/*
Copyright 2020 The Kubernetes Authors.
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 io.kubernetes.client;

import static io.kubernetes.client.KubernetesConstants.*;

import com.google.gson.reflect.TypeToken;
import io.kubernetes.client.custom.IOTrio;
import io.kubernetes.client.openapi.ApiClient;
import io.kubernetes.client.openapi.ApiException;
import io.kubernetes.client.openapi.Configuration;
import io.kubernetes.client.openapi.apis.CoreV1Api;
import io.kubernetes.client.openapi.models.V1Pod;
import io.kubernetes.client.openapi.models.V1Status;
import io.kubernetes.client.openapi.models.V1StatusCause;
import io.kubernetes.client.openapi.models.V1StatusDetails;
import io.kubernetes.client.util.Streams;
import io.kubernetes.client.util.WebSocketStreamHandler;
import io.kubernetes.client.util.WebSockets;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.lang.reflect.Type;
import java.net.URLEncoder;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.function.BiConsumer;
import java.util.function.Consumer;
import java.util.function.Supplier;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class Exec {
  private static final Logger log = LoggerFactory.getLogger(Exec.class);

  private ApiClient apiClient;

  private Consumer<Throwable> onUnhandledError;

  /** Simple Exec API constructor, uses default configuration */
  public Exec() {
    this(Configuration.getDefaultApiClient());
  }

  /**
   * Exec API Constructor
   *
   * @param apiClient The api client to use.
   */
  public Exec(ApiClient apiClient) {
    this.apiClient = apiClient;
  }

  /**
   * Get the API client for these exec operations.
   *
   * @return The API client that will be used.
   */
  public ApiClient getApiClient() {
    return apiClient;
  }

  /**
   * Set the API client for subsequent exec operations.
   *
   * @param apiClient The new API client to use.
   */
  public void setApiClient(ApiClient apiClient) {
    this.apiClient = apiClient;
  }

  /**
   * Get a {@link Consumer<Throwable>} that will be accepted if there is any unhandled exception
   * while the websocket communication is happening.
   *
   * @return The {@link Consumer<Throwable>} that will be used.
   */
  public Consumer<Throwable> getOnUnhandledError() {
    return onUnhandledError;
  }

  /**
   * Set the {@link Consumer<Throwable>} that will be accepted if there is any unhandled exception
   * while the websocket communication is happening.
   *
   * @param onUnhandledError The new {@link Consumer<Throwable>} to use.
   */
  public void setOnUnhandledError(Consumer<Throwable> onUnhandledError) {
    this.onUnhandledError = onUnhandledError;
  }

  /**
   * Setup a Builder for the given namespace, name and command
   *
   * @param namespace The namespace of the Pod
   * @param name The name of the Pod
   * @param command The command to run
   */
  public ExecutionBuilder newExecutionBuilder(String namespace, String name, String[] command) {
    return new ExecutionBuilder(namespace, name, command);
  }

  /**
   * Execute a command in a container. If there are multiple containers in the pod, uses the first
   * container in the Pod.
   *
   * @param namespace The namespace of the Pod
   * @param name The name of the Pod
   * @param command The command to run
   * @param stdin If true, pass a stdin stream into the container
   */
  public Process exec(String namespace, String name, String[] command, boolean stdin)
      throws ApiException, IOException {
    return exec(namespace, name, command, null, stdin, false);
  }

  /**
   * Execute a command in a container. If there are multiple containers in the pod, uses the first
   * container in the Pod.
   *
   * @param pod The pod where the command is run.
   * @param command The command to run
   * @param stdin If true, pass a stdin stream into the container
   */
  public Process exec(V1Pod pod, String[] command, boolean stdin) throws ApiException, IOException {
    return exec(pod, command, pod.getSpec().getContainers().get(0).getName(), stdin, false);
  }

  /**
   * Execute a command in a container. If there are multiple containers in the pod, uses the first
   * container in the Pod.
   *
   * @param namespace The namespace of the Pod
   * @param name The name of the Pod
   * @param command The command to run
   * @param stdin If true, pass a stdin stream into the container
   * @param tty If true, stdin is a tty.
   */
  public Process exec(String namespace, String name, String[] command, boolean stdin, boolean tty)
      throws ApiException, IOException {
    return exec(namespace, name, command, null, stdin, tty);
  }

  /**
   * Execute a command in a container. If there are multiple containers in the pod, uses the first
   * container in the Pod.
   *
   * @param pod The pod where the command is run.
   * @param command The command to run
   * @param stdin If true, pass a stdin stream into the container
   * @param tty If true, stdin is a tty.
   */
  public Process exec(V1Pod pod, String[] command, boolean stdin, boolean tty)
      throws ApiException, IOException {
    return exec(pod, command, pod.getSpec().getContainers().get(0).getName(), stdin, tty);
  }

