import Link from "next/link"

import { EmptyState } from "@/shared/components/ui/empty-state"
import { Badge } from "@/shared/components/ui/badge"
import { Button } from "@/shared/components/ui/button"
import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
import { formatDate } from "@/shared/lib/utils"
import { getStudentHomeworkAssignments } from "@/modules/homework/data-access"
import { getCurrentStudentUser } from "@/modules/users/data-access"
import { Inbox } from "lucide-react"

export const dynamic = "force-dynamic"

const getStatusVariant = (status: string): "default" | "secondary" | "outline" => {
  if (status === "graded") return "default"
  if (status === "submitted") return "secondary"
  if (status === "in_progress") return "secondary"
  return "outline"
}

const getStatusLabel = (status: string) => {
  if (status === "graded") return "Graded"
  if (status === "submitted") return "Submitted"
  if (status === "in_progress") return "In progress"
  return "Not started"
}

const getActionLabel = (status: string) => {
  if (status === "graded") return "Review"
  if (status === "submitted") return "View"
  if (status === "in_progress") return "Continue"
  return "Start"
}

const getActionVariant = (status: string): "default" | "secondary" | "outline" => {
  if (status === "graded" || status === "submitted") return "outline"
  return "default"
}

const isAnswered = (status: string) => status === "submitted" || status === "graded"

export default async function StudentAssignmentsPage() {
  const student = await getCurrentStudentUser()

  if (!student) {
    return (
      <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
        <EmptyState title="No user found" description="Create a student user to see assignments." icon={Inbox} />
      </div>
    )
  }

  const assignments = await getStudentHomeworkAssignments(student.id)
  const hasAssignments = assignments.length > 0
  const assignmentsBySubject = assignments.reduce((acc, assignment) => {
    const subject = assignment.subjectName?.trim() || "Other"
    const existing = acc.get(subject)
    if (existing) {
      existing.push(assignment)
    } else {
      acc.set(subject, [assignment])
    }
    return acc
  }, new Map<string, typeof assignments>())
  const subjectEntries = Array.from(assignmentsBySubject.entries()).sort((a, b) => a[0].localeCompare(b[0]))

  return (
    <div className="h-full flex-1 flex-col space-y-8 p-8 md:flex">
      {!hasAssignments ? (
        <EmptyState title="No assignments" description="You have no assigned homework right now." icon={Inbox} />
      ) : (
        <div className="space-y-6">
          {subjectEntries.map(([subject, items]) => {
            const answeredItems = items.filter((a) => isAnswered(a.progressStatus))
            const unansweredItems = items.filter((a) => !isAnswered(a.progressStatus))

            return (
              <div key={subject} className="space-y-3">
              <div className="text-sm font-semibold text-muted-foreground">{subject}</div>
              {unansweredItems.length > 0 && (
                <div className="space-y-3">
                  <div className="text-xs font-semibold uppercase tracking-wide text-muted-foreground">未答题</div>
                  <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-3">
                    {unansweredItems.map((a) => (
                      <Card key={a.id} className="flex h-full flex-col overflow-hidden transition-all hover:shadow-md">
                        <CardHeader className="gap-2 pb-3">
                          <div className="flex items-start justify-between gap-3">
                            <CardTitle className="text-base">
                              <Link href={`/student/learning/assignments/${a.id}`} className="hover:underline">
                                {a.title}
                              </Link>
                            </CardTitle>
                            <Badge variant={getStatusVariant(a.progressStatus)} className="capitalize">
                              {getStatusLabel(a.progressStatus)}
                            </Badge>
                          </div>
                          <div className="text-xs text-muted-foreground">
                            <span>Due {a.dueAt ? formatDate(a.dueAt) : "-"}</span>
                            <span className="px-2">•</span>
                            <span>
                              Attempts {a.attemptsUsed}/{a.maxAttempts}
                            </span>
                          </div>
                        </CardHeader>
                        <CardContent className="mt-auto flex items-center justify-between">
                          <div className="text-sm">
                            <div className="text-muted-foreground">Score</div>
                            <div className="font-medium tabular-nums">{a.latestScore ?? "-"}</div>
                          </div>
                          <Button asChild size="sm" variant={getActionVariant(a.progressStatus)}>
                            <Link href={`/student/learning/assignments/${a.id}`}>
                              {getActionLabel(a.progressStatus)}
                            </Link>
                          </Button>
                        </CardContent>
                      </Card>
                    ))}
                  </div>
                </div>
              )}
              {answeredItems.length > 0 && (
                <div className="space-y-3">
                  <div className="text-xs font-semibold uppercase tracking-wide text-muted-foreground">已答题</div>
                  <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-3">
                    {answeredItems.map((a) => (
                      <Card key={a.id} className="flex h-full flex-col overflow-hidden transition-all hover:shadow-md">
                        <CardHeader className="gap-2 pb-3">
                          <div className="flex items-start justify-between gap-3">
                            <CardTitle className="text-base">
                              <Link href={`/student/learning/assignments/${a.id}`} className="hover:underline">
                                {a.title}
                              </Link>
                            </CardTitle>
                            <Badge variant={getStatusVariant(a.progressStatus)} className="capitalize">
                              {getStatusLabel(a.progressStatus)}
                            </Badge>
                          </div>
                          <div className="text-xs text-muted-foreground">
                            <span>Due {a.dueAt ? formatDate(a.dueAt) : "-"}</span>
                            <span className="px-2">•</span>
                            <span>
                              Attempts {a.attemptsUsed}/{a.maxAttempts}
                            </span>
                          </div>
                        </CardHeader>
                        <CardContent className="mt-auto flex items-center justify-between">
                          <div className="text-sm">
                            <div className="text-muted-foreground">Score</div>
                            <div className="font-medium tabular-nums">{a.latestScore ?? "-"}</div>
                          </div>
                          <Button asChild size="sm" variant={getActionVariant(a.progressStatus)}>
                            <Link href={`/student/learning/assignments/${a.id}`}>
                              {getActionLabel(a.progressStatus)}
                            </Link>
                          </Button>
                        </CardContent>
                      </Card>
                    ))}
                  </div>
                </div>
              )}
            </div>
          )})}
        </div>
      )}
    </div>
  )
}