/* SPDX-License-Identifier: GPL-2.0-only
 *
 *  Generic bitmap / 8 bpp image bitstreamer for packed pixel framebuffers
 *
 *      Rewritten by:
 *      Copyright (C)  2025 Zsolt Kajtar (soci@c64.rulez.org)
 *
 *      Based on previous work of:
 *      Copyright (C)  June 1999 James Simmons
 *      Anton Vorontsov <avorontsov@ru.mvista.com>
 *      Pavel Pisa <pisa@cmp.felk.cvut.cz>
 *      Antonino A. Daplas <adaplas@gmail.com>
 *      and others
 *
 * NOTES:
 *
 * Handles native and foreign byte order on both endians, standard and
 * reverse pixel order in a byte (<8 BPP), word length of 32/64 bits,
 * bits per pixel from 1 to the word length. Handles line lengths at byte
 * granularity while maintaining aligned accesses.
 *
 * Optimized routines for word aligned 1, 2, 4 pixel per word for high
 * bpp modes and 4 pixel at a time operation for low bpp.
 *
 * The color image is expected to be one byte per pixel, and values should
 * not exceed the bitdepth or the pseudo palette (if used).
 */
#include "fb_draw.h"

/* bitmap image iterator, one pixel at a time */
struct fb_bitmap_iter {
        const u8 *data;
        unsigned long colors[2];
        int width, i;
};

static bool fb_bitmap_image(void *iterator, unsigned long *pixels, int *bits)
{
        struct fb_bitmap_iter *iter = iterator;

        if (iter->i < iter->width) {
                int bit = ~iter->i & (BITS_PER_BYTE-1);
                int byte = iter->i++ / BITS_PER_BYTE;

                *pixels = iter->colors[(iter->data[byte] >> bit) & 1];
                return true;
        }
        iter->data += BITS_TO_BYTES(iter->width);
        iter->i = 0;
        return false;
}

/* color image iterator, one pixel at a time */
struct fb_color_iter {
        const u8 *data;
        const u32 *palette;
        struct fb_reverse reverse;
        int shift;
        int width, i;
};

static bool fb_color_image(void *iterator, unsigned long *pixels, int *bits)
{
        struct fb_color_iter *iter = iterator;

        if (iter->i < iter->width) {
                unsigned long color = iter->data[iter->i++];

                if (iter->palette)
                        color = iter->palette[color];
                *pixels = color << iter->shift;
                if (iter->reverse.pixel)
                        *pixels = fb_reverse_bits_long(*pixels);
                return true;
        }
        iter->data += iter->width;
        iter->i = 0;
        return false;
}

/* bitmap image iterator, 4 pixels at a time */
struct fb_bitmap4x_iter {
        const u8 *data;
        u32 fgxcolor, bgcolor;
        int width, i;
        const u32 *expand;
        int bpp;
        bool top;
};

static bool fb_bitmap4x_image(void *iterator, unsigned long *pixels, int *bits)
{
        struct fb_bitmap4x_iter *iter = iterator;
        u8 data;

        if (iter->i >= BITS_PER_BYTE/2) {
                iter->i -= BITS_PER_BYTE/2;
                iter->top = !iter->top;
                if (iter->top)
                        data = *iter->data++ >> BITS_PER_BYTE/2;
                else
                        data = iter->data[-1] & ((1 << BITS_PER_BYTE/2)-1);
        } else if (iter->i != 0) {
                *bits = iter->bpp * iter->i;
                if (iter->top)
                        data = iter->data[-1] & ((1 << BITS_PER_BYTE/2)-1);
                else
                        data = *iter->data++ >> BITS_PER_BYTE/2;
#ifndef __LITTLE_ENDIAN
                data >>= BITS_PER_BYTE/2 - iter->i;
#endif
                iter->i = 0;
        } else {
                *bits = iter->bpp * BITS_PER_BYTE/2;
                iter->i = iter->width;
                iter->top = false;
                return false;
        }
        *pixels = (iter->fgxcolor & iter->expand[data]) ^ iter->bgcolor;
#ifndef __LITTLE_ENDIAN
        *pixels <<= BITS_PER_LONG - *bits;
#endif
        return true;
}

/* draw a line a group of pixels at a time */
static __always_inline void fb_bitblit(bool (*get)(void *iter, unsigned long *pixels,
                                                   int *bits),
                                       void *iter, int bits, struct fb_address *dst,
                                       struct fb_reverse reverse)
{
        unsigned long pixels, val, mask, old;
        int offset = 0;
        int shift = dst->bits;

        if (shift) {
                old = fb_read_offset(0, dst);
                val = fb_reverse_long(old, reverse);
                val &= ~fb_right(~0UL, shift);
        } else {
                old = 0;
                val = 0;
        }

        while (get(iter, &pixels, &bits)) {
                val |= fb_right(pixels, shift);
                shift += bits;

                if (shift < BITS_PER_LONG)
                        continue;

                val = fb_reverse_long(val, reverse);
                fb_write_offset(val, offset++, dst);
                shift &= BITS_PER_LONG - 1;
                val = !shift ? 0 : fb_left(pixels, bits - shift);
        }

        if (shift) {
                mask = ~fb_pixel_mask(shift, reverse);
                val = fb_reverse_long(val, reverse);
                if (offset || !dst->bits)
                        old = fb_read_offset(offset, dst);
                fb_write_offset(fb_comp(val, old, mask), offset, dst);
        }
}

