import Link from "next/link"
import {
  AlertTriangle,
  ChevronRight,
  GraduationCap,
  PenTool,
  TrendingDown,
  TrendingUp,
  Minus,
} from "lucide-react"

import { Avatar, AvatarFallback, AvatarImage } from "@/shared/components/ui/avatar"
import { Badge } from "@/shared/components/ui/badge"
import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
import { cn, getInitials } from "@/shared/lib/utils"
import type { ChildDashboardData } from "@/modules/parent/types"

type TrendDirection = "up" | "down" | "flat" | "unknown"

const computeTrend = (trend: { percentage: number }[]): TrendDirection => {
  if (trend.length < 2) return "unknown"
  const latest = trend[trend.length - 1].percentage
  const prev = trend[trend.length - 2].percentage
  if (latest > prev) return "up"
  if (latest < prev) return "down"
  return "flat"
}

const TrendIcon = ({ direction }: { direction: TrendDirection }) => {
  if (direction === "up") {
    return <TrendingUp className="h-3 w-3 text-emerald-600" aria-label="improving" />
  }
  if (direction === "down") {
    return <TrendingDown className="h-3 w-3 text-destructive" aria-label="declining" />
  }
  if (direction === "flat") {
    return <Minus className="h-3 w-3 text-muted-foreground" aria-label="stable" />
  }
  return null
}

export function ChildCard({ child }: { child: ChildDashboardData }) {
  const { basicInfo, homeworkSummary, gradeTrend } = child
  const ranking = gradeTrend.ranking
  const latestGrade = gradeTrend.recent[0]
  const childName = basicInfo.name ?? "Child"
  const hasOverdue = homeworkSummary.overdueCount > 0
  const trendDirection = computeTrend(gradeTrend.trend)

  return (
    <Link
      href={`/parent/children/${basicInfo.id}`}
      prefetch
      aria-label={`View ${childName}'s details${hasOverdue ? `, ${homeworkSummary.overdueCount} overdue homework` : ""}`}
      className="block focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 rounded-md"
    >
      <Card
        className={cn(
          "hover:bg-muted/50 transition-colors h-full",
          hasOverdue && "border-destructive/40 bg-destructive/5",
        )}
      >
        <CardHeader className="flex flex-row items-center gap-4 space-y-0">
          <Avatar className="h-12 w-12">
            <AvatarImage src={basicInfo.image ?? undefined} alt={childName} />
            <AvatarFallback>{getInitials(basicInfo.name)}</AvatarFallback>
          </Avatar>
          <div className="flex-1 min-w-0 space-y-1">
            <CardTitle className="text-base truncate">{basicInfo.name ?? "Unnamed"}</CardTitle>
            <div className="flex flex-wrap items-center gap-2 text-xs text-muted-foreground">
              {basicInfo.className ? (
                <Badge variant="secondary" className="text-xs">
                  {basicInfo.className}
                </Badge>
              ) : null}
              {basicInfo.gradeName ? <span>{basicInfo.gradeName}</span> : null}
              {basicInfo.relation ? <span>· {basicInfo.relation}</span> : null}
            </div>
          </div>
          {hasOverdue ? (
            <AlertTriangle
              className="h-5 w-5 text-destructive shrink-0"
              aria-label={`${homeworkSummary.overdueCount} overdue`}
            />
          ) : (
            <ChevronRight className="h-4 w-4 text-muted-foreground shrink-0" />
          )}
        </CardHeader>
        <CardContent className="space-y-3">
          <div className="grid grid-cols-3 gap-2 text-center">
            <div className="rounded-md bg-muted/50 p-2">
              <div className="text-xs text-muted-foreground flex items-center justify-center gap-1">
                <PenTool className="h-3 w-3" aria-hidden />
                Pending
              </div>
              <div className="text-lg font-semibold tabular-nums">
                {homeworkSummary.pendingCount}
              </div>
            </div>
            <div
              className={cn(
                "rounded-md p-2",
                hasOverdue ? "bg-destructive/10" : "bg-muted/50",
              )}
            >
              <div
                className={cn(
                  "text-xs flex items-center justify-center gap-1",
                  hasOverdue ? "text-destructive" : "text-muted-foreground",
                )}
              >
                <AlertTriangle className="h-3 w-3" aria-hidden />
                Overdue
              </div>
              <div
                className={cn(
                  "text-lg font-bold tabular-nums",
                  hasOverdue && "text-destructive",
                )}
              >
                {homeworkSummary.overdueCount}
              </div>
            </div>
            <div className="rounded-md bg-muted/50 p-2">
              <div className="text-xs text-muted-foreground flex items-center justify-center gap-1">
                <GraduationCap className="h-3 w-3" aria-hidden />
                Avg
              </div>
              <div className="text-lg font-semibold tabular-nums">
                {ranking ? `${Math.round(ranking.percentage)}%` : "-"}
              </div>
            </div>
          </div>
          {latestGrade ? (
            <div className="text-xs text-muted-foreground flex items-center gap-1">
              <span className="shrink-0">Latest:</span>
              <span className="font-medium text-foreground tabular-nums shrink-0">
                {latestGrade.score}/{latestGrade.maxScore}
              </span>
              <TrendIcon direction={trendDirection} />
              <span className="truncate">({latestGrade.assignmentTitle})</span>
            </div>
          ) : null}
        </CardContent>
      </Card>
    </Link>
  )
}