import { createError, defineEventHandler } from 'h3'
import { and, count, db, eq, exists, schedules, semesters, songs, votes } from '~/drizzle/db'

export default defineEventHandler(async (event) => {
  // 检查认证和权限
  const user = event.context.user
  if (!user || !['ADMIN', 'SUPER_ADMIN'].includes(user.role)) {
    throw createError({
      statusCode: 403,
      message: '需要管理员权限'
    })
  }

  try {
    // 获取所有学期
    const semesterList = await db.select().from(semesters).orderBy(semesters.createdAt)

    // 获取每个学期的统计数据
    const semesterStats = await Promise.all(
      semesterList.map(async (semester) => {
        // 统计该学期的歌曲数量
        const [totalSongsResult, totalSchedulesResult, totalRequestsResult] = await Promise.all([
          db
            .select({ count: count() })
            .from(songs)
            .where(eq(songs.semester, semester.name)),

          // 统计该学期的排期数量（通过关联歌曲）
          db
            .select({ count: count() })
            .from(schedules)
            .innerJoin(songs, eq(schedules.songId, songs.id))
            .where(eq(songs.semester, semester.name)),

          // 统计该学期有投票的歌曲数量
          db
            .select({ count: count() })
            .from(songs)
            .where(
              and(
                eq(songs.semester, semester.name),
                exists(db.select().from(votes).where(eq(votes.songId, songs.id)))
              )
            )
        ])

        const [totalSongs, totalSchedules, totalRequests] = [
          totalSongsResult[0]?.count || 0,
          totalSchedulesResult[0]?.count || 0,
          totalRequestsResult[0]?.count || 0
        ]

        return {
          semester: semester.name,
          totalSongs,
          totalSchedules,
          totalRequests,
          isActive: semester.isActive
        }
      })
    )

    return semesterStats
  } catch (error) {
    console.error('获取学期对比数据失败:', error)
    throw createError({
      statusCode: 500,
      message: '获取学期对比数据失败'
    })
  }
})