#pragma once

#include <map>
#include <memory>
#include <optional>
#include <random>
#include <set>
#include <string>
#include <utility>
#include <vector>

#include <QColor>
#include <QElapsedTimer>
#include <QOpenGLWidget>
#include <QPoint>
#include <QPointF>
#include <QRectF>
#include <QTimer>
#include <QVector2D>

#include "Blueprint.h"
#include "BuildModeController.h"
#include "BlueprintModeExitedEvent.h"
#include "BlueprintPlacementRequestedEvent.h"
#include "BuilderModeExitedEvent.h"
#include "BuildingType.h"
#include "BuildingTypeSelectedEvent.h"
#include "BuildingId.h"
#include "DeconstructModeChangedEvent.h"
#include "DeconstructModeToggleRequestedEvent.h"
#include "EventHandler.h"
#include "ExitBlueprintModeRequestedEvent.h"
#include "ExitBuilderModeRequestedEvent.h"
#include "DebugDrawToggleRequestedEvent.h"
#include "GhostRotationRequestedEvent.h"
#include "InputMapper.h"
#include "ModeCancelRequestedEvent.h"
#include "PanDirectionChangedEvent.h"
#include "PauseToggleRequestedEvent.h"
#include "SpeedStepRequestedEvent.h"
#include "DebugDrawToggledEvent.h"
#include "ArtifactCountChangedEvent.h"
#include "BeamFiredEvent.h"
#include "CommandRequestedEvent.h"
#include "SchematicChoiceOption.h"
#include "WinEvent.h"
#include "SpeedChangeRequestedEvent.h"

#include "entt/entity/entity.hpp"
#include "BeltDragPath.h"
#include "CommandManager.h"
#include "EntitySelectionChangedEvent.h"
#include "GameConfig.h"
#include "PlacementRules.h"
#include "Rotation.h"
#include "SelectionController.h"
#include "Tick.h"
#include "TickDriver.h"
#include "TunnelCompletion.h"
#include "VisualsConfig.h"
#include "WorldCamera.h"
#include "WorldCoordinates.h"
#include "WorldRenderer.h"

struct Command;
struct ParsedReplay;
class ItemIconCache;
class ReplayPlayer;
class Simulation;
class QPainter;

class GameWorldView : public QOpenGLWidget,
                      public CombinedEventHandler<BeamFiredEvent,
                                                  BuildingTypeSelectedEvent,
                                                  ExitBuilderModeRequestedEvent,
                                                  DeconstructModeToggleRequestedEvent,
                                                  BlueprintPlacementRequestedEvent,
                                                  ExitBlueprintModeRequestedEvent,
                                                  SpeedChangeRequestedEvent,
                                                  PanDirectionChangedEvent,
                                                  PauseToggleRequestedEvent,
                                                  SpeedStepRequestedEvent,
                                                  GhostRotationRequestedEvent,
                                                  ModeCancelRequestedEvent,
                                                  DebugDrawToggleRequestedEvent,
                                                  CommandRequestedEvent>
{
    Q_OBJECT

public:
    // itemIcons is the window-wide per-item icon cache (REQ-UI-ITEM-ICON); not
    // owned, must outlive this widget.
    GameWorldView(Simulation* sim, const GameConfig* config,
                  const VisualsConfig* visuals, const std::string& configDir,
                  ItemIconCache* itemIcons, const ParsedReplay* replay,
                  QWidget* parent = nullptr);
    ~GameWorldView() override;

    double getGameSpeed() const;
    bool isDebugDrawEnabled() const;
    void resetFrameTimer();
    void setGameSpeed(double multiplier);
    void resetForNewGame();

protected:
    void initializeGL() override;
    void paintGL() override;
    // Only forwards to the input mapper; every key this widget acts on reaches it
    // as a published action instead (REQ-UI-HOTKEYS).
    void keyPressEvent(QKeyEvent* event) override;
    void keyReleaseEvent(QKeyEvent* event) override;
    // Key-up never arrives for a key that was still held when focus moved away —
    // to a modal dialog, another widget, or another window. Any held action would
    // otherwise stay held forever, so focus loss drops all of them.
    void focusOutEvent(QFocusEvent* event) override;
    void mousePressEvent(QMouseEvent* event) override;
    void mouseMoveEvent(QMouseEvent* event) override;
    void mouseReleaseEvent(QMouseEvent* event) override;

