import type { ListResponse } from "$lib/types";

/**
 * UI list page size (explicit `limit=` on fetches).
 * API default when limit is omitted remains 50 (pagination.go); keep requests explicit.
 */
export const DEFAULT_PAGE_SIZE = 25;
export const MAX_PAGE_LIMIT = 200;
/** Cap for filter/option dropdowns (API maxPageLimit). */
export const OPTION_LIST_LIMIT = 200;
/** Cap for category/tree loads (API maxTreePageLimit). */
export const TREE_LIST_LIMIT = 2000;
/** Dashboard / checklist recent jobs strip - avoid unbounded job list payloads. */
export const RECENT_JOBS_LIMIT = 10;
export const SEARCH_DEBOUNCE_MS = 300;

export function clampLimit(limit: number, max = MAX_PAGE_LIMIT): number {
	if (!Number.isFinite(limit) || limit <= 0) return DEFAULT_PAGE_SIZE;
	return Math.min(Math.floor(limit), max);
}

/** True for aborted fetch/AbortController errors (DOMException or Error). */
export function isAbortError(err: unknown): boolean {
	return (
		(err instanceof DOMException && err.name === "AbortError") ||
		(err instanceof Error && err.name === "AbortError")
	);
}

/** Run async work over items with a fixed concurrency cap; preserves result order. */
export async function mapPool<
	T,
	R
>(items: readonly T[], concurrency: number, fn: (item: T, index: number) => Promise<R>): Promise<R[]> {
	const n = items.length;
	if (n === 0) return [];
	const limit = Math.max(1, Math.min(Math.floor(concurrency) || 1, n));
	const results = new Array<R>(n);
	let next = 0;
	async function worker() {
		while (true) {
			const i = next++;
			if (i >= n) return;
			results[i] = await fn(items[i]!, i);
		}
	}
	await Promise.all(Array.from({ length: limit }, () => worker()));
	return results;
}

/** 1-based page -> offset for limit/offset APIs. */
export function pageOffset(page: number, pageSize = DEFAULT_PAGE_SIZE): number {
	const p = Math.max(1, Math.floor(Number(page)) || 1);
	const size = clampLimit(pageSize);
	return (p - 1) * size;
}

/**
	* Align with apps/api/internal/catalog MaxOffsetWithoutCursor.
	* Product list rejects OFFSET above this without cursor/after_id.
	*/
export const MAX_OFFSET_WITHOUT_CURSOR = 5000;

/** Last 1-based page still reachable via OFFSET alone. */
export function maxOffsetSafePage(pageSize = DEFAULT_PAGE_SIZE): number {
	const size = clampLimit(pageSize);
	return Math.floor(MAX_OFFSET_WITHOUT_CURSOR / size) + 1;
}

/**
	* Clamp a requested page so OFFSET stays within the API keyset gate.
	* Deep URL pages fall back to page 1 (cursor-first — do not deep-OFFSET).
	*/
export function clampPageForOffset(
	page: number,
	pageSize = DEFAULT_PAGE_SIZE
): number {
	const p = Math.max(1, Math.floor(Number(page)) || 1);
	if (pageOffset(p, pageSize) <= MAX_OFFSET_WITHOUT_CURSOR) return p;
	return 1;
}

/** Safe OFFSET for a page, or null when the page requires a keyset cursor. */
export function offsetOrNullForPage(
	page: number,
	pageSize = DEFAULT_PAGE_SIZE
): number | null {
	const offset = pageOffset(page, pageSize);
	if (offset > MAX_OFFSET_WITHOUT_CURSOR) return null;
	return offset;
}

function readTrimmedString(payload: unknown, key: string): string | null {
	if (!payload || typeof payload !== "object" || Array.isArray(payload)) return null;
	const value = (payload as Record<string, unknown>)[key];
	if (typeof value !== "string") return null;
	const trimmed = value.trim();
	return trimmed ? trimmed : null;
}

/** Opaque keyset bookmark from product list responses (`next_cursor`). */
export function unwrapNextCursor(payload: unknown): string | null {
	return readTrimmedString(payload, "next_cursor");
}

