// PROGRAM sandpile
// 1次元の砂山のモデル

#include "TrueBASIC.h"
int main();
void initial(int height[], int N[], int *L, int *IC1_, int *IC2_);
void check(int height[], int L, int move[], int *unstable);
void slide(int height[], int L, int move[], int IC1_);
void show_distribution(int N[], int L, int grain, int IC2_);

int main()
{
    int IC1_ = 1, IC2_ = 2, grain, height[52], L, move[101], N[52], 
        topple, unstable;

    GWopen(0);

    initial(height, N, &L, &IC1_, &IC2_);
    grain = 0;
    do
    {
        ++(height[1]);                      // 最初の格子点に砂粒を加える
        GWselvp(IC1_);
        GWsetogn(0, L + height[1]);
        GWsrect(1.1f, height[1] - 0.4f, 1.9f, height[1] + 0.4f, BLUE);
        topple = 0;                         // 崩れ落ちる砂粒の数
        ++grain;                            // 加えられた砂粒の数
        do
        {
            check(height, L, move, &unstable);
            if(unstable == 1)
            {
                slide(height, L, move, IC1_);
                ++topple;
            }
        } while(!(unstable == 0));
        ++(N[topple]);
        show_distribution(N, L, grain, IC2_);
    } while(!TBkeyinput());

    GWquit();
    return 0;
}

void initial(int height[], int N[], int *L, int *IC1_, int *IC2_)
{
    int i, topple;
    char Stmp1_[_LBUFF_];

    GWsetogn(0, 1);
    GWvport(0.0f, 0.0f, 0.7f*GWaspect(1), 1.0f);
    GWinput("lattice size L = ", Stmp1_, _LBUFF_);
    sscanf(Stmp1_, "%d", L);                // L = 20 としてみよ
    for(i = 1; i <= (*L); ++i)
        height[i] = 0;
    height[(*L) + 1] = 0;                   // 境界条件
    GWindow(-1.0f, -2.0f, (*L)+1.0f, 40.0f);
    GWsetpen(BLACK, -1, -1, 4);
    GWline(1.0f, -0.05f, (*L)+1.0f, -0.05f);
    GWsavevp(*IC1_);
    // 配列の初期化
    for(topple = 0; topple <= (*L); ++topple)
        N[topple] = 0;
    GWvport(0.72f*GWaspect(1), 0.4f, GWaspect(1), 1.0f);
    GWindow(-0.1f, -0.05f, (*L)+1.0f, 1.01f);
    GWline(0.0f, -0.01f, (*L)+0.2f, -0.01f);
    GWline(-0.05f, -0.01f, -0.05f, 1.0f);
    GWsavevp(*IC2_);
    GWsetogn(1, 0);
}

void check(int height[], int L, int move[], int *unstable)
{
    int i;

    (*unstable) = 0;
    for(i = 1; i <= L; ++i)
    {
        if(height[i] - height[i + 1] > 1)
        {
            move[i] = 1;
            (*unstable) = 1;
        }
        else
            move[i] = 0;
    }
}

void slide(int height[], int L, int move[], int IC1_)
{
    int i;

    GWselvp(IC1_);
    for(i = 1; i <= L; ++i)
    {
        if(move[i] == 1)
        {
            GWerase(i*L+height[i], -1);
            --(height[i]);                  // 砂粒が崩れ落ちる
            if(i < L)
            {
                // 次の格子点が砂粒を受けるとる
                ++(height[i + 1]);
                GWsetogn(0, (i + 1)*L+height[i + 1]);
                GWsrect(i + 0.1f, height[i + 1] - 0.4f, 
                       i + 0.9f, height[i + 1] + 0.4f, BLUE);
            }
        }
    }
}

void show_distribution(int N[], int L, int grain, int IC2_)
{
    int topple;

    // 前の図を消去
    GWselvp(IC2_);
    for(topple = 0; topple <= L; ++topple)
    {
        if(N[topple] > 0)
        {
            GWerase(topple+10000, -1);
            GWsetogn(0, topple+10000);
            GWsrect((float)(topple), 0.0f, 
                   (float)(topple+0.2), (float)N[topple]/(float)grain, BLACK);
        }
    }
}