function IsValidURL(url) {
	try {
		new URL(url);
		return true;
	} catch (err) {
		return false;
	}
}

function RandomString() {
	const characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"
	let res = ""

	for (let i = 0; i < 8; i++) {
		res += characters.charAt(Math.floor(Math.random() * characters.length))
	}

	return res
}

export default {
	async fetch(request, env, ctx) {
		let request_url = new URL(request.url)

		if (request.method == "POST") {
			if (request_url.pathname.toLowerCase() == "/upload" && request.headers.get("token") == env.ACCESS_TOKEN) {
				let url = (await request.json()).URL

				if (IsValidURL(url)) {
					let slug = RandomString()

					while (true) {
						if (await env.stored_urls.get(slug) == null) {
							if (await env.stored_urls.put(slug, url) !== undefined) {
								return new Response(`{"error": {"code": 503, "message": "KV limit reached."}}`, {status: 503})
							} else {
								break
							}
						}

						slug = RandomString()
					}

					return new Response(`{"data": {"slug": "${slug}"}}`, {status: 200})
				} else {
					return new Response(`{"error": {"code": 400, "message": "Invalid URL."}}`, {status: 400})
				}
			}

			return new Response(`{"error": {"code": 403, "message": "Unauthorized."}}`, {status: 403})
		} else if (request.method == "GET") {
			let slug = request_url.pathname.substring(1)

			if (slug.length > 0) {
				let url = await env.stored_urls.get(slug)

				if (url !== null) {
					return Response.redirect(url, 301)
				}
			}

			return new Response(`{"error": {"code": 404, "message": "Redirect not found."}}`, {status: 404})
		}
	},
};