import { db } from '~/drizzle/db'
import { semesters, songs } from '~/drizzle/schema'
import { eq, and, ne } from 'drizzle-orm'

export default defineEventHandler(async (event) => {
  // 检查用户认证和权限
  const user = event.context.user

  if (!user) {
    throw createError({
      statusCode: 401,
      message: '需要登录才能访问'
    })
  }

  if (!['ADMIN', 'SUPER_ADMIN', 'SONG_ADMIN'].includes(user.role)) {
    throw createError({
      statusCode: 403,
      message: '只有管理员才能管理学期'
    })
  }

  const semesterId = parseInt(event.context.params?.id || '0')

  if (!semesterId || isNaN(semesterId)) {
    throw createError({
      statusCode: 400,
      message: '无效的学期ID'
    })
  }

  const body = await readBody(event)
  const nextName = typeof body.name === 'string' ? body.name.trim() : ''

  if (!nextName) {
    throw createError({
      statusCode: 400,
      message: '学期名称不能为空'
    })
  }

  // 检查学期是否存在
  const currentSemesterResult = await db
    .select()
    .from(semesters)
    .where(eq(semesters.id, semesterId))
    .limit(1)

  if (currentSemesterResult.length === 0) {
    throw createError({
      statusCode: 404,
      message: '学期不存在'
    })
  }

  // 检查新名称是否与其他学期冲突
  const existingSemesterResult = await db
    .select()
    .from(semesters)
    .where(and(eq(semesters.name, nextName), ne(semesters.id, semesterId)))
    .limit(1)

  if (existingSemesterResult.length > 0) {
    throw createError({
      statusCode: 400,
      message: '该学期名称已存在'
    })
  }

  const oldName = currentSemesterResult[0].name

  if (oldName === nextName) {
    return currentSemesterResult[0]
  }

  // 更新学期名称及关联歌曲数据
  const result = await db.transaction(async (tx) => {
    const updateResult = await tx
      .update(semesters)
      .set({ name: nextName })
      .where(eq(semesters.id, semesterId))
      .returning()

    if (updateResult.length > 0) {
      // 同步更新歌曲表中的学期名称引用
      await tx.update(songs).set({ semester: nextName }).where(eq(songs.semester, oldName))
    }

    return updateResult[0]
  })

  return result
})