  /**
   * Execute a command in a container. If there are multiple containers in the pod, uses the first
   * container in the Pod.
   *
   * @param pod The pod where the command is run.
   * @param command The command to run
   * @param container The container in the Pod where the command is run.
   * @param stdin If true, pass a stdin stream into the container.
   * @param tty If true, stdin is a TTY (only applies if stdin is true)
   */
  public Process exec(V1Pod pod, String[] command, String container, boolean stdin, boolean tty)
      throws ApiException, IOException {
    if (container == null) {
      container = pod.getSpec().getContainers().get(0).getName();
    }
    return exec(
        pod.getMetadata().getNamespace(),
        pod.getMetadata().getName(),
        command,
        container,
        stdin,
        tty);
  }

  /**
   * Execute a command in a container. If there are multiple containers in the pod, uses the first
   * container in the Pod.
   *
   * @param namespace The namespace of the Pod
   * @param name The name of the Pod
   * @param command The command to run
   * @param container The container in the Pod where the command is run.
   * @param stdin If true, pass a stdin stream into the container.
   * @param tty If true, stdin is a TTY (only applies if stdin is true)
   */
  public Process exec(
      String namespace, String name, String[] command, String container, boolean stdin, boolean tty)
      throws ApiException, IOException {
    return new ExecutionBuilder(namespace, name, command)
        .setContainer(container)
        .setStdin(stdin)
        .setTty(tty)
        .setOnUnhandledError(onUnhandledError)
        .execute();
  }

  /**
   * A convenience method. Executes a command remotely on a pod and monitors for events in that
   * execution. The monitored events are: <br>
   * - connection established (onOpen) <br>
   * - connection closed (onClosed) <br>
   * - execution error occurred (onError) <br>
   * This method also allows to specify a MAX timeout for the execution and returns a future in
   * order to monitor the execution flow. <br>
   * onError and onClosed callbacks are invoked asynchronously, in a separate thread. <br>
   *
   * @param namespace a namespace the target pod "lives" in
   * @param podName a name of the pod to exec the command on
   * @param onOpen a callback invoked upon the connection established event.
   * @param onClosed a callback invoked upon the process termination. Return code might not always
   *     be there. N.B. this callback is invoked before the returned {@link Future} is completed.
   * @param onError a callback to handle k8s errors (NOT the command errors/stderr!)
   * @param timeoutMs timeout in milliseconds for the execution. I.e. the execution will take this
   *     many ms or less. If the timeout command is running longer than the allowed timeout, the
   *     command will be "asked" to terminate gracefully. If the command is still running after the
   *     grace period, the sigkill will be issued. If null is passed, the timeout will not be used
   *     and will wait for process to exit itself.
   * @param tty whether you need tty to pipe the data. TTY mode will trim some binary data in order
   *     to make it possible to show on screen (tty)
   * @param command a tokenized command to run on the pod
   * @return a {@link Future} promise representing this execution. Unless something goes south, the
   *     promise will contain the process return exit code. If the timeoutMs is non-null and the
   *     timeout expires before the process exits, promise will contain {@link Integer#MAX_VALUE}.
   * @throws IOException
   */
  public Future<Integer> exec(
      String namespace,
      String podName,
      Consumer<IOTrio> onOpen,
      BiConsumer<Integer, IOTrio> onClosed,
      BiConsumer<Throwable, IOTrio> onError,
      Long timeoutMs,
      boolean tty,
      String... command)
      throws IOException {
    CompletableFuture<Integer> future = new CompletableFuture<>();
    IOTrio io = new IOTrio();
    String cmdStr = Arrays.toString(command);
    BiConsumer<Throwable, IOTrio> errHandler =
        (err, errIO) -> {
          if (onError != null) {
            onError.accept(err, errIO);
          }
        };
    try {
      Process process = exec(namespace, podName, command, null, true, tty);

      io.onClose(
          (code, timeout) -> {
            process.destroy();
            waitForProcessToExit(process, timeout, cmdStr, err -> errHandler.accept(err, io));
            // processWaitingThread will handle the rest
          });
      io.setStdin(process.getOutputStream());
      io.setStdout(process.getInputStream());
      io.setStderr(process.getErrorStream());
      runAsync(
          "Process-Waiting-Thread-" + command[0] + "-" + podName,
          () -> {
            Supplier<Integer> returnCode = process::exitValue;
            try {
              log.debug("Waiting for process to close in {} ms: {}", timeoutMs, cmdStr);
              boolean beforeTimeout =
                  waitForProcessToExit(
                      process, timeoutMs, cmdStr, err -> errHandler.accept(err, io));
              if (!beforeTimeout) {
                returnCode = () -> Integer.MAX_VALUE;
              }
            } catch (Exception e) {
              errHandler.accept(e, io);
            }
            log.debug("process.onExit({}): {}", returnCode.get(), cmdStr);
            if (onClosed != null) {
              onClosed.accept(returnCode.get(), io);
            }
            future.complete(returnCode.get());
          });
      if (onOpen != null) {
        onOpen.accept(io);
      }
    } catch (ApiException e) {
      errHandler.accept(e, io);
      future.completeExceptionally(e);
    }
    return future;
  }

