rogue/src/engine/systems/LootSystem.ts

import { type Item, type ActorType } from "../../core/types";
import { 
  createMeleeWeapon, 
  createArmour, 
  createConsumable,
  createAmmo,
  MELEE_WEAPONS,
  ARMOUR
} from "../../core/config/Items";
import { 
  WEAPON_VARIANTS, 
  ARMOUR_VARIANTS,
  type WeaponVariantId,
  type ArmourVariantId
} from "../../core/config/ItemVariants";
import { UpgradeManager } from "../systems/UpgradeManager";

/**
 * Loot drop configuration.
 * Chances are cumulative (checked in order).
 */
export const LOOT_CONFIG = {
  // Base chance any item drops at all (per enemy)
  baseDropChance: 0.25,

  // Type weights (what kind of item drops)
  typeWeights: {
    weapon: 30,
    armour: 25,
    consumable: 35,
    ammo: 10,
  },

  // Rarity chances (applied after type is chosen)
  rarityChances: {
    base: 0.60,        // 60% just base item
    variant: 0.30,     // 30% has a variant
    upgraded: 0.10,    // 10% has upgrade applied
  },

  // Per-enemy type drop chance modifiers
  enemyDropModifiers: {
    rat: 0.8,
    bat: 0.9,
    // Add more enemy types as needed
  } as Record<ActorType, number>,
};

/**
 * Generate a random loot item based on the loot configuration.
 * Returns null if no item drops.
 */
export function generateLoot(
  random: () => number, 
  enemyType?: ActorType,
  floorLevel: number = 1
): Item | null {
  // Check base drop chance (modified by enemy type)
  let dropChance: number = LOOT_CONFIG.baseDropChance;
  if (enemyType && LOOT_CONFIG.enemyDropModifiers[enemyType]) {
    dropChance *= LOOT_CONFIG.enemyDropModifiers[enemyType];
  }
  
  // Higher floor = slightly more drops
  dropChance += floorLevel * 0.02;
  dropChance = Math.min(dropChance, 0.6); // Cap at 60%

  if (random() > dropChance) {
    return null;
  }

  // Determine item type
  const itemType = pickWeightedRandom(LOOT_CONFIG.typeWeights, random);

  // Determine rarity tier
  const rarityRoll = random();
  let hasVariant = false;
  let hasUpgrade = false;

  if (rarityRoll >= (1 - LOOT_CONFIG.rarityChances.upgraded)) {
    // Top 10%: upgraded (implies has variant too)
    hasVariant = true;
    hasUpgrade = true;
  } else if (rarityRoll >= (1 - LOOT_CONFIG.rarityChances.upgraded - LOOT_CONFIG.rarityChances.variant)) {
    // Next 30%: variant only
    hasVariant = true;
  }
  // Otherwise: base item (60%)

  // Generate the item
  let item: Item | null = null;

  switch (itemType) {
    case "weapon": {
      const weaponIds = Object.keys(MELEE_WEAPONS) as (keyof typeof MELEE_WEAPONS)[];
      const weaponId = weaponIds[Math.floor(random() * weaponIds.length)];
      
      let variant: WeaponVariantId | undefined;
      if (hasVariant) {
        const variantIds = Object.keys(WEAPON_VARIANTS) as WeaponVariantId[];
        variant = variantIds[Math.floor(random() * variantIds.length)];
      }
      
      item = createMeleeWeapon(weaponId, variant);
      break;
    }
    
    case "armour": {
      const armourIds = Object.keys(ARMOUR) as (keyof typeof ARMOUR)[];
      const armourId = armourIds[Math.floor(random() * armourIds.length)];
      
      let variant: ArmourVariantId | undefined;
      if (hasVariant) {
        const variantIds = Object.keys(ARMOUR_VARIANTS) as ArmourVariantId[];
        variant = variantIds[Math.floor(random() * variantIds.length)];
      }
      
      item = createArmour(armourId, variant);
      break;
    }
    
    case "consumable": {
      // Only drop health potions and throwing daggers, not upgrade scrolls
      const droppableConsumables = ["health_potion", "throwing_dagger"] as const;
      const consumableId = droppableConsumables[Math.floor(random() * droppableConsumables.length)];
      const quantity = 1 + Math.floor(random() * 2); // 1-2
      
      item = createConsumable(consumableId, quantity);
      break;
    }
    
    case "ammo": {
      const quantity = 5 + Math.floor(random() * 10); // 5-14
      item = createAmmo("ammo_9mm", quantity);
      break;
    }
  }

  // Apply upgrade if rolled
  if (item && hasUpgrade) {
    UpgradeManager.applyUpgrade(item);
  }

  return item;
}

/**
 * Pick from weighted options.
 */
function pickWeightedRandom(
  weights: Record<string, number>, 
  random: () => number
): string {
  const entries = Object.entries(weights);
  const total = entries.reduce((sum, [, w]) => sum + w, 0);
  let roll = random() * total;
  
  for (const [key, weight] of entries) {
    roll -= weight;
    if (roll <= 0) {
      return key;
    }
  }
  
  return entries[entries.length - 1][0];
}