import * as plugins from './taskbuffer.plugins.js';
import { Task } from './taskbuffer.classes.task.js';
import { TaskConstraintGroup } from './taskbuffer.classes.taskconstraintgroup.js';
import {
  AbstractDistributedCoordinator,
  type IDistributedTaskRequestResult,
} from './taskbuffer.classes.distributedcoordinator.js';
import type { ITaskMetadata, ITaskExecutionReport, IScheduledTaskInfo, ITaskEvent, IConstrainedTaskEntry } from './taskbuffer.interfaces.js';
import { logger } from './taskbuffer.logging.js';

export interface ICronJob {
  cronString: string;
  taskName: string;
  job: any;
}

export interface ITaskManagerConstructorOptions {
  distributedCoordinator?: AbstractDistributedCoordinator;
}

export class TaskManager {
  public randomId = plugins.smartunique.shortId();
  public taskMap = new plugins.lik.ObjectMap<Task<any, any, any>>();
  public readonly taskSubject = new plugins.smartrx.rxjs.Subject<ITaskEvent>();
  private taskSubscriptions = new Map<Task<any, any, any>, plugins.smartrx.rxjs.Subscription>();
  private cronJobManager = new plugins.smarttime.CronManager();
  public options: ITaskManagerConstructorOptions = {
    distributedCoordinator: null,
  };

  // Constraint system
  public constraintGroups: TaskConstraintGroup<any>[] = [];
  private constraintQueue: IConstrainedTaskEntry[] = [];
  private drainTimer: ReturnType<typeof setTimeout> | null = null;

  constructor(options: ITaskManagerConstructorOptions = {}) {
    this.options = Object.assign(this.options, options);
  }

  public getTaskByName(taskName: string): Task<any, any, any> {
    return this.taskMap.findSync((task) => task.name === taskName);
  }

  public addTask(task: Task<any, any, any>): void {
    if (!task.name) {
      throw new Error('Task must have a name to be added to taskManager');
    }
    this.taskMap.add(task);
    const subscription = task.eventSubject.subscribe((event) => {
      this.taskSubject.next(event);
    });
    this.taskSubscriptions.set(task, subscription);
  }

  public removeTask(task: Task<any, any, any>): void {
    this.taskMap.remove(task);
    const subscription = this.taskSubscriptions.get(task);
    if (subscription) {
      subscription.unsubscribe();
      this.taskSubscriptions.delete(task);
    }
  }

  public addAndScheduleTask(task: Task<any, any, any>, cronString: string) {
    this.addTask(task);
    this.scheduleTaskByName(task.name, cronString);
  }

  // Constraint group management
  public addConstraintGroup(group: TaskConstraintGroup<any>): void {
    this.constraintGroups.push(group);
  }

  public removeConstraintGroup(name: string): void {
    this.constraintGroups = this.constraintGroups.filter((g) => g.name !== name);
  }

  // Core constraint evaluation
  public async triggerTaskConstrained(task: Task<any, any, any>, input?: any): Promise<any> {
    // Gather applicable constraints
    const applicableGroups: Array<{ group: TaskConstraintGroup<any>; key: string }> = [];
    for (const group of this.constraintGroups) {
      const key = group.getConstraintKey(task, input);
      if (key !== null) {
        applicableGroups.push({ group, key });
      }
    }

    // No constraints apply → check shouldExecute then trigger directly
    if (applicableGroups.length === 0) {
      const shouldRun = await this.checkAllShouldExecute(task, input);
      if (!shouldRun) {
        return undefined;
      }
      return task.trigger(input);
    }

    // Check if all constraints allow running
    const allCanRun = applicableGroups.every(({ group, key }) => group.canRun(key));
    if (allCanRun) {
      return this.executeWithConstraintTracking(task, input, applicableGroups);
    }

    // Blocked → enqueue with deferred promise and cached constraint keys
    const deferred = plugins.smartpromise.defer<any>();
    const constraintKeys = new Map<string, string>();
    for (const { group, key } of applicableGroups) {
      constraintKeys.set(group.name, key);
    }
    this.constraintQueue.push({ task, input, deferred, constraintKeys });
    return deferred.promise;
  }

  private async checkAllShouldExecute(task: Task<any, any, any>, input?: any): Promise<boolean> {
    for (const group of this.constraintGroups) {
      const shouldRun = await group.checkShouldExecute(task, input);
      if (!shouldRun) {
        return false;
      }
    }
    return true;
  }

  private async executeWithConstraintTracking(
    task: Task<any, any, any>,
    input: any,
    groups: Array<{ group: TaskConstraintGroup<any>; key: string }>,
  ): Promise<any> {
    // Acquire slots synchronously to prevent race conditions
    for (const { group, key } of groups) {
      group.acquireSlot(key);
    }