  protected void runAsync(String taskName, Runnable task) {
    Thread thread = new Thread(task);
    thread.setName(taskName);
    thread.start();
  }

  private boolean waitForProcessToExit(
      Process process, Long timeoutMs, String cmdStr, Consumer<Exception> onError) {
    boolean beforeTimeout = true;
    if (timeoutMs != null && timeoutMs >= 0) {
      boolean exited = false;
      try {
        exited = process.waitFor(timeoutMs, TimeUnit.MILLISECONDS);
      } catch (InterruptedException e) {
        onError.accept(e);
      }
      log.debug("Process closed={}: {}", exited, cmdStr);
      if (!exited && process.isAlive()) {
        beforeTimeout = false;
        log.warn("Process timed out after {} ms. Shutting down: {}", timeoutMs, cmdStr);
        process.destroy();
      }
    } else {
      try {
        process.waitFor();
      } catch (InterruptedException e) {
        onError.accept(e);
      }
    }
    return beforeTimeout;
  }

  public final class ExecutionBuilder {
    private final String namespace;
    private final String name;
    private final String[] command;

    private String container;

    private boolean stdin;
    private boolean stdout;
    private boolean stderr;
    private boolean tty;
    private Consumer<Throwable> onUnhandledError;

    private ExecutionBuilder(String namespace, String name, String[] command) {
      this.namespace = namespace;
      this.name = name;
      this.command = command;
      this.stdin = true;
      this.stdout = true;
      this.stderr = true;
    }

    public String getName() {
      return name;
    }

    public String getNamespace() {
      return namespace;
    }

    public String[] getCommand() {
      return command;
    }

    public String getContainer() {
      return container;
    }

    public ExecutionBuilder setContainer(String container) {
      this.container = container;
      return this;
    }

    public boolean getStdin() {
      return stdin;
    }

    public ExecutionBuilder setStdin(boolean stdin) {
      this.stdin = stdin;
      return this;
    }

    public boolean getStdout() {
      return stdout;
    }

    public ExecutionBuilder setStdout(boolean stdout) {
      this.stdout = stdout;
      return this;
    }

    public boolean getStderr() {
      return stderr;
    }

    public ExecutionBuilder setStderr(boolean stderr) {
      this.stderr = stderr;
      return this;
    }

    public boolean getTty() {
      return tty;
    }

    public ExecutionBuilder setTty(boolean tty) {
      this.tty = tty;
      return this;
    }

    public Consumer<Throwable> getOnUnhandledError() {
      return onUnhandledError;
    }

    public ExecutionBuilder setOnUnhandledError(Consumer<Throwable> onUnhandledError) {
      this.onUnhandledError = onUnhandledError;
      return this;
    }

    private String makePath() {
      String[] encodedCommand = new String[command.length];
      for (int i = 0; i < command.length; i++) {
        try {
          encodedCommand[i] = URLEncoder.encode(command[i], "UTF-8");
        } catch (UnsupportedEncodingException ex) {
          throw new RuntimeException("some thing wrong happend: " + ex.getMessage());
        }
      }
      return "/api/v1/namespaces/"
          + namespace
          + "/pods/"
          + name
          + "/exec?"
          + "stdin="
          + stdin
          + "&stdout="
          + stdout
          + "&stderr="
          + stderr
          + "&tty="
          + tty
          + (container != null ? "&container=" + container : "")
          + "&command="
          + StringUtils.join(encodedCommand, "&command=");
    }

    public Process execute() throws ApiException, IOException {
      if (container == null) {
        CoreV1Api api = new CoreV1Api(apiClient);
        V1Pod pod = api.readNamespacedPod(name, namespace, "false");
        container = pod.getSpec().getContainers().get(0).getName();
      }

      ExecProcess exec = new ExecProcess(apiClient, onUnhandledError);
      WebSocketStreamHandler handler = exec.getHandler();
      WebSockets.stream(makePath(), "GET", apiClient, handler);

      return exec;
    }
  }

  static int parseExitCode(ApiClient client, InputStream inputStream) {
    try {
      Type returnType = new TypeToken<V1Status>() {}.getType();
      String body;
      try (final Reader reader = new InputStreamReader(inputStream)) {
        body = Streams.toString(reader);
      }

