"use client";

/**
 * The "All" tab of /quizzes, as a drill-down:
 *
 *   All → Books → a book → its quizzes
 *       → Lectures & Conversations → a year → its quizzes
 *       → Other quizzes (stand-alone)
 *
 * Where you are lives in the URL (?in=books&book=bg, ?in=lectures&year=1972)
 * so a refresh, Back, or a shared link lands in the same place. Every level
 * only offers categories that actually hold quizzes; a stale or hand-typed
 * URL pointing at an empty one falls back to its parent.
 */

import Link from "next/link";
import {
  BookOpen,
  CalendarDays,
  ChevronRight,
  ClipboardCheck,
  Mic,
} from "lucide-react";
import type { QuizCard } from "@/lib/quiz";
import { groupQuizzes, type QuizGroup } from "@/lib/quiz-groups";
import { QuizCategoryCard } from "./quiz-category-card";
import { QuizGrid } from "./quiz-grid";

export type QuizBrowsePath = {
  in?: string | null;
  book?: string | null;
  year?: string | null;
};

const BOOKS = "books";
const LECTURES = "lectures";
const OTHER = "other";

/** /quizzes URL for a browse position (the All tab is the default). */
export function quizzesHref(p: QuizBrowsePath): string {
  const qs = new URLSearchParams();
  if (p.in) qs.set("in", p.in);
  if (p.book) qs.set("book", p.book);
  if (p.year) qs.set("year", p.year);
  const s = qs.toString();
  return s ? `/quizzes?${s}` : "/quizzes";
}

export function QuizBrowser({
  quizzes,
  path,
}: {
  quizzes: QuizCard[];
  path: QuizBrowsePath;
}) {
  const { books, lectures, other } = groupQuizzes(quizzes);
  const all = (gs: QuizGroup[]) => gs.flatMap((g) => g.quizzes);

  const book =
    path.in === BOOKS ? books.find((g) => g.key === path.book) : undefined;
  const year =
    path.in === LECTURES
      ? lectures.find((g) => g.key === path.year)
      : undefined;

  // Books → a book: its quizzes.
  if (book) {
    return (
      <Level crumbs={[["Books", quizzesHref({ in: BOOKS })], [book.label]]}>
        <QuizGrid quizzes={book.quizzes} />
      </Level>
    );
  }
  // Lectures → a year: its quizzes.
  if (year) {
    return (
      <Level
        crumbs={[
          ["Lectures & Conversations", quizzesHref({ in: LECTURES })],
          [year.label],
        ]}
      >
        <QuizGrid quizzes={year.quizzes} />
      </Level>
    );
  }
  // Books: a card per book.
  if (path.in === BOOKS && books.length > 0) {
    return (
      <Level crumbs={[["Books"]]}>
        <CardGrid>
          {books.map((g) => (
            <QuizCategoryCard
              key={g.key}
              href={quizzesHref({ in: BOOKS, book: g.key })}
              label={g.label}
              quizzes={g.quizzes}
              icon={<BookOpen className="size-5" />}
            />
          ))}
        </CardGrid>
      </Level>
    );
  }
  // Lectures: a card per year.
  if (path.in === LECTURES && lectures.length > 0) {
    return (
      <Level crumbs={[["Lectures & Conversations"]]}>
        <CardGrid>
          {lectures.map((g) => (
            <QuizCategoryCard
              key={g.key}
              href={quizzesHref({ in: LECTURES, year: g.key })}
              label={g.label}
              quizzes={g.quizzes}
              icon={<CalendarDays className="size-5" />}
            />
          ))}
        </CardGrid>
      </Level>
    );
  }
  // Stand-alone quizzes.
  if (path.in === OTHER && other.length > 0) {
    return (
      <Level crumbs={[["Other quizzes"]]}>
        <QuizGrid quizzes={other} />
      </Level>
    );
  }

  // Top level: one card per category that has quizzes.
  return (
    <CardGrid>
      {books.length > 0 && (
        <QuizCategoryCard
          href={quizzesHref({ in: BOOKS })}
          label="Books"
          quizzes={all(books)}
          icon={<BookOpen className="size-5" />}
        />
      )}
      {lectures.length > 0 && (
        <QuizCategoryCard
          href={quizzesHref({ in: LECTURES })}
          label="Lectures & Conversations"
          quizzes={all(lectures)}
          icon={<Mic className="size-5" />}
        />
      )}
      {other.length > 0 && (
        <QuizCategoryCard
          href={quizzesHref({ in: OTHER })}
          label="Other quizzes"
          quizzes={other}
          icon={<ClipboardCheck className="size-5" />}
        />
      )}
    </CardGrid>
  );
}

function CardGrid({ children }: { children: React.ReactNode }) {
  return (
    <div className="grid grid-cols-1 gap-3 sm:grid-cols-2 [&>*]:min-w-0">
      {children}
    </div>
  );
}

/** A level below the top: a breadcrumb back up, then its content. */
function Level({
  crumbs,
  children,
}: {
  /** [label, href?] — the last (current) one has no link. */
  crumbs: [string, string?][];
  children: React.ReactNode;
}) {
  return (
    <div className="space-y-4">
      <nav
        aria-label="Quiz categories"
        className="flex min-w-0 flex-wrap items-center gap-x-1.5 gap-y-1 text-sm"
      >
        <Link
          href={quizzesHref({})}
          className="text-muted-foreground hover:text-foreground"
        >
          All quizzes
        </Link>
        {crumbs.map(([label, href]) => (
          <span key={label} className="flex min-w-0 items-center gap-1.5">
            <ChevronRight className="size-3.5 shrink-0 text-muted-foreground" />
            {href ? (
              <Link
                href={href}
                className="truncate text-muted-foreground hover:text-foreground"
              >
                {label}
              </Link>
            ) : (
              <span className="truncate font-medium text-foreground">
                {label}
              </span>
            )}
          </span>
        ))}
      </nav>
      {children}
    </div>
  );
}