export interface NotificationStats {
  tokensSaved: number;
  pruned: number;
}

export interface CompressNotificationParams {
  compressedTokens: number;
  summaryTokens: number;
  messagesCompressed: number;
  topic: string;
  summary?: string;
  showCompression?: boolean;
}

/**
 * Format token count for display (e.g. 12400 -> "~12.4K").
 */
function formatTokens(tokens: number): string {
  if (tokens >= 1000) {
    return `~${(tokens / 1000).toFixed(1)}K`;
  }
  return `~${tokens}`;
}

/**
 * Build minimal notification message.
 * Returns undefined if nothing to report.
 */
export function buildMinimalMessage(
  stats: NotificationStats,
): string | undefined {
  if (stats.tokensSaved === 0 && stats.pruned === 0) return undefined;
  return `DCP: ${formatTokens(stats.tokensSaved)} tokens saved (${stats.pruned} items pruned)`;
}

/**
 * Build detailed notification message with pruned tool names.
 * Deduplicates tool names. Falls back to minimal when list is empty.
 */
export function buildDetailedMessage(
  stats: NotificationStats,
  prunedTools: string[],
): string | undefined {
  const base = buildMinimalMessage(stats);
  if (!base) return undefined;
  const unique = [...new Set(prunedTools)];
  if (unique.length === 0) return base;
  return `${base}\nPruned: ${unique.join(", ")}`;
}

/**
 * Build minimal compression notification.
 * Format: "DCP: ~12.4K tokens compressed (~2.1K summary, 5 messages)"
 */
export function buildCompressNotificationMinimal(
  params: CompressNotificationParams,
): string {
  const plural = params.messagesCompressed === 1 ? "message" : "messages";
  return `DCP: ${formatTokens(params.compressedTokens)} tokens compressed (${formatTokens(params.summaryTokens)} summary, ${params.messagesCompressed} ${plural})`;
}

/**
 * Build detailed compression notification with topic and optional summary.
 * Summary text is only included when showCompression is true.
 */
export function buildCompressNotificationDetailed(
  params: CompressNotificationParams,
): string {
  let msg = buildCompressNotificationMinimal(params);
  msg += `\nTopic: ${params.topic}`;
  if (params.showCompression && params.summary) {
    msg += `\nSummary (${formatTokens(params.summaryTokens)}): ${params.summary}`;
  }
  return msg;
}