package com.tuoheng.machine.command;

import com.tuoheng.machine.instruction.*;
import com.tuoheng.machine.mqtt.MqttCallbackRegistry;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;

import java.util.concurrent.CompletableFuture;
import java.util.concurrent.Executor;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledThreadPoolExecutor;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;

/**
 * 事务执行器（完全异步化版本）
 *
 * 设计说明：
 * 1. 完全异步：不阻塞任何线程，所有操作都通过 CompletableFuture 链式调用
 * 2. 高并发：可以同时处理数万个命令，不会创建大量线程
 * 3. 资源高效：线程只在真正需要执行任务时才使用，不会浪费在等待上
 *
 * 性能优势：
 * - 传统方式：10万个命令 = 10万个阻塞线程 = 系统崩溃
 * - 异步方式：10万个命令 = 200个工作线程 + 10万个 CompletableFuture = 正常运行
 */
@Slf4j
@Component
public class TransactionExecutor {

    private final MqttCallbackRegistry callbackRegistry;
    private final Executor commandExecutor;
    private final ScheduledExecutorService timeoutScheduler;

    public TransactionExecutor(
            MqttCallbackRegistry callbackRegistry,
            @Qualifier("commandExecutor") Executor commandExecutor) {
        this.callbackRegistry = callbackRegistry;
        this.commandExecutor = commandExecutor;

        // 创建一个专门用于超时检查的调度器（核心线程数较小）
        this.timeoutScheduler = new ScheduledThreadPoolExecutor(
            2,
            r -> {
                Thread t = new Thread(r, "timeout-scheduler");
                t.setDaemon(true);
                return t;
            }
        );

        log.info("事务执行器初始化完成（完全异步模式）");
    }

    /**
     * 执行事务（完全异步）
     *
     * @param transaction 事务定义
     * @param context 执行上下文
     * @return CompletableFuture，不会阻塞调用线程
     */
    public CompletableFuture<CommandResult> executeTransaction(Transaction transaction, InstructionContext context) {
        log.info("开始执行事务: transaction={}, sn={}", transaction.getName(), context.getSn());

        long startTime = System.currentTimeMillis();

        // 直接返回异步执行的结果，不创建新线程
        return executeInstructionTreeAsync(transaction, context, startTime, transaction.getRootInstruction());
    }

    /**
     * 异步执行指令树
     *
     * @param transaction 事务定义
     * @param context 执行上下文
     * @param startTime 事务开始时间
     * @param currentInstruction 当前要执行的指令
     * @return CompletableFuture
     */
    private CompletableFuture<CommandResult> executeInstructionTreeAsync(
            Transaction transaction,
            InstructionContext context,
            long startTime,
            Instruction currentInstruction) {

        // 检查根指令
        if (currentInstruction == null) {
            log.error("事务没有根指令: transaction={}", transaction.getName());
            return CompletableFuture.completedFuture(
                CommandResult.failure(transaction.getCommandType(), "事务没有根指令")
            );
        }

        // 检查事务是否超时
        if (System.currentTimeMillis() - startTime > transaction.getTimeoutMs()) {
            log.warn("事务执行超时: transaction={}, sn={}", transaction.getName(), context.getSn());
            return CompletableFuture.completedFuture(
                CommandResult.timeout(transaction.getCommandType())
            );
        }

        log.debug("执行指令: instruction={}", currentInstruction.getName());

        // 异步执行当前指令
        Instruction finalCurrentInstruction = currentInstruction;
        return executeInstructionAsync(currentInstruction, context)
            .thenCompose(result -> {
                // 根据执行结果获取下游指令
                Instruction nextInstruction = finalCurrentInstruction.getNextInstruction(result.isSuccess());

                if (nextInstruction != null) {
                    // 有下游指令，递归执行
                    log.debug("根据执行结果选择下游指令: success={}, nextInstruction={}",
                            result.isSuccess(), nextInstruction.getName());
                    return executeInstructionTreeAsync(transaction, context, startTime, nextInstruction);
                } else {
                    // 没有下游指令，当前指令的结果就是事务的结果
                    if (!result.isSuccess()) {
                        log.error("指令执行失败（无下游指令）: instruction={}, error={}",
                                finalCurrentInstruction.getName(), result.getErrorMessage());
                        return CompletableFuture.completedFuture(
                            CommandResult.failure(
                                transaction.getCommandType(),
                                result.getErrorMessage(),
                                finalCurrentInstruction.getName()
                            )
                        );
                    } else {
                        log.info("指令执行成功（无下游指令），事务完成: instruction={}, sn={}",
                                finalCurrentInstruction.getName(), context.getSn());
                        return CompletableFuture.completedFuture(
                            CommandResult.success(transaction.getCommandType())
                        );
                    }
                }
            });
    }

