/**
 * Pure command-palette search helpers (filter + rank).
 * No Svelte / i18n / $app — safe for node:test.
 */

export type PaletteSearchItem = {
	id: string;
	label: string;
	keywords: string;
};

/** Trim + lowercase; empty when the user has not typed a query yet. */
export function normalizePaletteQuery(query: string): string {
	return query.trim().toLowerCase();
}

function escapeRegExp(value: string): string {
	return value.replace(/[.*+?^${}()|[\]\\]/g, "\\$&");
}

/** True when `token` starts a whole word in `hay` (space-separated). */
function wordStartsWith(hay: string, token: string): boolean {
	if (!token) return false;
	return new RegExp(`(?:^|\\s)${escapeRegExp(token)}`).test(hay);
}

/**
 * Score one query token against label + keywords.
 * Higher = better match. 0 = no match.
 */
export function scorePaletteToken(token: string, label: string, keywords: string): number {
	const t = token.trim().toLowerCase();
	if (!t) return 0;
	const lab = label.toLowerCase();
	const keys = keywords.toLowerCase();

	if (lab === t) return 100;
	if (lab.startsWith(t)) return 80;
	if (wordStartsWith(lab, t)) return 70;
	if (lab.includes(t)) return 50;
	if (wordStartsWith(keys, t)) return 40;
	if (keys.includes(t)) return 20;
	return 0;
}

/**
 * Score an item for a full query. Multi-token queries use AND:
 * every token must score > 0; total is the sum.
 * Empty query scores 1 (preserve input order when idle).
 */
export function scorePaletteItem(query: string, item: PaletteSearchItem): number {
	const q = normalizePaletteQuery(query);
	if (!q) return 1;

	const tokens = q.split(/\s+/).filter(Boolean);
	let total = 0;
	for (const token of tokens) {
		const part = scorePaletteToken(token, item.label, item.keywords);
		if (part <= 0) return 0;
		total += part;
	}
	return total;
}

/**
 * Filter out non-matches and rank by score (desc), then label (asc).
 * Empty / whitespace query returns items in original order.
 */
export function filterAndRankPaletteItems<T extends PaletteSearchItem>(
	query: string,
	items: readonly T[]
): T[] {
	const q = normalizePaletteQuery(query);
	if (!q) return [...items];

	return items
		.map((item) => ({ item, score: scorePaletteItem(q, item) }))
		.filter((row) => row.score > 0)
		.sort((a, b) => {
			if (b.score !== a.score) return b.score - a.score;
			return a.item.label.localeCompare(b.item.label);
		})
		.map((row) => row.item);
}

/**
 * Platform-aware shortcut hint for discoverability (⌘K vs Ctrl+K).
 * Pass `platform` in tests; defaults to `navigator.platform` / `userAgent` in browser.
 */
export function commandPaletteShortcutLabel(
	platform?: string | null,
	userAgent?: string | null
): string {
	const p = (platform ?? "").toLowerCase();
	const ua = (userAgent ?? "").toLowerCase();
	const hay = `${p} ${ua}`;
	if (
		hay.includes("mac") ||
		hay.includes("iphone") ||
		hay.includes("ipad") ||
		hay.includes("ipod")
	) {
		return "⌘K";
	}
	return "Ctrl+K";
}

/** Resolve shortcut from the current environment (SSR-safe). */
export function commandPaletteShortcutLabelFromEnv(): string {
	if (typeof navigator === "undefined") return "Ctrl+K";
	return commandPaletteShortcutLabel(navigator.platform, navigator.userAgent);
}