/*
 * Copyright (C) 2020, KylinSoft Co., Ltd.
 *
 * This program 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.
 *
 * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#include "FastScaler_Scale.h"

#include "FastScaler_Scale_Generic.h"
#include "common/TempBuffer.h"
#include <cassert>

/*
==== Fallback MipMapper ====

Uses 'wannabe-SIMD': 4x 16-bit values in normal 64-bit registers. This works as long as overflow is avoided.
Performs best on 64-bit systems, but even on 32-bit it should still be reasonably good.

It's important that this function is force-inlined because this allows the compiler to eliminate the inner loops for common mipmap factors.
*/

inline __attribute__((always_inline))
void MipMap_BGRA_Fallback_Dynamic(unsigned int in_w, unsigned int in_h, const uint8_t* in_data, int in_stride,
                                  uint8_t* out_data, int out_stride, unsigned int mx, unsigned int my) {
    const uint64_t mask = vec4x16(0xff);
    const uint64_t offset = vec4x16(1u << (mx + my - 1));
    unsigned int wrem = in_w & ((1u << mx) - 1);
    unsigned int hrem = in_h & ((1u << my) - 1);
    for(unsigned int out_j = 0; out_j < (in_h >> my); ++out_j) {
        const uint32_t *in = (const uint32_t*) (in_data + in_stride * (int) (out_j << my));
        uint32_t *out = (uint32_t*) (out_data + out_stride * (int) out_j);
        for(unsigned int out_i = 0; out_i < (in_w >> mx); ++out_i) {
            uint64_t sum = 0;
            const uint32_t *in2 = in;
            for(unsigned int mj = 0; mj < (1u << my); ++mj) {
                for(unsigned int mi = 0; mi < (1u << mx); ++mi) {
                    uint64_t c = in2[mi];
                    sum += ((c << 24) | c) & mask;
                }
                in2 = (const uint32_t*) ((const uint8_t*) in2 + in_stride);
            }
            in += (1u << mx);
            uint64_t q = ((sum + offset) >> (mx + my)) & mask;
            *(out++) = ((uint32_t) (q >> 24)) | ((uint32_t) q);
        }
        if(wrem != 0) {
            uint64_t sum = 0;
            const uint32_t *in2 = in;
            for(unsigned int mj = 0; mj < (1u << my); ++mj) {
                for(unsigned int mi = 0; mi < wrem - 1; ++mi) {
                    uint64_t c = in2[mi];
                    sum += ((c << 24) | c) & mask;
                }
                uint64_t c = in2[wrem - 1];
                sum += (((c << 24) | c) & mask) * ((1u << mx) - (wrem - 1));
                in2 = (const uint32_t*) ((const uint8_t*) in2 + in_stride);
            }
            uint64_t q = ((sum + offset) >> (mx + my)) & mask;
            *out = ((uint32_t) (q >> 24)) | ((uint32_t) q);
        }
    }
    if(hrem != 0) {
        unsigned int out_j = in_h >> my;
        const uint32_t *in = (const uint32_t*) (in_data + in_stride * (int) (out_j << my));
        uint32_t *out = (uint32_t*) (out_data + out_stride * (int) out_j);
        for(unsigned int out_i = 0; out_i < (in_w >> mx); ++out_i) {
            uint64_t sum = 0;
            const uint32_t *in2 = in;
            for(unsigned int mj = 0; mj < hrem - 1; ++mj) {
                for(unsigned int mi = 0; mi < (1u << mx); ++mi) {
                    uint64_t c = in2[mi];
                    sum += ((c << 24) | c) & mask;
                }
                in2 = (const uint32_t*) ((const uint8_t*) in2 + in_stride);
            }
            for(unsigned int mi = 0; mi < (1u << mx); ++mi) {
                uint64_t c = in2[mi];
                sum += (((c << 24) | c) & mask) * ((1u << my) - (hrem - 1));
            }
            in += (1u << mx);
            uint64_t q = ((sum + offset) >> (mx + my)) & mask;
            *(out++) = ((uint32_t) (q >> 24)) | ((uint32_t) q);
        }
        if(wrem != 0) {
            uint64_t sum = 0;
            const uint32_t *in2 = in;
            for(unsigned int mj = 0; mj < hrem - 1; ++mj) {
                for(unsigned int mi = 0; mi < wrem - 1; ++mi) {
                    uint64_t c = in2[mi];
                    sum += ((c << 24) | c) & mask;
                }
                uint64_t c = in2[wrem - 1];
                sum += (((c << 24) | c) & mask) * ((1u << mx) - (wrem - 1));
                in2 = (const uint32_t*) ((const uint8_t*) in2 + in_stride);
            }
            for(unsigned int mi = 0; mi < wrem - 1; ++mi) {
                uint64_t c = in2[mi];
                sum += (((c << 24) | c) & mask) * ((1u << my) - (hrem - 1));
            }
            uint64_t c = in2[wrem - 1];
            sum += (((c << 24) | c) & mask) * ((1u << my) - (hrem - 1)) * ((1u << mx) - (wrem - 1));
            uint64_t q = ((sum + offset) >> (mx + my)) & mask;
            *out = ((uint32_t) (q >> 24)) | ((uint32_t) q);
        }
    }
}