    /**
     * 异步执行单个指令
     *
     * @param instruction 指令
     * @param context 执行上下文
     * @return CompletableFuture<InstructionResult>
     */
    private CompletableFuture<InstructionResult> executeInstructionAsync(
            Instruction instruction,
            InstructionContext context) {

        log.debug("开始执行指令: instruction={}, sn={}", instruction.getName(), context.getSn());

        // a. 判断是否可以执行
        if (!instruction.canExecute(context)) {
            String error = "指令不满足执行条件";
            log.warn("指令不满足执行条件: instruction={}, sn={}", instruction.getName(), context.getSn());
            InstructionResult result = InstructionResult.failure(error);
            instruction.onComplete(context, result);
            return CompletableFuture.completedFuture(result);
        }

        // b. 在线程池中执行远程调用（避免阻塞当前线程）
        return CompletableFuture.supplyAsync(() -> {
            try {
                instruction.executeRemoteCall(context);
                log.debug("远程调用已发送: instruction={}", instruction.getName());
                return true;
            } catch (Exception e) {
                log.error("远程调用失败: instruction={}, sn={}", instruction.getName(), context.getSn(), e);
                return false;
            }
        }, commandExecutor).thenCompose(remoteCallSuccess -> {
            if (!remoteCallSuccess) {
                InstructionResult result = InstructionResult.failure("远程调用失败");
                instruction.onComplete(context, result);
                return CompletableFuture.completedFuture(result);
            }

            // c. 等待方法回调（异步）
            CallbackConfig methodCallback = instruction.getMethodCallbackConfig(context);
            if (methodCallback != null) {
                return waitForCallbackAsync(methodCallback, context)
                    .thenCompose(methodResult -> {
                        if (!methodResult.isSuccess()) {
                            instruction.onComplete(context, methodResult);
                            return CompletableFuture.completedFuture(methodResult);
                        }

                        // d. 等待状态回调（异步）
                        CallbackConfig stateCallback = instruction.getStateCallbackConfig(context);
                        if (stateCallback != null) {
                            return waitForCallbackAsync(stateCallback, context)
                                .thenApply(stateResult -> {
                                    instruction.onComplete(context, stateResult);
                                    return stateResult;
                                });
                        }

                        // 没有状态回调，直接成功
                        InstructionResult result = InstructionResult.success();
                        instruction.onComplete(context, result);
                        return CompletableFuture.completedFuture(result);
                    });
            }

            // 没有方法回调，检查是否有状态回调
            CallbackConfig stateCallback = instruction.getStateCallbackConfig(context);
            if (stateCallback != null) {
                return waitForCallbackAsync(stateCallback, context)
                    .thenApply(stateResult -> {
                        instruction.onComplete(context, stateResult);
                        return stateResult;
                    });
            }

            // 没有任何回调，直接成功
            InstructionResult result = InstructionResult.success();
            instruction.onComplete(context, result);
            return CompletableFuture.completedFuture(result);
        });
    }

    /**
     * 异步等待回调（不阻塞线程）
     *
     * 关键改进：
     * 1. 不使用 future.get() 阻塞线程
     * 2. 使用 ScheduledExecutorService 实现超时
     * 3. 完全基于回调机制
     *
     * @param callbackConfig 回调配置
     * @param context 执行上下文
     * @return CompletableFuture<InstructionResult>
     */
    private CompletableFuture<InstructionResult> waitForCallbackAsync(
            CallbackConfig callbackConfig,
            InstructionContext context) {

        CompletableFuture<InstructionResult> future = new CompletableFuture<>();
        AtomicBoolean callbackReceived = new AtomicBoolean(false);

        // 注册回调（包含 tid/bid 过滤）
        String callbackId = callbackRegistry.registerCallback(
            callbackConfig.getTopic(),
            messageBody -> {
                // 使用 CAS 确保只处理一次
                if (callbackReceived.compareAndSet(false, true)) {
                    // 判断消息是否匹配
                    if (callbackConfig.matches(messageBody)) {
                        future.complete(InstructionResult.success(messageBody));
                        log.debug("收到匹配的回调消息: topic={}", callbackConfig.getTopic());
                    }
                }
            },
            callbackConfig.getTimeoutMs(),
            callbackConfig.getTidFieldPath(),
            callbackConfig.getExpectedTid(),
            callbackConfig.getBidFieldPath(),
            callbackConfig.getExpectedBid()
        );

        // 设置超时（不阻塞线程）
        timeoutScheduler.schedule(() -> {
            // 使用 CAS 确保只处理一次
            if (callbackReceived.compareAndSet(false, true)) {
                future.complete(InstructionResult.timeout());
                log.warn("等待回调超时: topic={}, timeout={}ms",
                    callbackConfig.getTopic(), callbackConfig.getTimeoutMs());
            }
        }, callbackConfig.getTimeoutMs(), TimeUnit.MILLISECONDS);

        // 清理回调（无论成功还是超时）
        return future.whenComplete((result, throwable) -> {
            callbackRegistry.unregisterCallback(callbackId);
        });
    }
}