import { Injectable, OnModuleInit, OnModuleDestroy } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';
import neo4j, { Driver, Session, Transaction } from 'neo4j-driver';

/**
 * Neo4j知识图谱服务
 * 用于存储和查询用户时间线、实体关系等
 */
@Injectable()
export class Neo4jService implements OnModuleInit, OnModuleDestroy {
  private driver: Driver;

  constructor(private configService: ConfigService) {}

  async onModuleInit() {
    const uri = this.configService.get<string>('NEO4J_URI') || 'bolt://localhost:7687';
    const user = this.configService.get<string>('NEO4J_USER') || 'neo4j';
    const password = this.configService.get<string>('NEO4J_PASSWORD') || 'password';

    this.driver = neo4j.driver(uri, neo4j.auth.basic(user, password), {
      maxConnectionPoolSize: 50,
      connectionAcquisitionTimeout: 30000,
    });

    // 验证连接
    try {
      await this.driver.verifyConnectivity();
      console.log('[Neo4j] Connected successfully');

      // 初始化schema
      await this.initializeSchema();
    } catch (error) {
      console.error('[Neo4j] Connection failed:', error);
    }
  }

  async onModuleDestroy() {
    await this.driver?.close();
  }

  /**
   * 获取会话
   */
  getSession(): Session {
    return this.driver.session();
  }

  /**
   * 执行读查询
   */
  async read<T>(query: string, params?: Record<string, unknown>): Promise<T[]> {
    const session = this.getSession();
    try {
      const result = await session.run(query, params);
      return result.records.map(record => record.toObject() as T);
    } finally {
      await session.close();
    }
  }

  /**
   * 执行写查询
   */
  async write<T>(query: string, params?: Record<string, unknown>): Promise<T[]> {
    const session = this.getSession();
    try {
      const result = await session.executeWrite(tx => tx.run(query, params));
      return result.records.map(record => record.toObject() as T);
    } finally {
      await session.close();
    }
  }

  /**
   * 初始化图谱Schema（约束和索引）
   */
  private async initializeSchema() {
    const session = this.getSession();
    try {
      // 用户节点约束
      await session.run(`
        CREATE CONSTRAINT user_id IF NOT EXISTS
        FOR (u:User) REQUIRE u.id IS UNIQUE
      `);

      // 对话节点约束
      await session.run(`
        CREATE CONSTRAINT conversation_id IF NOT EXISTS
        FOR (c:Conversation) REQUIRE c.id IS UNIQUE
      `);

      // 知识实体约束
      await session.run(`
        CREATE CONSTRAINT entity_id IF NOT EXISTS
        FOR (e:Entity) REQUIRE e.id IS UNIQUE
      `);

      // 事件节点约束
      await session.run(`
        CREATE CONSTRAINT event_id IF NOT EXISTS
        FOR (e:Event) REQUIRE e.id IS UNIQUE
      `);

      // 时间索引
      await session.run(`
        CREATE INDEX event_timestamp IF NOT EXISTS
        FOR (e:Event) ON (e.timestamp)
      `);

      // 类别索引
      await session.run(`
        CREATE INDEX entity_category IF NOT EXISTS
        FOR (e:Entity) ON (e.category)
      `);

      console.log('[Neo4j] Schema initialized');
    } catch (error) {
      // 约束可能已存在，忽略错误
      console.log('[Neo4j] Schema initialization skipped (may already exist)');
    } finally {
      await session.close();
    }
  }

  // ========== 用户时间线操作 ==========

  /**
   * 创建用户节点
   */
  async createUserNode(userId: string, properties?: Record<string, unknown>): Promise<void> {
    await this.write(
      `
      MERGE (u:User {id: $userId})
      SET u += $properties, u.updatedAt = datetime()
      `,
      { userId, properties: properties || {} },
    );
  }

  /**
   * 记录用户事件（时间线）
   */
  async recordUserEvent(params: {
    userId: string;
    eventId: string;
    eventType: string;
    content: string;
    timestamp?: Date;
    metadata?: Record<string, unknown>;
  }): Promise<void> {
    const { userId, eventId, eventType, content, metadata } = params;
    const timestamp = params.timestamp || new Date();

    await this.write(
      `
      MATCH (u:User {id: $userId})
      CREATE (e:Event {
        id: $eventId,
        type: $eventType,
        content: $content,
        timestamp: datetime($timestamp),
        metadata: $metadata
      })
      CREATE (u)-[:HAS_EVENT]->(e)

      WITH u, e
      OPTIONAL MATCH (u)-[:HAS_EVENT]->(prev:Event)
      WHERE prev.timestamp < e.timestamp AND prev.id <> e.id
      WITH e, prev
      ORDER BY prev.timestamp DESC
      LIMIT 1
      FOREACH (_ IN CASE WHEN prev IS NOT NULL THEN [1] ELSE [] END |
        CREATE (prev)-[:FOLLOWED_BY]->(e)
      )
      `,
      {
        userId,
        eventId,
        eventType,
        content,
        timestamp: timestamp.toISOString(),
        metadata: JSON.stringify(metadata || {}),
      },
    );
  }

