// Distributed under the MIT License (MIT) (see accompanying LICENSE file)

#pragma once

#include "ImGuiInteroperability.h"
#include "Utilities/Arrays.h"


// Collects and stores input state and updates for ImGui IO.
class FImGuiInputState
{
public:

	// Characters buffer.
	using FCharactersBuffer = ImGuiInterops::ImGuiTypes::FInputCharactersBuffer;

	// Array for mouse button states.
	using FMouseButtonsArray = ImGuiInterops::ImGuiTypes::FMouseButtonsArray;

	// Array for key states.
	using FKeysArray = ImGuiInterops::ImGuiTypes::FKeysArray;

	// Pair of indices defining range in mouse buttons array.
	using FMouseButtonsIndexRange = Utilities::TArrayIndexRange<FMouseButtonsArray, uint32>;

	// Pair of indices defining range in keys array.
	using FKeysIndexRange = Utilities::TArrayIndexRange<FKeysArray, uint32>;

	// Create empty state with whole range instance with the whole update state marked as dirty.
	FImGuiInputState();

	// Get reference to input characters buffer.
	const FCharactersBuffer& GetCharacters() const { return InputCharacters; }

	// Get number of characters in input characters buffer.
	int32 GetCharactersNum()  const { return InputCharactersNum; }

	// Add a character to the characters buffer. We can store and send to ImGui up to 16 characters per frame. Any
	// character beyond that limit will be discarded.
	// @param Char - Character to add
	void AddCharacter(TCHAR Char);

	// Get reference to the array with key down states.
	const FKeysArray& GetKeys() const { return KeysDown; }

	// Get possibly empty range of indices bounding dirty part of the keys array.
	const FKeysIndexRange& GetKeysUpdateRange() const { return KeysUpdateRange; }

	// Change state of the key in the keys array and expand range bounding dirty part of the array.
	// @param KeyIndex - Index of the key
	// @param bIsDown - True, if key is down
	void SetKeyDown(uint32 KeyIndex, bool bIsDown);

	// Get reference to the array with mouse button down states.
	const FMouseButtonsArray& GetMouseButtons() const { return MouseButtonsDown; }

	// Get possibly empty range of indices bounding dirty part of the mouse buttons array.
	const FMouseButtonsIndexRange& GetMouseButtonsUpdateRange() const { return MouseButtonsUpdateRange; }

	// Change state of the button in the mouse buttons array and expand range bounding dirty part of the array.
	// @param MouseIndex - Index of the mouse button
	// @param bIsDown - True, if button is down
	void SetMouseDown(uint32 MouseIndex, bool IsDown);

	// Get mouse wheel delta accumulated during the last frame.
	float GetMouseWheelDelta() const { return MouseWheelDelta; }

	// Add mouse wheel delta.
	// @param DeltaValue - Mouse wheel delta to add
	void AddMouseWheelDelta(float DeltaValue) { MouseWheelDelta += DeltaValue; }

	// Get the current mouse position.
	const FVector2D& GetMousePosition() const { return MousePosition; }

	// Set mouse position.
	// @param Position - New mouse position
	void SetMousePosition(const FVector2D& Position) { MousePosition = Position; }

	// Clear state and mark as dirty.
	void ClearState();

	// Clear part of the state that is meant to be updated in every frame like: accumulators, buffers and information
	// about dirty parts of keys or mouse buttons arrays.
	void ClearUpdateState();

private:

	void ClearCharacters();

	FVector2D MousePosition = FVector2D::ZeroVector;
	float MouseWheelDelta = 0.f;

	FMouseButtonsArray MouseButtonsDown;
	FMouseButtonsIndexRange MouseButtonsUpdateRange;

	FCharactersBuffer InputCharacters;
	uint32 InputCharactersNum = 0;

	FKeysArray KeysDown;
	FKeysIndexRange KeysUpdateRange;
};