/*
    Copyright 2016-2017 StapleButter

    This file is part of melonDS.

    melonDS is free software: you can redistribute it and/or modify it under
    the terms of the GNU General Public License as published by the Free
    Software Foundation, either version 3 of the License, or (at your option)
    any later version.

    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with melonDS. If not, see http://www.gnu.org/licenses/.
*/

#include <stdio.h>
#include <string.h>
#include "NDS.h"
#include "GPU3D.h"


namespace GPU3D
{
namespace SoftRenderer
{

u8 ColorBuffer[256*192 * 4];
u32 DepthBuffer[256*192];


bool Init()
{
    return true;
}

void DeInit()
{
    //
}

void Reset()
{
    memset(ColorBuffer, 0, 256*192 * 4);
    memset(DepthBuffer, 0, 256*192 * 4);
}


void RenderPixel(u32 attr, s32 x, s32 y, s32 z, u8 vr, u8 vg, u8 vb)
{
    u32* depth = &DepthBuffer[(256*y) + x];

    bool passdepth = false;
    if (attr & (1<<14))
    {
        s32 diff = *depth - z;
        if ((u32)(diff + 0x200) <= 0x400)
            passdepth = true;
    }
    else
    if (z < *depth)
        passdepth = true;

    if (!passdepth) return;

    u8* pixel = &ColorBuffer[((256*y) + x) * 4];
    pixel[0] = vr;
    pixel[1] = vg;
    pixel[2] = vb;
    pixel[3] = 31; // TODO: alpha

    // TODO: optional update for translucent pixels
    *depth = z;
}

void RenderPolygon(Polygon* polygon)
{
    int nverts = polygon->NumVertices;

    int vtop = 0, vbot = 0;
    s32 ytop = 191, ybot = 0;
    s32 scrcoords[10][4];

    // find the topmost and bottommost vertices of the polygon

    for (int i = 0; i < nverts; i++)
    {
        Vertex* vtx = polygon->Vertices[i];

        s32 posX, posY, posZ, posW;
        s32 w = vtx->Position[3];
        if (w == 0)
        {
            posX = 0;
            posY = 0;
            posZ = 0;
            posW = 0x1000;
        }
        else
        {
            // TODO: find a way to avoid doing 3 divisions :/
            posX = ((s64)vtx->Position[0] << 12) / w;
            posY = ((s64)vtx->Position[1] << 12) / w;
            posZ = ((s64)vtx->Position[2] << 12) / w;
            posW = w;
        }

        s32 scrX = (((posX + 0x1000) * Viewport[2]) >> 13) + Viewport[0];
        s32 scrY = (((posY + 0x1000) * Viewport[3]) >> 13) + Viewport[1];
        s32 scrZ = (((s64)(posZ + 0x1000) * 0xFFFFFF) >> 13);
        if (scrX > 255) scrX = 255;
        if (scrY > 191) scrY = 191;
        if (scrZ > 0xFFFFFF) scrZ = 0xFFFFFF;
        if (scrX < 0) { printf("!! bad X %d\n", scrX); scrX = 0;}
        if (scrY < 0) { printf("!! bad Y %d\n", scrY); scrY = 0;}
        if (scrZ < 0) { printf("!! bad Z %d %d\n", scrZ, vtx->Position[2]); scrZ = 0;}

        scrcoords[i][0] = scrX;
        scrcoords[i][1] = 191 - scrY;
        scrcoords[i][2] = scrZ;
        scrcoords[i][3] = posW;

        if (scrcoords[i][1] < ytop)
        {
            ytop = scrcoords[i][1];
            vtop = i;
        }
        if (scrcoords[i][1] > ybot)
        {
            ybot = scrcoords[i][1];
            vbot = i;
        }
        //if (vtx->Color[0]==63 && vtx->Color[1]==0 && vtx->Color[2]==0)
        //printf("v%d: %d,%d  Z=%f  W=%f  %d  %d\n", i, scrX, 191-scrY, vtx->Position[2]/4096.0f, vtx->Position[3]/4096.0f,
        //       polygon->FacingView, vtx->Clipped);
    }

