/**
 * content KnowledgePoint Resolver（v2.1 M1）
 *
 * Apollo Federation 子图：KnowledgePoint Entity
 * - @key(fields: "id") 支持跨子图引用
 * - @ResolveReference 使用 DataLoader 批量加载（ADR-035）
 */
import {
  Resolver,
  Query,
  Args,
  ID,
  ResolveReference,
  ObjectType,
  Field,
  Directive,
} from "@nestjs/graphql";
import {
  DataLoaderService,
  type KnowledgePointEntity,
} from "../dataloader.service.js";
import {
  Permissions,
  RequirePermission,
} from "../../middleware/permission.guard.js";

/**
 * KnowledgePoint ObjectType（Federation @key）
 * 对应 content_knowledge_points 表
 */
@ObjectType()
@Directive(`@key(fields: "id")`)
export class KnowledgePoint {
  @Field(() => ID)
  id!: string;

  @Field()
  chapterId!: string;

  @Field()
  title!: string;

  @Field(() => String, { nullable: true })
  description: string | null = null;

  @Field()
  difficulty!: number;

  @Field()
  createdAt!: Date;

  @Field()
  updatedAt!: Date;
}

@Resolver(() => KnowledgePoint)
export class KnowledgePointResolver {
  constructor(private readonly loader: DataLoaderService) {}

  /**
   * Federation Reference Resolver
   *
   * 当其他子图通过 @key 引用 KnowledgePoint 时，Router 调用此方法解析。
   * 使用 DataLoader 批量加载，消除 N+1 查询（ADR-035）。
   */
  @ResolveReference()
  async resolveReference(ref: {
    id: string;
  }): Promise<KnowledgePointEntity | null> {
    return this.loader.knowledgePointLoader.load(ref.id);
  }

  /**
   * Query: knowledgePoint(id) → KnowledgePoint
   * 通过 Apollo Router 访问，直连被 RouterAuthGuard 拒绝（ADR-036）
   */
  @Query(() => KnowledgePoint, { nullable: true })
  @RequirePermission(Permissions.CONTENT_KNOWLEDGE_POINT_READ)
  async knowledgePoint(
    @Args("id", { type: () => ID }) id: string,
  ): Promise<KnowledgePointEntity | null> {
    return this.loader.knowledgePointLoader.load(id);
  }
}