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feature: split guaranteed and chance drop groups respecting NumberOfMaximumItemDrops #753

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ca5311d
feature: split guaranteed and chance drop groups respecting NumberOfM…
eduardosmaniotto Apr 12, 2026
2a39837
code review: apply codacy warning fix
eduardosmaniotto Apr 12, 2026
1fbe51a
code review: apply gemini suggestion
eduardosmaniotto Apr 12, 2026
74947ea
feature: increase _guaranteedDropGroups max size
eduardosmaniotto Apr 15, 2026
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125 changes: 94 additions & 31 deletions src/GameLogic/DefaultDropGenerator.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,14 +18,19 @@ public class DefaultDropGenerator : IDropGenerator
/// </summary>
public static readonly int BaseMoneyDrop = 7;

private static readonly int DropLevelMaxGap = 12;
private const int DropLevelMaxGap = 12;
private const int JewelOfChaosMaxMonsterLevel = 66;
private const int JewelOfChaosGroup = 12;
private const int JewelOfChaosNumber = 15;
private const int SkillDropChancePercent = 50;

private readonly IRandomizer _randomizer;

/// <summary>
/// A re-useable list of drop item groups.
/// A re-usable list of drop item groups.
/// </summary>
private readonly List<DropItemGroup> _dropGroups = new(64);
private readonly List<DropItemGroup> _chanceDropGroups = new(64);
private readonly List<DropItemGroup> _guaranteedDropGroups = new(16);

private readonly AsyncLock _lock = new();

Expand All @@ -52,7 +57,7 @@ public DefaultDropGenerator(GameConfiguration config, IRandomizer randomizer)
this._droppableItems = config.Items.Where(i => i.DropsFromMonsters).ToList();
this._ancientItems = this._droppableItems.Where(
i => i.PossibleItemSetGroups.Any(
o => o.Options?.PossibleOptions.Any(
g => g.Options?.PossibleOptions.Any(
o => object.Equals(o.OptionType, ItemOptionTypes.AncientOption)) ?? false))
.ToList();
}
Expand All @@ -68,51 +73,81 @@ public DefaultDropGenerator(GameConfiguration config, IRandomizer randomizer)
}

using var l = await this._lock.LockAsync();
this._dropGroups.Clear();
if (monster.DropItemGroups.MaxBy(g => g.Chance) is { Chance: >= 1.0 } alwaysDrops)
{
this._dropGroups.Add(alwaysDrops);
}
else if (monster.ObjectKind == NpcObjectKind.Destructible)
this._guaranteedDropGroups.Clear();
this._chanceDropGroups.Clear();

if (monster.ObjectKind == NpcObjectKind.Destructible)
{
this._dropGroups.AddRange(monster.DropItemGroups ?? []);
this.PartitionDropGroups(monster.DropItemGroups ?? []);
}
else
{
this._dropGroups.AddRange(monster.DropItemGroups ?? []);
this._dropGroups.AddRange(character.DropItemGroups ?? []);
this._dropGroups.AddRange(map.DropItemGroups ?? []);
this._dropGroups.AddRange(await GetQuestItemGroupsAsync(player).ConfigureAwait(false) ?? []);

this._dropGroups.RemoveAll(g => !IsGroupRelevant(monster, g));
this._dropGroups.Sort((x, y) => x.Chance.CompareTo(y.Chance));
this.PartitionDropGroups(monster.DropItemGroups ?? []);
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this.PartitionDropGroups(character.DropItemGroups ?? [], monster);
this.PartitionDropGroups(map.DropItemGroups ?? [], monster);
this.PartitionDropGroups(await GetQuestItemGroupsAsync(player).ConfigureAwait(false) ?? [], monster);
}

var totalChance = this._dropGroups.Sum(g => g.Chance);
uint money = 0;
IList<Item>? droppedItems = null;
for (int i = 0; i < monster.NumberOfMaximumItemDrops; i++)
var remainingDrops = monster.NumberOfMaximumItemDrops;

// Guaranteed groups, no random selection needed.
foreach (var group in this._guaranteedDropGroups)
{
var group = this.SelectRandomGroup(this._dropGroups, totalChance);
if (group is null)
if (remainingDrops <= 0)
{
continue;
break;
}

var item = this.GenerateItemDropOrMoney(monster, group, gainedExperience, out var droppedMoney);
if (item is not null)
{
droppedItems ??= new List<Item>(1);
droppedItems ??= new List<Item>(monster.NumberOfMaximumItemDrops);
droppedItems.Add(item);
}

if (droppedMoney is not null)
{
money += droppedMoney.Value;
}

remainingDrops--;
}

// Chance based groups with random selection
if (remainingDrops > 0 && this._chanceDropGroups.Count > 0)
{
double totalChance = 0;
foreach (var group in this._chanceDropGroups)
{
totalChance += group.Chance;
}

