"use client"

// Kontosammenslåing ("Del 2", ADR-080) -- bekreftelsessiden lenken sendt til
// MÅL-kontoens (taperens) e-post peker til. INGEN sesjon kreves (kan åpnes
// på en annen enhet enn den som ba om sammenslåingen, samme prinsipp som
// e-postbytte-bekreftelse) -- selve token-en ER beviset på eierskap.
//
// To steg, ALDRI automatisk: 1) hent en FERSK forhåndsvisning ved lasting
// (les-only, konsumerer ikke token), 2) krev et eksplisitt "Bekreft
// sammenslåing"-trykk før selve utførelsen -- en lenke skal aldri kunne
// utløse en irreversibel handling bare ved å bli åpnet.

import { useEffect, useState } from "react"
import Link from "next/link"
import { AlertTriangle, CheckCircle2, Merge, XCircle } from "lucide-react"
import { Button } from "@/components/ui/button"

type Status = "loading" | "ready" | "confirming" | "success" | "error"

type ApiOrgMembershipPreview = {
  organization_id: string
  organization_name: string
  keeper_role: string | null
  loser_role: string | null
  resulting_role: string
}

type ApiOrgPlayerPreview = {
  organization_id: string
  organization_name: string
  keeper_has_player: boolean
  loser_has_player: boolean
  colliding_registrations: number
}

type ApiMergePreview = {
  keeper_id: string
  keeper_display_name: string
  keeper_email: string | null
  loser_id: string
  loser_display_name: string
  loser_email: string | null
  organization_memberships: ApiOrgMembershipPreview[]
  player_links: ApiOrgPlayerPreview[]
  friend_count: number
  shared_friend_count: number
  were_friends_with_each_other: boolean
  round_count: number
  secondary_email_count: number
}

const ROLE_LABELS: Record<string, string> = { owner: "eier", admin: "administrator", member: "medlem" }

export function AccountMergeConfirmForm({ token }: { token: string }) {
  const [status, setStatus] = useState<Status>("loading")
  const [preview, setPreview] = useState<ApiMergePreview | null>(null)
  const [error, setError] = useState<string | null>(null)

  useEffect(() => {
    let cancelled = false
    async function load() {
      try {
        const res = await fetch(`/auth/account-merge/token/${token}`, { credentials: "include" })
        if (!res.ok) {
          const body = await res.json().catch(() => null)
          throw new Error(body?.detail?.message ?? "Lenken er ugyldig, brukt eller utløpt.")
        }
        const data: ApiMergePreview = await res.json()
        if (!cancelled) {
          setPreview(data)
          setStatus("ready")
        }
      } catch (err) {
        if (!cancelled) {
          setError(err instanceof Error ? err.message : "Noe gikk galt. Prøv igjen.")
          setStatus("error")
        }
      }
    }
    void load()
    return () => {
      cancelled = true
    }
  }, [token])

  async function handleConfirm() {
    setStatus("confirming")
    setError(null)
    try {
      const res = await fetch("/auth/account-merge/confirm", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        credentials: "include",
        body: JSON.stringify({ token }),
      })
      if (!res.ok) {
        const body = await res.json().catch(() => null)
        throw new Error(body?.detail?.message ?? "Klarte ikke å slå sammen kontoene.")
      }
      setStatus("success")
    } catch (err) {
      setError(err instanceof Error ? err.message : "Noe gikk galt. Prøv igjen.")
      setStatus("ready")
    }
  }

  if (status === "loading") {
    return (
      <div className="flex w-full flex-col items-center gap-4 rounded-3xl border border-border bg-card p-8 text-center shadow-lg shadow-black/5">
        <div
          aria-hidden="true"
          className="size-10 animate-spin rounded-full border-4 border-primary/20 border-t-primary"
        />
        <p className="text-sm text-muted-foreground" role="status">
          Henter forhåndsvisning …
        </p>
      </div>
    )
  }

  if (status === "success") {
    return (
      <div className="flex w-full flex-col items-center gap-5 rounded-3xl border border-border bg-card p-6 text-center shadow-lg shadow-black/5 sm:p-8">
        <div className="flex size-16 items-center justify-center rounded-2xl bg-primary/15">
          <CheckCircle2 aria-hidden="true" className="size-8 text-primary" />
        </div>
        <div className="flex flex-col gap-2">
          <h2 className="text-2xl font-extrabold tracking-tight text-balance">Kontoene er slått sammen</h2>
          <p className="text-sm leading-relaxed text-muted-foreground text-pretty">
            Alt er nå flyttet over. Denne kontoen finnes ikke lenger -- logg inn med den kontoen du
            slo sammen til.
          </p>
        </div>
        <Link href="/logg-inn" className="text-sm font-semibold text-primary transition-colors hover:text-primary/80">
          Til innlogging
        </Link>
      </div>
    )
  }

