"use client"

import { useState, useTransition } from "react"
import { useRouter } from "next/navigation"
import { toast } from "sonner"
import { useTranslations } from "next-intl"
import { BookOpen, CheckCircle2, XCircle } from "lucide-react"

import {
  AlertDialog,
  AlertDialogAction,
  AlertDialogCancel,
  AlertDialogContent,
  AlertDialogDescription,
  AlertDialogFooter,
  AlertDialogHeader,
  AlertDialogTitle,
  AlertDialogTrigger,
} from "@/shared/components/ui/alert-dialog"
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 { EmptyState } from "@/shared/components/ui/empty-state"

import {
  COURSE_SELECTION_STATUS_BADGE_VARIANTS,
  COURSE_SELECTION_STATUS_LABEL_KEYS,
  ELECTIVE_STATUS_BADGE_VARIANTS,
  ELECTIVE_STATUS_LABEL_KEYS,
  SELECTION_MODE_LABEL_KEYS,
} from "../constants"
import type {
  CourseSelectionWithDetails,
  ElectiveCourseWithDetails,
} from "../types"
import { selectCourseAction, dropCourseAction } from "../actions"

export function StudentSelectionView({
  availableCourses,
  mySelections,
}: {
  availableCourses: ElectiveCourseWithDetails[]
  mySelections: CourseSelectionWithDetails[]
}) {
  const router = useRouter()
  const t = useTranslations("elective")
  const [pendingId, setPendingId] = useState<string | null>(null)
  const [isPending, startTransition] = useTransition()

  const activeSelections = mySelections.filter((s) =>
    ["selected", "enrolled", "waitlist"].includes(s.status)
  )
  const selectedCourseIds = new Set(
    activeSelections.map((s) => s.courseId)
  )

  const handleSelect = (courseId: string) => {
    setPendingId(courseId)
    startTransition(async () => {
      const formData = new FormData()
      formData.set("courseId", courseId)
      const res = await selectCourseAction(null, formData)
      if (res.success) {
        toast.success(res.message || t("student.selectSuccess"))
        router.refresh()
      } else {
        toast.error(res.message ?? t("errors.unexpected"))
      }
      setPendingId(null)
    })
  }

  const handleDrop = (courseId: string) => {
    setPendingId(courseId)
    startTransition(async () => {
      const formData = new FormData()
      formData.set("courseId", courseId)
      const res = await dropCourseAction(null, formData)
      if (res.success) {
        toast.success(res.message || t("student.dropSuccess"))
        router.refresh()
      } else {
        toast.error(res.message ?? t("errors.unexpected"))
      }
      setPendingId(null)
    })
  }

  return (
    <div className="space-y-8">
      <section className="space-y-4">
        <div className="flex items-center justify-between">
          <h3 className="text-lg font-semibold">{t("student.mySelections")}</h3>
          <span className="text-sm text-muted-foreground">
            {activeSelections.length}
          </span>
        </div>
        {activeSelections.length === 0 ? (
          <EmptyState
            title={t("list.empty")}
            description={t("description.student")}
            icon={BookOpen}
            className="h-auto border-none shadow-none"
          />
        ) : (
          <div className="grid grid-cols-1 gap-4 md:grid-cols-2 lg:grid-cols-3">
            {activeSelections.map((sel) => (
              <Card key={sel.id}>
                <CardHeader className="flex flex-row items-start justify-between gap-2 space-y-0">
                  <CardTitle className="text-base">
                    {sel.courseName ?? t("errors.notFound")}
                  </CardTitle>
                  <Badge variant={COURSE_SELECTION_STATUS_BADGE_VARIANTS[sel.status]}>
                    {t(COURSE_SELECTION_STATUS_LABEL_KEYS[sel.status])}
                  </Badge>
                </CardHeader>
                <CardContent className="space-y-3">
                  {sel.courseCapacity !== null && sel.courseEnrolledCount !== null ? (
                    <p className="text-xs text-muted-foreground">
                      {t("fields.enrolled")}: {sel.courseEnrolledCount}/{sel.courseCapacity}
                    </p>
                  ) : null}
                  {sel.lotteryRank ? (
                    <p className="text-xs text-muted-foreground">
                      #{sel.lotteryRank}
                    </p>
                  ) : null}
                  <AlertDialog>
                    <AlertDialogTrigger asChild>
                      <Button
                        variant="outline"
                        size="sm"
                        className="text-destructive hover:text-destructive"
                        disabled={isPending && pendingId === sel.courseId}
                      >
                        <XCircle className="mr-1 h-3 w-3" />
                        {t("actions.drop")}
                      </Button>
                    </AlertDialogTrigger>
                    <AlertDialogContent>
                      <AlertDialogHeader>
                        <AlertDialogTitle>{t("student.confirmDrop")}</AlertDialogTitle>
                        <AlertDialogDescription>
                          {t("student.confirmDrop")}
                        </AlertDialogDescription>
                      </AlertDialogHeader>
                      <AlertDialogFooter>
                        <AlertDialogCancel>{t("actions.cancel")}</AlertDialogCancel>
                        <AlertDialogAction
                          onClick={() => handleDrop(sel.courseId)}
                        >
                          {t("actions.drop")}
                        </AlertDialogAction>
                      </AlertDialogFooter>
                    </AlertDialogContent>
                  </AlertDialog>
                </CardContent>
              </Card>
            ))}
          </div>
        )}
      </section>

