/** @file cached diigo items as RSS 2.0, in the shape of diigo's RSS export. */

import type { Item } from "./items.js";

/** characters XML 1.0 forbids (the C0 controls but tab, LF, CR);
 * diigo's export carries some raw, so strict parsers reject it */
const XML_FORBIDDEN = /[\u0000-\u0008\u000B\u000C\u000E-\u001F]/g;

/** text as one or more CDATA sections: forbidden characters dropped,
 * a literal `]]>` split across two sections */
function cdata(text: string): string {
	return `<![CDATA[${text.replace(XML_FORBIDDEN, "").replaceAll("]]>", "]]]]><![CDATA[>")}]]>`;
}

const str = (v: unknown): string => (typeof v === "string" ? v : "");
const list = (v: unknown): Record<string, unknown>[] => (Array.isArray(v) ? (v as Record<string, unknown>[]) : []);

/**
 * the packed description diigo's export uses:
 * `Tags:a,b;Description:…;Annotations and Sticky notes:…` — tags
 * comma-separated (`no_tag` when none), then each highlight as
 * `Highlight:<text>\n` followed by its sticky notes, one
 * `Sticky notes:<text>\n` each (notes may span lines). A diigo *note*
 * item's body (`note_content`) comes first, as a `Highlight:` line.
 */
export function itemDescription(item: Item): string {
	const tags = str(item.tags) || "no_tag";
	const body = str(item.note_content) ? `Highlight:${str(item.note_content)}\n` : "";
	const notes = list(item.annotations)
		.map((a) => `Highlight:${str(a.content)}\n${list(a.stickyNotes).map((n) => `Sticky notes:${str(n.content)}\n`).join("")}`)
		.join("");
	return `Tags:${tags};Description:${str(item.description)};Annotations and Sticky notes:${body}${notes}`;
}

/** one `<item>`: title, link, packed description. The title is whole
 * (diigo's export cuts titles at 255 characters). */
export function rssItem(item: Item): string {
	return `<item><title>${cdata(str(item.title))}</title><link>${cdata(str(item.url))}</link><description>${cdata(itemDescription(item))}</description></item>`;
}

/**
 * a whole feed
 *
 * @param channel `pubDate` in RFC 822 form is the caller's to supply
 * (no clock here)
 */
export function toRss(items: Item[], channel: { title: string; pubDate: string }): string {
	return `<?xml version="1.0"?>
<rss version="2.0">
<channel>
<title>${cdata(channel.title)}</title>
<link></link>
<pubDate>${channel.pubDate}</pubDate>
<lastBuildDate>${channel.pubDate}</lastBuildDate>
${items.map(rssItem).join("\n")}
</channel>
</rss>
`;
}