/** Tie-break id from product list responses (`next_after_id`). */
export function unwrapNextAfterId(payload: unknown): string | null {
	return readTrimmedString(payload, "next_after_id");
}

export type SequentialNextQuery = { cursor: string } | { after_id: string };

/** Bookmark that loads a page: `null` = first page (no cursor), else keyset query. */
export type PageBookmark = SequentialNextQuery | null;

/**
 * @deprecated Products UI always uses keyset (preferSequentialPagination).
 * Kept for older callers that multiply by page size.
 */
export const OFFSET_SAFE_MAX_PAGES = 0;

/**
 * Products list: always prefer sequential keyset (cursor/after_id) over OFFSET.
 * API rejects offset > MaxOffsetWithoutCursor (5000) without a cursor.
 */
export function preferSequentialPagination(
	_total?: number | null,
	_pageSize = DEFAULT_PAGE_SIZE
): boolean {
	return true;
}

/** Params for sequential "next" when the API returned a keyset bookmark.
 * Prefers opaque `cursor` over `after_id`. Null -> caller should use offset.
 */
export function sequentialNextQuery(
	nextCursor?: string | null,
	nextAfterId?: string | null
): SequentialNextQuery | null {
	const cursor = typeof nextCursor === "string" ? nextCursor.trim() : "";
	if (cursor) return { cursor };
	const afterId = typeof nextAfterId === "string" ? nextAfterId.trim() : "";
	if (afterId) return { after_id: afterId };
	return null;
}

/** Fresh stack for page 1 (no cursor). */
export function resetPageBookmarks(): PageBookmark[] {
	return [null];
}

/** Bookmark that loads 1-based `page`, or `undefined` if that page was not visited. */
export function bookmarkForPage(
	stack: readonly PageBookmark[],
	page: number
): PageBookmark | undefined {
	const p = Math.max(1, Math.floor(Number(page)) || 1);
	if (p === 1) return null;
	const idx = p - 1;
	if (idx < 0 || idx >= stack.length) return undefined;
	return stack[idx] ?? undefined;
}

/** Record the bookmark used to load 1-based `page` (truncates any deeper entries). */
export function recordPageBookmark(
	stack: readonly PageBookmark[],
	page: number,
	bookmark: PageBookmark
): PageBookmark[] {
	const p = Math.max(1, Math.floor(Number(page)) || 1);
	const out = stack.slice(0, p - 1);
	while (out.length < p - 1) out.push(null);
	out.push(bookmark);
	return out;
}

export function debounce<Args extends unknown[]>(
	fn: (...args: Args) => void,
	ms: number
): ((...args: Args) => void) & { cancel: () => void } {
	let timer: ReturnType<typeof setTimeout> | null = null;
	const wrapped = ((...args: Args) => {
		if (timer) clearTimeout(timer);
		timer = setTimeout(() => {
			timer = null;
			fn(...args);
		}, ms);
	}) as ((...args: Args) => void) & { cancel: () => void };
	wrapped.cancel = () => {
		if (timer) clearTimeout(timer);
		timer = null;
	};
	return wrapped;
}

const NAMED_LIST_KEYS = [
	"products",
	"categories",
	"attributes",
	"category_attributes",
	"api_keys",
	"files",
	"feeds",
	"export_feeds",
	"variables",
	"jobs",
	"members",
	"team",
	"items",
	"data",
	"fields",
	"groups",
	"campaigns",
	"templates",
	"orders",
	"reviews",
	"tickets",
	"notifications",
	"messages"
] as const;

export function unwrapList<T>(payload: ListResponse<T> | Record<string, unknown> | T[]): T[] {
	if (Array.isArray(payload)) return payload;
	if (!payload || typeof payload !== "object") return [];
	const record = payload as Record<string, unknown>;
	for (const key of NAMED_LIST_KEYS) {
		const value = record[key];
		if (Array.isArray(value)) return value as T[];
	}
	return [];
}

export function unwrapTotal(payload: unknown): number | null {
	if (!payload || typeof payload !== "object" || Array.isArray(payload)) return null;
	const total = (payload as Record<string, unknown>).total;
	return typeof total === "number" ? total : null;
}