for (int i = 0; i < remainingDrops; i++)
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{
var group = this.SelectRandomGroup(this._chanceDropGroups, totalChance);
if (group is null)
{
continue;
}

var item = this.GenerateItemDropOrMoney(monster, group, gainedExperience, out var droppedMoney);
if (item is not null)
{
droppedItems ??= new List<Item>(monster.NumberOfMaximumItemDrops);
droppedItems.Add(item);
}

if (droppedMoney is not null)
{
money += droppedMoney.Value;
}
}
}

this._dropGroups.Clear();
this._guaranteedDropGroups.Clear();
this._chanceDropGroups.Clear();
return (droppedItems ?? Enumerable.Empty<Item>(), money > 0 ? money : null);
}

Expand Down Expand Up @@ -185,7 +220,7 @@ protected void ApplyRandomOptions(Item item)

if (item.CanHaveSkill())
{
item.HasSkill = this._randomizer.NextRandomBool(50);
item.HasSkill = this._randomizer.NextRandomBool(SkillDropChancePercent);
}
}

Expand Down Expand Up @@ -280,6 +315,26 @@ private static bool IsGroupRelevant(MonsterDefinition monsterDefinition, DropIte
return true;
}

private void PartitionDropGroups(IEnumerable<DropItemGroup> groups, MonsterDefinition? monster = null)
{
foreach (var group in groups)
{
if (monster is not null && !IsGroupRelevant(monster, group))
{
continue;
}

if (group.Chance >= 1.0)
{
this._guaranteedDropGroups.Add(group);
}
else
{
this._chanceDropGroups.Add(group);
}
}
}

private Item? GenerateItemDrop(DropItemGroup selectedGroup, ICollection<ItemDefinition> possibleItems)
{
var item = selectedGroup.ItemType switch
Expand Down Expand Up @@ -333,9 +388,13 @@ private void ApplyOption(Item item, ItemOptionDefinition option)
var itemOptionLink = new ItemOptionLink
{
ItemOption = newOption,
Level = newOption?.LevelDependentOptions.Select(ldo => ldo.Level)
Level = newOption.LevelDependentOptions
.Select(ldo => ldo.Level)
.Concat(newOption.LevelDependentOptions.Count > 0 ? [1] : []) // For base def/dmg opts level 1 is not an ItemOptionOfLevel entry
.Distinct().Where(l => l <= this._maxItemOptionLevelDrop).SelectRandom() ?? 0,
.Distinct()
.Where(l => l <= this._maxItemOptionLevelDrop)
.DefaultIfEmpty(0)
.SelectRandom(),
};
item.ItemOptions.Add(itemOptionLink);
}
Expand All @@ -361,7 +420,9 @@ private void ApplyOption(Item item, ItemOptionDefinition option)

private void ApplyRandomAncientOption(Item item)
{
var ancientSet = item.Definition?.PossibleItemSetGroups.Where(g => g!.Options?.PossibleOptions.Any(o => object.Equals(o.OptionType, ItemOptionTypes.AncientOption)) ?? false).SelectRandom(this._randomizer);
var ancientSet = item.Definition?.PossibleItemSetGroups
.Where(g => g!.Options?.PossibleOptions.Any(o => object.Equals(o.OptionType, ItemOptionTypes.AncientOption)) ?? false)
.SelectRandom(this._randomizer);
if (ancientSet is null)
{
return;
Expand All @@ -383,12 +444,14 @@ private void AddRandomExcOptions(Item item)
var possibleItemOptions = item.Definition!.PossibleItemOptions;
var excellentOptions = possibleItemOptions.FirstOrDefault(
o => o.PossibleOptions.Any(p => object.Equals(p.OptionType, ItemOptionTypes.Excellent)));

if (excellentOptions is null)
{
return;
}

var existingOptionCount = item.ItemOptions.Count(o => object.Equals(o.ItemOption?.OptionType, ItemOptionTypes.Excellent));

for (int i = existingOptionCount; i < excellentOptions.MaximumOptionsPerItem; i++)
{
if (i == 0)
Expand Down Expand Up @@ -444,10 +507,10 @@ private void AddRandomExcOptions(Item item)
{
filteredPossibleItems = [.. selectedGroup.PossibleItems.Where(it => it.DropLevel <= monsterLevel)];

if (monsterLevel > 66)
if (monsterLevel > JewelOfChaosMaxMonsterLevel)
{
// Jewel of Chaos doesn't drop after a certain monster level
filteredPossibleItems.RemoveAll(it => it.Group == 12 && it.Number == 15);
filteredPossibleItems.RemoveAll(it => it.Group == JewelOfChaosGroup && it.Number == JewelOfChaosNumber);
}
}
else
Expand Down