"use client";

import { useState, useEffect, useCallback } from "react";
import { useParams, useRouter } from "next/navigation";
import { FlashcardViewer } from "@/components/flashcards/FlashcardViewer";
import { CardManager } from "@/components/flashcards/CardManager";
import { ShareMenu } from "@/components/ui/ShareMenu";


interface Card {
  id: string;
  front: string;
  back: string;
  sortOrder: number;
}

interface DeckData {
  id: string;
  name: string;
  description: string | null;
  cards: Card[];
  class: { slug: string; name: string };
  progress: Array<{
    mode: "SEQUENTIAL" | "SHUFFLED";
    currentIndex: number;
    orderJson: string;
    cardResultsJson: string | null;
    sessionId: string;
    revision: number;
    updatedAt: string;
  }>;
}

export default function DeckStudyPage() {
  const params = useParams();
  const router = useRouter();
  const classSlug = params.classSlug as string;
  const deckId = params.deckId as string;
  const [deck, setDeck] = useState<DeckData | null>(null);
  const [loading, setLoading] = useState(true);
  const [view, setView] = useState<"study" | "manage">("study");
  const [restartKey, setRestartKey] = useState(0);

  async function handleRestart() {
    if (!deck) return;
    
    const responses = await Promise.all(
      deck.progress.map((progress) =>
        fetch("/api/progress", {
          method: "DELETE",
          headers: { "Content-Type": "application/json" },
          body: JSON.stringify({
            contentType: "DECK",
            contentId: deck.id,
            mode: progress.mode,
            sessionId: progress.sessionId,
          }),
        })
      )
    ).catch(() => null);
    if (!responses || responses.some((response) => !response.ok)) {
      window.alert("The session could not be restarted. Your saved progress was kept.");
      return;
    }
    
    // Clear locally and force remount
    setDeck({ ...deck, progress: [] });
    setRestartKey(k => k + 1);
  }

  const fetchDeck = useCallback(async () => {
    try {
      const res = await fetch(`/api/decks/${deckId}`);
      if (!res.ok) throw new Error("Not found");
      const data = await res.json();
      setDeck(data);
    } catch {
      router.push(`/${classSlug}/flashcards`);
    } finally {
      setLoading(false);
    }
  }, [deckId, classSlug, router]);

  useEffect(() => {
    const timer = window.setTimeout(() => void fetchDeck(), 0);
    return () => window.clearTimeout(timer);
  }, [fetchDeck]);

  if (loading || !deck) {
    return (
      <div className="max-w-4xl mx-auto px-4 sm:px-6 lg:px-8 py-8">
        <div className="animate-subtle-pulse">
          <div className="h-8 bg-bg-surface-alt rounded w-1/3 mb-4" />
          <div className="h-64 bg-bg-surface rounded-xl border border-border-light" />
        </div>
      </div>
    );
  }

  return (
    <div className="mx-auto w-full max-w-5xl py-1 md:py-3">
      {/* Header */}
      <div className="mb-7 flex flex-col items-start justify-between gap-4 rounded-2xl border border-border-light bg-bg-surface/70 p-4 shadow-[var(--shadow-card)] sm:p-5 md:flex-row md:items-center">
        <div>
          <button
            onClick={() => router.push(`/${classSlug}/flashcards`)}
            className="inline-flex items-center gap-1 text-sm text-text-muted hover:text-text-heading mb-2 transition-colors cursor-pointer"
          >
            <svg className="w-4 h-4" fill="none" stroke="currentColor" viewBox="0 0 24 24">
              <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M15 19l-7-7 7-7" />
            </svg>
            Back to decks
          </button>
          <p className="text-xs font-bold uppercase tracking-[0.16em] text-primary">Flashcard session</p>
          <h1 className="editorial-title mt-1 text-3xl text-text-heading">{deck.name}</h1>
          {deck.description && (
            <p className="text-sm text-text-secondary mt-1">{deck.description}</p>
          )}
        </div>

        {/* View toggle & Share */}
        <div className="flex items-center justify-between w-full md:w-auto gap-2 md:gap-4 self-end md:self-auto">
          {view === "study" && (
            <button
              onClick={handleRestart}
              className="p-1.5 rounded-lg text-text-muted hover:text-text-heading hover:bg-bg-surface-alt transition-all duration-200 cursor-pointer"
              title="Restart Session"
            >
              <svg className="w-5 h-5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
                <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M4 4v5h.582m15.356 2A8.001 8.001 0 004.582 9m0 0H9m11 11v-5h-.581m0 0a8.003 8.003 0 01-15.357-2m15.357 2H15" />
              </svg>
            </button>
          )}
          
          <div className="flex items-center gap-2 md:gap-4 ml-auto">
            <ShareMenu targetType="DECK" contentId={deck.id} classSlug={classSlug} />
            
            <div className="flex rounded-xl border border-border-light bg-bg-surface-alt p-1">
              <button
                onClick={() => setView("study")}
                className={`px-4 py-2 rounded-md text-sm font-medium transition-all duration-200 cursor-pointer ${
                  view === "study"
                    ? "bg-bg-surface text-text-heading shadow-sm"
                    : "text-text-muted hover:text-text-heading"
                }`}
              >
                Study
              </button>
              <button
                onClick={() => setView("manage")}
                className={`px-4 py-2 rounded-md text-sm font-medium transition-all duration-200 cursor-pointer ${
                  view === "manage"
                    ? "bg-bg-surface text-text-heading shadow-sm"
                    : "text-text-muted hover:text-text-heading"
                }`}
              >
                Manage
              </button>
            </div>
          </div>
        </div>
      </div>

      {/* Content */}
      {view === "study" ? (
        <FlashcardViewer 
          key={restartKey}
          cards={deck.cards} 
          deckId={deck.id} 
          initialProgress={
            deck.progress?.length 
              ? deck.progress.sort((a, b) => new Date(b.updatedAt).getTime() - new Date(a.updatedAt).getTime())[0] 
              : null
          }
        />
      ) : (
        <CardManager
          cards={deck.cards}
          deckId={deck.id}
          onCardsChanged={fetchDeck}
        />
      )}
    </div>
  );
}