    // Check shouldExecute after acquiring slots
    const shouldRun = await this.checkAllShouldExecute(task, input);
    if (!shouldRun) {
      // Release slots and drain queue
      for (const { group, key } of groups) {
        group.releaseSlot(key);
      }
      this.drainConstraintQueue();
      return undefined;
    }

    try {
      return await task.trigger(input);
    } finally {
      // Release slots
      for (const { group, key } of groups) {
        group.releaseSlot(key);
      }
      this.drainConstraintQueue();
    }
  }

  private drainConstraintQueue(): void {
    let shortestCooldown = Infinity;
    const stillQueued: IConstrainedTaskEntry[] = [];

    for (const entry of this.constraintQueue) {
      const applicableGroups: Array<{ group: TaskConstraintGroup<any>; key: string }> = [];
      for (const group of this.constraintGroups) {
        const key = group.getConstraintKey(entry.task, entry.input);
        if (key !== null) {
          applicableGroups.push({ group, key });
        }
      }

      // No constraints apply anymore (group removed?) → check shouldExecute then run
      if (applicableGroups.length === 0) {
        this.checkAllShouldExecute(entry.task, entry.input).then((shouldRun) => {
          if (!shouldRun) {
            entry.deferred.resolve(undefined);
            return;
          }
          entry.task.trigger(entry.input).then(
            (result) => entry.deferred.resolve(result),
            (err) => entry.deferred.reject(err),
          );
        });
        continue;
      }

      const allCanRun = applicableGroups.every(({ group, key }) => group.canRun(key));
      if (allCanRun) {
        // executeWithConstraintTracking handles shouldExecute check internally
        this.executeWithConstraintTracking(entry.task, entry.input, applicableGroups).then(
          (result) => entry.deferred.resolve(result),
          (err) => entry.deferred.reject(err),
        );
      } else {
        stillQueued.push(entry);
        // Track shortest cooldown for timer scheduling
        for (const { group, key } of applicableGroups) {
          const remaining = group.getCooldownRemaining(key);
          if (remaining > 0 && remaining < shortestCooldown) {
            shortestCooldown = remaining;
          }
        }
      }
    }

    this.constraintQueue = stillQueued;

    // Schedule next drain if there are cooldown-blocked entries
    if (this.drainTimer) {
      clearTimeout(this.drainTimer);
      this.drainTimer = null;
    }
    if (stillQueued.length > 0 && shortestCooldown < Infinity) {
      this.drainTimer = setTimeout(() => {
        this.drainTimer = null;
        this.drainConstraintQueue();
      }, shortestCooldown + 1);
    }
  }

  public async triggerTaskByName(taskName: string): Promise<any> {
    const taskToTrigger = this.getTaskByName(taskName);
    if (!taskToTrigger) {
      throw new Error(`No task with the name ${taskName} found.`);
    }
    return this.triggerTaskConstrained(taskToTrigger);
  }

  public async triggerTask(task: Task<any, any, any>) {
    return this.triggerTaskConstrained(task);
  }

  public scheduleTaskByName(taskName: string, cronString: string) {
    const taskToSchedule = this.getTaskByName(taskName);
    if (!taskToSchedule) {
      throw new Error(`No task with the name ${taskName} found.`);
    }
    this.handleTaskScheduling(taskToSchedule, cronString);
  }

  private handleTaskScheduling(task: Task<any, any, any>, cronString: string) {
    const cronJob = this.cronJobManager.addCronjob(
      cronString,
      async (triggerTime: number) => {
        this.logTaskState(task);
        if (this.options.distributedCoordinator) {
          const announcementResult = await this.performDistributedConsultation(
            task,
            triggerTime,
          );
          if (!announcementResult.shouldTrigger) {
            logger.log('info', 'Distributed coordinator result: NOT EXECUTING');
            return;
          } else {
            logger.log('info', 'Distributed coordinator result: CHOSEN AND EXECUTING');
          }
        }
        try {
          await this.triggerTaskConstrained(task);
        } catch (err) {
          logger.log('error', `TaskManager: scheduled task "${task.name || 'unnamed'}" failed: ${err instanceof Error ? err.message : String(err)}`);
        }
      },
    );
    task.cronJob = cronJob;
  }

  private logTaskState(task: Task<any, any, any>) {
    logger.log('info', `Taskbuffer schedule triggered task >>${task.name}<<`);
    const bufferState = task.buffered
      ? `buffered with max ${task.bufferMax} buffered calls`
      : `unbuffered`;
    logger.log('info', `Task >>${task.name}<< is ${bufferState}`);
  }

  private async performDistributedConsultation(
    task: Task<any, any, any>,
    triggerTime: number,
  ): Promise<IDistributedTaskRequestResult> {
    logger.log('info', 'Found a distributed coordinator, performing consultation.');

    return this.options.distributedCoordinator.fireDistributedTaskRequest({
      submitterId: this.randomId,
      requestResponseId: plugins.smartunique.shortId(),
      status: 'requesting',
      taskExecutionParallel: 1,
      taskExecutionTime: triggerTime,
      taskExecutionTimeout: task.timeout,
      taskName: task.name,
      taskVersion: task.version,
    });
  }