  /**
   * 获取用户时间线
   */
  async getUserTimeline(
    userId: string,
    options?: { limit?: number; beforeDate?: Date; eventTypes?: string[] },
  ): Promise<Array<{
    id: string;
    type: string;
    content: string;
    timestamp: Date;
    metadata: Record<string, unknown>;
  }>> {
    let query = `
      MATCH (u:User {id: $userId})-[:HAS_EVENT]->(e:Event)
    `;

    const params: Record<string, unknown> = { userId };

    if (options?.beforeDate) {
      query += ` WHERE e.timestamp < datetime($beforeDate)`;
      params.beforeDate = options.beforeDate.toISOString();
    }

    if (options?.eventTypes?.length) {
      const typeCondition = options.beforeDate ? ' AND' : ' WHERE';
      query += `${typeCondition} e.type IN $eventTypes`;
      params.eventTypes = options.eventTypes;
    }

    query += `
      RETURN e.id as id, e.type as type, e.content as content,
             e.timestamp as timestamp, e.metadata as metadata
      ORDER BY e.timestamp DESC
      LIMIT $limit
    `;
    params.limit = options?.limit || 20;

    const results = await this.read<{
      id: string;
      type: string;
      content: string;
      timestamp: { toString: () => string };
      metadata: string;
    }>(query, params);

    return results.map(r => ({
      id: r.id,
      type: r.type,
      content: r.content,
      timestamp: new Date(r.timestamp.toString()),
      metadata: JSON.parse(r.metadata || '{}'),
    }));
  }

  // ========== 知识图谱操作 ==========

  /**
   * 创建知识实体
   */
  async createEntity(params: {
    id: string;
    name: string;
    type: string;
    category?: string;
    properties?: Record<string, unknown>;
  }): Promise<void> {
    await this.write(
      `
      MERGE (e:Entity {id: $id})
      SET e.name = $name,
          e.type = $type,
          e.category = $category,
          e += $properties,
          e.updatedAt = datetime()
      `,
      {
        id: params.id,
        name: params.name,
        type: params.type,
        category: params.category || '',
        properties: params.properties || {},
      },
    );
  }

  /**
   * 创建实体关系
   */
  async createRelation(params: {
    fromId: string;
    toId: string;
    relationType: string;
    properties?: Record<string, unknown>;
  }): Promise<void> {
    // 动态创建关系类型
    const relationQuery = `
      MATCH (from:Entity {id: $fromId})
      MATCH (to:Entity {id: $toId})
      MERGE (from)-[r:${params.relationType}]->(to)
      SET r += $properties, r.updatedAt = datetime()
    `;

    await this.write(relationQuery, {
      fromId: params.fromId,
      toId: params.toId,
      properties: params.properties || {},
    });
  }

  /**
   * 查询相关实体
   */
  async findRelatedEntities(
    entityId: string,
    options?: { relationTypes?: string[]; maxDepth?: number; limit?: number },
  ): Promise<Array<{
    entity: { id: string; name: string; type: string };
    relation: string;
    depth: number;
  }>> {
    const maxDepth = options?.maxDepth || 2;
    const limit = options?.limit || 20;

    let relationPattern = '*1..' + maxDepth;
    if (options?.relationTypes?.length) {
      relationPattern = options.relationTypes.join('|') + relationPattern;
    }

    const query = `
      MATCH path = (start:Entity {id: $entityId})-[r:${relationPattern}]-(related:Entity)
      WHERE start <> related
      RETURN related.id as id, related.name as name, related.type as type,
             type(r) as relation, length(path) as depth
      ORDER BY depth ASC
      LIMIT $limit
    `;

    const results = await this.read<{
      id: string;
      name: string;
      type: string;
      relation: string;
      depth: number;
    }>(query, { entityId, limit });

    return results.map(r => ({
      entity: { id: r.id, name: r.name, type: r.type },
      relation: r.relation,
      depth: r.depth,
    }));
  }

  /**
   * 搜索实体
   */
  async searchEntities(
    keyword: string,
    options?: { category?: string; type?: string; limit?: number },
  ): Promise<Array<{ id: string; name: string; type: string; score: number }>> {
    let query = `
      MATCH (e:Entity)
      WHERE e.name CONTAINS $keyword
    `;

    const params: Record<string, unknown> = { keyword };

    if (options?.category) {
      query += ` AND e.category = $category`;
      params.category = options.category;
    }

    if (options?.type) {
      query += ` AND e.type = $type`;
      params.type = options.type;
    }

    query += `
      RETURN e.id as id, e.name as name, e.type as type,
             CASE WHEN e.name STARTS WITH $keyword THEN 1.0 ELSE 0.5 END as score
      ORDER BY score DESC
      LIMIT $limit
    `;
    params.limit = options?.limit || 10;

    return this.read(query, params);
  }

  // ========== 对话关联 ==========

  /**
   * 关联对话与实体
   */
  async linkConversationToEntity(
    conversationId: string,
    entityId: string,
    mentionType: 'MENTIONED' | 'DISCUSSED' | 'ASKED_ABOUT',
  ): Promise<void> {
    await this.write(
      `
      MERGE (c:Conversation {id: $conversationId})
      WITH c
      MATCH (e:Entity {id: $entityId})
      MERGE (c)-[r:${mentionType}]->(e)
      SET r.timestamp = datetime()
      `,
      { conversationId, entityId },
    );
  }

  /**
   * 获取对话相关实体
   */
  async getConversationEntities(conversationId: string): Promise<Array<{
    entity: { id: string; name: string; type: string };
    mentionType: string;
  }>> {
    const results = await this.read<{
      id: string;
      name: string;
      type: string;
      mentionType: string;
    }>(
      `
      MATCH (c:Conversation {id: $conversationId})-[r]->(e:Entity)
      RETURN e.id as id, e.name as name, e.type as type, type(r) as mentionType
      `,
      { conversationId },
    );

    return results.map(r => ({
      entity: { id: r.id, name: r.name, type: r.type },
      mentionType: r.mentionType,
    }));
  }
}