"use client"

import { useEffect, useState } from "react"
import Link from "next/link"
import { ArrowLeft, Check, Circle, Trophy } from "lucide-react"
import { cn } from "@/lib/utils"

// --- Types (matcher API-kontrakten i app/routers/tournaments.py sin leaderboard-endepunkt)

type ApiTeamStanding = {
  team_id: string
  team_name: string
  color: string | null
  points: number
}

type ApiSessionStanding = {
  session_id: string
  sequence: number
  name: string | null
  points_by_team: Record<string, number>
  matches_total: number
  matches_decided: number
}

type ApiLeaderboard = {
  teams: [ApiTeamStanding, ApiTeamStanding]
  matches_total: number
  matches_decided: number
  sessions: ApiSessionStanding[]
}

// --- Formatting helpers ----------------------------------------------------

function formatPoints(value: number): string {
  return value.toLocaleString("nb-NO", { maximumFractionDigits: 1 })
}

function sessionTitle(s: ApiSessionStanding): string {
  return s.name?.trim() || `Økt ${s.sequence}`
}

// --- Component -------------------------------------------------------------

export function TournamentLeaderboard({
  organizationId,
  tournamentId,
  tournamentName,
}: {
  organizationId: string
  tournamentId: string
  tournamentName: string
}) {
  const [board, setBoard] = useState<ApiLeaderboard | null>(null)
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState<string | null>(null)

  useEffect(() => {
    let cancelled = false
    async function load() {
      try {
        const res = await fetch(`/orgs/${organizationId}/tournaments/${tournamentId}/leaderboard`, {
          credentials: "include",
        })
        if (!res.ok) throw new Error(`load failed: ${res.status}`)
        const data: ApiLeaderboard = await res.json()
        if (cancelled) return
        setBoard({ ...data, sessions: [...data.sessions].sort((a, b) => a.sequence - b.sequence) })
      } catch {
        if (!cancelled) setError("Klarte ikke å laste leaderboardet. Prøv å laste siden på nytt.")
      } finally {
        if (!cancelled) setLoading(false)
      }
    }
    void load()
    return () => {
      cancelled = true
    }
  }, [organizationId, tournamentId])

  const detailHref = `/tournaments/${tournamentId}?org=${organizationId}&name=${encodeURIComponent(tournamentName)}`
  const programHref = `/tournaments/${tournamentId}/program?org=${organizationId}&name=${encodeURIComponent(tournamentName)}`

  return (
    <div className="flex min-h-[100dvh] flex-col bg-background">
      <header className="sticky top-0 z-10 border-b border-border bg-background/80 backdrop-blur">
        <div className="mx-auto flex w-full max-w-4xl items-center gap-3 px-5 py-4">
          <Link
            href={detailHref}
            aria-label="Tilbake til turnering"
            className="flex size-10 shrink-0 items-center justify-center rounded-xl border border-border bg-card text-muted-foreground transition-colors hover:bg-accent/50 hover:text-foreground"
          >
            <ArrowLeft aria-hidden="true" className="size-5" />
          </Link>
          <div className="flex min-w-0 flex-col">
            <span className="text-xs font-semibold uppercase tracking-wide text-muted-foreground">
              Turnering
            </span>
            <h1 className="truncate text-xl font-extrabold tracking-tight text-foreground">
              {tournamentName}
            </h1>
          </div>
        </div>

        <nav className="mx-auto flex w-full max-w-4xl items-center gap-2 px-5 pb-3" aria-label="Turneringsseksjoner">
          <Link
            href={detailHref}
            className="rounded-full px-4 py-2 text-sm font-semibold text-muted-foreground transition-colors hover:bg-accent/60 hover:text-foreground"
          >
            Lag og spillere
          </Link>
          <Link
            href={programHref}
            className="rounded-full px-4 py-2 text-sm font-semibold text-muted-foreground transition-colors hover:bg-accent/60 hover:text-foreground"
          >
            Program
          </Link>
          <span
            aria-current="page"
            className="rounded-full bg-primary px-4 py-2 text-sm font-bold text-primary-foreground"
          >
            Leaderboard
          </span>
        </nav>
      </header>

      <main className="mx-auto w-full max-w-4xl flex-1 px-5 py-6 sm:py-8">
        <div className="mb-5 flex flex-col gap-1">
          <h2 className="text-base font-bold text-foreground">Stilling</h2>
          <p className="text-sm leading-relaxed text-muted-foreground text-pretty">
            Totalt antall poeng summert på tvers av alle økter, oppdatert etter hvert som matcher
            avgjøres.
          </p>
        </div>

        {error && (
          <p role="alert" className="mb-4 text-sm font-medium text-destructive">
            {error}
          </p>
        )}

        {loading || !board ? (
          <div className="flex justify-center py-16">
            <div
              aria-hidden="true"
              className="size-10 animate-spin rounded-full border-4 border-primary/20 border-t-primary"
            />
          </div>
        ) : (
          <>
            {(() => {
              const [teamA, teamB] = board.teams
              const leaderId =
                teamA.points === teamB.points ? null : teamA.points > teamB.points ? teamA.team_id : teamB.team_id
              return (
                <>
                  <Scoreboard teamA={teamA} teamB={teamB} leaderId={leaderId} />
                  <p className="mt-3 text-center text-sm font-medium text-muted-foreground">
                    {board.matches_decided} av {board.matches_total} matcher avgjort
                  </p>
                  <div className="mt-8 flex flex-col gap-3">
                    <h3 className="text-sm font-bold text-foreground">Poeng per økt</h3>
                    {board.sessions.length === 0 ? (
                      <p className="text-sm text-muted-foreground">Ingen økter opprettet ennå.</p>
                    ) : (
                      board.sessions.map((s) => (
                        <SessionRow key={s.session_id} session={s} teamA={teamA} teamB={teamB} />
                      ))
                    )}
                  </div>
                </>
              )
            })()}
          </>
        )}
      </main>
    </div>
  )
}