private slots:
    void onFrame();

private:
    void handleEvent(std::shared_ptr<const BeamFiredEvent> event) override;
    void handleEvent(std::shared_ptr<const BuildingTypeSelectedEvent> event) override;
    void handleEvent(std::shared_ptr<const ExitBuilderModeRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const DeconstructModeToggleRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const BlueprintPlacementRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const ExitBlueprintModeRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const SpeedChangeRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const PanDirectionChangedEvent> event) override;
    void handleEvent(std::shared_ptr<const PauseToggleRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const SpeedStepRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const GhostRotationRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const ModeCancelRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const DebugDrawToggleRequestedEvent> event) override;
    void handleEvent(std::shared_ptr<const CommandRequestedEvent> event) override;

    // Enqueue a sim command onto the CommandManager (the single mutation path).
    void enqueueCommand(std::shared_ptr<const Command> command);

    // Enqueue a plain (unconfigured) building placement.
    void enqueuePlaceBuilding(BuildingType type, QPoint anchor, Rotation rotation);

    // True if the player can currently afford to place one building of `type`.
    // Used to pre-validate placements whose UI follow-up depends on success.
    bool canAfford(BuildingType type) const;

    // Screen-anchored chrome, drawn after the world (see WorldRenderer): these
    // need no world transform, which is exactly why they stayed here.
    void drawScreenSpace(QPainter& painter);
    // Threat and production readout shown while debug draw is on (F3). Positioned
    // in pixels at the top-left corner, so it belongs with the chrome rather than
    // with the world.
    void drawDebugOverlay(QPainter& painter);
    // Vignette-style border shown while the game is paused (speed 0x, REQ-UI-PAUSE-BORDER)
    // to make the paused state hard to miss: a black frame whose alpha fades from 50% at
    // the viewport edges to 0% toward the center.
    void drawPauseBorder(QPainter& painter);
    // Vignette-style border shown while deconstruct mode is active (REQ-UI-DECONSTRUCT-BORDER),
    // tinted with the deconstruct overlay color (including its configured alpha) from
    // visuals.toml instead of black.
    void drawDeconstructBorder(QPainter& painter);
    // Shared drawing for the pause/deconstruct vignettes: a mitred picture-frame border
    // whose alpha fades from `edgeColor` (with its own alpha) at the viewport edge to
    // fully transparent toward the center.
    void drawVignetteBorder(QPainter& painter, const QColor& edgeColor);
    void drawReplayOverlay(QPainter& painter);

    // Gathers the interaction state the renderer needs for this frame.
    WorldRenderFrame makeRenderFrame() const;

    // The world <-> widget transform for the current viewport size and scroll
    // position. Cheap to build and deliberately not cached: it is a snapshot that
    // a resize or a scroll invalidates, so every user takes a fresh one.
    WorldCoordinates getCoordinates() const;

    float    getAsteroidLeftEdge() const;
    float    getEnemyStationRightEdge() const;
    // The camera's current pan limits, read fresh from the simulation each frame:
    // both edges move with asteroid expansion and with pushes (REQ-GW-SCROLL-LIMIT).
    ScrollBounds getScrollBounds() const;

    // canPlaceBuilding (PlacementRules) against this view's simulation.
    bool     canPlaceBuildingHere(BuildingType type, QPoint anchor, Rotation rot) const;
    std::optional<BuildingId> buildingAtTile(QPoint tile) const;
    std::optional<BuildingId> siteAtTile(QPoint tile) const;

    void     placeBlueprintAtTile(QPoint center);

    // Drops despawned or fully-collected debris from the selection
    // (REQ-UI-DEBRIS-CLICK-SELECT). Called each frame from onFrame().
    void                     pruneDespawnedDebris();
    // Drops despawned or dead actors from the selection (REQ-UI-ENTITY-CLICK-SELECT).
    // Called each frame from onFrame().
    void                     pruneDespawnedActors();
    // Resolves a click into the selection it should produce, applying the category
    // precedence of REQ-UI-SELECTION-CATEGORIES; the controller owns what that then
    // does to the existing selection. Returns false when the click hit nothing,
    // which is the only case that goes on to start a box drag.
    bool                     selectAtPoint(QPoint tile, QVector2D worldPos, bool additive);
    void                     selectInBox(bool additive);
    void                     stepSpeed(int delta);
    void                     placeAtTile(QPoint tile);

