import { StudentDashboard } from "@/modules/dashboard/components/student-dashboard/student-dashboard-view"
import { getStudentClasses, getStudentSchedule } from "@/modules/classes/data-access"
import { getStudentDashboardGrades, getStudentHomeworkAssignments } from "@/modules/homework/data-access"
import { getCurrentStudentUser } from "@/modules/users/data-access"
import { EmptyState } from "@/shared/components/ui/empty-state"
import { UserX } from "lucide-react"
import type { StudentHomeworkProgressStatus } from "@/modules/homework/types"

export const dynamic = "force-dynamic"

export const metadata = { title: "Dashboard - Next_Edu" }

const toWeekday = (d: Date): 1 | 2 | 3 | 4 | 5 | 6 | 7 => {
  // getDay() 返回 0(周日)-6(周六)，转换为 1-7（周一为 1）
  const WEEKDAY_MAP = [7, 1, 2, 3, 4, 5, 6] as const
  const day = d.getDay()
  if (day < 0 || day > 6) {
    throw new Error(`Invalid day from getDay(): ${day}`)
  }
  return WEEKDAY_MAP[day]
}

export default async function StudentDashboardPage() {
  const student = await getCurrentStudentUser()
  if (!student) {
    return (
      <EmptyState
        title="No user found"
        description="Create a student user to see dashboard."
        icon={UserX}
        className="border-none shadow-none h-auto"
      />
    )
  }

  const [classes, schedule, assignments, grades] = await Promise.all([
    getStudentClasses(student.id),
    getStudentSchedule(student.id),
    getStudentHomeworkAssignments(student.id),
    getStudentDashboardGrades(student.id),
  ])

  const now = new Date()
  const in7Days = new Date(now)
  in7Days.setDate(in7Days.getDate() + 7)

  // 单次遍历统计，避免重复 filter（PERF-04）
  let dueSoonCount = 0
  let overdueCount = 0
  let gradedCount = 0
  for (const a of assignments) {
    const status: StudentHomeworkProgressStatus = a.progressStatus
    if (status === "graded") {
      gradedCount++
      continue
    }
    if (!a.dueAt) continue
    const due = new Date(a.dueAt)
    if (due >= now && due <= in7Days) {
      dueSoonCount++
    } else if (due < now) {
      overdueCount++
    }
  }

  const todayWeekday = toWeekday(now)
  const todayScheduleItems = schedule
    .filter((s) => s.weekday === todayWeekday)
    .map((s) => ({
      id: s.id,
      classId: s.classId,
      className: s.className,
      course: s.course,
      startTime: s.startTime,
      endTime: s.endTime,
      location: s.location ?? null,
    }))
    .sort((a, b) => a.startTime.localeCompare(b.startTime))

  const upcomingAssignments = [...assignments]
    .sort((a, b) => {
      const aDue = a.dueAt ? new Date(a.dueAt).getTime() : Number.POSITIVE_INFINITY
      const bDue = b.dueAt ? new Date(b.dueAt).getTime() : Number.POSITIVE_INFINITY
      return aDue - bDue
    })
    .slice(0, 6)

  return (
    <div className="space-y-8">
      <StudentDashboard
        studentName={student.name}
        enrolledClassCount={classes.length}
        dueSoonCount={dueSoonCount}
        overdueCount={overdueCount}
        gradedCount={gradedCount}
        todayScheduleItems={todayScheduleItems}
        upcomingAssignments={upcomingAssignments}
        grades={grades}
      />
    </div>
  )
}