/*
 * Copyright 2013-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.cli;

import com.facebook.buck.util.MoreFiles;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.io.Files;

import java.io.BufferedReader;
import java.io.File;
import java.io.InputStreamReader;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Path;
import java.nio.file.Paths;

/**
 * This class creates a terminal command for Buck that creates a sample Buck project in the
 * directory the user specifies. It copies from {@link #PATH_TO_QUICKSTART_DIR} to the
 * directory specified. It then asks the user for the location of the Android SDK so Buck can
 * successfully build the quickstart project. It will fail if it cannot find the template directory,
 * or if it is unable to write to the destination directory.
 */
public class QuickstartCommand extends AbstractCommandRunner<QuickstartCommandOptions> {

  private static final Path PATH_TO_QUICKSTART_DIR = Paths.get(
      System.getProperty(
          "buck.quickstart_origin_dir",
          new File("src/com/facebook/buck/cli/quickstart/android").getAbsolutePath()
      )
  );

  public QuickstartCommand(CommandRunnerParams params) {
    super(params);
  }

  @Override
  QuickstartCommandOptions createOptions(BuckConfig buckConfig) {
    return new QuickstartCommandOptions(buckConfig);
  }

  /**
   * Runs the command "buck quickstart", which copies a template project into a new directory to
   * give the user a functional buck project. It copies from
   * src/com/facebook/buck/cli/quickstart/android to the directory specified. It then asks the user
   * for the location of the Android SDK so Buck cansuccessfully build the quickstart project. It
   * will fail if it cannot find the template directory or if it is unable to write to the
   * destination directory.
   *
   * @param options an object representing command line options
   * @return status code - zero means no problem
   * @throws IOException if the command fails to read from the template project or write to the
   *     new project
   */
  @Override
  int runCommandWithOptionsInternal(QuickstartCommandOptions options) throws IOException {
    String projectDir = options.getDestDir().trim();
    if (projectDir.isEmpty()) {
      projectDir = promptForPath("Enter the directory where you would like to create the " +
          "project: ");
    }

    File dir = new File(projectDir);
    while (!dir.isDirectory() && !dir.mkdirs() && !projectDir.isEmpty()) {
      projectDir = promptForPath("Cannot create project directory. Enter another directory: ");
      dir = new File(projectDir);
    }
    if (projectDir.isEmpty()) {
      getStdErr().println("No project directory specified. Aborting quickstart.");
      return 1;
    }

    String sdkLocation = options.getAndroidSdkDir();
    if (sdkLocation.isEmpty()) {
      sdkLocation = promptForPath("Enter your Android SDK's location: ");
    }

    File sdkLocationFile = new File(sdkLocation);
    if (!sdkLocationFile.isDirectory()) {
      getStdErr().println("WARNING: That Android SDK directory does not exist.");
    }

    sdkLocation = sdkLocationFile.getAbsoluteFile().toString();

    Path origin = PATH_TO_QUICKSTART_DIR;
    Path destination = Paths.get(projectDir);
    MoreFiles.copyRecursively(origin, destination);

    File out = new File(projectDir + "/local.properties");
    Files.write("sdk.dir=" + sdkLocation + "\n", out, StandardCharsets.UTF_8);

    getStdOut().print(
      Files.toString(origin.resolve("README.md").toFile(), StandardCharsets.UTF_8)
    );
    getStdOut().flush();

    return 0;
  }

  private String promptForPath(String prompt) throws IOException {
    getStdOut().print(prompt);
    getStdOut().flush();
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    return expandTilde(br.readLine().trim());
  }

  /**
   * A simple function to convert "~" to the home directory (i.e. /home/user) in paths. It does not
   * support the shortcut for other users' home directories, "~user". If the path does not start
   * with "~/", then this function returns the same string it was given.
   *
   * @param path an absolute path string that begins with "~/"
   * @return an absolute path with an expanded home directory
   */
  protected static String expandTilde(String path) {
    return expandTildeInternal(System.getProperty("user.home"), path);
  }

  @VisibleForTesting
  static String expandTildeInternal(String homeDir, String path) {
    if (path.startsWith("~/")) {
      return homeDir + path.substring(1);
    } else if (path.equals("~")) {
      return homeDir;
    } else {
      return path;
    }
  }

  @Override
  String getUsageIntro() {
    return "generates a default project directory";
  }
}