#pragma once

#include <optional>
#include <string>
#include <vector>

#include <QPoint>
#include <QWidget>

#include "entt/entity/entity.hpp"

#include "BeltSystem.h"
#include "Building.h"
#include "BuildingId.h"
#include "DebugDrawToggledEvent.h"
#include "EntitySelectionChangedEvent.h"
#include "EventHandler.h"
#include "GameConfig.h"
#include "PlayerCommandsAppliedEvent.h"
#include "RecipesConfig.h"
#include "ScrapSelectionChangedEvent.h"
#include "SelectionChangedEvent.h"
#include "ShipLayout.h"
#include "ShipsConfig.h"
#include "Tick.h"
#include "TickAdvancedEvent.h"

class Simulation;
class ShipLayoutPreview;
class ShipStatsPanel;
class QLabel;
class QListWidget;
class QPushButton;
class QVBoxLayout;

class SelectedBuildingPanel : public QWidget,
                               public CombinedEventHandler<TickAdvancedEvent,
                                                           PlayerCommandsAppliedEvent,
                                                           EntitySelectionChangedEvent,
                                                           SelectionChangedEvent,
                                                           ScrapSelectionChangedEvent,
                                                           DebugDrawToggledEvent>
{
    Q_OBJECT

public:
    SelectedBuildingPanel(Simulation* sim, const GameConfig* config,
                          QWidget* parent = nullptr);
    ~SelectedBuildingPanel() override;

private:
    void handleEvent(std::shared_ptr<const TickAdvancedEvent> event) override;
    void handleEvent(std::shared_ptr<const PlayerCommandsAppliedEvent> event) override;
    void handleEvent(std::shared_ptr<const EntitySelectionChangedEvent> event) override;
    void handleEvent(std::shared_ptr<const SelectionChangedEvent> event) override;
    void handleEvent(std::shared_ptr<const ScrapSelectionChangedEvent> event) override;
    void handleEvent(std::shared_ptr<const DebugDrawToggledEvent> event) override;

private slots:
    void onSelectRecipeClicked();
    void onClearBelt();
    void onSplitterFilterChanged();

private:
    // Why the selection display is being refreshed. A periodic tick only needs a
    // lightweight content update (e.g. a construction site's progress label),
    // whereas an applied player command may have changed the configuration and
    // needs a full structural rebuild.
    enum class RefreshReason
    {
        PeriodicTick,
        CommandApplied
    };

    void onSelectionChanged(const std::vector<BuildingId>& ids);
    void refreshSelectionDisplay(RefreshReason reason);
    void rebuild();
    void hideAllWidgets();
    void clearContent();
    void buildEmpty();
    void buildSingle(BuildingId id);
    void buildMulti(const std::vector<BuildingId>& ids);
    void refreshScrapTotal();
    // "Scrap: N" for the summed remaining amount of the selected piles (REQ-UI-SCRAP-PANEL).
    QString scrapTotalText() const;
    void refreshBuffers(const Building* b);
    void refreshSiteProgress(const ConstructionSite* s);
    void updateShipyardLayoutWidgets(BuildingType type,
                                     const std::string& recipeId,
                                     const std::optional<ShipLayoutConfig>& shipLayout);
    void buildSplitterFilters(const std::optional<BeltSystem::SplitterInfo>& info);
    const RecipeDef* findRecipe(const Building* b) const;
    const ShipDef*   findShipDef(const std::string& id) const;
    std::vector<std::string> getAllItemIds() const;

    Simulation*        m_sim;
    const GameConfig*  m_config;
    std::vector<BuildingId> m_selectedBuildingIds;

    QVBoxLayout* m_layout;
    QLabel*      m_titleLabel;
    QPushButton* m_recipeSelectButton;
    QPushButton* m_clearBeltBtn;
    QLabel*      m_filterALabel;
    QListWidget* m_filterAList;
    QLabel*      m_filterBLabel;
    QListWidget* m_filterBList;
    QLabel*      m_buffersLabel;

    ShipLayoutPreview* m_layoutPreview;
    QPushButton*       m_configureLayoutBtn;

    std::optional<BuildingId> m_singleBuildingId;
    bool         m_singleIsSite = false;  // selected single entity is a construction site
    QPoint       m_splitterTile;
    std::string  m_currentRecipeId;

    bool m_debugDraw = false;
    // The selected ships/defence stations. Shares the "field" selection category with
    // scrap (m_selectedScrap): both can be non-empty at once (REQ-UI-SELECTION-CATEGORIES).
    std::vector<entt::entity> m_selectedEntities;
    ShipStatsPanel* m_entityStatsPanel;
    QLabel*         m_entityTitleLabel;
    QLabel*         m_stationStatsLabel;
    QLabel*         m_entitySummaryLabel;

    std::vector<entt::entity> m_selectedScrap;
    QLabel*                   m_scrapLabel;

    // Renders the combined field selection (actors + scrap): a single-actor stats panel
    // or a multi-actor summary, plus the scrap total when scrap is also selected
    // (REQ-UI-FIELD-MULTI-SELECTION).
    void buildFieldSelection();
    void buildEntityShip(entt::entity entity);
    void buildEntityStation(entt::entity entity);
    void buildEntitySummary();
    void refreshEntityStats();
    void clearEntityDisplay();
};