void MipMap_BGRA_Fallback(unsigned int in_w, unsigned int in_h, const uint8_t* in_data, int in_stride,
                          uint8_t* out_data, int out_stride, unsigned int mx, unsigned int my) {
    assert(mx + my <= 8);
    switch((mx << 4) | my) {
        case 0x00: assert(false); break;
        case 0x01: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 0, 1); break;
        case 0x02: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 0, 2); break;
        case 0x03: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 0, 3); break;
        case 0x10: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 1, 0); break;
        case 0x11: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 1, 1); break;
        case 0x12: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 1, 2); break;
        case 0x13: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 1, 3); break;
        case 0x20: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 2, 0); break;
        case 0x21: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 2, 1); break;
        case 0x22: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 2, 2); break;
        case 0x23: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 2, 3); break;
        case 0x30: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 3, 0); break;
        case 0x31: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 3, 1); break;
        case 0x32: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 3, 2); break;
        case 0x33: MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, 3, 3); break;
        default:   MipMap_BGRA_Fallback_Dynamic(in_w, in_h, in_data, in_stride, out_data, out_stride, mx, my); break;
    }
}

/*
==== Fallback Bilinear Scaler ====

Uses 'wannabe-SIMD' like the mipmapper. It's slightly less efficient here because of the multiplications, but still much faster than plain 32-bit integers.
*/

void Bilinear_BGRA_Fallback(unsigned int in_w, unsigned int in_h, const uint8_t* in_data, int in_stride,
                            unsigned int out_w, unsigned int out_h, uint8_t* out_data, int out_stride,
                            unsigned int mx, unsigned int my) {
    assert(in_w > 1 && in_h > 1); //TODO// support size 1?
    assert(out_w > 1 && out_h > 1); //TODO// support size 1?
    assert(in_w < (1 << 28) && in_h < (1 << 28));
    assert(out_w < (1 << 28) && out_w < (1 << 28));

    // precompute horizontal offsets and fractions
    TempBuffer<unsigned int> x_offset_table, x_fraction_table;
    x_offset_table.Alloc(out_w);
    x_fraction_table.Alloc(out_w);
    for(unsigned int out_i = 0; out_i < out_w; ++out_i) {
        Bilinear_MapIndex(out_i, in_w, out_w, mx, x_offset_table[out_i], x_fraction_table[out_i]);
    }

    const uint64_t mask = vec4x16(0xff);
    const uint64_t offset = vec4x16(128);

    // scale
    for(unsigned int out_j = 0; out_j < out_h; ++out_j) {
        unsigned int y_offset, y_fraction;
        Bilinear_MapIndex(out_j, in_h, out_h, my, y_offset, y_fraction);
        unsigned int y_fraction_inv = 256 - y_fraction;
        unsigned int *x_offset_ptr = x_offset_table.GetData(), *x_fraction_ptr = x_fraction_table.GetData();
        const uint32_t *in1 = (const uint32_t*) (in_data + in_stride * (int) y_offset);
        const uint32_t *in2 = (const uint32_t*) (in_data + in_stride * ((int) y_offset + 1));
        uint32_t *out = (uint32_t*) (out_data + out_stride * (int) out_j);
        for(unsigned int out_i = 0; out_i < out_w; ++out_i) {
            unsigned int x_offset = *(x_offset_ptr++), x_fraction = *(x_fraction_ptr++), x_fraction_inv = 256 - x_fraction;
            uint64_t c[4] = {in1[x_offset], in1[x_offset + 1], in2[x_offset], in2[x_offset + 1]};
            uint64_t p[4] = {((c[0] << 24) | c[0]) & mask, ((c[1] << 24) | c[1]) & mask, ((c[2] << 24) | c[2]) & mask, ((c[3] << 24) | c[3]) & mask};
            uint64_t q[2] = {((p[0] * x_fraction_inv + p[1] * x_fraction + offset) >> 8) & mask, ((p[2] * x_fraction_inv + p[3] * x_fraction + offset) >> 8) & mask};
            uint64_t r = ((q[0] * y_fraction_inv + q[1] * y_fraction + offset) >> 8) & mask;
            *(out++) = ((uint32_t) (r >> 24)) | ((uint32_t) r);
        }
    }

}

void Scale_BGRA_Fallback(unsigned int in_w, unsigned int in_h, const uint8_t* in_data, int in_stride,
                         unsigned int out_w, unsigned int out_h, uint8_t* out_data, int out_stride) {
    Scale_BGRA_Generic(in_w, in_h, in_data, in_stride, out_w, out_h, out_data, out_stride, MipMap_BGRA_Fallback, Bilinear_BGRA_Fallback);
}
