// ■伸縮する棒と二つの球
//   左ボタンクリックで大きな球の位置を指定。。
#include "myWin.h"
#include "stdlib.h"
#include "time.h"
#include "math.h"
#define frand()((double)rand()/(RAND_MAX+1))
typedef struct{	double X, Y;} point;
typedef struct{
	point Position, Velocity,Acc;
	double Mass;
} mass;
static double SpringLength; //バネの長さ
static double Kfact;        //バネ定数
static double Myu ;   //粘性抵抗
static double Gravity;//重力
static mass P1;//質点1
static mass P2;//質点2
static point Force ;//力
static HDC hBuff; static HBITMAP hBM;     //ビットマップ表示用
void drawLine(int X1, int Y1, int X2, int Y2, int Color, int bColor){//■バネ部分
	HPEN pen=CreatePen(PS_SOLID, 3, Color)  ; SelectObject(hBuff, pen)  ;
	MoveToEx(hBuff,X1,Y1,NULL);LineTo(hBuff, X2, Y2); DeleteObject(pen);
	pen=CreatePen(PS_SOLID, 1, bColor)  ; SelectObject(hBuff, pen)  ;
	MoveToEx(hBuff,X1,Y1,NULL);LineTo(hBuff, X2, Y2); DeleteObject(pen);
}
void drawEllipse(int X1, int Y1, int X2, int Y2, int lColor, int bColor){//■ボール
	HPEN pen=CreatePen(PS_SOLID, 1, lColor)  ; SelectObject(hBuff, pen)  ;
	HBRUSH brush=CreateSolidBrush(bColor)    ; SelectObject(hBuff, brush);
	Ellipse(hBuff,X1,Y1, X2,Y2)              ; DeleteObject(brush)       ;
	DeleteObject(pen);
}
void drawBox(int X1, int Y1, int X2, int Y2, int lColor, int bColor){//
	HPEN pen=CreatePen(PS_NULL, 1, lColor)  ; SelectObject(hBuff, pen)  ;
	HBRUSH brush=CreateHatchBrush(HS_FDIAGONAL, bColor); SelectObject(hBuff, brush);
	Rectangle(hBuff,X1,Y1, X2,Y2); DeleteObject(brush) ; DeleteObject(pen) ;
    pen=CreatePen(PS_SOLID,2,lColor) ;SelectObject(hBuff, pen);
	MoveToEx(hBuff,X1,Y1,NULL);LineTo(hBuff, X2, Y1); DeleteObject(pen);
}
void crearBitmap(){                                         //■ビットマップクリア
	SelectObject(hBuff,GetStockObject(NULL_PEN));
	PatBlt(hBuff,0, 0,1000,400,WHITENESS);
}
void update(){//■変更
  double DX = P1.Position.X - P2.Position.X;
  double DY = P1.Position.Y - P2.Position.Y;
  double DL = sqrt(DX * DX + DY * DY), HX = DX / DL, HY = DY / DL;
  double FL = -Kfact * (DL - SpringLength);
  Force.X = HX * FL,  Force.Y = HY * FL;
  P1.Acc.X = Force.X * 0.5 / P1.Mass;
  P1.Acc.Y = Force.Y * 0.5 / P1.Mass;
  P2.Acc.X = -Force.X * 0.5 / P2.Mass;
  P2.Acc.Y = -Force.Y * 0.5 / P2.Mass;
  P1.Velocity.X = (P1.Acc.X + P1.Velocity.X) * (1 - Myu);
  P1.Velocity.Y = (P1.Acc.Y + P1.Velocity.Y + Gravity) * (1 - Myu);
  P2.Velocity.X = (P2.Acc.X + P2.Velocity.X) * (1 - Myu);
  P2.Velocity.Y = (P2.Acc.Y + P2.Velocity.Y + Gravity) * (1 - Myu);
  P1.Position.X = P1.Position.X + P1.Velocity.X;
  P1.Position.Y = P1.Position.Y + P1.Velocity.Y;
  P2.Position.X = P2.Position.X + P2.Velocity.X;
  P2.Position.Y = P2.Position.Y + P2.Velocity.Y;
  if(P1.Position.Y > 245){
    P1.Position.Y = 245; P1.Velocity.Y = -P1.Velocity.Y;
