/**
 * 会话管理查询模块
 * 负责会话列表与单会话基础信息查询
 */

import Database from 'better-sqlite3'
import * as fs from 'fs'
import * as path from 'path'
import { openDatabase, getDbDir, getDbPath, getCacheDir } from '../core'
import {
  getCache,
  computeAndSetOverviewCache,
  computeAndSetMembersCache,
  CACHE_KEY_OVERVIEW,
  CACHE_KEY_MEMBERS,
  type OverviewCache,
  type MembersCache,
} from '../../database/sessionCache'

interface DbMeta {
  name: string
  platform: string
  type: string
  imported_at: number
  group_id: string | null
  group_avatar: string | null
  owner_id: string | null
}

/**
 * 判断是否为聊天会话数据库
 * 通过核心三表（meta/member/message）存在性快速识别
 */
function isChatSessionDb(db: Database.Database): boolean {
  const requiredTableCount = db
    .prepare("SELECT COUNT(*) as cnt FROM sqlite_master WHERE type='table' AND name IN ('meta', 'member', 'message')")
    .get() as { cnt: number }
  return requiredTableCount.cnt === 3
}

/**
 * 获取私聊对方成员的头像
 * 逻辑参考 private-chat/index.vue 的 otherMemberAvatar
 */
function getPrivateChatMemberAvatar(db: Database.Database, sessionName: string, ownerId: string | null): string | null {
  // 获取所有非系统消息成员（按消息数排序）
  const members = db
    .prepare(
      `SELECT
        m.platform_id as platformId,
        COALESCE(m.group_nickname, m.account_name, m.platform_id) as name,
        m.avatar
      FROM member m
      WHERE COALESCE(m.account_name, '') != '系统消息'
      ORDER BY (SELECT COUNT(*) FROM message WHERE sender_id = m.id) DESC`
    )
    .all() as Array<{ platformId: string; name: string; avatar: string | null }>

  if (members.length === 0) return null

  // 1. 优先排除 ownerId，找到另一成员的头像
  if (ownerId) {
    const other = members.find((m) => m.platformId !== ownerId)
    if (other?.avatar) return other.avatar
  }

  // 2. 尝试匹配会话名称（私聊名称通常是对方昵称）
  const sameName = members.find((m) => m.name === sessionName)
  if (sameName?.avatar) return sameName.avatar

  // 3. 如果只有两个成员且有 ownerId，取另一个（即使没有头像也返回 null）
  // 如果没有 ownerId，返回第一个有头像的成员
  const firstWithAvatar = members.find((m) => m.avatar)
  return firstWithAvatar?.avatar || null
}

/**
 * 获取所有会话列表
 */
export function getAllSessions(): any[] {
  const dbDir = getDbDir()
  if (!fs.existsSync(dbDir)) {
    return []
  }

  const sessions: any[] = []
  const files = fs.readdirSync(dbDir).filter((f) => f.endsWith('.db'))

  for (const file of files) {
    const sessionId = file.replace('.db', '')
    const dbPath = path.join(dbDir, file)

    try {
      const db = new Database(dbPath)
      db.pragma('journal_mode = WAL')

      // 跳过非聊天会话数据库（例如内部索引库）
      if (!isChatSessionDb(db)) {
        db.close()
        continue
      }

      const meta = db.prepare('SELECT * FROM meta LIMIT 1').get() as DbMeta | undefined

      if (meta) {
        // 优先从缓存读取，未命中则实时查询并生成缓存
        const cacheDir = getCacheDir()
        let overview = getCache<OverviewCache>(sessionId, CACHE_KEY_OVERVIEW, cacheDir)
        if (!overview && cacheDir) {
          try {
            overview = computeAndSetOverviewCache(db, sessionId, cacheDir)
          } catch {
            // 缓存计算失败不影响正常流程
          }
        }

        const messageCount =
          overview?.totalMessages ??
          (
            db
              .prepare(
                `SELECT COUNT(*) as count
               FROM message msg
               JOIN member m ON msg.sender_id = m.id
               WHERE COALESCE(m.account_name, '') != '系统消息'`
              )
              .get() as { count: number }
          ).count
        const memberCount =
          overview?.totalMembers ??
          (
            db
              .prepare(
                `SELECT COUNT(*) as count
               FROM member
               WHERE COALESCE(account_name, '') != '系统消息'`
              )
              .get() as { count: number }
          ).count

        // 私聊：获取对方成员头像
        let memberAvatar: string | null = null
        if (meta.type === 'private') {
          memberAvatar = getPrivateChatMemberAvatar(db, meta.name, meta.owner_id)
        }