  public descheduleTaskByName(taskName: string) {
    const task = this.getTaskByName(taskName);
    if (task && task.cronJob) {
      this.cronJobManager.removeCronjob(task.cronJob);
      task.cronJob = null;
    }
    if (this.cronJobManager.cronjobs.isEmpty) {
      this.cronJobManager.stop();
    }
  }

  public async descheduleTask(task: Task<any, any, any>) {
    await this.descheduleTaskByName(task.name);
  }

  public getScheduleForTaskName(taskName: string): string | null {
    const task = this.getTaskByName(taskName);
    return task && task.cronJob ? task.cronJob.cronExpression : null;
  }

  public async start() {
    if (this.options.distributedCoordinator) {
      await this.options.distributedCoordinator.start();
    }
    this.cronJobManager.start();
  }

  public async stop() {
    this.cronJobManager.stop();
    if (this.options.distributedCoordinator) {
      await this.options.distributedCoordinator.stop();
    }
    for (const [, subscription] of this.taskSubscriptions) {
      subscription.unsubscribe();
    }
    this.taskSubscriptions.clear();
    if (this.drainTimer) {
      clearTimeout(this.drainTimer);
      this.drainTimer = null;
    }
  }

  // Get metadata for a specific task
  public getTaskMetadata(taskName: string): ITaskMetadata | null {
    const task = this.getTaskByName(taskName);
    if (!task) return null;
    return task.getMetadata();
  }

  // Get metadata for all tasks
  public getAllTasksMetadata(): ITaskMetadata[] {
    return this.taskMap.getArray().map(task => task.getMetadata());
  }

  // Get scheduled tasks with their schedules and next run times
  public getScheduledTasks(): IScheduledTaskInfo[] {
    const scheduledTasks: IScheduledTaskInfo[] = [];

    for (const task of this.taskMap.getArray()) {
      if (task.cronJob) {
        scheduledTasks.push({
          name: task.name || 'unnamed',
          schedule: task.cronJob.cronExpression,
          nextRun: new Date(task.cronJob.getNextExecutionTime()),
          lastRun: task.lastRun,
          steps: task.getStepsMetadata?.(),
          metadata: task.getMetadata(),
        });
      }
    }

    return scheduledTasks;
  }

  // Get next scheduled runs across all tasks
  public getNextScheduledRuns(limit: number = 10): Array<{ taskName: string; nextRun: Date; schedule: string }> {
    const scheduledRuns = this.getScheduledTasks()
      .map(task => ({
        taskName: task.name,
        nextRun: task.nextRun,
        schedule: task.schedule,
      }))
      .sort((a, b) => a.nextRun.getTime() - b.nextRun.getTime())
      .slice(0, limit);

    return scheduledRuns;
  }

  public getTasksByLabel(key: string, value: string): Task<any, any, any>[] {
    return this.taskMap.getArray().filter(task => task.labels[key] === value);
  }

  public getTasksMetadataByLabel(key: string, value: string): ITaskMetadata[] {
    return this.getTasksByLabel(key, value).map(task => task.getMetadata());
  }

  // Add, execute, and remove a task while collecting metadata
  public async addExecuteRemoveTask<T, TSteps extends ReadonlyArray<{ name: string; description: string; percentage: number }>>(
    task: Task<T, TSteps, any>,
    options?: {
      schedule?: string;
      trackProgress?: boolean;
    }
  ): Promise<ITaskExecutionReport> {
    // Add task to manager
    this.addTask(task);

    // Optionally schedule it
    if (options?.schedule) {
      this.scheduleTaskByName(task.name!, options.schedule);
    }

    const startTime = Date.now();

    try {
      // Execute the task through constraints
      const result = await this.triggerTaskConstrained(task);

      // Collect execution report
      const report: ITaskExecutionReport = {
        taskName: task.name || 'unnamed',
        startTime,
        endTime: Date.now(),
        duration: Date.now() - startTime,
        steps: task.getStepsMetadata(),
        stepsCompleted: task.getStepsMetadata()
          .filter(step => step.status === 'completed')
          .map(step => step.name),
        progress: task.getProgress(),
        result,
      };

      // Remove task from manager
      this.removeTask(task);

      // Deschedule if it was scheduled
      if (options?.schedule && task.name) {
        this.descheduleTaskByName(task.name);
      }

      return report;
    } catch (error) {
      // Create error report
      const errorReport: ITaskExecutionReport = {
        taskName: task.name || 'unnamed',
        startTime,
        endTime: Date.now(),
        duration: Date.now() - startTime,
        steps: task.getStepsMetadata(),
        stepsCompleted: task.getStepsMetadata()
          .filter(step => step.status === 'completed')
          .map(step => step.name),
        progress: task.getProgress(),
        error: error as Error,
      };

      // Remove task from manager even on error
      this.removeTask(task);

      // Deschedule if it was scheduled
      if (options?.schedule && task.name) {
        this.descheduleTaskByName(task.name);
      }

      throw errorReport;
    }
  }
}