      <section className="space-y-4">
        <div className="flex items-center justify-between">
          <h3 className="text-lg font-semibold">{t("student.availableCourses")}</h3>
          <span className="text-sm text-muted-foreground">
            {availableCourses.length}
          </span>
        </div>
        {availableCourses.length === 0 ? (
          <EmptyState
            title={t("list.emptyStudent")}
            description={t("description.student")}
            icon={BookOpen}
            className="h-auto border-none shadow-none"
          />
        ) : (
          <div className="grid grid-cols-1 gap-4 md:grid-cols-2 lg:grid-cols-3">
            {availableCourses.map((course) => {
              const isFull = course.enrolledCount >= course.capacity
              const alreadySelected = selectedCourseIds.has(course.id)
              const isPendingThis = isPending && pendingId === course.id
              return (
                <Card key={course.id} className="flex h-full flex-col" role="article" aria-label={course.name}>
                  <CardHeader className="flex flex-row items-start justify-between gap-2 space-y-0">
                    <CardTitle className="line-clamp-2 text-base">{course.name}</CardTitle>
                    <Badge variant={ELECTIVE_STATUS_BADGE_VARIANTS[course.status]}>
                      {t(ELECTIVE_STATUS_LABEL_KEYS[course.status])}
                    </Badge>
                  </CardHeader>
                  <CardContent className="flex flex-1 flex-col gap-3">
                    <div className="flex flex-wrap items-center gap-2 text-xs text-muted-foreground">
                      {course.subjectName ? (
                        <Badge variant="outline">{course.subjectName}</Badge>
                      ) : null}
                      <span>{t("fields.credit")}: {course.credit}</span>
                      <span>· {t(SELECTION_MODE_LABEL_KEYS[course.selectionMode])}</span>
                    </div>
                    {course.description ? (
                      <p className="line-clamp-2 text-sm text-muted-foreground">
                        {course.description}
                      </p>
                    ) : null}
                    <div className="grid grid-cols-2 gap-2 text-xs">
                      <div>
                        <span className="text-muted-foreground">{t("fields.teacher")}:</span>{" "}
                        <span className="font-medium">{course.teacherName ?? "—"}</span>
                      </div>
                      <div>
                        <span className="text-muted-foreground">{t("fields.capacity")}:</span>{" "}
                        <span className="font-medium">
                          {course.enrolledCount}/{course.capacity}
                          {isFull ? ` (${t("student.capacityFull")})` : ""}
                        </span>
                      </div>
                    </div>
                    {course.schedule ? (
                      <p className="text-xs text-muted-foreground">
                        <span className="font-medium">{t("fields.schedule")}:</span> {course.schedule}
                      </p>
                    ) : null}
                    <div className="mt-auto pt-2">
                      {alreadySelected ? (
                        <Button variant="secondary" size="sm" disabled>
                          <CheckCircle2 className="mr-1 h-3 w-3" />
                          {t("student.selected")}
                        </Button>
                      ) : (
                        <Button
                          size="sm"
                          disabled={isPendingThis}
                          onClick={() => handleSelect(course.id)}
                        >
                          {isPendingThis ? t("actions.select") + "..." : t("actions.select")}
                        </Button>
                      )}
                    </div>
                  </CardContent>
                </Card>
              )
            })}
          </div>
        )}
      </section>
    </div>
  )
}