import Link from "next/link"
import { Suspense } from "react"
import { BarChart3 } from "lucide-react"

import { getClassHomeworkInsights, getTeacherClasses } from "@/modules/classes/data-access"
import { InsightsFilters } from "@/modules/classes/components/insights-filters"
import { EmptyState } from "@/shared/components/ui/empty-state"
import { Skeleton } from "@/shared/components/ui/skeleton"
import { Badge } from "@/shared/components/ui/badge"
import { Card, CardContent, CardHeader, CardTitle } from "@/shared/components/ui/card"
import { Button } from "@/shared/components/ui/button"
import { Table, TableBody, TableCell, TableHead, TableHeader, TableRow } from "@/shared/components/ui/table"
import { formatDate } from "@/shared/lib/utils"

export const dynamic = "force-dynamic"

type SearchParams = { [key: string]: string | string[] | undefined }

const getParam = (params: SearchParams, key: string) => {
  const v = params[key]
  return Array.isArray(v) ? v[0] : v
}

const formatNumber = (v: number | null, digits = 1) => {
  if (typeof v !== "number" || Number.isNaN(v)) return "-"
  return v.toFixed(digits)
}

function InsightsResultsFallback() {
  return (
    <div className="space-y-4">
      <div className="grid gap-4 md:grid-cols-3">
        {Array.from({ length: 3 }).map((_, idx) => (
          <div key={idx} className="rounded-lg border bg-card">
            <div className="p-6">
              <Skeleton className="h-5 w-28" />
              <Skeleton className="mt-3 h-8 w-20" />
            </div>
          </div>
        ))}
      </div>
      <div className="rounded-md border bg-card">
        <div className="p-4">
          <Skeleton className="h-8 w-full" />
        </div>
        <div className="space-y-2 p-4 pt-0">
          {Array.from({ length: 8 }).map((_, idx) => (
            <Skeleton key={idx} className="h-10 w-full" />
          ))}
        </div>
      </div>
    </div>
  )
}

async function InsightsResults({ searchParams }: { searchParams: Promise<SearchParams> }) {
  const params = await searchParams
  const classId = getParam(params, "classId")

  if (!classId || classId === "all") {
    return (
      <EmptyState
        icon={BarChart3}
        title="Select a class to view insights"
        description="Pick a class to see latest homework and historical score statistics."
        className="h-[360px] bg-card"
      />
    )
  }

  const insights = await getClassHomeworkInsights({ classId, limit: 50 })
  if (!insights) {
    return (
      <EmptyState
        icon={BarChart3}
        title="Class not found"
        description="This class may not exist or is not accessible."
        className="h-[360px] bg-card"
      />
    )
  }

  const hasAssignments = insights.assignments.length > 0

  if (!hasAssignments) {
    return (
      <EmptyState
        icon={BarChart3}
        title="No homework data for this class"
        description="No homework assignments were targeted to students in this class yet."
        className="h-[360px] bg-card"
      />
    )
  }

  const latest = insights.latest

  return (
    <div className="space-y-6">
      <div className="grid gap-4 md:grid-cols-3">
        <Card>
          <CardHeader className="pb-2">
            <CardTitle className="text-sm font-medium">Students</CardTitle>
          </CardHeader>
          <CardContent>
            <div className="text-2xl font-bold">{insights.studentCounts.total}</div>
            <div className="text-xs text-muted-foreground">
              Active {insights.studentCounts.active} · Inactive {insights.studentCounts.inactive}
            </div>
          </CardContent>
        </Card>
        <Card>
          <CardHeader className="pb-2">
            <CardTitle className="text-sm font-medium">Assignments</CardTitle>
          </CardHeader>
          <CardContent>
            <div className="text-2xl font-bold">{insights.assignments.length}</div>
            <div className="text-xs text-muted-foreground">Latest: {latest ? formatDate(latest.createdAt) : "-"}</div>
          </CardContent>
        </Card>
        <Card>
          <CardHeader className="pb-2">
            <CardTitle className="text-sm font-medium">Overall scores</CardTitle>
          </CardHeader>
          <CardContent>
            <div className="text-2xl font-bold">{formatNumber(insights.overallScores.avg, 1)}</div>
            <div className="text-xs text-muted-foreground">
              Median {formatNumber(insights.overallScores.median, 1)} · Count {insights.overallScores.count}
            </div>
          </CardContent>
        </Card>
      </div>

