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libs/mission-logic/src/lib/encounter-resolver.ts

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+import {
+  EncounterResult,
+  MissionDifficulty,
+  MissionState,
+  ResolveEncounterInput,
+  SurvivorStats
+} from '@fog-explorer/api-interfaces';
+
+import { applyPerkModifiers, clamp } from './perk-math';
+
+const DIFFICULTY_BASE: Record<MissionDifficulty, number> = {
+  [MissionDifficulty.Easy]: 0.72,
+  [MissionDifficulty.Normal]: 0.6,
+  [MissionDifficulty.Hard]: 0.48,
+  [MissionDifficulty.Nightmare]: 0.38
+};
+
+export function resolveEncounter(input: ResolveEncounterInput): EncounterResult {
+  const baseChance = DIFFICULTY_BASE[input.difficulty];
+  const perkBoost = input.perkIds.length * 0.015;
+  const statBoost =
+    input.stats.stealth * 0.002 + input.stats.teamwork * 0.002 + input.stats.luck * 0.002;
+  const successChance = clamp(
+    applyPerkModifiers(baseChance + perkBoost + statBoost, []),
+    0.05,
+    0.95
+  );
+  const roll = seededRoll(input.seed ?? input.tickIndex);
+
+  if (roll <= successChance) {
+    return {
+      outcome: 'success',
+      text: 'The survivor outplayed the fog and advanced.',
+      successChance,
+      roll,
+      nextState: MissionState.InProgress,
+      nextStats: { ...input.stats, health: Math.min(100, input.stats.health + 1) }
+    };
+  }
+
+  const injuryThreshold = successChance + 0.25;
+  if (roll <= injuryThreshold) {
+    const injured = applyDamage(input.stats, 14);
+    return {
+      outcome: 'injury',
+      text: 'A close call leaves the survivor injured.',
+      successChance,
+      roll,
+      nextState: injured.health <= 0 ? MissionState.Failed : MissionState.InProgress,
+      nextStats: injured
+    };
+  }
+
+  return {
+    outcome: 'sacrifice',
+    text: 'The fog claims another soul.',
+    successChance,
+    roll,
+    nextState: MissionState.Failed,
+    nextStats: { ...input.stats, health: 0 }
+  };
+}
+
+function applyDamage(stats: SurvivorStats, amount: number): SurvivorStats {
+  return {
+    ...stats,
+    health: Math.max(0, stats.health - amount)
+  };
+}
+
+function seededRoll(seed: number): number {
+  const normalized = Math.abs(Math.sin(seed * 99991)) * 10000;
+  return normalized - Math.floor(normalized);
+}