlugin> builder) {
    if (enabled) {
      builder.add(new AnnotationProcessingPlugin(this));
    }
  }

  private final Map<String, CompilationUnit> units = new HashMap<>();

  public void recordUnit(CompilationUnit unit) {
    units.put(unit.getPath(), unit);
  }

  private Manifest buildManifestProto() {
    Manifest.Builder builder = Manifest.newBuilder();

    List<String> keys = new ArrayList<>(units.keySet());
    Collections.sort(keys);
    for (String key : keys) {
      CompilationUnit unit = units.get(key);
      builder.addCompilationUnit(unit);
    }

    return builder.build();
  }

  public void emitManifestProto() throws IOException {
    if (!enabled) {
      return;
    }
    try (OutputStream out = Files.newOutputStream(manifestProto)) {
      buildManifestProto().writeTo(out);
    } catch (IOException ex) {
      throw new IOException("Cannot write manifest to " + manifestProto, ex);
    }
  }
}