      {latest && (
        <Card>
          <CardHeader className="flex flex-col gap-2 md:flex-row md:items-center md:justify-between">
            <div>
              <CardTitle className="text-base">Latest assignment</CardTitle>
              <div className="mt-1 flex items-center gap-2 text-sm text-muted-foreground">
                <span className="font-medium text-foreground">{latest.title}</span>
                <Badge variant="outline" className="capitalize">
                  {latest.status}
                </Badge>
                <span>·</span>
                <span>{formatDate(latest.createdAt)}</span>
                {latest.dueAt ? (
                  <>
                    <span>·</span>
                    <span>Due {formatDate(latest.dueAt)}</span>
                  </>
                ) : null}
              </div>
            </div>
            <div className="flex items-center gap-2">
              <Button asChild variant="outline" size="sm">
                <Link href={`/teacher/homework/assignments/${latest.assignmentId}`}>Open</Link>
              </Button>
              <Button asChild variant="outline" size="sm">
                <Link href={`/teacher/homework/assignments/${latest.assignmentId}/submissions`}>Submissions</Link>
              </Button>
            </div>
          </CardHeader>
          <CardContent className="grid gap-4 md:grid-cols-5">
            <div>
              <div className="text-sm text-muted-foreground">Targeted</div>
              <div className="text-lg font-semibold">{latest.targetCount}</div>
            </div>
            <div>
              <div className="text-sm text-muted-foreground">Submitted</div>
              <div className="text-lg font-semibold">{latest.submittedCount}</div>
            </div>
            <div>
              <div className="text-sm text-muted-foreground">Graded</div>
              <div className="text-lg font-semibold">{latest.gradedCount}</div>
            </div>
            <div>
              <div className="text-sm text-muted-foreground">Average</div>
              <div className="text-lg font-semibold">{formatNumber(latest.scoreStats.avg, 1)}</div>
            </div>
            <div>
              <div className="text-sm text-muted-foreground">Median</div>
              <div className="text-lg font-semibold">{formatNumber(latest.scoreStats.median, 1)}</div>
            </div>
          </CardContent>
        </Card>
      )}

      <div className="rounded-md border bg-card">
        <Table>
          <TableHeader>
            <TableRow>
              <TableHead>Assignment</TableHead>
              <TableHead>Status</TableHead>
              <TableHead>Due</TableHead>
              <TableHead className="text-right">Targeted</TableHead>
              <TableHead className="text-right">Submitted</TableHead>
              <TableHead className="text-right">Graded</TableHead>
              <TableHead className="text-right">Avg</TableHead>
              <TableHead className="text-right">Median</TableHead>
              <TableHead className="text-right">Min</TableHead>
              <TableHead className="text-right">Max</TableHead>
            </TableRow>
          </TableHeader>
          <TableBody>
            {insights.assignments.map((a) => (
              <TableRow key={a.assignmentId}>
                <TableCell className="font-medium">
                  <Link href={`/teacher/homework/assignments/${a.assignmentId}`} className="hover:underline">
                    {a.title}
                  </Link>
                  <div className="text-xs text-muted-foreground">Created {formatDate(a.createdAt)}</div>
                </TableCell>
                <TableCell>
                  <Badge variant="outline" className="capitalize">
                    {a.status}
                  </Badge>
                </TableCell>
                <TableCell>{a.dueAt ? formatDate(a.dueAt) : "-"}</TableCell>
                <TableCell className="text-right">{a.targetCount}</TableCell>
                <TableCell className="text-right">{a.submittedCount}</TableCell>
                <TableCell className="text-right">{a.gradedCount}</TableCell>
                <TableCell className="text-right">{formatNumber(a.scoreStats.avg, 1)}</TableCell>
                <TableCell className="text-right">{formatNumber(a.scoreStats.median, 1)}</TableCell>
                <TableCell className="text-right">{formatNumber(a.scoreStats.min, 0)}</TableCell>
                <TableCell className="text-right">{formatNumber(a.scoreStats.max, 0)}</TableCell>
              </TableRow>
            ))}
          </TableBody>
        </Table>
      </div>
    </div>
  )
}

export default async function ClassInsightsPage({ searchParams }: { searchParams: Promise<SearchParams> }) {
  const classes = await getTeacherClasses()

  return (
    <div className="flex h-full flex-col space-y-8 p-8">
      <div className="flex flex-col justify-between space-y-4 md:flex-row md:items-center md:space-y-0">
        <div>
          <h2 className="text-2xl font-bold tracking-tight">Class Insights</h2>
          <p className="text-muted-foreground">Latest homework and historical score statistics for a class.</p>
        </div>
      </div>

      <div className="space-y-4">
        <Suspense fallback={<div className="h-10 w-full animate-pulse rounded-md bg-muted" />}>
          <InsightsFilters classes={classes} />
        </Suspense>

        <Suspense fallback={<InsightsResultsFallback />}>
          <InsightsResults searchParams={searchParams} />
        </Suspense>
      </div>
    </div>
  )
}