    // draw, line per line

    int lcur = vtop, rcur = vtop;
    int lnext, rnext;
    s32 lstep, rstep;
    //s32 xmin, xmax;

    if (polygon->FacingView)
    {
        lnext = lcur + 1;
        if (lnext >= nverts) lnext = 0;
        rnext = rcur - 1;
        if (rnext < 0) rnext = nverts - 1;
    }
    else
    {
        lnext = lcur - 1;
        if (lnext < 0) lnext = nverts - 1;
        rnext = rcur + 1;
        if (rnext >= nverts) rnext = 0;
    }

    /*if ((scrcoords[lnext][1] - scrcoords[lcur][1]) == 0) lstep = 0; else
    lstep = ((scrcoords[lnext][0] - scrcoords[lcur][0]) << 12) / (scrcoords[lnext][1] - scrcoords[lcur][1]);
    if ((scrcoords[rnext][1] - scrcoords[rcur][1]) == 0) rstep = 0; else
    rstep = ((scrcoords[rnext][0] - scrcoords[rcur][0]) << 12) / (scrcoords[rnext][1] - scrcoords[rcur][1]);*/

    //xmin = scrcoords[lcur][0] << 12;
    //xmax = scrcoords[rcur][0] << 12;

    for (s32 y = ytop; y <= ybot; y++)
    {
        if (y < ybot)
        {
            while (y == scrcoords[lnext][1])
            {
                lcur = lnext;

                if (polygon->FacingView)
                {
                    lnext = lcur + 1;
                    if (lnext >= nverts) lnext = 0;
                }
                else
                {
                    lnext = lcur - 1;
                    if (lnext < 0) lnext = nverts - 1;
                }

                //lstep = ((scrcoords[lnext][0] - scrcoords[lcur][0]) << 12) / (scrcoords[lnext][1] - scrcoords[lcur][1]);
                //xmin = scrcoords[lcur][0] << 12;
                if (lcur == vbot) break;
            }

            while (y == scrcoords[rnext][1])
            {
                rcur = rnext;

                if (polygon->FacingView)
                {
                    rnext = rcur - 1;
                    if (rnext < 0) rnext = nverts - 1;
                }
                else
                {
                    rnext = rcur + 1;
                    if (rnext >= nverts) rnext = 0;
                }

                //rstep = ((scrcoords[rnext][0] - scrcoords[rcur][0]) << 12) / (scrcoords[rnext][1] - scrcoords[rcur][1]);
                //xmax = scrcoords[rcur][0] << 12;
                if (rcur == vbot) break;
            }
        }

        Vertex* vlcur = polygon->Vertices[lcur];
        Vertex* vlnext = polygon->Vertices[lnext];
        Vertex* vrcur = polygon->Vertices[rcur];
        Vertex* vrnext = polygon->Vertices[rnext];

        s32 lfactor, rfactor;

        if (scrcoords[lnext][1] == scrcoords[lcur][1])
            lfactor = 0;
        else
            lfactor = ((y - scrcoords[lcur][1]) << 12) / (scrcoords[lnext][1] - scrcoords[lcur][1]);

        if (scrcoords[rnext][1] == scrcoords[rcur][1])
            rfactor = 0;
        else
            rfactor = ((y - scrcoords[rcur][1]) << 12) / (scrcoords[rnext][1] - scrcoords[rcur][1]);

        s32 xl = scrcoords[lcur][0] + (((scrcoords[lnext][0] - scrcoords[lcur][0]) * lfactor) >> 12);
        s32 xr = scrcoords[rcur][0] + (((scrcoords[rnext][0] - scrcoords[rcur][0]) * rfactor) >> 12);

        if (xl<0 || xr>255) continue; // hax

        s32 zl = scrcoords[lcur][2] + (((s64)(scrcoords[lnext][2] - scrcoords[lcur][2]) * lfactor) >> 12);
        s32 zr = scrcoords[rcur][2] + (((s64)(scrcoords[rnext][2] - scrcoords[rcur][2]) * rfactor) >> 12);

        s32 wl = scrcoords[lcur][3] + (((s64)(scrcoords[lnext][3] - scrcoords[lcur][3]) * lfactor) >> 12);
        s32 wr = scrcoords[rcur][3] + (((s64)(scrcoords[rnext][3] - scrcoords[rcur][3]) * rfactor) >> 12);

