#pragma once

#include <sophia/entity.hpp>
#include <sophia/frame_info.hpp>
#include <sophia/handles.hpp>
#include <sophia/math.hpp>
#include <sophia/scene.hpp>
#include <sophia/ui/panel.hpp>
#include <sophia/ui/ui.hpp>

/**
 * Shows the scene through its active camera. Click a sprite to select it,
 * drag it to move it (in Move mode).
 *
 * Picking and moving are 2D: they assume an orthographic camera rotated only
 * around Z, and work in the z = 0 plane.
 */
class ViewportPanel : public sophia::Panel {
 public:
  ViewportPanel(sophia::UI& ui, sophia::RenderTargetHandle target,
                sophia::Scene& scene, sophia::Entity& selected)
      : Panel{{.name = "Viewport",
               .windowFlags = ImGuiWindowFlags_NoScrollbar |
                              ImGuiWindowFlags_NoScrollWithMouse}},
        ui{ui},
        target{target},
        scene{scene},
        selected{selected} {}

  void onUpdate(const sophia::FrameInfo& frameInfo) override;

 private:
  // Where the scene image is on screen this frame, and the camera looking
  // through it.
  struct ViewportTransform {
    ImVec2 origin;
    ImVec2 size;
    glm::mat4 viewProjection;
    glm::mat4 inverseViewProjection;

    ImVec2 worldToScreen(const glm::vec3& world) const;
    glm::vec2 screenToWorld(const ImVec2& screen) const;
  };

  void drawToolbar();
  void drawGrid(ImVec2 origin, ImVec2 size);
  void handleInput(const ViewportTransform& viewport);
  void drawSelection(const ViewportTransform& viewport);

  // The top-most sprite under `world`, or a null Entity.
  sophia::Entity pick(glm::vec2 world);

  sophia::UI& ui;
  sophia::RenderTargetHandle target;
  sophia::Scene& scene;
  sophia::Entity& selected;

  enum class GizmoMode { Move, Rotate, Scale };

  GizmoMode gizmoMode = GizmoMode::Move;
  bool showGrid = true;
  // Set while a drag that started on the selected entity is moving it.
  bool dragging = false;
};