openthebox/src/OpenTheBox/Simulation/GameSimulation.cs

using OpenTheBox.Core;
using OpenTheBox.Core.Enums;
using OpenTheBox.Core.Items;
using OpenTheBox.Data;
using OpenTheBox.Simulation.Actions;
using OpenTheBox.Simulation.Events;

namespace OpenTheBox.Simulation;

/// <summary>
/// The BLACK BOX. Zero I/O. Central orchestrator for all game logic.
/// All game actions are processed through this class, which dispatches to the appropriate
/// engine and runs post-processing passes (auto-activation, meta unlocks).
/// </summary>
public class GameSimulation
{
    private readonly ContentRegistry _registry;
    private readonly Random _rng;
    private readonly BoxEngine _boxEngine;
    private readonly InteractionEngine _interactionEngine;
    private readonly MetaEngine _metaEngine;
    private readonly ResourceEngine _resourceEngine;
    private readonly CraftingEngine _craftingEngine;

    public GameSimulation(ContentRegistry registry, Random? rng = null)
    {
        _registry = registry;
        _rng = rng ?? new Random();
        _boxEngine = new BoxEngine(registry);
        _interactionEngine = new InteractionEngine(registry);
        _metaEngine = new MetaEngine();
        _resourceEngine = new ResourceEngine();
        _craftingEngine = new CraftingEngine();
    }

    /// <summary>
    /// Processes a game action against the current state, returning all resulting events in order.
    /// This is the single entry point for all game logic.
    /// </summary>
    public List<GameEvent> ProcessAction(GameAction action, GameState state)
    {
        var events = new List<GameEvent>();

        switch (action)
        {
            case OpenBoxAction openBox:
                events.AddRange(HandleOpenBox(openBox, state));
                break;

            case UseItemAction useItem:
                events.AddRange(HandleUseItem(useItem, state));
                break;

            case CraftAction craft:
                events.AddRange(HandleCraft(craft, state));
                break;

            case StartAdventureAction startAdventure:
                events.AddRange(HandleStartAdventure(startAdventure, state));
                break;

            case ChangeLocaleAction changeLocale:
                events.AddRange(HandleChangeLocale(changeLocale, state));
                break;

            case EquipCosmeticAction equipCosmetic:
                events.AddRange(HandleEquipCosmetic(equipCosmetic, state));
                break;

            case SaveGameAction:
                // Save is handled externally; simulation just acknowledges
                events.Add(new MessageEvent("save.acknowledged"));
                break;
        }

        return events;
    }

    private List<GameEvent> HandleOpenBox(OpenBoxAction action, GameState state)
    {
        var events = new List<GameEvent>();

        // Find the box item in inventory
        var boxItem = state.Inventory.FirstOrDefault(i => i.Id == action.BoxInstanceId);
        if (boxItem is null)
        {
            events.Add(new MessageEvent("error.item_not_found"));
            return events;
        }

        // Consume the box item
        state.RemoveItem(boxItem.Id);
        events.Add(new ItemConsumedEvent(boxItem.Id));

        // Open the box
        var boxEvents = _boxEngine.Open(boxItem.DefinitionId, state, _rng);
        events.AddRange(boxEvents);

        state.TotalBoxesOpened++;

        // Collect newly received items for post-processing
        var newItems = boxEvents.OfType<ItemReceivedEvent>().Select(e => e.Item).ToList();

        // Run chain reaction pass
        events.AddRange(_interactionEngine.RunChainReactions(newItems, state, _rng));

        // Run meta pass
        events.AddRange(_metaEngine.ProcessNewItems(newItems, state, _registry));

        // Run crafting auto-check (new materials may trigger recipes)
        events.AddRange(_craftingEngine.AutoCraftCheck(state, _registry));

        return events;
    }

    private List<GameEvent> HandleUseItem(UseItemAction action, GameState state)
    {
        var events = new List<GameEvent>();

        var item = state.Inventory.FirstOrDefault(i => i.Id == action.ItemInstanceId);
        if (item is null)
        {
            events.Add(new MessageEvent("error.item_not_found"));
            return events;
        }

        var itemDef = _registry.GetItem(item.DefinitionId);
        if (itemDef is null)
        {
            events.Add(new MessageEvent("error.definition_not_found"));
            return events;
        }

        // Check if it's a consumable resource item
        if (itemDef.ResourceType.HasValue)
        {
            events.AddRange(_resourceEngine.ProcessConsumable(item, state, _registry));
            return events;
        }

        // Otherwise, check interaction rules
        var interactionEvents = _interactionEngine.RunChainReactions([item], state, _rng);
        events.AddRange(interactionEvents);

        return events;
    }

    private List<GameEvent> HandleCraft(CraftAction action, GameState state)
    {
        // Crafting is now automatic — delegate to the CraftingEngine
        return _craftingEngine.AutoCraftCheck(state, _registry);
    }

    private List<GameEvent> HandleStartAdventure(StartAdventureAction action, GameState state)
    {
        var events = new List<GameEvent>();

        if (!state.UnlockedAdventures.Contains(action.Theme))
        {
            events.Add(new MessageEvent("error.adventure_locked"));
            return events;
        }

        events.Add(new AdventureStartedEvent(action.Theme));

        return events;
    }

    private static List<GameEvent> HandleChangeLocale(ChangeLocaleAction action, GameState state)
    {
        var events = new List<GameEvent>();

        state.CurrentLocale = action.NewLocale;
        events.Add(new MessageEvent("locale.changed", [action.NewLocale.ToString()]));

        return events;
    }

    private List<GameEvent> HandleEquipCosmetic(EquipCosmeticAction action, GameState state)
    {
        var events = new List<GameEvent>();

        var item = state.Inventory.FirstOrDefault(i => i.Id == action.ItemInstanceId);
        if (item is null)
        {
            events.Add(new MessageEvent("error.item_not_found"));
            return events;
        }

        var itemDef = _registry.GetItem(item.DefinitionId);
        if (itemDef?.CosmeticSlot is null || itemDef.CosmeticValue is null)
        {
            events.Add(new MessageEvent("error.not_a_cosmetic"));
            return events;
        }

        var slot = itemDef.CosmeticSlot.Value;
        var value = itemDef.CosmeticValue;

        if (!state.Appearance.ApplyCosmetic(slot, value))
        {
            events.Add(new MessageEvent("error.cosmetic_apply_failed"));
            return events;
        }

        events.Add(new CosmeticEquippedEvent(slot, value));

        return events;
    }
}