	if(abs(P1.Velocity.Y)>2) Beep(700,25);
  }
  if(P2.Position.Y > 255){
    P2.Position.Y = 255;P2.Velocity.Y = -P2.Velocity.Y;
    if(abs(P2.Velocity.Y)>2) Beep(1400,25);
  }
}
void initData(){//初期設定
	P1.Mass = 1500;	P2.Mass = 200; SpringLength = 100;
	Myu = 0.02;	Kfact = 10; Gravity = 0.98;
	srand((int)time(NULL));
	P1.Position.Y = 10; P1.Position.X = 300;
	P2.Position.Y = 0;P2.Position.X = 20;
}
void display(){//■表示
	crearBitmap(); 
	drawBox(0,265, 500, 300, 0,0x55FF);
	int X1 = (int)P1.Position.X, Y1 = (int)P1.Position.Y;
    int X2 = (int)P2.Position.X, Y2 = (int)P2.Position.Y;
	drawLine(X1+10, Y1+10, X2+5, Y2+5, 0x77, 0x7777);
	drawEllipse(X1,Y1,X1+20,Y1+20, 0, 0xFF7700);
	drawEllipse(X2,Y2,X2+10,Y2+10, 0, 0xFF);
}
void procTimer(HWND hw, WPARAM wp,LPARAM lp){               //■タイマー処理
	double X1 = P1.Position.X,  Y1 = P1.Position.Y;
	double X2 = P2.Position.X,  Y2 = P2.Position.Y;
	if(abs(P1.Velocity.X) < 0.8 && abs(P1.Velocity.Y) < 0.8 &&
		abs(P2.Velocity.X) < 0.8 && abs(P2.Velocity.Y) < 0.8 &&
		P1.Position.Y > 244 && P2.Position.Y > 254 )
		KillTimer(hw,1);
 
	update();
	display(); InvalidateRect(hw,NULL,TRUE);
}
void procLButtonDown(HWND hw, WPARAM wp,LPARAM lp){         //■左ボタン処理
	P1.Position.X=(double)(LOWORD(lp))-10; 
	P1.Position.Y=(double)(HIWORD(lp))-10; 
	display(); InvalidateRect(hw,NULL,TRUE);
	SetTimer(hw,1,50,NULL);  //画面キャプチャするときはここをコメント
}
void procRButtonDown(HWND hw, WPARAM wp,LPARAM lp){         //■左ボタン処理
    update();//画面キャプチャするときは右ボタンで次の画面に進む（タイマーの替わり）
	display(); InvalidateRect(hw,NULL,TRUE);
}
void initBitmap(HWND hw){                                   //■ビットマップ初期設定
	HDC hdc=GetDC(hw); hBM=CreateCompatibleBitmap(hdc,1000,400);
	hBuff=CreateCompatibleDC(hdc); SelectObject(hBuff,hBM);
	crearBitmap(); ReleaseDC(hw,hdc);
}
void procCreate(HWND hw, WPARAM wp,LPARAM lp){              //■Create時処理
	SetWindowText(hw,TEXT("伸縮する棒と２つの球（左クリックで大きな球の位置指定）"));
	MoveWindow(hw,0,0,500,400,TRUE);
	initBitmap(hw);	initData();display(); InvalidateRect(hw,NULL,TRUE);
	SetTimer(hw,1,50,NULL);  //画面キャプチャするときはここをコメント
}
void procPaint(HWND hw, WPARAM wp,LPARAM lp){               //■Paint時処理
	PAINTSTRUCT ps;	HDC hdc=BeginPaint(hw, &ps);
	BitBlt(hdc, 0,0,1000,400,hBuff,0,0,SRCCOPY);
	EndPaint(hw,&ps);
}
LRESULT CALLBACK WndProc(HWND hw, UINT msg, WPARAM wp,LPARAM lp){//■Window Procedure
	switch(msg){
	case WM_DESTROY       : PostQuitMessage(0)         ; return 0;
	case WM_CREATE        : procCreate(hw,wp,lp)       ; return 0;
	case WM_PAINT         : procPaint(hw,wp,lp)        ; return 0;
	case WM_TIMER         : procTimer(hw,wp,lp)        ; return 0;
	case WM_LBUTTONDOWN   : procLButtonDown(hw,wp,lp)  ; break;
	case WM_RBUTTONDOWN   : procRButtonDown(hw,wp,lp)  ; break;
	}
	return DefWindowProc(hw,msg,wp,lp);
}