import { proficiencyBonus } from "./creature-types.js";

export interface InitiativeResult {
	readonly modifier: number;
	readonly passive: number;
}

/**
 * Calculates initiative modifier and passive initiative from creature stats.
 * Returns undefined for combatants without bestiary creature data.
 */
export function calculateInitiative(creature: {
	readonly dexScore: number;
	readonly cr: string;
	readonly initiativeProficiency: number;
}): InitiativeResult {
	const dexMod = Math.floor((creature.dexScore - 10) / 2);
	const pb = proficiencyBonus(creature.cr);
	const modifier = dexMod + (creature.initiativeProficiency ?? 0) * pb;
	return { modifier, passive: 10 + modifier };
}

/**
 * Formats an initiative modifier with explicit sign.
 * Uses U+2212 (−) for negative values.
 */
export function formatInitiativeModifier(modifier: number): string {
	if (modifier >= 0) return `+${modifier}`;
	return `\u2212${Math.abs(modifier)}`;
}