rpg-mcp

/** * PHASE-2: Social Hearing Mechanics - Stealth vs Perception Opposed Rolls * * Implements D&D 5e-style opposed checks for eavesdropping detection: * - Speaker rolls Stealth (d20 + DEX modifier + stealthBonus) * - Listener rolls Perception (d20 + WIS modifier + perceptionBonus) * - If listener's total >= speaker's total, they hear the conversation */ import { Character, NPC } from '../../schema/character.js'; export interface OpposedRollResult { // Speaker (trying to be stealthy) speakerRoll: number; // Raw d20 roll speakerModifier: number; // DEX mod + stealthBonus speakerTotal: number; // Roll + modifier // Listener (trying to perceive) listenerRoll: number; // Raw d20 roll listenerModifier: number; // WIS mod + perceptionBonus listenerTotal: number; // Roll + modifier // Result success: boolean; // Did listener hear it? margin: number; // How much they beat/missed by } /** * Calculate ability modifier from ability score (D&D 5e formula) * * @param abilityScore - Ability score (1-30, typically 3-20) * @returns Modifier (-5 to +10 typically) */ export function getModifier(abilityScore: number): number { return Math.floor((abilityScore - 10) / 2); } /** * Roll a d20 (1-20) */ function rollD20(): number { return Math.floor(Math.random() * 20) + 1; } /** * Perform a Stealth vs Perception opposed roll * * Speaker tries to hide their conversation (Stealth check) * Listener tries to overhear (Perception check) * * @param speaker - Character attempting stealth * @param listener - Character attempting perception * @param environmentModifier - Optional modifier from environment (e.g., -5 for noisy tavern) * @returns Detailed result of the opposed roll */ export function rollStealthVsPerception( speaker: Character | NPC, listener: Character | NPC, environmentModifier: number = 0 ): OpposedRollResult { // Speaker's Stealth check const speakerRoll = rollD20(); const dexModifier = getModifier(speaker.stats.dex); const speakerStealthBonus = speaker.stealthBonus || 0; const speakerModifier = dexModifier + speakerStealthBonus; const speakerTotal = speakerRoll + speakerModifier; // Listener's Perception check const listenerRoll = rollD20(); const wisModifier = getModifier(listener.stats.wis); // Fixed: should be listener's WIS, not speaker's const listenerPerceptionBonus = listener.perceptionBonus || 0; const listenerModifier = wisModifier + listenerPerceptionBonus + environmentModifier; const listenerTotal = listenerRoll + listenerModifier; // Listener succeeds if their total >= speaker's total const success = listenerTotal >= speakerTotal; const margin = listenerTotal - speakerTotal; return { speakerRoll, speakerModifier, speakerTotal, listenerRoll, listenerModifier, listenerTotal, success, margin }; } /** * Determine environment modifier based on atmospherics * * @param atmospherics - Room atmospheric effects * @returns Modifier to apply to Perception checks */ export function getEnvironmentModifier(atmospherics: string[]): number { let modifier = 0; // SILENCE makes it easier to hear (no background noise) if (atmospherics.includes('SILENCE')) { modifier += 5; } // FOG doesn't affect hearing (visual only) // DARKNESS doesn't affect hearing // ANTIMAGIC doesn't affect natural hearing return modifier; } /** * Check if character is deafened (cannot hear) * * @param character - Character to check * @returns true if character cannot hear */ export function isDeafened(character: Character | NPC): boolean { return character.conditions?.some(c => c.name === 'DEAFENED') || false; } /** * Batch process opposed rolls for multiple listeners * * Optimized for scenarios where one speaker is heard by many listeners * * @param speaker - The character speaking * @param listeners - Array of characters trying to hear * @param environmentModifier - Modifier from environment * @returns Map of listenerId -> OpposedRollResult */ export function batchRollStealthVsPerception( speaker: Character | NPC, listeners: Array<Character | NPC>, environmentModifier: number = 0 ): Map<string, OpposedRollResult> { const results = new Map<string, OpposedRollResult>(); for (const listener of listeners) { // Skip deafened listeners if (isDeafened(listener)) { continue; } const result = rollStealthVsPerception(speaker, listener, environmentModifier); results.set(listener.id, result); } return results; }