---
import type { CollectionEntry } from 'astro:content';
import { getCollection } from 'astro:content';
import FormattedDate from './FormattedDate.astro';

export interface Props {
	headingLevel?: 1 | 2 | 3 | 4 | 5 | 6,
	hideAuthor?: boolean,
	hideSubheadings?: boolean,
	maxEntries?: number,
};

const { headingLevel = 2, hideSubheadings = false, hideAuthor = false, maxEntries } = Astro.props;

const allPosts = (await getCollection('blog')).filter((post) => !post.data.hidden);

const posts = maxEntries === undefined
	? allPosts
	: allPosts.sort(sortByPubDateDescending).slice(0, maxEntries);

const distinctYears: number[] = posts
	.map(post => pubDate(post).getFullYear())
	.reduce<number[]>((acc, curr) => acc.includes(curr) ? acc : [...acc, curr], [])
	.sort((a, b) => b - a);

function matchesYear(year: number) {
	return (post: CollectionEntry<'blog'>) => pubDate(post).getFullYear() === year;
}

function sortByPubDateDescending(post1: CollectionEntry<'blog'>, post2: CollectionEntry<'blog'>) {
	const date1 = pubDate(post1).getTime();
	const date2 = pubDate(post2).getTime();
	return date2 - date1;
}

function pubDate(post: CollectionEntry<'blog'>): Date {
  if (post.data.pubDate) {
    return post.data.pubDate;
  }
  const date = new Date(post.id);
  if (isNaN(date.valueOf())) {
    throw new Error(`Post ${post.id} does not have a valid publication date.`);
  }
  return date;
}

const HeadingElem = `h${headingLevel} class="p-name"`;
const SubHeadingElem = `h${headingLevel + 1}`;
const SubSubHeadingElem = `h${headingLevel + 2}`;
const AuthorElem = `p${hideAuthor ? " hidden" : ""}`;

const canonicalBlogUrl = new URL('blog', Astro.site)
---

<section class="h-feed">
	<HeadingElem>
		My blog
	</HeadingElem>

	<aside>
		<AuthorElem>
			This blog is written by <a class="p-author h-card" href="/">Joe Carstairs</a>
		</AuthorElem>

		<p hidden>
			<a class="u-url" href={canonicalBlogUrl}>Permalink</a>
		</p>
	</aside>

	<slot />

	{ hideSubheadings
	  ? <ul>
			{ posts.sort(sortByPubDateDescending).map(post => (
				<li class="h-entry">
  				<SubSubHeadingElem>
  					<a class="u-url p-name" href={`/blog/${post.id}`}>{post.data.title}</a>
  				</SubSubHeadingElem>
					<p class="p-summary" set:html={post.data.description} />
					<FormattedDate className="dt-published" date={pubDate(post)} />
				</li>
			)) }
			</ul>
	  : distinctYears.map(year => (
		<SubHeadingElem>{year}</SubHeadingElem>
		<ul>
			{ posts.filter(matchesYear(year)).sort(sortByPubDateDescending).map(post => (
				<li class="h-entry">
  				<SubSubHeadingElem>
  					<a class="u-url p-name" href={`/blog/${post.id}`}>{post.data.title}</a>
  				</SubSubHeadingElem>
					<p class="p-summary" set:html={post.data.description} />
					<FormattedDate className="dt-published" date={pubDate(post)} />
				</li>
			)) }
		</ul>
	)) }

	{ (maxEntries !== undefined && maxEntries < allPosts.length)
		? <p class="full-feed-link"><a href="/blog">All blog posts</a></p>
		: <></>
	}
</section>
