#include "mesh.h"
#include <stdlib.h>
#include <math.h>
#ifndef MATH_ASM_AVAILABLE
#include "../ASM/math_c_fallback.h"
#endif

#define POS(n,x,y,z,nx,ny,nz,u,v,r,g,b,a) {x,y,z, nx,ny,nz, u,v, r,g,b,a}

static Mesh* create_mesh(ID3D11Device* dev, const void* verts, uint32_t vc, const uint32_t* idx, uint32_t ic, uint32_t stride) {
    Mesh* m = (Mesh*)calloc(1, sizeof(Mesh));
    m->stride = stride; m->vcount = vc; m->icount = ic;
    D3D11_BUFFER_DESC bd = {0};
    D3D11_SUBRESOURCE_DATA sd = {0};
    bd.ByteWidth = stride * vc; bd.Usage = D3D11_USAGE_DEFAULT; bd.BindFlags = D3D11_BIND_VERTEX_BUFFER;
    sd.pSysMem = verts;
    dev->lpVtbl->CreateBuffer(dev, &bd, &sd, &m->vb);
    if (idx && ic > 0) {
        bd.ByteWidth = sizeof(uint32_t) * ic; bd.BindFlags = D3D11_BIND_INDEX_BUFFER;
        sd.pSysMem = idx;
        dev->lpVtbl->CreateBuffer(dev, &bd, &sd, &m->ib);
    }
    return m;
}

void mesh_destroy(Mesh* m) {
    if (!m) return;
    if (m->ib) m->ib->lpVtbl->Release(m->ib);
    if (m->vb) m->vb->lpVtbl->Release(m->vb);
    free(m);
}

void mesh_draw(Mesh* m, ID3D11DeviceContext* ctx) {
    UINT stride = m->stride, offset = 0;
    ctx->lpVtbl->IASetVertexBuffers(ctx, 0, 1, &m->vb, &stride, &offset);
    if (m->ib) {
        ctx->lpVtbl->IASetIndexBuffer(ctx, m->ib, DXGI_FORMAT_R32_UINT, 0);
        ctx->lpVtbl->DrawIndexed(ctx, m->icount, 0, 0);
    } else {
        ctx->lpVtbl->Draw(ctx, m->vcount, 0);
    }
}

Mesh* mesh_create_cube(ID3D11Device* dev) {
    typedef struct { float p[3], n[3], uv[2], c[4]; } V;
    V v[24] = {
        POS(0,-.5f,-.5f,-.5f, 0,0,-1, 0,1, 1,1,1,1), POS(1, .5f,-.5f,-.5f, 0,0,-1, 1,1, 1,1,1,1),
        POS(2, .5f, .5f,-.5f, 0,0,-1, 1,0, 1,1,1,1), POS(3,-.5f, .5f,-.5f, 0,0,-1, 0,0, 1,1,1,1),
        POS(4, .5f,-.5f, .5f, 0,0, 1, 0,1, 1,1,1,1), POS(5,-.5f,-.5f, .5f, 0,0, 1, 1,1, 1,1,1,1),
        POS(6,-.5f, .5f, .5f, 0,0, 1, 1,0, 1,1,1,1), POS(7, .5f, .5f, .5f, 0,0, 1, 0,0, 1,1,1,1),
        POS(8,-.5f, .5f,-.5f, 0,1, 0, 0,1, 1,1,1,1), POS(9, .5f, .5f,-.5f, 0,1, 0, 1,1, 1,1,1,1),
        POS(10,.5f, .5f, .5f, 0,1, 0, 1,0, 1,1,1,1), POS(11,-.5f, .5f, .5f, 0,1, 0, 0,0, 1,1,1,1),
        POS(12,-.5f,-.5f, .5f, 0,-1,0, 0,1, 1,1,1,1), POS(13,.5f,-.5f, .5f, 0,-1,0, 1,1, 1,1,1,1),
        POS(14,.5f,-.5f,-.5f, 0,-1,0, 1,0, 1,1,1,1), POS(15,-.5f,-.5f,-.5f, 0,-1,0, 0,0, 1,1,1,1),
        POS(16,.5f,-.5f,-.5f, 1,0, 0, 0,1, 1,1,1,1), POS(17,.5f,-.5f, .5f, 1,0, 0, 1,1, 1,1,1,1),
        POS(18,.5f, .5f, .5f, 1,0, 0, 1,0, 1,1,1,1), POS(19,.5f, .5f,-.5f, 1,0, 0, 0,0, 1,1,1,1),
        POS(20,-.5f,-.5f, .5f, -1,0,0, 0,1, 1,1,1,1), POS(21,-.5f,-.5f,-.5f, -1,0,0, 1,1, 1,1,1,1),
        POS(22,-.5f, .5f,-.5f, -1,0,0, 1,0, 1,1,1,1), POS(23,-.5f, .5f, .5f, -1,0,0, 0,0, 1,1,1,1),
    };
    uint32_t idx[36];
    for (int i = 0; i < 6; i++) { int b = i*4; idx[i*6]=b; idx[i*6+1]=b+1; idx[i*6+2]=b+2; idx[i*6+3]=b; idx[i*6+4]=b+2; idx[i*6+5]=b+3; }
    return create_mesh(dev, v, 24, idx, 36, sizeof(V));
}