    // Re-resolves the tunnel ghost type and completion partner from the current
    // ghost tile, rotation, and sub-tile cursor position, storing both on the build
    // mode controller. Only meaningful in tunnel mode (REQ-BLD-TUNNEL-MODE).
    void         updateTunnelGhost();
    // Belt drag placement (REQ-BLD-BELT-DRAG).
    // Recomputes the drag path from its anchor to cursorTile using the current ghost
    // orientation, and stores it on the build mode controller.
    void                          recomputeBeltDragPath(QPoint cursorTile);
    // resolveBeltDragPath (PlacementRules) against this view's simulation.
    std::vector<BeltDragResolved> resolveBeltDragPath() const;
    // Enqueues placements and rotate-in-place commands for the resolved path.
    void                          applyBeltDragPath();

    // Turns the ghost and refreshes everything that depends on its facing: placement
    // validity, the tunnel completion match, and an in-progress belt drag's path.
    // The mode transitions themselves live on m_buildMode.
    void     rotateGhost(bool clockwise);

    // Beam lifetime in game ticks so beams freeze with the simulation when
    // paused or slowed, instead of fading on wall-clock time (REQ-SHP-FIRING-BEAM).
    static constexpr Tick    kBeamLifetimeTicks      = secondsToTicks(0.3);

    Simulation*          m_sim;
    const GameConfig*    m_config;
    const VisualsConfig* m_visuals;

    // Funnels all player input into the single Simulation::apply chokepoint.
    CommandManager m_commandManager;
    // A Reset command was enqueued; reset the view after the next drain applies it.
    bool           m_viewResetPending = false;
    // Non-null => view-only playback: ticks are driven by the recorded stream and
    // live input is ignored (the CommandManager is in replay mode).
    std::unique_ptr<ReplayPlayer> m_replayPlayer;

    // Draws the world; this widget supplies the interaction state each frame and
    // keeps only the screen-anchored chrome for itself.
    std::unique_ptr<WorldRenderer> m_renderer;

    TickDriver    m_tickDriver;
    QElapsedTimer m_frameTimer;
    std::mt19937  m_rng;
    double        m_gameSpeedMultiplier;
    double        m_prevNonZeroSpeed;
    // Horizontal view position (REQ-UI-SCROLL). Owns the scroll position itself;
    // this widget only supplies the pan intent and the simulation-derived bounds.
    WorldCamera   m_camera;

    QTimer* m_renderTimer;

    std::vector<ActiveBeam> m_activeBeams;

    // The active build mode (builder / blueprint / deconstruct, or none) and the
    // ghost, tunnel and belt-drag state belonging to it. Owns the transitions
    // between them; this widget supplies the parts that need the simulation.
    BuildModeController m_buildMode;

    // Last known cursor position in world (tile) units; used to pick the belt-drag
    // end tile closest to the cursor when snapping to a building (REQ-BLD-BELT-DRAG)
    // and to resolve the tunnel ghost sub-tile (REQ-BLD-TUNNEL-MODE).
    QVector2D                            m_cursorWorldPos;

    bool     m_debugDraw;

    // Owns the selection across all three categories and the rules for moving
    // between them (REQ-UI-SELECTION-CATEGORIES), including publishing the change
    // events. This widget only resolves what was hit.
    SelectionController   m_selection;
    bool                  m_boxSelecting;
    QPoint                m_boxStartTile;
    QPoint                m_boxCurrentTile;

    // Interprets this widget's key events into semantic actions and publishes them
    // (REQ-UI-HOTKEYS). Owned here for now because this is the widget that holds
    // focus; everything it produces travels by event, so it can move to a
    // window-wide owner later without touching its consumers.
    InputMapper m_inputMapper;

    // Latest pan direction published by the input mapper (REQ-UI-SCROLL), fed to
    // the camera each frame. Cached from the event payload rather than re-read:
    // input has no other source of truth (see PanDirectionChangedEvent).
    PanDirection m_panDirection = PanDirection::None;
    bool m_gameOverShown;
    bool m_winShown;
    bool m_schematicChoiceShown;

    Tick m_lastTick          = Tick(-1);
    int  m_lastBlocks        = -1;
    int  m_lastExpansionCost = -1;
    int  m_lastBossCounter   = -1;
    Tick m_lastBossCountdown = Tick(-1);
    int  m_lastArtifactCount = -1;
    int  m_lastUnlockedBuildingCount = -1;
};