/**
 * Time parsing utilities for status gatherers
 */

const TIME_UNITS: Record<string, number> = {
	h: 60 * 60 * 1000,
	d: 24 * 60 * 60 * 1000,
	w: 7 * 24 * 60 * 60 * 1000,
};

/**
 * Parse time constraint string to milliseconds
 * @example parseTimeConstraint("24h") → 86400000
 * @example parseTimeConstraint("7d") → 604800000
 * @example parseTimeConstraint("2w") → 1209600000
 */
export function parseTimeConstraint(input: string): number {
	const match = input.match(/^(\d+)([hdw])$/i);
	if (!match) {
		throw new Error(
			`Invalid time constraint: ${input}. Use format like "24h", "7d", or "2w"`,
		);
	}
	const [, value, unit] = match;
	const multiplier = TIME_UNITS[unit.toLowerCase()];
	if (!multiplier) {
		throw new Error(`Unknown time unit: ${unit}`);
	}
	return parseInt(value, 10) * multiplier;
}

/**
 * Get cutoff Date from milliseconds offset
 */
export function toCutoffDate(ms: number): Date {
	return new Date(Date.now() - ms);
}

/**
 * Convert to git --since format
 * @example toGitSince(86400000) → "2024-12-21T12:00:00"
 */
export function toGitSince(ms: number): string {
	return toCutoffDate(ms).toISOString().replace("Z", "");
}

/**
 * Convert to ISO 8601 duration for Linear
 * @example toISOPeriod(86400000) → "-P1D" (1 day)
 * @example toISOPeriod(604800000) → "-P7D" (7 days)
 */
export function toISOPeriod(ms: number): string {
	const hours = ms / (60 * 60 * 1000);
	if (hours < 24) {
		return `-PT${Math.round(hours)}H`;
	}
	const days = Math.round(hours / 24);
	return `-P${days}D`;
}

/**
 * Convert to human-readable relative time
 * @example toRelativeTime(new Date(Date.now() - 3600000)) → "1 hour ago"
 */
export function toRelativeTime(date: Date | string): string {
	const d = typeof date === "string" ? new Date(date) : date;
	const ms = Date.now() - d.getTime();

	if (ms < 60 * 1000) return "just now";
	if (ms < 60 * 60 * 1000) {
		const mins = Math.floor(ms / (60 * 1000));
		return `${mins} minute${mins === 1 ? "" : "s"} ago`;
	}
	if (ms < 24 * 60 * 60 * 1000) {
		const hours = Math.floor(ms / (60 * 60 * 1000));
		return `${hours} hour${hours === 1 ? "" : "s"} ago`;
	}
	const days = Math.floor(ms / (24 * 60 * 60 * 1000));
	return `${days} day${days === 1 ? "" : "s"} ago`;
}

/**
 * Filter items by updated_at field within time window
 */
export function filterByTime<
	T extends { updated_at?: string; updatedAt?: string },
>(items: T[], ms: number): T[] {
	const cutoff = toCutoffDate(ms);
	return items.filter((item) => {
		const updatedAt = item.updated_at || item.updatedAt;
		if (!updatedAt) return false;
		return new Date(updatedAt) >= cutoff;
	});
}

/**
 * Format time constraint for display
 * @example formatTimeConstraint("24h") → "last 24 hours"
 */
export function formatTimeConstraint(input: string): string {
	const match = input.match(/^(\d+)([hdw])$/i);
	if (!match) return input;

	const [, value, unit] = match;
	const num = parseInt(value, 10);

	switch (unit.toLowerCase()) {
		case "h":
			return `last ${num} hour${num === 1 ? "" : "s"}`;
		case "d":
			return `last ${num} day${num === 1 ? "" : "s"}`;
		case "w":
			return `last ${num} week${num === 1 ? "" : "s"}`;
		default:
			return input;
	}
}