      V1Status status = client.getJSON().deserialize(body, returnType);
      if (status == null) {
        return -1;
      }
      if (V1STATUS_SUCCESS.equals(status.getStatus())) return 0;

      if (V1STATUS_REASON_NONZEROEXITCODE.equals(status.getReason())) {
        V1StatusDetails details = status.getDetails();
        if (details != null) {
          List<V1StatusCause> causes = details.getCauses();
          if (causes != null) {
            for (V1StatusCause cause : causes) {
              if (V1STATUS_CAUSE_REASON_EXITCODE.equals(cause.getReason())) {
                try {
                  return Integer.parseInt(cause.getMessage());
                } catch (NumberFormatException nfe) {
                  log.error("Error parsing exit code from status channel response", nfe);
                }
              }
            }
          }
        }
      }
    } catch (Throwable t) {
      log.error("Error parsing exit code from status channel response", t);
    }

    // Unable to parse the exit code from the content
    return -1;
  }

  public static class ExecProcess extends Process {
    private final WebSocketStreamHandler streamHandler;
    private final Consumer<Throwable> onUnhandledError;
    private int statusCode = -1;
    private boolean isAlive = true;
    private final Map<Integer, InputStream> input = new HashMap<>();
    private final CountDownLatch latch = new CountDownLatch(1);

    public ExecProcess(final ApiClient apiClient) throws IOException {
      this(apiClient, Throwable::printStackTrace);
    }

    public ExecProcess(final ApiClient apiClient, final Consumer<Throwable> onUnhandledError)
        throws IOException {
      this.onUnhandledError =
          Optional.ofNullable(onUnhandledError).orElse(Throwable::printStackTrace);
      this.streamHandler =
          new WebSocketStreamHandler() {
            @Override
            protected void handleMessage(int stream, InputStream inStream) throws IOException {
              if (stream == 3) {
                int exitCode = parseExitCode(apiClient, inStream);
                if (exitCode >= 0) {
                  // notify of process completion
                  synchronized (ExecProcess.this) {
                    statusCode = exitCode;
                    isAlive = false;
                  }
                }
                inStream.close();
                // Stream ID of `3` delivers the status of exec connection from
                // kubelet,
                // closing the connection upon 0 exit-code.
                this.close();
                ExecProcess.this.latch.countDown();
              } else super.handleMessage(stream, inStream);
            }

            @Override
            public void failure(Throwable ex) {
              super.failure(ex);
              ExecProcess.this.onUnhandledError.accept(ex);

              synchronized (ExecProcess.this) {
                // Try for a pretty unique error code, so if someone searches
                // they'll find this
                // code.
                statusCode = -1975219;
                isAlive = false;
                ExecProcess.this.latch.countDown();
              }
            }

            @Override
            public void close() {
              // notify of process completion
              synchronized (ExecProcess.this) {
                if (isAlive) {
                  isAlive = false;
                  ExecProcess.this.latch.countDown();
                }
              }

              super.close();
            }
          };
    }

    // Protected to facilitate unit testing.
    protected WebSocketStreamHandler getHandler() {
      return streamHandler;
    }

    @Override
    public OutputStream getOutputStream() {
      return streamHandler.getOutputStream(0);
    }

    @Override
    public InputStream getInputStream() {
      return getInputStream(1);
    }

    @Override
    public InputStream getErrorStream() {
      return getInputStream(2);
    }

    public InputStream getConnectionErrorStream() {
      return getInputStream(3);
    }

    public OutputStream getResizeStream() {
      return streamHandler.getOutputStream(4);
    }

    private synchronized InputStream getInputStream(int stream) {
      if (!input.containsKey(stream)) {
        input.put(stream, streamHandler.getInputStream(stream));
      }
      return input.get(stream);
    }

    @Override
    public int waitFor() throws InterruptedException {
      this.latch.await();
      return statusCode;
    }

    @Override
    public boolean waitFor(long timeout, TimeUnit unit) throws InterruptedException {
      this.latch.await(timeout, unit);
      return !isAlive();
    }

    @Override
    public synchronized int exitValue() {
      if (isAlive) throw new IllegalThreadStateException();
      return statusCode;
    }

    @Override
    public synchronized boolean isAlive() {
      return isAlive;
    }

    @Override
    public void destroy() {
      streamHandler.close();
      for (InputStream in : input.values()) {
        try {
          in.close();
        } catch (IOException ex) {
          log.error("Error on close", ex);
        }
      }
    }
  }
}
