// Copyright (C) 2020 The Android Open Source Project
//
// 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 gerrit;

import com.google.gerrit.entities.Patch;
import com.google.gerrit.server.patch.FilePathAdapter;
import com.google.gerrit.server.patch.filediff.FileDiffOutput;
import com.google.gerrit.server.rules.StoredValues;
import com.googlecode.prolog_cafe.exceptions.PrologException;
import com.googlecode.prolog_cafe.lang.ListTerm;
import com.googlecode.prolog_cafe.lang.Operation;
import com.googlecode.prolog_cafe.lang.Predicate;
import com.googlecode.prolog_cafe.lang.Prolog;
import com.googlecode.prolog_cafe.lang.StructureTerm;
import com.googlecode.prolog_cafe.lang.SymbolTerm;
import com.googlecode.prolog_cafe.lang.Term;
import java.io.IOException;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;
import java.util.stream.Collectors;
import org.eclipse.jgit.lib.FileMode;
import org.eclipse.jgit.lib.Repository;
import org.eclipse.jgit.revwalk.RevCommit;
import org.eclipse.jgit.revwalk.RevWalk;
import org.eclipse.jgit.treewalk.TreeWalk;
import org.eclipse.jgit.treewalk.filter.PathFilterGroup;

/** Exports list of Strings that each represent a file name in the current patchset. */
public class PRED_files_1 extends Predicate.P1 {
  private static final SymbolTerm file = SymbolTerm.intern("file", 3);

  PRED_files_1(Term a1, Operation n) {
    arg1 = a1;
    cont = n;
  }

  @Override
  public Operation exec(Prolog engine) throws PrologException {
    engine.setB0();
    Term a1 = arg1.dereference();
    Term listHead = Prolog.Nil;

    try (RevWalk revWalk = new RevWalk(StoredValues.REPOSITORY.get(engine))) {
      RevCommit commit = revWalk.parseCommit(StoredValues.getPatchSet(engine).commitId());
      Collection<FileDiffOutput> modifiedFiles = StoredValues.DIFF_LIST.get(engine).values();
      Set<String> submodules =
          getAllSubmodulePaths(StoredValues.REPOSITORY.get(engine), commit, modifiedFiles);
      for (FileDiffOutput fileDiff : modifiedFiles) {
        if (fileDiff.newPath().isPresent() && Patch.isMagic(fileDiff.newPath().get())) {
          continue;
        }
        String newPath =
            FilePathAdapter.getNewPath(
                fileDiff.oldPath(), fileDiff.newPath(), fileDiff.changeType());
        SymbolTerm fileNameTerm = SymbolTerm.create(newPath);
        SymbolTerm changeType = SymbolTerm.create(fileDiff.changeType().getCode());
        SymbolTerm fileType;
        if (submodules.contains(newPath)) {
          fileType = SymbolTerm.create("SUBMODULE");
        } else {
          fileType = SymbolTerm.create("REGULAR");
        }
        listHead =
            new ListTerm(new StructureTerm(file, fileNameTerm, changeType, fileType), listHead);
      }
    } catch (IOException ex) {
      return engine.fail();
    }
    if (!a1.unify(listHead, engine.trail)) {
      return engine.fail();
    }
    return cont;
  }

  /** Returns the paths for all {@code GITLINK} files. */
  private static Set<String> getAllSubmodulePaths(
      Repository repository, RevCommit commit, Collection<FileDiffOutput> modifiedFiles)
      throws PrologException, IOException {
    Set<String> submodules = new HashSet<>();
    try (TreeWalk treeWalk = new TreeWalk(repository)) {
      treeWalk.addTree(commit.getTree());
      Set<String> allPaths =
          modifiedFiles.stream()
              .map(f -> FilePathAdapter.getNewPath(f.oldPath(), f.newPath(), f.changeType()))
              .filter(f -> !Patch.isMagic(f))
              .collect(Collectors.toSet());
      treeWalk.setFilter(PathFilterGroup.createFromStrings(allPaths));

      while (treeWalk.next()) {
        if (treeWalk.getFileMode() == FileMode.GITLINK) {
          submodules.add(treeWalk.getPathString());
        }
      }
      return submodules;
    }
  }
}