import { randomUUID } from 'node:crypto';
import type {
  EnqueueJobInput,
  ListJobsOptions,
  QueueJob,
  QueueJobStatus,
  QueueStore,
} from './types.js';

function cloneValue<T>(value: T): T {
  return JSON.parse(JSON.stringify(value)) as T;
}

export class MemoryQueueStore implements QueueStore {
  private queues = new Map<string, Map<string, QueueJob>>();

  async enqueue<TPayload = unknown>(
    queueName: string,
    input: EnqueueJobInput<TPayload>
  ): Promise<QueueJob<TPayload>> {
    const queue = this.getQueue(queueName);
    if (input.idempotencyKey) {
      const existing = [...queue.values()].find(job => job.idempotencyKey === input.idempotencyKey);
      if (existing) return cloneValue(existing) as QueueJob<TPayload>;
    }

    const now = new Date();
    const job: QueueJob<TPayload> = {
      id: input.id || randomUUID(),
      queueName,
      type: input.type,
      payload: input.payload,
      status: 'queued',
      attempts: 0,
      maxAttempts: input.maxAttempts ?? 3,
      createdAt: now.toISOString(),
      scheduledAt: new Date(now.getTime() + (input.delayMs ?? 0)).toISOString(),
      progress: input.progress,
      metadata: input.metadata,
      idempotencyKey: input.idempotencyKey,
      productId: input.productId,
      userId: input.userId,
    };
    queue.set(job.id, cloneValue(job));
    return cloneValue(job);
  }

  async get<TPayload = unknown, TResult = unknown>(
    queueName: string,
    id: string
  ): Promise<QueueJob<TPayload, TResult> | undefined> {
    const job = this.getQueue(queueName).get(id);
    return job ? (cloneValue(job) as QueueJob<TPayload, TResult>) : undefined;
  }

  async list<TPayload = unknown, TResult = unknown>(
    queueName: string,
    options?: ListJobsOptions
  ): Promise<Array<QueueJob<TPayload, TResult>>> {
    const jobs = [...this.getQueue(queueName).values()]
      .filter(job => !options?.status || job.status === options.status)
      .sort((a, b) => b.createdAt.localeCompare(a.createdAt));
    return cloneValue(jobs.slice(0, options?.limit ?? 50)) as Array<QueueJob<TPayload, TResult>>;
  }

  async claimNext<TPayload = unknown, TResult = unknown>(
    queueName: string,
    workerId: string,
    leaseMs: number,
    now = new Date()
  ): Promise<QueueJob<TPayload, TResult> | undefined> {
    const queue = this.getQueue(queueName);
    const candidates = [...queue.values()]
      .filter(job => this.isClaimable(job, now))
      .sort(
        (a, b) =>
          a.scheduledAt.localeCompare(b.scheduledAt) || a.createdAt.localeCompare(b.createdAt)
      );
    const next = candidates[0];
    if (!next) return undefined;

    next.status = 'running';
    next.attempts += 1;
    next.startedAt = next.startedAt || now.toISOString();
    next.leaseOwner = workerId;
    next.leaseExpiresAt = new Date(now.getTime() + leaseMs).toISOString();
    queue.set(next.id, cloneValue(next));
    return cloneValue(next) as QueueJob<TPayload, TResult>;
  }

  async patch<TPayload = unknown, TResult = unknown>(
    queueName: string,
    id: string,
    patch: Partial<QueueJob<TPayload, TResult>>
  ): Promise<QueueJob<TPayload, TResult> | undefined> {
    const queue = this.getQueue(queueName);
    const current = queue.get(id);
    if (!current) return undefined;

    const merged = {
      ...current,
      ...patch,
    };
    queue.set(id, cloneValue(merged));
    return cloneValue(merged) as QueueJob<TPayload, TResult>;
  }

  async clear(queueName?: string): Promise<void> {
    if (queueName) {
      this.queues.delete(queueName);
      return;
    }
    this.queues.clear();
  }

  private getQueue(queueName: string): Map<string, QueueJob> {
    if (!this.queues.has(queueName)) {
      this.queues.set(queueName, new Map());
    }
    return this.queues.get(queueName)!;
  }

  private isClaimable(job: QueueJob, now: Date): boolean {
    if (job.status === 'queued') {
      return job.scheduledAt <= now.toISOString();
    }
    if (job.status === 'running') {
      return !job.leaseExpiresAt || job.leaseExpiresAt <= now.toISOString();
    }
    return false;
  }
}

export function isTerminalStatus(status: QueueJobStatus): boolean {
  return ['succeeded', 'failed', 'dead_letter', 'cancelled'].includes(status);
}