/*
 * Licensed to Julian Hyde under one or more contributor license
 * agreements.  See the NOTICE file distributed with this work
 * for additional information regarding copyright ownership.
 * Julian Hyde licenses this file to you 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 net.hydromatic.morel;

import com.google.common.collect.ImmutableList;
import org.checkerframework.checker.nullness.qual.Nullable;
import org.slf4j.Logger;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.StringReader;
import java.io.StringWriter;
import java.io.Writer;
import java.util.List;
import java.util.function.BiConsumer;
import java.util.stream.Stream;

/**
 * Unsafe methods to be used by tests.
 *
 * <p>Contains methods that call JDK methods that the
 * <a href="https://github.com/policeman-tools/forbidden-apis">forbidden
 * APIs checker</a> does not approve of.
 *
 * <p>This class is excluded from the check, so methods called via this class
 * will not fail the build.
 *
 * <p>Why is this in {@code core/src/test} and not in {@code testkit/src/main}?
 * Because some of the methods (e.g. {@link #runAppProcess}) are so unsafe that
 * they must not be on the class-path of production code.
 */
public abstract class TestUnsafe {
  /**
   * Runs an external application process.
   *
   * @param argumentList  command name and its arguments
   * @param directory  working directory
   * @param logger    if not null, command and exit status will be logged here
   * @param appInput  if not null, data will be copied to application's stdin
   * @param appOutput if not null, data will be captured from application's
   *                  stdout and stderr
   * @return application process exit value
   */
  public static int runAppProcess(List<String> argumentList, File directory,
      @Nullable Logger logger, @Nullable Reader appInput,
      @Nullable Writer appOutput) throws IOException, InterruptedException {

    // WARNING: ProcessBuilder is security-sensitive. Its use is currently
    // safe because this code is under "core/test". Developers must not move
    // this code into "core/main".
    final ProcessBuilder pb = new ProcessBuilder(argumentList);
    pb.directory(directory);
    pb.redirectErrorStream(true);
    if (logger != null) {
      logger.info("start process: " + pb.command());
    }
    Process p = pb.start();

    // Setup the input/output streams to the subprocess.
    // The buffering here is arbitrary. Javadocs strongly encourage
    // buffering, but the size needed is very dependent on the
    // specific application being run, the size of the input
    // provided by the caller, and the amount of output expected.
    // Since this method is currently used only by unit tests,
    // large-ish fixed buffer sizes have been chosen. If this
    // method becomes used for something in production, it might
    // be better to have the caller provide them as arguments.
    if (appInput != null) {
      OutputStream out =
          new BufferedOutputStream(
              p.getOutputStream(),
              100 * 1024);
      int c;
      while ((c = appInput.read()) != -1) {
        out.write(c);
      }
      out.flush();
    }
    if (appOutput != null) {
      InputStream in =
          new BufferedInputStream(
              p.getInputStream(),
              100 * 1024);
      int c;
      while ((c = in.read()) != -1) {
        appOutput.write(c);
      }
      appOutput.flush();
      in.close();
    }
    p.waitFor();

    int status = p.exitValue();
    if (logger != null) {
      logger.info("exit status=" + status + " from " + pb.command());
    }
    return status;
  }

  /** Returns whether we seem are in a valid environment. */
  public static boolean haveGit() {
    // Is there a '.git' directory? If not, we may be in a source tree
    // unzipped from a tarball.
    final File base = TestUtil.getBaseDir(TestUnsafe.class);
    final File gitDir = new File(base, ".git");
    if (!gitDir.exists()
        || !gitDir.isDirectory()
        || !gitDir.canRead()) {
      return false;
    }

    // Execute a simple git command. If it fails, we're probably not in a
    // valid git environment.
    final List<String> argumentList =
        ImmutableList.of("git", "--version");
    try {
      final StringWriter sw = new StringWriter();
      int status =
          runAppProcess(argumentList, base, null, null, sw);
      final String s = sw.toString();
      if (status != 0) {
        return false;
      }
    } catch (Exception e) {
      return false;
    }
    return true;
  }

  /** Returns a list of Java files in git. */
  public static List<File> getJavaFiles() {
    return getGitFiles("*.java");
  }

  /** Returns a list of text files in git. */
  public static List<File> getTextFiles() {
    return getGitFiles("*.java", "*.jj", "*.md", "*.properties",
        "*.sh", "*.sml", "*.smli", "*.txt", "*.xml", "*.yml");
  }

  /** Returns a list of files in git matching a given pattern or patterns.
   *
   * <p>Assumes running Linux or macOS, and that git is available. */
  public static List<File> getGitFiles(String... patterns) {
    String s;
    try {
      final List<String> argumentList =
          ImmutableList.<String>builder().add("git").add("ls-files")
              .add(patterns).build();
      final File base = TestUtil.getBaseDir(TestUnsafe.class);
      try {
        final StringWriter sw = new StringWriter();
        int status =
            runAppProcess(argumentList, base, null, null, sw);
        if (status != 0) {
          throw new RuntimeException("command " + argumentList
              + ": exited with status " + status);
        }
        s = sw.toString();
      } catch (Exception e) {
        throw new RuntimeException("command " + argumentList
            + ": failed with exception", e);
      }

      final ImmutableList.Builder<File> files = ImmutableList.builder();
      try (StringReader r = new StringReader(s);
           BufferedReader br = new BufferedReader(r)) {
        for (;;) {
          String line = br.readLine();
          if (line == null) {
            break;
          }
          files.add(new File(base, line));
        }
      }
      return files.build();
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  /** Returns the subject / body pairs of the {@code n} most recent commits. */
  public static void getCommitMessages(int n,
      BiConsumer<String, String> consumer) {
    // Generate log like this:
    //
    //   ===
    //   subject
    //
    //   body
    //   ===
    //   subject 2
    //
    //   body2
    //
    // then split on "===\n"
    final File base = TestUtil.getBaseDir(TestUnsafe.class);
    final List<String> argumentList =
        ImmutableList.of("git", "log", "-n" + n, "--pretty=format:===%n%B");
    try {
      final StringWriter sw = new StringWriter();
      int status =
          runAppProcess(argumentList, base, null, null, sw);
      String s = sw.toString();
      if (status != 0) {
        throw new RuntimeException("command " + argumentList
            + ": exited with status " + status
            + (s.isEmpty() ? "" : "; output [" + s + "]"));
      }
      Stream.of(s.split("===\n")).forEach(s2 -> {
        if (s2.isEmpty()) {
          return; // ignore empty subject & body
        }
        int i = s2.indexOf("\n");
        if (i < 0) {
          i = s2.length(); // no linefeed; treat entire chunk as subject
        }
        String subject = s2.substring(0, i);
        while (i < s2.length() && s2.charAt(i) == '\n') {
          ++i; // skip multiple linefeeds between subject and body
        }
        String body = s2.substring(i);
        consumer.accept(subject, body);
      });
    } catch (Exception e) {
      throw new RuntimeException("command " + argumentList
          + ": failed with exception", e);
    }
  }
}

// End TestUnsafe.java
