/** Braille spinner frames for animated running indicator. */
export const SPINNER = ["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"];

/** Tool name → human-readable action for activity descriptions. */
const TOOL_DISPLAY: Record<string, string> = {
  read: "reading",
  bash: "running command",
  edit: "editing",
  write: "writing",
  grep: "searching",
  find: "finding files",
  ls: "listing",
};

/** Format milliseconds as human-readable duration: "11.2s". */
export function formatMs(ms: number): string {
  return `${(ms / 1000).toFixed(1)}s`;
}

/** Format a token count compactly: "500 token", "12.3k token", "1.2M token". */
export function formatTokens(count: number): string {
  if (count >= 1_000_000) return `${(count / 1_000_000).toFixed(1)}M token`;
  if (count >= 1_000) return `${(count / 1_000).toFixed(1)}k token`;
  return `${count} token`;
}

/** Format turn count with optional max limit: "↻5≤30" or "↻5". */
export function formatTurns(turnCount: number, maxTurns?: number | null): string {
  return maxTurns != null ? `↻${turnCount}≤${maxTurns}` : `↻${turnCount}`;
}

/** Truncate text to a single line, max `len` chars. */
function truncateLine(text: string, len = 60): string {
  const line = text
    .split("\n")
    .find((l) => l.trim())
    ?.trim() ?? "";
  if (line.length <= len) return line;
  return `${line.slice(0, len)}...`;
}

/** Build a human-readable activity string from currently-running tools or response text. */
export function describeActivity(
  activeTools: readonly string[],
  responseText?: string,
): string {
  if (activeTools.length > 0) {
    const groups = new Map<string, number>();
    for (const toolName of activeTools) {
      const action = TOOL_DISPLAY[toolName] ?? toolName;
      groups.set(action, (groups.get(action) ?? 0) + 1);
    }

    const parts: string[] = [];
    for (const [action, count] of groups) {
      if (count > 1) {
        parts.push(`${action} ${count} ${action === "searching" ? "patterns" : "files"}`);
      } else {
        parts.push(action);
      }
    }
    return `${parts.join(", ")}…`;
  }

  if (responseText && responseText.trim().length > 0) {
    return truncateLine(responseText);
  }

  return "thinking…";
}