---
import { getCollection } from "astro:content";
import type { CollectionEntry } from "astro:content";
import type { Lang } from "@/i18n";

interface Props {
    post: CollectionEntry<"blog">;
    lang: Lang;
}

const { post, lang } = Astro.props;

const allPosts = await getCollection("blog");

// 只保留当前语言
const sameLangPosts = allPosts.filter((p) => {
    const [postLang] = p.id.split("/");
    return postLang === lang;
});

// 按日期倒序：越新越靠前
const sortedPosts = [...sameLangPosts].sort(
    (a, b) =>
        new Date(b.data.pubDate).getTime() - new Date(a.data.pubDate).getTime(),
);

// 找当前文章位置
const currentIndex = sortedPosts.findIndex((p) => p.id === post.id);

// 更旧的一篇
const prevPost =
    currentIndex < sortedPosts.length - 1
        ? sortedPosts[currentIndex + 1]
        : null;

// 更新的一篇
const nextPost = currentIndex > 0 ? sortedPosts[currentIndex - 1] : null;

const getSlugFromId = (id: string) => id.split("/").slice(1).join("/");

const prevSlug = prevPost ? getSlugFromId(prevPost.id) : null;
const nextSlug = nextPost ? getSlugFromId(nextPost.id) : null;
---

<nav class="post-nav" aria-label="Post navigation">
    <div class="post-nav-item post-nav-next">
        {
            nextPost && nextSlug && (
                <a href={`/${lang}/posts/${nextSlug}/`}>
                    <span class="post-nav-label">
                        {lang === "zh" ? "上一篇" : "Previous"}
                    </span>
                    <span class="post-nav-title">{nextPost.data.title}</span>
                </a>
            )
        }
    </div>

    <div class="post-nav-item post-nav-prev">
        {
            prevPost && prevSlug && (
                <a href={`/${lang}/posts/${prevSlug}/`}>
                    <span class="post-nav-label">
                        {lang === "zh" ? "下一篇" : "Next"}
                    </span>
                    <span class="post-nav-title">{prevPost.data.title}</span>
                </a>
            )
        }
    </div>
</nav>

<style>
    .post-nav {
        display: grid;
        grid-template-columns: 1fr 1fr;
        gap: 1rem;
        margin-top: 3rem;
        padding-top: 1.5rem;
        border-top: 1px dashed rgba(128, 128, 128, 0.5);
    }

    .post-nav-item {
        min-width: 0;
    }

    .post-nav-prev {
        text-align: right;
    }

    .post-nav a {
        display: block;
        text-decoration: none;
        color: inherit;
    }

    .post-nav-label {
        display: block;
        font-size: 0.9rem;
        opacity: 0.65;
        margin-bottom: 0.35rem;
    }

    .post-nav-title {
        display: block;
        font-size: 1rem;
        line-height: 1.5;
    }
</style>