import { ApiError, badRequest } from "@/lib/api/errors";
import { decodeCursor, encodeCursor } from "@/lib/search/cursor";
import { buildQsirchQuery } from "@/lib/search/queryBuilder";
import { mapQsirchItemToSearchItem } from "@/lib/search/pathMapping";

/**
 * Qsirch provider (sync-first).
 *
 * Auth model:
 * - Qsirch requests are authenticated using QTS session cookies (NAS_SID / NAS_USER).
 * - We obtain NAS_SID via the QTS auth endpoint:
 *     /cgi-bin/authLogin.cgi?user=...&pwd=...&serviceKey=1&...
 *
 * Notes:
 * - We cache NAS_SID in-memory and refresh on 401 responses.
 * - We do NOT expose Qsirch/QTS internals to API clients.
 */

function isBlank(v) {
	return v === undefined || v === null || String(v).trim() === "";
}

function normalizeBaseUrl(baseUrl) {
	const raw = String(baseUrl || "").trim();
	if (!raw) return null;

	// Basic normalization: remove trailing slash.
	return raw.endsWith("/") ? raw.slice(0, -1) : raw;
}

function encodePasswordForQts(password) {
	// QNAP docs mention an "ezEncode" step; the examples show base64 encoding.
	// We encode UTF-8 bytes as base64.
	return Buffer.from(String(password), "utf8").toString("base64");
}

function extractXmlTagValue(xml, tag) {
	const re1 = new RegExp(`<${tag}><!\\[CDATA\\[(.*?)\\]\\]><\\/${tag}>`, "i");
	const re2 = new RegExp(`<${tag}>(.*?)<\\/${tag}>`, "i");

	const m1 = String(xml).match(re1);
	if (m1 && m1[1]) return m1[1].trim();

	const m2 = String(xml).match(re2);
	if (m2 && m2[1]) return m2[1].trim();

	return null;
}

async function qtsLogin({ baseUrl, account, password, fetchImpl }) {
	const url = new URL(`${baseUrl}/cgi-bin/authLogin.cgi`);

	url.searchParams.set("user", account);
	url.searchParams.set("pwd", encodePasswordForQts(password));
	url.searchParams.set("serviceKey", "1");
	url.searchParams.set("remme", "0");

	// Random param often used by QNAP examples to avoid caching.
	url.searchParams.set("r", String(Math.random()));

	let res;
	try {
		res = await fetchImpl(url.toString(), {
			method: "GET",
			headers: { Accept: "text/xml, application/xml, text/plain, */*" },
			cache: "no-store",
		});
	} catch (err) {
		throw new ApiError({
			status: 500,
			code: "SEARCH_BACKEND_UNAVAILABLE",
			message: "Internal server error",
			cause: err,
		});
	}

	const text = await res.text().catch(() => "");

	// QTS auth endpoint typically returns 200 even for failed logins
	// and indicates the outcome in the XML body.
	const authSid = extractXmlTagValue(text, "authSid");

	if (!authSid) {
		const errorValue = extractXmlTagValue(text, "errorValue");
		throw new ApiError({
			status: 500,
			code: "SEARCH_BACKEND_UNAVAILABLE",
			message: "Internal server error",
			details: errorValue ? { errorValue } : undefined,
		});
	}

	return authSid;
}

function buildCookieHeader({ account, sid }) {
	// Minimal cookies required for many QTS-protected requests.
	// Additional cookies may exist in browser sessions, but NAS_USER+NAS_SID
	// is typically sufficient for server-to-server calls.
	return `NAS_USER=${account}; NAS_SID=${sid}`;
}

function buildSnippet(content, q) {
	if (typeof content !== "string") return undefined;

	// Collapse whitespace for stable UI rendering.
	const text = content.replace(/\s+/g, " ").trim();
	if (!text) return undefined;

	// If we have a query term, attempt to center the snippet around it.
	const needle =
		typeof q === "string" && q.trim() ? q.trim().toLowerCase() : null;

	const MAX = 240;

	if (!needle) {
		return text.length > MAX ? `${text.slice(0, MAX)}…` : text;
	}

	const hay = text.toLowerCase();
	const idx = hay.indexOf(needle);

	if (idx === -1) {
		return text.length > MAX ? `${text.slice(0, MAX)}…` : text;
	}

	const start = Math.max(0, idx - 80);
	const end = Math.min(text.length, start + MAX);

	const chunk = text.slice(start, end).trim();
	if (!chunk) return undefined;

	return (start > 0 ? "…" : "") + chunk + (end < text.length ? "…" : "");
}

export function createQsirchProvider({
	baseUrl,
	account,
	password,
	pathPrefix,
	dateField = "modified",
	mode = "sync",
}) {
	const base = normalizeBaseUrl(baseUrl);

	if (!base || isBlank(account) || isBlank(password) || isBlank(pathPrefix)) {
		throw new ApiError({
			status: 500,
			code: "SEARCH_BACKEND_UNAVAILABLE",
			message: "Internal server error",
		});
	}

	let cachedSid = null;
	let sidPromise = null;

	async function getSid(fetchImpl) {
		if (cachedSid) return cachedSid;
		if (sidPromise) return sidPromise;

		sidPromise = (async () => {
			const sid = await qtsLogin({
				baseUrl: base,
				account,
				password,
				fetchImpl,
			});
			cachedSid = sid;
			return sid;
		})();

		try {
			return await sidPromise;
		} finally {
			sidPromise = null;
		}
	}

	async function qsirchSearchOnce({ fetchImpl, sid, q, limit, offset }) {
		const url = new URL(`${base}/qsirch/latest/api/search/`);

