import { tryParseJson } from "@oh-my-pi/pi-utils";
import type { RenderResult, SpecialHandler } from "./types";
import { buildResult, formatIsoDate, htmlToBasicMarkdown, loadPage } from "./types";

interface SOQuestion {
	title: string;
	body: string;
	score: number;
	owner: { display_name: string };
	creation_date: number;
	tags: string[];
	answer_count: number;
	is_answered: boolean;
}

interface SOAnswer {
	body: string;
	score: number;
	is_accepted: boolean;
	owner: { display_name: string };
	creation_date: number;
}

// Standalone SE network sites (not *.stackexchange.com subdomains)
const STANDALONE_SE_SITES: Record<string, string> = {
	"stackoverflow.com": "stackoverflow",
	"superuser.com": "superuser",
	"serverfault.com": "serverfault",
	"askubuntu.com": "askubuntu",
	"mathoverflow.net": "mathoverflow",
	"stackapps.com": "stackapps",
};

/**
 * Extract the API site parameter from a Stack Exchange hostname
 * Returns null if not a recognized SE site
 */
function getSiteParam(hostname: string): string | null {
	// Remove www. prefix if present
	const host = hostname.replace(/^www\./, "");

	// Check standalone sites first
	if (STANDALONE_SE_SITES[host]) {
		return STANDALONE_SE_SITES[host];
	}

	// Handle *.stackexchange.com subdomains (e.g., unix.stackexchange.com → unix)
	const seMatch = host.match(/^([a-z0-9-]+)\.stackexchange\.com$/);
	if (seMatch) {
		return seMatch[1];
	}

	return null;
}

/**
 * Handle Stack Exchange network URLs via API
 * Supports stackoverflow.com, *.stackexchange.com, superuser.com, serverfault.com, askubuntu.com, etc.
 */
export const handleStackOverflow: SpecialHandler = async (
	url: string,
	timeout: number,
	signal?: AbortSignal,
): Promise<RenderResult | null> => {
	try {
		const parsed = new URL(url);
		const site = getSiteParam(parsed.hostname);
		if (!site) return null;

		// Extract question ID from URL patterns like /questions/12345/...
		const match = parsed.pathname.match(/\/questions\/(\d+)/);
		if (!match) return null;

		const questionId = match[1];
		const fetchedAt = new Date().toISOString();

		// Fetch question with answers
		const apiUrl = `https://api.stackexchange.com/2.3/questions/${questionId}?order=desc&sort=votes&site=${site}&filter=withbody`;
		const qResult = await loadPage(apiUrl, { timeout, signal });

		if (!qResult.ok) return null;

		const qData = tryParseJson<{ items: SOQuestion[] }>(qResult.content);
		if (!qData?.items?.length) return null;

		const question = qData.items[0];

		let md = `# ${question.title}\n\n`;
		md += `**Score:** ${question.score} · **Answers:** ${question.answer_count}`;
		md += question.is_answered ? " (Answered)" : "";
		md += `\n**Tags:** ${question.tags.join(", ")}\n`;
		md += `**Asked by:** ${question.owner.display_name} · ${formatIsoDate(question.creation_date * 1000)}\n\n`;
		md += `---\n\n## Question\n\n${await htmlToBasicMarkdown(question.body)}\n\n`;

		// Fetch answers
		const aUrl = `https://api.stackexchange.com/2.3/questions/${questionId}/answers?order=desc&sort=votes&site=${site}&filter=withbody`;
		const aResult = await loadPage(aUrl, { timeout, signal });

		if (aResult.ok) {
			const aData = tryParseJson<{ items: SOAnswer[] }>(aResult.content);
			if (aData?.items?.length) {
				md += `---\n\n## Answers\n\n`;
				for (const answer of aData.items.slice(0, 5)) {
					const accepted = answer.is_accepted ? " (Accepted)" : "";
					md += `### Score: ${answer.score}${accepted} · by ${answer.owner.display_name}\n\n`;
					md += `${await htmlToBasicMarkdown(answer.body)}\n\n---\n\n`;
				}
			}
		}

		return buildResult(md, {
			url,
			method: "stackexchange",
			fetchedAt,
			notes: [`Fetched via Stack Exchange API (site=${site})`],
		});
	} catch {}

	return null;
};