        // 摘要数量：安全查询（chat_session 表可能不存在）
        let summaryCount = 0
        try {
          const hasChatSessionTable = db
            .prepare("SELECT COUNT(*) as cnt FROM sqlite_master WHERE type='table' AND name='chat_session'")
            .get() as { cnt: number }
          if (hasChatSessionTable.cnt > 0) {
            summaryCount = (
              db
                .prepare("SELECT COUNT(*) as count FROM chat_session WHERE summary IS NOT NULL AND summary != ''")
                .get() as { count: number }
            ).count
          }
        } catch {
          // 忽略查询错误
        }

        sessions.push({
          id: sessionId,
          name: meta.name,
          platform: meta.platform,
          type: meta.type,
          importedAt: meta.imported_at,
          messageCount,
          memberCount,
          dbPath,
          groupId: meta.group_id || null,
          groupAvatar: meta.group_avatar || null,
          ownerId: meta.owner_id || null,
          memberAvatar, // 私聊对方头像
          summaryCount,
          aiConversationCount: 0, // 将在 IPC 层由主进程填充
        })
      }

      db.close()
    } catch (error) {
      console.error(`[Worker] Failed to read database ${file}:`, error)
    }
  }

  return sessions.sort((a, b) => b.importedAt - a.importedAt)
}

/**
 * 获取单个会话信息
 */
export function getSession(sessionId: string): any | null {
  const db = openDatabase(sessionId)
  if (!db) return null

  const meta = db.prepare('SELECT * FROM meta LIMIT 1').get() as DbMeta | undefined
  if (!meta) return null

  const overview = getCache<OverviewCache>(sessionId, CACHE_KEY_OVERVIEW, getCacheDir())

  const messageCount =
    overview?.totalMessages ??
    (
      db
        .prepare(
          `SELECT COUNT(*) as count
         FROM message msg
         JOIN member m ON msg.sender_id = m.id
         WHERE COALESCE(m.account_name, '') != '系统消息'`
        )
        .get() as { count: number }
    ).count

  const memberCount =
    overview?.totalMembers ??
    (
      db
        .prepare(
          `SELECT COUNT(*) as count
         FROM member
         WHERE COALESCE(account_name, '') != '系统消息'`
        )
        .get() as { count: number }
    ).count

  return {
    id: sessionId,
    name: meta.name,
    platform: meta.platform,
    type: meta.type,
    importedAt: meta.imported_at,
    messageCount,
    memberCount,
    dbPath: getDbPath(sessionId),
    groupId: meta.group_id || null,
    groupAvatar: meta.group_avatar || null,
    ownerId: meta.owner_id || null,
  }
}

/**
 * 获取聊天概览（AI 工具使用）
 * 优先从缓存读取，miss 则计算回填
 */
export function getChatOverview(sessionId: string, topN: number = 10) {
  const db = openDatabase(sessionId)
  if (!db) return null

  const meta = db.prepare('SELECT * FROM meta LIMIT 1').get() as DbMeta | undefined
  if (!meta) return null

  const cacheDir = getCacheDir()

  // 读取 overview 缓存
  let overview = getCache<OverviewCache>(sessionId, CACHE_KEY_OVERVIEW, cacheDir)
  if (!overview) {
    try {
      overview = computeAndSetOverviewCache(db, sessionId, cacheDir)
    } catch {
      // fallback: 实时查询
    }
  }

  // 读取 members 缓存
  let membersCache = getCache<MembersCache>(sessionId, CACHE_KEY_MEMBERS, cacheDir)
  if (!membersCache) {
    try {
      membersCache = computeAndSetMembersCache(db, sessionId, cacheDir)
    } catch {
      // fallback: 无成员数据
    }
  }

  // 从缓存计算 Top N 活跃成员
  let topMembers: Array<{ id: number; name: string; count: number }> = []
  if (membersCache?.members) {
    topMembers = Object.entries(membersCache.members)
      .map(([id, stat]) => ({ id: Number(id), name: stat.name, count: stat.count }))
      .sort((a, b) => b.count - a.count)
      .slice(0, topN)
  }

  // fallback 统计值
  const totalMessages =
    overview?.totalMessages ??
    (
      db
        .prepare(
          `SELECT COUNT(*) as count FROM message msg
           JOIN member m ON msg.sender_id = m.id
           WHERE COALESCE(m.account_name, '') != '系统消息'`
        )
        .get() as { count: number }
    ).count

  const totalMembers =
    overview?.totalMembers ??
    (
      db.prepare(`SELECT COUNT(*) as count FROM member WHERE COALESCE(account_name, '') != '系统消息'`).get() as {
        count: number
      }
    ).count

  return {
    name: meta.name,
    platform: meta.platform,
    type: meta.type,
    totalMessages,
    totalMembers,
    firstMessageTs: overview?.firstMessageTs ?? null,
    lastMessageTs: overview?.lastMessageTs ?? null,
    topMembers,
  }
}