Mesh* mesh_create_plane(ID3D11Device* dev, float size) {
    typedef struct { float p[3], n[3], uv[2], c[4]; } V;
    float h = size * 0.5f;
    V v[4] = {
        {{-h,0,h},{0,1,0},{0,1},{1,1,1,1}},
        {{ h,0,h},{0,1,0},{1,1},{1,1,1,1}},
        {{ h,0,-h},{0,1,0},{1,0},{1,1,1,1}},
        {{-h,0,-h},{0,1,0},{0,0},{1,1,1,1}},
    };
    uint32_t idx[6] = {0,1,2,0,2,3};
    return create_mesh(dev, v, 4, idx, 6, sizeof(V));
}

Mesh* mesh_create_sphere(ID3D11Device* dev, float r, int seg) {
    typedef struct { float p[3], n[3], uv[2], c[4]; } V;
    int vc = (seg+1)*(seg+1);
    V* v = (V*)malloc(vc * sizeof(V));
    int vi = 0;
    for (int lat = 0; lat <= seg; lat++) {
        float theta = 3.14159265f * lat / seg;
        float st = sinf(theta), ct = cosf(theta);
        for (int lon = 0; lon <= seg; lon++) {
            float phi = 2.0f * 3.14159265f * lon / seg;
            float sp = sinf(phi), cp = cosf(phi);
            float nx = cp*st, ny = ct, nz = sp*st;
            v[vi].p[0] = nx*r; v[vi].p[1] = ny*r; v[vi].p[2] = nz*r;
            v[vi].n[0] = nx; v[vi].n[1] = ny; v[vi].n[2] = nz;
            v[vi].uv[0] = (float)lon/seg; v[vi].uv[1] = (float)lat/seg;
            v[vi].c[0]=1; v[vi].c[1]=1; v[vi].c[2]=1; v[vi].c[3]=1;
            vi++;
        }
    }
    int ic = seg*seg*6;
    uint32_t* idx = (uint32_t*)malloc(ic * sizeof(uint32_t));
    int ii = 0;
    for (int lat = 0; lat < seg; lat++) {
        for (int lon = 0; lon < seg; lon++) {
            uint32_t f = lat*(seg+1)+lon, s = f+seg+1;
            idx[ii++]=f; idx[ii++]=s; idx[ii++]=f+1;
            idx[ii++]=s; idx[ii++]=s+1; idx[ii++]=f+1;
        }
    }
    Mesh* m = create_mesh(dev, v, vc, idx, ic, sizeof(V));
    free(v); free(idx);
    return m;
}