  if (status === "error" || !preview) {
    return (
      <div className="flex w-full flex-col items-center gap-5 rounded-3xl border border-border bg-card p-6 text-center shadow-lg shadow-black/5 sm:p-8">
        <div className="flex size-16 items-center justify-center rounded-2xl bg-destructive/15">
          <XCircle aria-hidden="true" className="size-8 text-destructive" />
        </div>
        <div className="flex flex-col gap-2">
          <h2 className="text-2xl font-extrabold tracking-tight text-balance">Kunne ikke bekrefte</h2>
          <p className="text-sm leading-relaxed text-muted-foreground text-pretty">{error}</p>
        </div>
        <Link href="/account" className="text-sm font-semibold text-primary transition-colors hover:text-primary/80">
          Til kontoinnstillinger
        </Link>
      </div>
    )
  }

  return (
    <div className="flex w-full flex-col gap-5 rounded-3xl border border-border bg-card p-6 shadow-lg shadow-black/5 sm:p-8">
      <div className="flex flex-col items-center gap-3 text-center">
        <div className="flex size-14 items-center justify-center rounded-2xl bg-muted">
          <Merge aria-hidden="true" className="size-7 text-muted-foreground" />
        </div>
        <h2 className="text-xl font-extrabold tracking-tight text-balance">Bekreft kontosammenslåing</h2>
        <p className="text-sm leading-relaxed text-muted-foreground text-pretty">
          {preview.keeper_display_name}
          {preview.keeper_email ? ` (${preview.keeper_email})` : ""} har bedt om å slå denne kontoen (
          {preview.loser_display_name}
          {preview.loser_email ? `, ${preview.loser_email}` : ""}) sammen med sin.
        </p>
      </div>

      <ul className="flex flex-col gap-1.5 rounded-2xl border border-border bg-background p-3 text-sm text-foreground">
        {preview.organization_memberships.map((m) => (
          <li key={m.organization_id}>
            {m.organization_name}: blir {ROLE_LABELS[m.resulting_role] ?? m.resulting_role}
          </li>
        ))}
        {preview.player_links.map((p) => (
          <li key={p.organization_id}>
            {p.organization_name}: spiller-koblingen slås sammen
            {p.colliding_registrations > 0
              ? ` (${p.colliding_registrations} dobbeltregistrering${p.colliding_registrations === 1 ? "" : "er"} ryddes opp)`
              : ""}
          </li>
        ))}
        {preview.round_count > 0 && <li>{preview.round_count} runde{preview.round_count === 1 ? "" : "r"} flyttes over</li>}
        {preview.friend_count > 0 && (
          <li>
            {preview.friend_count} venn{preview.friend_count === 1 ? "" : "er"} flyttes over
            {preview.shared_friend_count > 0 ? ` (${preview.shared_friend_count} felles, slås sammen)` : ""}
          </li>
        )}
        {preview.were_friends_with_each_other && <li>Dere var venner med hverandre -- fjernes ved sammenslåing</li>}
        {preview.secondary_email_count > 0 && (
          <li>
            {preview.secondary_email_count} ekstra e-postadresse{preview.secondary_email_count === 1 ? "" : "r"} flyttes over
          </li>
        )}
      </ul>

      <div className="flex flex-col gap-3 rounded-2xl border border-destructive/40 bg-destructive/5 p-4">
        <div className="flex items-start gap-2">
          <AlertTriangle aria-hidden="true" className="mt-0.5 size-5 shrink-0 text-destructive" />
          <p className="text-sm font-semibold text-foreground text-pretty">
            Dette kan ikke angres. Denne kontoen ({preview.loser_display_name}) slettes helt så snart
            du bekrefter.
          </p>
        </div>
        <Button
          type="button"
          variant="destructive"
          disabled={status === "confirming"}
          onClick={handleConfirm}
          className="min-h-12 w-full justify-center gap-2 rounded-xl text-base font-bold"
        >
          <Merge aria-hidden="true" className="size-5" />
          {status === "confirming" ? "Slår sammen …" : "Bekreft sammenslåing"}
        </Button>
      </div>

      {error && <p className="text-sm font-medium text-destructive text-pretty">{error}</p>}
    </div>
  )
}