#ifndef AC_UNDOABLE_H
#define AC_UNDOABLE_H
#include<functional>
#include<vector>
namespace AC {
	/// <summary>
	/// 撤銷重做管理對象
	/// 最少行數實現,采用vector+下標浮動實現，性能也是很好的。
	/// ceate by xin 2022.7.5
	/// </summary>
	class Undoable
	{
	public:
		/// <summary>
		/// 撤銷
		/// </summary>
		void Undo();
		/// <summary>
		/// 重做
		/// </summary>
		void Redo();
		/// <summary>
		/// 清除
		/// </summary>
		void Clear();
		/// <summary>
		/// 添加操作
		/// </summary>
		/// <param name="undo">撤銷</param>
		/// <param name="redo">重做</param>
		void Add(std::function<void()> undo, std::function<void()> redo);
	private:	
		//記錄的步驟
		std::vector<std::pair<std::function<void()>, std::function<void()>>> _steps;
		//當前操作的下標
		int _index = -1;
	};
}
#endif

#include "Undoable.h"
namespace AC {
	void Undoable::Undo(){
		if (_index > -1)
			_steps[_index--].first();		
	}
	void Undoable::Redo(){
		if (_index < (int)_steps.size() - 1)
			_steps[++_index].second();
	}
	void Undoable::Clear(){
		_steps.clear();
		_index = -1;
	}
	void Undoable::Add(std::function<void()> undo, std::function<void()> redo){
		if (++_index < (int)_steps.size())
			_steps.resize(_index);
		_steps.push_back({ undo ,redo });
	}
}

//1、定義撤銷重做管理對象
AC::Undoable undoable;
//2、添加操作
undoable.Add(
	[=]() {
     //撤銷邏輯
	},	
	[=]() {
	 //重做邏輯		
	}
	);
//3、撤銷重做
//執行撤銷
undoable.Undo();
//執行重做
undoable.Redo();

#include<Windows.h>
#include<Windowsx.h>
#include<vector>
#include "Undoable.h"
//筆畫集合
std::vector<std::vector<POINT>*> strokes;
//窗口上下文
HDC hdc;
int xPos = 0;
int yPos = 0;
//撤銷重做管理對象
AC::Undoable undoable;
//窗口過程
static	LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	switch (msg)
	{
	case WM_LBUTTONDOWN:
		//記錄筆畫起點
		xPos = GET_X_LPARAM(lParam);
		yPos = GET_Y_LPARAM(lParam);
		strokes.push_back(new std::vector<POINT>());
		strokes.back()->push_back({ xPos ,yPos });
		MoveToEx(hdc, xPos, yPos, NULL);
		break;
	case WM_MOUSEMOVE:
		if ((wParam & MK_LBUTTON) != 0)
			//繪制筆畫
		{
			xPos = GET_X_LPARAM(lParam);
			yPos = GET_Y_LPARAM(lParam);
			LineTo(hdc, xPos, yPos);
			strokes.back()->push_back({ xPos ,yPos });
		}
		break;
	case WM_LBUTTONUP:
		//記錄筆畫撤銷重做
	{
		auto currentStroke = strokes.back();
		//補全一個點
		if (strokes.back()->size()==1)
		{
			xPos = GET_X_LPARAM(lParam);
			yPos = GET_Y_LPARAM(lParam);
			LineTo(hdc, xPos, yPos);
		}
		//記錄操作
		undoable.Add(	
			[=]() {
		    //撤銷邏輯
		    strokes.pop_back();
		    RECT rect;
		    GetClientRect(hwnd, &rect);
		    InvalidateRect(hwnd, &rect, 0);
			},
			[=]() {
		    //重做邏輯
		    strokes.push_back(currentStroke);
		    RECT rect;
		    GetClientRect(hwnd, &rect);
		    InvalidateRect(hwnd, &rect, 0);
			}
			);
	}
	break;
	case WM_PAINT:
	{
		//重繪筆畫
		RECT rect;
		GetClientRect(hwnd, &rect);
		FillRect(hdc, &rect, (HBRUSH)GetStockObject(WHITE_BRUSH));
		for (auto i : strokes)
		{
			MoveToEx(hdc, i->front().x, i->front().y, NULL);
			for (auto j : *i)
			{
				LineTo(hdc, j.x, j.y);
			}
		}
	}
	break;
	case WM_KEYDOWN:
		//響應消息
		if (wParam == 'Z')
		{
			//執行撤銷
			undoable.Undo();
		}
		if (wParam == 'Y')
		{
			//執行重做
			undoable.Redo();
		}
		break;
	case WM_DESTROY:
		PostQuitMessage(0);
		break;
	}
	return DefWindowProc(hwnd, msg, wParam, lParam);
}
void main() {
	//創建win32窗口
	WNDCLASS wndclass;
	wndclass.style = CS_HREDRAW | CS_VREDRAW;
	wndclass.lpfnWndProc = WndProc;
	wndclass.cbClsExtra = 0;
	wndclass.cbWndExtra = 0;
	wndclass.hInstance = GetModuleHandle(NULL);
	wndclass.hIcon = LoadIcon(NULL, IDI_APPLICATION);
	wndclass.hCursor = LoadCursor(NULL, IDC_ARROW);
	wndclass.hbrBackground = (HBRUSH)GetStockObject(WHITE_BRUSH);
	wndclass.lpszMenuName = 0;
	wndclass.lpszClassName = L"Win32Window";
	if (!RegisterClass(&wndclass))
	{
		MessageBox(NULL, TEXT("創建窗口失敗!"), L"", MB_ICONERROR);
	}
	auto hwnd = CreateWindowW(
		L"Win32Window",
		L"重做撤銷",
		WS_OVERLAPPEDWINDOW,
		0,
		0,
		640,
		360,
		NULL,
		NULL,
		GetModuleHandle(NULL),
		NULL
	);
	//顯示窗口
	ShowWindow(hwnd, SW_SHOW);
	//獲取窗口上下文
	hdc = GetDC(hwnd);
	HPEN  pen = ::CreatePen(PS_SOLID, 9, RGB(255, 0, 0));//創建一支紅色的畫筆
	auto oldPen = SelectObject(hdc, pen);
	MSG msg;
	HACCEL hAccelTable = NULL;
	// 主消息循環: 
	while (GetMessage(&msg, NULL, 0, 0))
	{
		switch (msg.message)
		{

		case WM_PAINT:

			break;
	
		case WM_DESTROY:
			PostQuitMessage(0);
			break;
		}
		if (!TranslateAccelerator(msg.hwnd, hAccelTable, &msg))
		{
			TranslateMessage(&msg);
			DispatchMessage(&msg);
		}
	}
	//銷毀資源
	SelectObject(hdc, oldPen);
	DeleteObject(oldPen);
	ReleaseDC(hwnd, hdc);
	DestroyWindow(hwnd);
}