        s64 perspfactorl1 = ((s64)(0x1000 - lfactor) << 12) / scrcoords[lcur][3];
        s64 perspfactorl2 = ((s64)lfactor << 12) / scrcoords[lnext][3];
        s64 perspfactorr1 = ((s64)(0x1000 - rfactor) << 12) / scrcoords[rcur][3];
        s64 perspfactorr2 = ((s64)rfactor << 12) / scrcoords[rnext][3];

        u32 rl = (((perspfactorl1 * vlcur->Color[0]) + (perspfactorl2 * vlnext->Color[0])) << 12) / (perspfactorl1 + perspfactorl2);
        u32 gl = (((perspfactorl1 * vlcur->Color[1]) + (perspfactorl2 * vlnext->Color[1])) << 12) / (perspfactorl1 + perspfactorl2);
        u32 bl = (((perspfactorl1 * vlcur->Color[2]) + (perspfactorl2 * vlnext->Color[2])) << 12) / (perspfactorl1 + perspfactorl2);

        u32 rr = (((perspfactorr1 * vrcur->Color[0]) + (perspfactorr2 * vrnext->Color[0])) << 12) / (perspfactorr1 + perspfactorr2);
        u32 gr = (((perspfactorr1 * vrcur->Color[1]) + (perspfactorr2 * vrnext->Color[1])) << 12) / (perspfactorr1 + perspfactorr2);
        u32 br = (((perspfactorr1 * vrcur->Color[2]) + (perspfactorr2 * vrnext->Color[2])) << 12) / (perspfactorr1 + perspfactorr2);

        s32 xdiv;
        if (xr == xl)
            xdiv = 0;
        else
            xdiv = 0x1000 / (xr - xl);

        for (s32 x = xl; x <= xr; x++)
        {
            s32 xfactor = (x - xl) * xdiv;

            s32 z = zl + (((s64)(zr - zl) * xfactor) >> 12);

            s32 perspfactor1 = ((0x1000 - xfactor) << 12) / wl;
            s32 perspfactor2 = (xfactor << 12) / wr;

            // possible optimization: only do color interpolation if the depth test passes
            u32 vr = (s64)((perspfactor1 * rl) + (perspfactor2 * rr)) / (perspfactor1 + perspfactor2);
            u32 vg = (s64)((perspfactor1 * gl) + (perspfactor2 * gr)) / (perspfactor1 + perspfactor2);
            u32 vb = (s64)((perspfactor1 * bl) + (perspfactor2 * br)) / (perspfactor1 + perspfactor2);

            RenderPixel(polygon->Attr, x, y, z, vr>>12, vg>>12, vb>>12);

            // Z debug
            /*u8 zerp = (w * 63) / 0xFFFFFF;
            pixel[0] = zerp;
            pixel[1] = zerp;
            pixel[2] = zerp;*/
        }
    }

    // DEBUG CODE
    /*for (int i = 0; i < nverts; i++)
    {
        s32 x = scrcoords[i][0];
        s32 y = scrcoords[i][1];

        u8* pixel = &ColorBuffer[((256*y) + x) * 4];
            pixel[0] = 63;
            pixel[1] = 63;
            pixel[2] = 63;
            pixel[3] = 31;
    }*/
}

void RenderFrame(Vertex* vertices, Polygon* polygons, int npolys)
{
    // TODO: render translucent polygons last

    // TODO proper clear color/depth support!
    for (int i = 0; i < 256*192; i++)
    {
        ((u32*)ColorBuffer)[i] = 0x00000000;
        DepthBuffer[i] = 0xFFFFFF;
    }

    for (int i = 0; i < npolys; i++)
    {
        /*printf("polygon %d: %d %d %d\n", i, polygons[i].Vertices[0]->Color[0], polygons[i].Vertices[0]->Color[1], polygons[i].Vertices[0]->Color[2]);
        for (int j = 0; j < polygons[i].NumVertices; j++)
            printf("  %d: %f %f %f\n",
                   j,
                   polygons[i].Vertices[j]->Position[0]/4096.0f,
                   polygons[i].Vertices[j]->Position[1]/4096.0f,
                   polygons[i].Vertices[j]->Position[2]/4096.0f);
*/
        //printf("polygon %d\n", i);
        //if (!polygons[i].Vertices[0]->Clipped) continue;
        //printf("polygon %d\n", i);
        RenderPolygon(&polygons[i]);
    }
}

u8* GetLine(int line)
{
    return &ColorBuffer[line * 256 * 4];
}

}
}