/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF 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 org.apache.flink.statefun.e2e.smoke.embedded;

import static org.apache.flink.statefun.e2e.smoke.driver.Types.COMMANDS_TYPE;
import static org.apache.flink.statefun.e2e.smoke.driver.Types.SOURCE_COMMANDS_TYPE;
import static org.apache.flink.statefun.e2e.smoke.driver.Types.isTypeOf;
import static org.apache.flink.statefun.e2e.smoke.driver.Types.packCommands;
import static org.apache.flink.statefun.e2e.smoke.driver.Types.packVerificationResult;
import static org.apache.flink.statefun.e2e.smoke.driver.Types.unpackCommands;
import static org.apache.flink.statefun.e2e.smoke.driver.Types.unpackSourceCommand;

import java.time.Duration;
import java.util.Objects;
import java.util.concurrent.CompletableFuture;
import org.apache.flink.statefun.e2e.smoke.driver.Constants;
import org.apache.flink.statefun.e2e.smoke.driver.Ids;
import org.apache.flink.statefun.e2e.smoke.generated.Command;
import org.apache.flink.statefun.e2e.smoke.generated.Commands;
import org.apache.flink.statefun.e2e.smoke.generated.SourceCommand;
import org.apache.flink.statefun.e2e.smoke.generated.VerificationResult;
import org.apache.flink.statefun.sdk.Address;
import org.apache.flink.statefun.sdk.AsyncOperationResult;
import org.apache.flink.statefun.sdk.Context;
import org.apache.flink.statefun.sdk.FunctionType;
import org.apache.flink.statefun.sdk.reqreply.generated.TypedValue;
import org.apache.flink.statefun.sdk.state.PersistedValue;

public final class CommandInterpreter {
  private final AsyncCompleter asyncCompleter;
  private final Ids ids;
  private static final Duration sendAfterDelay = Duration.ofMillis(1);

  public CommandInterpreter(Ids ids) {
    this.asyncCompleter = new AsyncCompleter();
    asyncCompleter.start();
    this.ids = Objects.requireNonNull(ids);
  }

  public void interpret(PersistedValue<Long> state, Context context, Object message) {
    if (message instanceof AsyncOperationResult) {
      @SuppressWarnings("unchecked")
      AsyncOperationResult<Commands, ?> res = (AsyncOperationResult<Commands, ?>) message;
      interpret(state, context, res.metadata());
      return;
    }
    if (!(message instanceof TypedValue)) {
      throw new IllegalStateException("Unexpected message: " + message);
    }
    TypedValue typedValue = (TypedValue) message;
    if (isTypeOf(typedValue, SOURCE_COMMANDS_TYPE)) {
      SourceCommand sourceCommand = unpackSourceCommand(typedValue);
      interpret(state, context, sourceCommand.getCommands());
    } else if (isTypeOf(typedValue, COMMANDS_TYPE)) {
      Commands commands = unpackCommands(typedValue);
      interpret(state, context, commands);
    } else {
      throw new IllegalArgumentException("Unknown message type " + typedValue.getTypename());
    }
  }

  private void interpret(PersistedValue<Long> state, Context context, Commands command) {
    for (Command cmd : command.getCommandList()) {
      if (cmd.hasIncrement()) {
        modifyState(state, context, cmd.getIncrement());
      } else if (cmd.hasAsyncOperation()) {
        registerAsyncOps(state, context, cmd.getAsyncOperation());
      } else if (cmd.hasSend()) {
        send(state, context, cmd.getSend());
      } else if (cmd.hasSendAfter()) {
        sendAfter(state, context, cmd.getSendAfter());
      } else if (cmd.hasSendEgress()) {
        sendEgress(state, context, cmd.getSendEgress());
      } else if (cmd.hasVerify()) {
        verify(state, context, cmd.getVerify());
      } else if (cmd.hasCancelSendAfter()) {
        cancelSendAfter(state, context, cmd.getCancelSendAfter());
      }
    }
  }

  private void verify(
      PersistedValue<Long> state,
      @SuppressWarnings("unused") Context context,
      Command.Verify verify) {
    int selfId = Integer.parseInt(context.self().id());
    long actual = state.getOrDefault(0L);
    long expected = verify.getExpected();
    VerificationResult verificationResult =
        VerificationResult.newBuilder()
            .setId(selfId)
            .setActual(actual)
            .setExpected(expected)
            .build();
    context.send(Constants.VERIFICATION_RESULT, packVerificationResult(verificationResult));
  }

  private void sendEgress(
      @SuppressWarnings("unused") PersistedValue<Long> state,
      Context context,
      @SuppressWarnings("unused") Command.SendEgress sendEgress) {
    context.send(Constants.OUT, TypedValue.getDefaultInstance());
  }

  private void sendAfter(
      @SuppressWarnings("unused") PersistedValue<Long> state,
      Context context,
      Command.SendAfter send) {
    FunctionType functionType = Constants.FN_TYPE;
    String id = ids.idOf(send.getTarget());
    TypedValue subCommands = packCommands(send.getCommands());
    if (send.getCancellationToken().isEmpty()) {
      context.sendAfter(sendAfterDelay, functionType, id, subCommands);
    } else {
      context.sendAfter(
          sendAfterDelay, new Address(functionType, id), subCommands, send.getCancellationToken());
    }
  }

  private void cancelSendAfter(
      @SuppressWarnings("unused") PersistedValue<Long> state,
      Context context,
      Command.CancelSendAfter cancelSendAfter) {
    String token = cancelSendAfter.getCancellationToken();
    context.cancelDelayedMessage(token);
  }

  private void send(
      @SuppressWarnings("unused") PersistedValue<Long> state, Context context, Command.Send send) {
    FunctionType functionType = Constants.FN_TYPE;
    String id = ids.idOf(send.getTarget());
    context.send(functionType, id, packCommands(send.getCommands()));
  }

  private void registerAsyncOps(
      @SuppressWarnings("unused") PersistedValue<Long> state,
      Context context,
      Command.AsyncOperation asyncOperation) {
    CompletableFuture<Boolean> future =
        asyncOperation.getFailure()
            ? asyncCompleter.successfulFuture()
            : asyncCompleter.failedFuture();

    Commands next = asyncOperation.getResolvedCommands();
    context.registerAsyncOperation(next, future);
  }

  private void modifyState(
      PersistedValue<Long> state,
      @SuppressWarnings("unused") Context context,
      @SuppressWarnings("unused") Command.IncrementState incrementState) {
    state.updateAndGet(n -> n == null ? 1 : n + 1);
  }
}