import { browser } from '$app/environment';
import type { JobRow } from './types.js';

export const TOKEN_STORAGE_KEY = 'evobgp_api_token';

export type Problem = {
	type?: string;
	title?: string;
	status?: number;
	detail?: string;
};

function getToken(): string | null {
	if (!browser) return null;
	return localStorage.getItem(TOKEN_STORAGE_KEY);
}

function mergeHeaders(init?: RequestInit, extraHeaders?: Record<string, string>): Headers {
	const h = new Headers(init?.headers);
	if (!h.has('Accept')) h.set('Accept', 'application/json');
	const t = getToken();
	if (t && !h.has('Authorization')) h.set('Authorization', `Bearer ${t}`);
	if (extraHeaders) {
		for (const [k, v] of Object.entries(extraHeaders)) {
			if (!h.has(k)) h.set(k, v);
		}
	}
	return h;
}

/**
 * Idempotency keys: `crypto.randomUUID()` exists only in secure contexts (HTTPS / localhost).
 * Over plain HTTP to a LAN IP it is often undefined — use getRandomValues or a fallback.
 */
function newIdempotencyKey(): string {
	const c = typeof globalThis !== 'undefined' ? globalThis.crypto : undefined;
	if (c?.randomUUID) return c.randomUUID();
	if (c?.getRandomValues) {
		const buf = new Uint8Array(16);
		c.getRandomValues(buf);
		buf[6] = (buf[6]! & 0x0f) | 0x40;
		buf[8] = (buf[8]! & 0x3f) | 0x80;
		const hex = [...buf].map((b) => b.toString(16).padStart(2, '0')).join('');
		return `${hex.slice(0, 8)}-${hex.slice(8, 12)}-${hex.slice(12, 16)}-${hex.slice(16, 20)}-${hex.slice(20)}`;
	}
	return `idem-${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 14)}`;
}

export class ApiError extends Error {
	constructor(
		public readonly status: number,
		message: string,
		public readonly problem?: Problem
	) {
		super(message);
	}
}

export async function apiFetch(path: string, init?: RequestInit): Promise<Response> {
	if (!browser) throw new Error('API is only available in the browser');
	return fetch(path, { ...init, headers: mergeHeaders(init) });
}

/** GET / DELETE без тела */
export async function apiJSON<T>(path: string, init?: RequestInit): Promise<T> {
	const res = await apiFetch(path, init);
	return parseResponse<T>(res);
}

/** POST / PATCH / PUT с JSON-телом и автоматическим Idempotency-Key */
export async function apiMutate<T = void>(
	path: string,
	method: 'POST' | 'PATCH' | 'PUT' | 'DELETE',
	body?: unknown,
	opts?: { idempotent?: boolean }
): Promise<T> {
	const headers: Record<string, string> = {};
	if (body !== undefined) headers['Content-Type'] = 'application/json';
	if (opts?.idempotent !== false) {
		headers['Idempotency-Key'] = newIdempotencyKey();
	}
	const res = await fetch(path, {
		method,
		headers: mergeHeaders({ headers }, headers),
		body: body !== undefined ? JSON.stringify(body) : undefined
	});
	return parseResponse<T>(res);
}

async function parseResponse<T>(res: Response): Promise<T> {
	if (res.status === 204 || res.status === 205) return undefined as T;
	const text = await res.text();
	if (!res.ok) {
		let problem: Problem | undefined;
		let detail = `HTTP ${res.status}`;
		try {
			problem = JSON.parse(text) as Problem;
			detail = problem.detail ?? problem.title ?? detail;
		} catch {
			if (text) detail = text;
		}
		throw new ApiError(res.status, detail, problem);
	}
	if (!text) return undefined as T;
	return JSON.parse(text) as T;
}

const terminalJobStatuses = new Set(['succeeded', 'failed', 'cancelled']);

/** Ожидает завершения фоновой задачи (poll GET /v1/jobs/{id}). */
export async function waitForJob(
	jobId: string,
	opts?: { pollMs?: number; timeoutMs?: number }
): Promise<JobRow> {
	const pollMs = opts?.pollMs ?? 400;
	const timeoutMs = opts?.timeoutMs ?? 120000;
	const deadline = Date.now() + timeoutMs;
	while (Date.now() < deadline) {
		const j = await apiJSON<JobRow>(`/v1/jobs/${jobId}`);
		if (terminalJobStatuses.has(j.status)) return j;
		await new Promise((r) => setTimeout(r, pollMs));
	}
	throw new Error(`Таймаут ожидания задачи ${jobId}`);
}