//
// Created by 14727 on 2022/11/19.
//

#include "device/Nurbs/nurbs_common.cuh"
#include "device/device_utils.cuh"
#include <cstdio>

__device__ void d_basisFunction(float *N_Texture, const float *knots, float u, int degree, int d_knotsCnt) {
    int m = d_knotsCnt - 1;
    for (int p = 0; p <= degree; p++) {
        for (int i = 0; i + p <= m - 1; i++) {
            if (p == 0) {
                if ((u > knots[i] || d_floatEqual(u, knots[i])) && (u < knots[i + 1])
                    ||
                    d_floatEqual(u, knots[i + 1]) && d_floatEqual(u, knots[m])) {
                    N_Texture[p * m + i] = 1.0;
                } else {
                    N_Texture[p * m + i] = 0.0;
                }
            } else {
                float Nip_1 = N_Texture[(p - 1) * m + i];
                float Ni1p_1 = N_Texture[(p - 1) * m + i + 1];
                float left = d_floatEqual(knots[i + p], knots[i]) ? 0 : (u - knots[i]) * Nip_1 /
                                                                        (knots[i + p] - knots[i]);
                float right = d_floatEqual(knots[i + p + 1], knots[i + 1]) ? 0 : (knots[i + p + 1] - u) * Ni1p_1 /
                                                                                 (knots[i + p + 1] - knots[i + 1]);
                N_Texture[p * m + i] = left + right;
            }
        }
    }
}

__global__ void g_basisTexture(float *nTexture, float *nTexture1, const float *d_knots, int d_pointsCnt, int d_knotsCnt,
                               int d_sampleCnt) {
    // 一维grid和一维block
    int idx = blockIdx.x * blockDim.x + threadIdx.x;  // 采样点编号
    float d_paramCeil = d_knots[d_knotsCnt - 1];
    float u = idx * d_paramCeil / (d_sampleCnt - 1);
    if (u > 1.0 * d_paramCeil) {
        return;
    }
    int d_degree = d_knotsCnt - 1 - d_pointsCnt;
    auto *N_dp = (float *) malloc((d_degree + 1) * (d_knotsCnt - 1) * sizeof(float));
    d_basisFunction(N_dp, d_knots, u, d_degree, d_knotsCnt);
    for (int i = 0; i < d_pointsCnt; i++) {
        nTexture[idx * d_pointsCnt + i] = N_dp[d_degree * (d_knotsCnt - 1) + i];
        nTexture1[idx * (d_pointsCnt + 1) + i] = N_dp[(d_degree - 1) * (d_knotsCnt - 1) + i];
    }
    nTexture1[idx * (d_pointsCnt + 1) + d_pointsCnt] = N_dp[(d_degree - 1) * (d_knotsCnt - 1) +
                                                            d_pointsCnt]; // nTexture1多记录一列数据
    d_safeFree(N_dp);
}

__global__ void
g_derTexture(float *derTexture, const float *nTexture1, const float *d_knots, int d_pointsCnt, int d_knotsCnt,
             int d_sampleCnt) {
    // 一维grid和一维block
    int idx = blockIdx.x * blockDim.x + threadIdx.x;  // 采样点编号
    if (idx >= d_sampleCnt) {
        return;
    }
    int degree = d_knotsCnt - 1 - d_pointsCnt;

//    printf("degree: %d\n", degree);
    for (int i = 0; i < d_pointsCnt; i++) {
        float left = d_floatEqual(d_knots[i + degree], d_knots[i]) ? 0 :
                     nTexture1[idx * (d_pointsCnt + 1) + i] * (degree - 1) / (d_knots[i + degree] - d_knots[i]);
        float right = d_floatEqual(d_knots[i + degree + 1], d_knots[i + 1]) ? 0 :
                      nTexture1[idx * (d_pointsCnt + 1) + i + 1] * (degree - 1) /
                      (d_knots[i + degree + 1] - d_knots[i + 1]);
        derTexture[idx * d_pointsCnt + i] = left - right;
//        printf("<%d, %d> -- %g \n", idx, i, left - right);
//        printf("nTex1: %g \n", nTexture1[idx * (d_pointsCnt + 1) + i]);
    }
}