import type { Context as ElysiaContext } from "elysia";
import { Readable } from "node:stream";
import { createReadableStreamFromZip, entriesByNaturalOrder, readZip } from "../util/zipwrap.ts";

const imageExtensions = new Set(["gif", "png", "jpeg", "bmp", "webp", "jpg", "avif"]);

const extensionToMime = (ext: string) => {
	if (ext === "jpg") return "image/jpeg";
	return `image/${ext}`;
};

type ResponseSet = Pick<ElysiaContext["set"], "status" | "headers">;

type RenderOptions = {
	path: string;
	page: number;
	reqHeaders: Headers;
	set: ResponseSet;
};

export async function renderComicPage({ path, page, reqHeaders, set }: RenderOptions) {
	const zip = await readZip(path);

	try {
		const entries = (await entriesByNaturalOrder(zip.reader)).filter((entry) => {
			const ext = entry.filename.split(".").pop()?.toLowerCase();
			return ext !== undefined && imageExtensions.has(ext);
		});

		if (page < 0 || page >= entries.length) {
			set.status = 404;
			await zip.reader.close();
			return null;
		}

		const entry = entries[page];
		const lastModified = entry.lastModDate ?? new Date();
		const ifModifiedSince = reqHeaders.get("if-modified-since");

		const headers = (set.headers ??= {} as Record<string, string | number>);
		headers["Date"] = new Date().toUTCString();
		headers["Last-Modified"] = lastModified.toUTCString();

		if (ifModifiedSince) {
			const cachedDate = new Date(ifModifiedSince);
			if (!Number.isNaN(cachedDate.valueOf()) && lastModified <= cachedDate) {
				set.status = 304;
				await zip.reader.close();
				return null;
			}
		}

		const readStream = await createReadableStreamFromZip(zip.reader, entry);
		const nodeReadable = new Readable({
			read() {
				// noop
			},
		});

		let zipClosed = false;
		const closeZip = async () => {
			if (!zipClosed) {
				zipClosed = true;
				await zip.reader.close();
			}
		};

		readStream.pipeTo(new WritableStream({
			write(chunk) {
				nodeReadable.push(chunk);
			},
			close() {
				nodeReadable.push(null);
			},
			abort(err) {
				nodeReadable.destroy(err);
			},
		})).catch((err) => {
			nodeReadable.destroy(err);
		});

		nodeReadable.on("close", () => {
			closeZip().catch(console.error);
		});
		nodeReadable.on("error", () => {
			closeZip().catch(console.error);
		});
		nodeReadable.on("end", () => {
			closeZip().catch(console.error);
		});

		const ext = entry.filename.split(".").pop()?.toLowerCase() ?? "jpeg";
		headers["Content-Type"] = extensionToMime(ext);
		if (typeof entry.uncompressedSize === "number") {
			headers["Content-Length"] = entry.uncompressedSize.toString();
		}

		set.status = 200;
		return nodeReadable;
	} catch (error) {
		await zip.reader.close();
		throw error;
	}
}