/**
 * Token estimation.
 *
 * Today this is a chars/4 heuristic (same as pi's `estimateTokens`). Keeping
 * every estimate behind this module is the seam for a future real tokenizer —
 * swap the implementation here and every collector picks it up.
 */

/** Estimate tokens for arbitrary text (chars/4, same heuristic as pi's estimateTokens). */
export const textTokens = (s: string | undefined | null): number =>
	s && s.trim().length > 0 ? Math.max(1, Math.ceil(s.trim().length / 4)) : 0;

/**
 * Skills appear in the prompt as name/description/location blocks; full
 * SKILL.md content is loaded on demand, not inlined. The flat pad keeps the
 * estimate above zero.
 */
const SKILL_PROMPT_PAD = 30;

export const skillPromptTokens = (
	name: string,
	description: string,
	filePath: string,
): number => textTokens(`${name} ${description} ${filePath}`) + SKILL_PROMPT_PAD;

/**
 * Interface for message estimators — pi's `estimateTokens` conforms to it;
 * tests inject a fake. Keeps `messagesSection` free of pi runtime imports so
 * it runs under any TS runner.
 */
export type MessageEstimator = (message: unknown) => number;