		// Required
		url.searchParams.set("q", q);

		// Pagination
		url.searchParams.set("limit", String(limit));
		url.searchParams.set("offset", String(offset));

		// Avoid heavy/irrelevant data
		url.searchParams.set("show_folder", "0"); // files only
		url.searchParams.set("show_hidden", "0");
		url.searchParams.set("show_absolute_path", "0"); // share path (not physical)
		url.searchParams.set("store_history", "0"); // do not store query history
		url.searchParams.set("tools", "0");
		url.searchParams.set("tools_resp", "1");
		url.searchParams.set("tools_limit_items", "50000");

		// Permission checks on QTS side (defense-in-depth)
		url.searchParams.set("file_status", "1");

		// We keep highlight params default-compatible but do not rely on them.
		url.searchParams.set("pre_highlight_tag", "<em>");
		url.searchParams.set("post_highlight_tag", "</em>");
		url.searchParams.set("highlight_limit", "250");

		const headers = {
			accept: "application/json",
			cookie: buildCookieHeader({ account, sid }),
		};

		const res = await fetchImpl(url.toString(), {
			method: "GET",
			headers,
			cache: "no-store",
		});

		return res;
	}

	async function qsirchSearch({ fetchImpl, q, limit, offset }) {
		let sid = await getSid(fetchImpl);

		// Try once with the cached sid.
		let res;
		try {
			res = await qsirchSearchOnce({ fetchImpl, sid, q, limit, offset });
		} catch (err) {
			throw new ApiError({
				status: 500,
				code: "SEARCH_BACKEND_UNAVAILABLE",
				message: "Internal server error",
				cause: err,
			});
		}

		// If SID expired, clear and retry once with a fresh SID.
		if (res.status === 401) {
			cachedSid = null;
			sid = await getSid(fetchImpl);

			res = await qsirchSearchOnce({ fetchImpl, sid, q, limit, offset });
		}

		if (!res.ok) {
			throw new ApiError({
				status: 500,
				code: "SEARCH_BACKEND_UNAVAILABLE",
				message: "Internal server error",
			});
		}

		let payload;
		try {
			payload = await res.json();
		} catch (err) {
			throw new ApiError({
				status: 500,
				code: "SEARCH_BACKEND_UNAVAILABLE",
				message: "Internal server error",
				cause: err,
			});
		}

		return payload;
	}

	return {
		/**
		 * @param {{
		 *   mode: "branch"|"multi"|"all",
		 *   branches: string[]|null,
		 *   q: string|null,
		 *   from: string|null,
		 *   to: string|null,
		 *   limit: number,
		 *   cursor: string|null
		 * }} input
		 */
		async search(input) {
			const fetchImpl = input?.fetchImpl || fetch;

			// We support sync now; async will be added later without changing the public API.
			// "auto" currently behaves like "sync" to keep behavior predictable.
			const effectiveMode = mode === "async" ? "async" : "sync";
			if (effectiveMode !== "sync") {
				throw new ApiError({
					status: 500,
					code: "SEARCH_BACKEND_UNAVAILABLE",
					message: "Internal server error",
				});
			}

			const { mode: searchMode, branches, q, from, to, limit } = input || {};

			if (!Number.isInteger(limit) || limit < 1) {
				throw badRequest("VALIDATION_SEARCH_LIMIT", "Invalid limit parameter");
			}

			const decoded = decodeCursor(input?.cursor || null);
			if (decoded.mode !== "sync") {
				throw badRequest("VALIDATION_SEARCH_CURSOR", "Invalid cursor");
			}

			const offset = decoded.offset;

			const qsirchQ = buildQsirchQuery({
				mode: searchMode,
				branches: branches || null,
				q,
				from,
				to,
				dateField,
				pathPrefix,
			});

			const payload = await qsirchSearch({
				fetchImpl,
				q: qsirchQ,
				limit,
				offset,
			});

			const total =
				typeof payload?.total === "number"
					? payload.total
					: Number(payload?.total);

			const rawItems = Array.isArray(payload?.items) ? payload.items : [];

			const items = rawItems
				.map((it) => {
					const mapped = mapQsirchItemToSearchItem(it, { pathPrefix });

					if (!mapped) return null;

					const snippet = buildSnippet(it?.content, q);

					const result = {
						branch: mapped.branch,
						date: mapped.date,
						year: mapped.year,
						month: mapped.month,
						day: mapped.day,
						filename: mapped.filename,
						relativePath: mapped.relativePath,
					};

					if (typeof it?.score === "number") result.score = it.score;
					if (snippet) result.snippet = snippet;

					return result;
				})
				.filter(Boolean);

			// Pagination:
			// Use rawItems.length (not mapped length) to avoid repeating pages if we drop items.
			const rawCount = rawItems.length;
			const hasMore =
				Number.isFinite(total) && rawCount > 0 && offset + rawCount < total;

			const nextCursor = hasMore
				? encodeCursor({ v: 1, mode: "sync", offset: offset + rawCount })
				: null;

			return { items, nextCursor };
		},
	};
}