/**
 * Article unlock strategies — find readable/archived versions of paywalled articles.
 * Three strategies tried in sequence: Wayback Machine, Google Cache, archive.ph.
 */

interface UnlockResult {
	success: boolean;
	strategy?: string;
	archiveUrl?: string;
	error?: string;
}

/** Try the Wayback Machine (web.archive.org). */
async function tryWaybackMachine(url: string): Promise<UnlockResult> {
	try {
		const apiUrl = `https://archive.org/wayback/available?url=${encodeURIComponent(url)}`;
		const res = await fetch(apiUrl, { signal: AbortSignal.timeout(10000) });
		if (!res.ok) return { success: false };

		const data = await res.json();
		const snapshot = data?.archived_snapshots?.closest;

		if (snapshot?.available && snapshot.url) {
			return {
				success: true,
				strategy: "Wayback Machine",
				archiveUrl: snapshot.url.replace(/^http:/, "https:"),
			};
		}
		return { success: false };
	} catch {
		return { success: false };
	}
}

/** Try Google Cache. */
async function tryGoogleCache(url: string): Promise<UnlockResult> {
	try {
		const cacheUrl = `https://webcache.googleusercontent.com/search?q=cache:${encodeURIComponent(url)}`;
		const res = await fetch(cacheUrl, {
			signal: AbortSignal.timeout(10000),
			redirect: "manual",
		});

		// Google cache returns 200 if cached, redirects/errors otherwise
		if (res.status === 200) {
			return {
				success: true,
				strategy: "Google Cache",
				archiveUrl: cacheUrl,
			};
		}
		return { success: false };
	} catch {
		return { success: false };
	}
}

/** Try archive.ph (archive.today). */
async function tryArchivePh(url: string): Promise<UnlockResult> {
	try {
		const checkUrl = `https://archive.ph/newest/${url}`;
		const res = await fetch(checkUrl, {
			signal: AbortSignal.timeout(10000),
			redirect: "manual",
		});

		// archive.ph returns 302 redirect to the archived page if it exists
		if (res.status === 301 || res.status === 302) {
			const location = res.headers.get("location");
			if (location) {
				return {
					success: true,
					strategy: "archive.ph",
					archiveUrl: location,
				};
			}
		}
		// Sometimes it returns 200 directly with the archived content
		if (res.status === 200) {
			return {
				success: true,
				strategy: "archive.ph",
				archiveUrl: checkUrl,
			};
		}
		return { success: false };
	} catch {
		return { success: false };
	}
}

/**
 * Try all unlock strategies in sequence. Returns the first successful result.
 */
export async function unlockArticle(url: string): Promise<UnlockResult> {
	// Validate URL
	try {
		new URL(url);
	} catch {
		return { success: false, error: "Invalid URL" };
	}

	// Try strategies in order
	const strategies = [tryWaybackMachine, tryGoogleCache, tryArchivePh];

	for (const strategy of strategies) {
		const result = await strategy(url);
		if (result.success) return result;
	}

	return { success: false, error: "No archived version found" };
}