"use client";

import React, { useEffect, useMemo, useState } from "react";
import { useRouter } from "next/navigation";

type ApiCategory = {
  id: string;
  name: string;
  slug: string;
  boards: { id: string; name: string; slug: string; type: string; requiresApproval: boolean }[];
};

type PostItem = {
  id: string;
  title: string;
  createdAt: string;
  boardId: string;
};

interface Props {
  categoryName?: string;
  categorySlug?: string;
}

export default function CategoryBoardBrowser({ categoryName, categorySlug }: Props) {
  const router = useRouter();
  const [categories, setCategories] = useState<ApiCategory[] | null>(null);
  const [selectedBoardId, setSelectedBoardId] = useState<string | null>(null);
  const [posts, setPosts] = useState<PostItem[] | null>(null);
  const [isLoadingPosts, setIsLoadingPosts] = useState(false);

  useEffect(() => {
    let isMounted = true;
    (async () => {
      const res = await fetch("/api/categories", { cache: "no-store" });
      const data = await res.json();
      if (!isMounted) return;
      setCategories(data.categories ?? []);
    })();
    return () => {
      isMounted = false;
    };
  }, []);

  const selectedCategory = useMemo(() => {
    if (!categories) return null;
    // 우선순위: 전달받은 카테고리명 -> 전달받은 슬러그 -> 기본(암실소문/main)
    const byName = categoryName ? categories.find((c) => c.name === categoryName) : null;
    if (byName) return byName;
    const bySlug = categorySlug ? categories.find((c) => c.slug === categorySlug) : null;
    if (bySlug) return bySlug;
    return (
      categories.find((c) => c.name === "암실소문") ||
      categories.find((c) => c.slug === "main") ||
      null
    );
  }, [categories, categoryName, categorySlug]);

  const boardIdToName = useMemo(() => {
    const map = new Map<string, string>();
    if (selectedCategory) {
      for (const b of selectedCategory.boards) map.set(b.id, b.name);
    }
    return map;
  }, [selectedCategory]);

  // 기본 보드 자동 선택: 선택된 카테고리의 첫 번째 보드
  useEffect(() => {
    if (!selectedBoardId && selectedCategory?.boards?.length) {
      setSelectedBoardId(selectedCategory.boards[0].id);
    }
  }, [selectedCategory, selectedBoardId]);

  useEffect(() => {
    if (!selectedBoardId) return;
    let isMounted = true;
    (async () => {
      try {
        setIsLoadingPosts(true);
        const params = new URLSearchParams({ pageSize: String(10), boardId: selectedBoardId });
        const res = await fetch(`/api/posts?${params.toString()}`, { cache: "no-store" });
        const data = await res.json();
        if (!isMounted) return;
        setPosts(data.items ?? []);
      } finally {
        if (isMounted) setIsLoadingPosts(false);
      }
    })();
    return () => {
      isMounted = false;
    };
  }, [selectedBoardId]);

  return (
    <div className="w-full h-full min-h-0 flex flex-col bg-white rounded-xl overflow-hidden">
      {/* 상단: 한 줄(row)로 카테고리 + 화살표 + 보드 pill 버튼들 */}
      <div className="px-3 py-2 border-b border-neutral-200">
        <div className="flex items-center gap-2 overflow-x-auto flex-nowrap">
          <button
            type="button"
            className="shrink-0 text-lg md:text-xl font-bold text-neutral-800 truncate"
            onClick={() => {
              const first = selectedCategory?.boards?.[0];
              if (first?.id) router.push(`/boards/${first.id}`);
            }}
            title={(selectedCategory?.name ?? categoryName ?? "").toString()}
          >
            {selectedCategory?.name ?? categoryName ?? ""}
          </button>
          <button
            type="button"
            aria-label="카테고리 첫 게시판 이동"
            className="shrink-0 w-6 h-6 rounded-full border border-neutral-300 text-neutral-500 hover:bg-neutral-50 flex items-center justify-center"
            onClick={() => {
              const first = selectedCategory?.boards?.[0];
              if (first?.id) router.push(`/boards/${first.id}`);
            }}
          >
            <svg width="12" height="12" viewBox="0 0 20 20" fill="currentColor" aria-hidden="true">
              <path d="M7 5l5 5-5 5" stroke="currentColor" strokeWidth="2" fill="none" strokeLinecap="round" strokeLinejoin="round" />
            </svg>
          </button>
          {selectedCategory?.boards?.map((b) => (
            <button
              key={b.id}
              className={`shrink-0 whitespace-nowrap text-xs px-3 py-1 rounded-full border transition-colors ${
                selectedBoardId === b.id
                  ? "bg-neutral-800 text-white border-neutral-800"
                  : "bg-white text-neutral-700 border-neutral-300 hover:bg-neutral-100"
              }`}
              onClick={() => setSelectedBoardId(b.id)}
            >
              {b.name}
            </button>
          ))}
        </div>
      </div>

      {/* 2행: 게시글 리스트 */}
      <div className="flex-1 min-h-0 overflow-y-auto p-3">
        {!selectedBoardId && (
          <div className="text-sm text-neutral-500">보드를 선택해 주세요.</div>
        )}
        {selectedBoardId && isLoadingPosts && (
          <div className="text-sm text-neutral-500">불러오는 중…</div>
        )}
        {selectedBoardId && !isLoadingPosts && posts && posts.length === 0 && (
          <div className="text-sm text-neutral-500">게시글이 없습니다.</div>
        )}

        <div className="grid grid-cols-1 gap-3">
          {posts?.map((p) => {
            const boardName = boardIdToName.get(p.boardId) ?? "";
            const dateStr = new Date(p.createdAt).toLocaleDateString();
            const imgSrc = `https://picsum.photos/seed/${p.id}/200/140`;
            return (
              <article key={p.id} className="w-full h-[140px] rounded-lg border border-neutral-200 overflow-hidden bg-white">
                <div className="h-full w-full grid grid-cols-[200px_1fr]">
                  <div className="w-[200px] h-full bg-neutral-100">
                    <img src={imgSrc} alt="썸네일" className="w-full h-full object-cover" />
                  </div>
                  <div className="flex flex-col justify-center gap-1 px-3">
                    <div className="text-[11px] text-neutral-500">{boardName}</div>
                    <div className="text-sm font-semibold line-clamp-2">{p.title}</div>
                    <div className="text-xs text-neutral-500">{dateStr}</div>
                  </div>
                </div>
              </article>
            );
          })}
        </div>
      </div>
    </div>
  );
}