import { Injectable, Logger, BadRequestException } from '@nestjs/common';
import * as crypto from 'crypto';
import { PrismaService } from '../../infrastructure/database/prisma.service';
import { OutboxRepository } from '../../infrastructure/outbox/outbox.repository';
import { SnapshotBuilderService } from '../ai-runtime/snapshot-builder.service';
import { AiJobLifecycleRepository, CreateJobInput } from './ai-job-lifecycle.repository';
import { JobDefinitionRegistry } from './job-definition-registry';
import { Prisma } from '@prisma/client';

/**
 * M-AI-03-06: AiJobCreationService
 *
 * 统一 Job 创建入口（internal-only）。
 * 在一个 Prisma Transaction 内原子创建：
 *   1. AiJob（lifecycleStatus = 'queued'）
 *   2. AiJobSnapshot（不可变输入快照）
 *   3. OutboxEvent（eventType = 'ai.job.enqueue'）
 *
 * 幂等性：AiJob 表的 @@unique([userId, jobType, idempotencyKey]) 保证
 * 重复 (userId, jobType, idempotencyKey) 返回已有 Job，不重复创建。
 *
 * 约束：
 * - 不向 BullMQ 直接入队（由 OutboxDispatcher 异步投递）
 * - 不调用 Provider
 * - 不创建业务结果
 */

export interface CreateAiJobInput {
  userId: string;
  jobType: string;
  triggerType: 'user_api' | 'admin_manual' | 'system_scheduled' | 'parent_job';
  targetType: string;
  targetId: string;
  /** 父 Job ID（Job 链场景） */
  parentJobId?: string;
  /** 幂等 Key。提供时启用幂等；不提供时每次创建新 Job */
  idempotencyKey?: string;
  /** 覆盖 Definition 默认值 */
  overrides?: {
    priority?: number;
    credentialMode?: 'platform_key' | 'user_deepseek_key';
    credentialId?: string;
  };
}

@Injectable()
export class AiJobCreationService {
  private readonly logger = new Logger(AiJobCreationService.name);

  constructor(
    private readonly prisma: PrismaService,
    private readonly lifecycleRepo: AiJobLifecycleRepository,
    private readonly registry: JobDefinitionRegistry,
    private readonly snapshotBuilder: SnapshotBuilderService,
    private readonly outboxRepo: OutboxRepository,
  ) {}

  /**
   * 创建 Job + Snapshot + Outbox（一个 Prisma Transaction 内）。
   *
   * 幂等：若 (userId, jobType, idempotencyKey) 已存在，返回已有 Job。
   */
  async createJob(input: CreateAiJobInput) {
    // 1. Resolve Definition（fail-fast：未知 JobType 在此拦截）
    const def = this.registry.get(input.jobType);

    // 2. Validate triggerType（TypeScript 编译期 + 运行时双重保护）
    if (input.triggerType && !['user_api', 'admin_manual', 'system_scheduled', 'parent_job'].includes(input.triggerType)) {
      throw new BadRequestException(`Invalid triggerType: ${input.triggerType}`);
    }

    // 3. Build snapshot（事务外：依赖外部 DB 读取，不应占用事务时间）
    const snapshot = await this.snapshotBuilder.buildSnapshot(
      input.userId,
      input.targetType,
      input.targetId,
    );

    const contentHash = this.computeHash(JSON.stringify(snapshot));

    // 4. Transaction: Job + Snapshot + Outbox（含幂等保护）
    const createFn = async (tx: Prisma.TransactionClient) => {
      // 4a. Create AiJob
      const jobInput: CreateJobInput = {
        userId: input.userId,
        jobType: input.jobType,
        triggerType: input.triggerType,
        queueName: def.queue.queueName,
        targetType: input.targetType,
        targetId: input.targetId,
        parentJobId: input.parentJobId,
        idempotencyKey: input.idempotencyKey,
        priority: input.overrides?.priority ?? def.queue.defaultPriority,
        credentialMode: input.overrides?.credentialMode ?? def.credential.defaultMode,
        credentialId: input.overrides?.credentialId,
        modelProvider: def.model.modelProvider,
        modelName: def.model.modelName,
        promptKey: def.prompt.promptKey,
        promptVersion: def.prompt.promptVersion,
        outputSchemaVersion: def.output.schemaVersion,
        inputSchemaVersion: def.input.schemaVersion,
        maxAttempts: def.execution.maxRetries,
        timeoutMs: def.execution.timeoutMs,
      };

      const job = await this.lifecycleRepo.createJob(tx, jobInput);

      // 4b. Create AiJobSnapshot
      await tx.aiJobSnapshot.create({
        data: {
          jobId: job.id,
          jobType: input.jobType,
          schemaVersion: def.input.schemaVersion,
          redactionVersion: '1.0',
          content: snapshot as any,
          contentHash,
        },
      });

      // 4c. Create OutboxEvent
      const dedupeKey = `ai.job.enqueue:${job.id}`;
      await this.outboxRepo.createInTransaction(tx, {
        eventType: 'ai.job.enqueue',
        aggregateType: 'AiJob',
        aggregateId: job.id,
        dedupeKey,
        payload: { jobId: job.id },
        availableAt: new Date(),
      });

      return job;  // job 在事务成功路径中使用，P2002 catch 路径中不用
    };

    try {
      const job = await this.prisma.$transaction(createFn);
      this.logger.log(
        `Job created: id=${job.id} type=${input.jobType} ` +
        `queue=${def.queue.queueName} snapshotHash=${contentHash}`,
      );
      return job;
    } catch (err: any) {
      // 幂等：并发重复创建 → UNIQUE 冲突（P2002）→ 返回已有 Job
      if (err?.code === 'P2002' && input.idempotencyKey) {
        const existing = await this.prisma.aiJob.findUniqueOrThrow({
          where: {
            userId_jobType_idempotencyKey: {
              userId: input.userId,
              jobType: input.jobType,
              idempotencyKey: input.idempotencyKey,
            },
          },
        });
        this.logger.log(
          `Idempotent return (P2002): jobId=${existing.id} ` +
          `key=${input.idempotencyKey}`,
        );
        return existing;
      }
      throw err;
    }
  }

  // ── helpers ──

  private computeHash(content: string): string {
    return crypto.createHash('sha256').update(content).digest('hex').substring(0, 16);
  }
}