// --- Scoreboard ------------------------------------------------------------

function Scoreboard({
  teamA,
  teamB,
  leaderId,
}: {
  teamA: ApiTeamStanding
  teamB: ApiTeamStanding
  leaderId: string | null
}) {
  return (
    <div className="grid grid-cols-[1fr_auto_1fr] items-stretch overflow-hidden rounded-3xl border border-border bg-card shadow-sm shadow-black/5">
      <TeamScore team={teamA} isLeader={leaderId === teamA.team_id} align="left" />
      <div className="flex items-center justify-center bg-border/40 px-2">
        <span className="text-sm font-bold uppercase tracking-wide text-muted-foreground">vs</span>
      </div>
      <TeamScore team={teamB} isLeader={leaderId === teamB.team_id} align="right" />
    </div>
  )
}

function TeamScore({
  team,
  isLeader,
  align,
}: {
  team: ApiTeamStanding
  isLeader: boolean
  align: "left" | "right"
}) {
  const color = team.color ?? "#64748b"
  return (
    <div
      className={cn(
        "relative flex flex-col gap-2 p-5 sm:p-6",
        align === "right" ? "items-end text-right" : "items-start text-left",
      )}
      style={{
        borderTop: `4px solid ${color}`,
        backgroundColor: isLeader ? `${color}14` : undefined,
      }}
    >
      <div className={cn("flex items-center gap-2", align === "right" && "flex-row-reverse")}>
        <span aria-hidden="true" className="size-3 shrink-0 rounded-full" style={{ backgroundColor: color }} />
        <span className="truncate text-sm font-bold text-foreground sm:text-base">{team.team_name}</span>
      </div>

      {isLeader && (
        <span className="inline-flex items-center gap-1 rounded-full bg-primary/15 px-2 py-0.5 text-xs font-bold text-foreground">
          <Trophy aria-hidden="true" className="size-3 fill-primary text-primary" />
          Leder
        </span>
      )}

      <span
        className={cn(
          "font-extrabold tabular-nums leading-none tracking-tight",
          isLeader ? "text-6xl sm:text-7xl" : "text-5xl sm:text-6xl text-foreground/80",
        )}
        style={isLeader ? { color } : undefined}
      >
        {formatPoints(team.points)}
      </span>
      <span className="text-xs font-medium uppercase tracking-wide text-muted-foreground">poeng</span>
    </div>
  )
}

// --- Session row -----------------------------------------------------------

function SessionRow({
  session,
  teamA,
  teamB,
}: {
  session: ApiSessionStanding
  teamA: ApiTeamStanding
  teamB: ApiTeamStanding
}) {
  const notStarted = session.matches_decided === 0
  const complete = session.matches_decided === session.matches_total
  const aPts = session.points_by_team[teamA.team_id] ?? 0
  const bPts = session.points_by_team[teamB.team_id] ?? 0
  const colorA = teamA.color ?? "#64748b"
  const colorB = teamB.color ?? "#64748b"

  return (
    <div className="rounded-3xl border border-border bg-card p-4 shadow-sm shadow-black/5 sm:p-5">
      <div className="flex items-center justify-between gap-3">
        <h4 className="text-base font-bold text-foreground">{sessionTitle(session)}</h4>
        {complete ? (
          <span className="inline-flex items-center gap-1 rounded-full bg-primary/15 px-2.5 py-1 text-xs font-semibold text-foreground">
            <Check aria-hidden="true" className="size-3.5 text-primary" />
            Fullført
          </span>
        ) : notStarted ? (
          <span className="inline-flex items-center gap-1 rounded-full bg-muted px-2.5 py-1 text-xs font-medium text-muted-foreground">
            <Circle aria-hidden="true" className="size-3" />
            Ikke startet ennå
          </span>
        ) : (
          <span className="text-xs font-medium text-muted-foreground">
            {session.matches_decided} av {session.matches_total} matcher avgjort
          </span>
        )}
      </div>

      <div className="mt-3 flex items-center gap-3">
        <div className="flex min-w-0 flex-1 items-center gap-2">
          <span aria-hidden="true" className="size-2.5 shrink-0 rounded-full" style={{ backgroundColor: colorA }} />
          <span className="truncate text-sm font-medium text-foreground">{teamA.team_name}</span>
        </div>

        <div className="flex shrink-0 items-center gap-1.5 tabular-nums">
          <span className={cn("text-lg font-extrabold", notStarted ? "text-muted-foreground" : "text-foreground")}>
            {formatPoints(aPts)}
          </span>
          <span className="text-sm font-semibold text-muted-foreground">–</span>
          <span className={cn("text-lg font-extrabold", notStarted ? "text-muted-foreground" : "text-foreground")}>
            {formatPoints(bPts)}
          </span>
        </div>

        <div className="flex min-w-0 flex-1 items-center justify-end gap-2">
          <span className="truncate text-right text-sm font-medium text-foreground">{teamB.team_name}</span>
          <span aria-hidden="true" className="size-2.5 shrink-0 rounded-full" style={{ backgroundColor: colorB }} />
        </div>
      </div>
    </div>
  )
}