/**
 * Minimal frontend-facing API client for the Lieferscheine backend.
 *
 * Goals:
 * - Centralize fetch defaults (credentials + no-store) to match backend caching rules.
 * - Provide a single, predictable error shape via ApiClientError.
 * - Offer thin domain helpers (login/logout/branches/...).
 *
 * Notes:
 * - JavaScript only (no TypeScript). We use JSDoc for "typed-by-convention".
 * - This client is intentionally small. It is not an SDK.
 */

/**
 * @typedef {Object} ApiErrorPayload
 * @property {{ message: string, code: string, details?: any }} error
 */

/**
 * A standardized client-side error type for API failures.
 * - status: HTTP status code (e.g. 401, 403, 404, 500)
 * - code: machine-readable error code (e.g. AUTH_UNAUTHENTICATED)
 * - message: human-readable message (safe to show in UI)
 * - details: optional structured payload (validation params etc.)
 */
export class ApiClientError extends Error {
	/**
	 * @param {{
	 *   status: number,
	 *   code: string,
	 *   message: string,
	 *   details?: any,
	 *   url?: string,
	 *   method?: string,
	 *   cause?: any
	 * }} input
	 */
	constructor({ status, code, message, details, url, method, cause }) {
		super(message, cause ? { cause } : undefined);
		this.name = "ApiClientError";
		this.status = status;
		this.code = code;
		if (details !== undefined) this.details = details;
		if (url) this.url = url;
		if (method) this.method = method;
	}
}

const DEFAULT_HEADERS = {
	Accept: "application/json",
};

/**
 * Resolve a request URL.
 * - If `path` is absolute (http/https), return as-is.
 * - If `baseUrl` is provided, resolve relative to it.
 * - Otherwise return the relative path (browser-friendly: "/api/...").
 *
 * @param {string} path
 * @param {string=} baseUrl
 * @returns {string}
 */
function resolveUrl(path, baseUrl) {
	if (/^https?:\/\//i.test(path)) return path;

	const base = (baseUrl || "").trim();
	if (!base) return path;

	return new URL(path, base.endsWith("/") ? base : `${base}/`).toString();
}

/**
 * Best-effort detection if response is JSON.
 *
 * @param {Response} response
 * @returns {boolean}
 */
function isJsonResponse(response) {
	const ct = response.headers.get("content-type") || "";
	return ct.toLowerCase().includes("application/json");
}

/**
 * Core fetch helper with:
 * - credentials: "include" (cookie-based session)
 * - cache: "no-store" (match backend freshness strategy)
 * - standardized error mapping into ApiClientError
 *
 * @param {string} path
 * @param {{
 *   method?: string,
 *   headers?: Record<string, string>,
 *   body?: any,
 *   baseUrl?: string,
 *   fetchImpl?: typeof fetch
 * }=} options
 * @returns {Promise<any>} parsed JSON payload (or null for empty responses)
 */
export async function apiFetch(path, options = {}) {
	const {
		method = "GET",
		headers = {},
		body,
		baseUrl,
		fetchImpl = fetch,
	} = options;

	const url = resolveUrl(path, baseUrl);

	// Build request init. We always set credentials + no-store.
	// For JSON bodies, we serialize and set Content-Type.
	const init = {
		method,
		credentials: "include",
		cache: "no-store",
		headers: { ...DEFAULT_HEADERS, ...headers },
	};

	if (body !== undefined) {
		// If the caller passes a string, we assume it is already serialized.
		// Otherwise we serialize as JSON.
		if (typeof body === "string") {
			init.body = body;
		} else {
			init.body = JSON.stringify(body);
			// Only set Content-Type if caller didn't provide it.
			if (!init.headers["Content-Type"]) {
				init.headers["Content-Type"] = "application/json";
			}
		}
	}

	let response;
	try {
		response = await fetchImpl(url, init);
	} catch (err) {
		// Network errors, DNS errors, connection refused, etc.
		throw new ApiClientError({
			status: 0,
			code: "CLIENT_NETWORK_ERROR",
			message: "Network error",
			url,
			method,
			cause: err,
		});
	}

	// Handle empty responses explicitly (e.g. some endpoints might return 204 later).
	if (response.status === 204) return null;

	// Prefer JSON when the server says it's JSON.
	if (isJsonResponse(response)) {
		let payload;
		try {
			payload = await response.json();
		} catch (err) {
			throw new ApiClientError({
				status: response.status,
				code: "CLIENT_INVALID_JSON",
				message: "Invalid JSON response",
				url,
				method,
				cause: err,
			});
		}

		if (response.ok) return payload;

		/** @type {ApiErrorPayload|any} */
		const maybeError = payload;

		// Map standardized backend errors
		if (maybeError?.error?.code && maybeError?.error?.message) {
			throw new ApiClientError({
				status: response.status,
				code: maybeError.error.code,
				message: maybeError.error.message,
				details: maybeError.error.details,
				url,
				method,
			});
		}

		// Fallback for non-standard error JSON
		throw new ApiClientError({
			status: response.status,
			code: "CLIENT_HTTP_ERROR",
			message: `Request failed with status ${response.status}`,
			details: payload,
			url,
			method,
		});
	}

	// Non-JSON response fallback (should be rare for current endpoints)
	const text = await response.text().catch(() => "");
	if (response.ok) return text || null;

	throw new ApiClientError({
		status: response.status,
		code: "CLIENT_HTTP_ERROR",
		message: text || `Request failed with status ${response.status}`,
		url,
		method,
	});
}

/* -------------------------------------------------------------------------- */
/* Domain helpers (thin wrappers)                                              */
/* -------------------------------------------------------------------------- */

/**
 * @param {{ username: string, password: string }} input
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function login(input, options) {
	return apiFetch("/api/auth/login", {
		method: "POST",
		body: input,
		...options,
	});
}

/**
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function logout(options) {
	return apiFetch("/api/auth/logout", { method: "GET", ...options });
}

/**
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function getBranches(options) {
	return apiFetch("/api/branches", { method: "GET", ...options });
}

/**
 * @param {string} branch
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function getYears(branch, options) {
	return apiFetch(`/api/branches/${encodeURIComponent(branch)}/years`, {
		method: "GET",
		...options,
	});
}

/**
 * @param {string} branch
 * @param {string} year
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function getMonths(branch, year, options) {
	return apiFetch(
		`/api/branches/${encodeURIComponent(branch)}/${encodeURIComponent(
			year
		)}/months`,
		{ method: "GET", ...options }
	);
}

/**
 * @param {string} branch
 * @param {string} year
 * @param {string} month
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function getDays(branch, year, month, options) {
	return apiFetch(
		`/api/branches/${encodeURIComponent(branch)}/${encodeURIComponent(
			year
		)}/${encodeURIComponent(month)}/days`,
		{ method: "GET", ...options }
	);
}

/**
 * @param {string} branch
 * @param {string} year
 * @param {string} month
 * @param {string} day
 * @param {{ baseUrl?: string, fetchImpl?: typeof fetch }=} options
 */
export function getFiles(branch, year, month, day, options) {
	const qs = new URLSearchParams({
		branch: String(branch),
		year: String(year),
		month: String(month),
		day: String(day),
	});

	return apiFetch(`/api/files?${qs.toString()}`, { method: "GET", ...options });
}