"use client";

import { Suspense, useSearchParams } from "react";
import Link from "next/link";
import {
  POSTS_PER_PAGE,
  blogCategories,
  categoryLabel,
  paginate,
  postsForCategory,
  type BlogPost,
} from "@/data/content";
import { useStaggerReveal } from "@/hooks/useAnimations";
import BlogPostCard from "@/components/BlogPostCard";
import "../styles/blog.css";

/** Sort posts newest-first by date (ISO display dates compare lexicographically). */
function sortPostsNewestFirst(posts: BlogPost[]): BlogPost[] {
  return [...posts].sort((a, b) => b.date.localeCompare(a.date));
}

type BlogListProps = {
  /**
   * Category slug (e.g. from /blog/category/[category]) that takes precedence
   * over the ?category= search param. The param still controls ?page=.
   */
  category?: string;
};

/**
 * The blog tab: a paginated, category-filterable stack of posts, newest first.
 *
 * useSearchParams() suspends during static rendering, so Next.js requires it
 * to sit inside a <Suspense> boundary -- /blog is statically rendered, which
 * is exactly why the default export wraps the inner component.
 */
export default function BlogList({ category: categoryProp }: BlogListProps) {
  return (
    <Suspense fallback={<div className="blog-list-fallback" />}
      >
      <BlogListInner categoryProp={categoryProp} />
    </Suspense>
  );
}

function BlogListInner({ categoryProp }: { categoryProp?: string }) {
  const searchParams = useSearchParams();

  const rawPage = searchParams.get("page") ?? "";
  const requestedPage = rawPage === "" ? 1 : Number(rawPage);
  const paramCategory = searchParams.get("category") ?? undefined;
  const category = categoryProp ?? paramCategory;

  const categories = blogCategories();
  const posts = sortPostsNewestFirst(postsForCategory(category));
  const { items, page, totalPages, total, startIndex, endIndex } = paginate(
    posts,
    requestedPage,
    POSTS_PER_PAGE
  );
  const visible = useStaggerReveal(items.length, 100);

  const activeCategory = category ?? "all";
  const activeCategoryLabel = category ? categoryLabel(category) : "All";

  return (
    <div style={{ padding: "48px 0", minWidth: 0 }}>
      <div
        style={{
          marginBottom: 8,
          fontFamily: "var(--mono)",
          fontSize: 11,
          color: "var(--muted)",
          letterSpacing: "0.08em",
          textTransform: "uppercase",
        }}
      >
        {"# blog"}
      </div>
      <h2
        style={{
          fontFamily: "var(--sans)",
          fontSize: 28,
          fontWeight: 700,
          color: "var(--fg)",
          margin: "0 0 16px 0",
          letterSpacing: "-0.01em",
        }}
      >
        {"Writing"}
      </h2>

      <div className="blog-count" aria-live="polite">
        {category ? `In ${activeCategoryLabel}: ` : ""}
        {total > 0 ? `showing ${startIndex}–${endIndex} of ${total}` : "no posts"}
      </div>

      <nav className="blog-category-filters" aria-label="Filter posts by category">
        <Link
          href={blogHref({})}
          className={"blog-category-chip" + (activeCategory === "all" ? " is-active" : "")}
          aria-current={activeCategory === "all" ? "page" : undefined}
        >
          {"all"}
        </Link>
        {categories.map((slug) => (
          <Link
            key={slug}
            href={blogHref({ category: slug })}
            className={"blog-category-chip" + (category === slug ? " is-active" : "")}
            aria-current={category === slug ? "page" : undefined}
          >
            {categoryLabel(slug)}
          </Link>
        ))}
      </nav>

      {items.length > 0 ? (
        // Keyed per category+page: useStaggerReveal only re-runs when its
        // count changes, so remounting the container re-triggers the reveal
        // even when consecutive pages hold the same number of posts.
        <div className="blog-list" key={`${activeCategory}-${page}`}>
          {items.map((post, i) => (
            <BlogPostCard key={post.id} post={post} visible={visible.has(i)} />
          ))}
        </div>
      ) : (
        <p className="blog-list-empty">No posts in this category yet.</p>
      )}

      <nav className="blog-pagination" aria-label="Blog pagination">
        {page > 1 ? (
          <Link className="blog-page-link expand-on-hover-button" href={blogHref({ page: page - 1, category })}>
            {"‹ Prev"}
          </Link>
        ) : (
          <span className="blog-page-link expand-on-hover-button" aria-disabled="true" tabIndex={-1}>
            {"‹ Prev"}
          </span>
        )}

        <div className="blog-page-numbers">
          {Array.from({ length: totalPages }, (_, i) => i + 1).map((n) =>
            n === page ? (
              <span key={n} className="blog-page-number is-active" aria-current="page">
                {n}
              </span>
            ) : (
              <Link key={n} className="blog-page-number" href={blogHref({ page: n, category })}>
                {n}
              </Link>
            )
          )}
        </div>

        {page < totalPages ? (
          <Link className="blog-page-link expand-on-hover-button" href={blogHref({ page: page + 1, category })}>
            {"Next ›"}
          </Link>
        ) : (
          <span className="blog-page-link expand-on-hover-button" aria-disabled="true" tabIndex={-1}>
            {"Next ›"}
          </span>
        )}
      </nav>
    </div>
  );
}

/**
 * Single source of truth for /blog URLs: /blog, /blog?page=2,
 * /blog?category=meta, /blog?category=meta&page=2. Omitted values are
 * dropped (page 1 is the default page, the missing category is "all"),
 * so chip links never carry a stale ?page=.
 */
function blogHref({ page, category }: { page?: number; category?: string } = {}): string {
  const params = new URLSearchParams();
  if (category) params.set("category", category);
  if (page !== undefined && page > 1) params.set("page", String(page));
  const qs = params.toString();
  return qs ? `/blog?${qs}` : "/blog";
}