/* draw a color image a pixel at a time */
static inline void fb_color_imageblit(const struct fb_image *image, struct fb_address *dst,
                                      unsigned int bits_per_line, const u32 *palette, int bpp,
                                      struct fb_reverse reverse)
{
        struct fb_color_iter iter;
        u32 height;

        iter.data = (const u8 *)image->data;
        iter.palette = palette;
        iter.reverse = reverse;
#ifdef __LITTLE_ENDIAN
        if (reverse.pixel)
                iter.shift = BITS_PER_BYTE - bpp;
        else
                iter.shift = 0;
#else
        if (reverse.pixel)
                iter.shift = BITS_PER_LONG - BITS_PER_BYTE;
        else
                iter.shift = BITS_PER_LONG - bpp;
#endif
        iter.width = image->width;
        iter.i = 0;

        height = image->height;
        while (height--) {
                fb_bitblit(fb_color_image, &iter, bpp, dst, reverse);
                fb_address_forward(dst, bits_per_line);
        }
}

#ifdef __LITTLE_ENDIAN
#define FB_GEN(a, b) (((a)/8+(((a)&4)<<((b)-2)) \
                       +(((a)&2)<<((b)*2-1))+(((a)&1u)<<((b)*3)))*((1<<(b))-1))
#define FB_GEN1(a) ((a)/8+((a)&4)/2+((a)&2)*2+((a)&1)*8)
#else
#define FB_GEN(a, b) (((((a)/8)<<((b)*3))+(((a)&4)<<((b)*2-2)) \
                       +(((a)&2)<<(b-1))+((a)&1u))*((1<<(b))-1))
#define FB_GEN1(a) (a)
#endif

#define FB_GENx(a) { FB_GEN(0, (a)), FB_GEN(1, (a)), FB_GEN(2, (a)), FB_GEN(3, (a)),    \
        FB_GEN(4, (a)), FB_GEN(5, (a)), FB_GEN(6, (a)), FB_GEN(7, (a)),                 \
        FB_GEN(8, (a)), FB_GEN(9, (a)), FB_GEN(10, (a)), FB_GEN(11, (a)),               \
        FB_GEN(12, (a)), FB_GEN(13, (a)), FB_GEN(14, (a)), FB_GEN(15, (a)) }

/* draw a 2 color image four pixels at a time (for 1-8 bpp only) */
static inline void fb_bitmap4x_imageblit(const struct fb_image *image, struct fb_address *dst,
                                         unsigned long fgcolor, unsigned long bgcolor, int bpp,
                                         unsigned int bits_per_line, struct fb_reverse reverse)
{
        static const u32 mul[BITS_PER_BYTE] = {
                0xf, 0x55, 0x249, 0x1111, 0x8421, 0x41041, 0x204081, 0x01010101
        };
        static const u32 expand[BITS_PER_BYTE][1 << 4] = {
                {
                        FB_GEN1(0), FB_GEN1(1), FB_GEN1(2), FB_GEN1(3),
                        FB_GEN1(4), FB_GEN1(5), FB_GEN1(6), FB_GEN1(7),
                        FB_GEN1(8), FB_GEN1(9), FB_GEN1(10), FB_GEN1(11),
                        FB_GEN1(12), FB_GEN1(13), FB_GEN1(14), FB_GEN1(15)
                },
                FB_GENx(2), FB_GENx(3), FB_GENx(4),
                FB_GENx(5), FB_GENx(6), FB_GENx(7), FB_GENx(8),
        };
        struct fb_bitmap4x_iter iter;
        u32 height;

        iter.data = (const u8 *)image->data;
        if (reverse.pixel) {
                fgcolor = fb_reverse_bits_long(fgcolor << (BITS_PER_BYTE - bpp));
                bgcolor = fb_reverse_bits_long(bgcolor << (BITS_PER_BYTE - bpp));
        }
        iter.fgxcolor = (fgcolor ^ bgcolor) * mul[bpp-1];
        iter.bgcolor = bgcolor * mul[bpp-1];
        iter.width = image->width;
        iter.i = image->width;
        iter.expand = expand[bpp-1];
        iter.bpp = bpp;
        iter.top = false;

        height = image->height;
        while (height--) {
                fb_bitblit(fb_bitmap4x_image, &iter, bpp * BITS_PER_BYTE/2, dst, reverse);
                fb_address_forward(dst, bits_per_line);
        }
}

/* draw a bitmap image 1 pixel at a time (for >8 bpp) */
static inline void fb_bitmap1x_imageblit(const struct fb_image *image, struct fb_address *dst,
                                         unsigned long fgcolor, unsigned long bgcolor, int bpp,
                                         unsigned int bits_per_line, struct fb_reverse reverse)
{
        struct fb_bitmap_iter iter;
        u32 height;

        iter.colors[0] = bgcolor;
        iter.colors[1] = fgcolor;
#ifndef __LITTLE_ENDIAN
        iter.colors[0] <<= BITS_PER_LONG - bpp;
        iter.colors[1] <<= BITS_PER_LONG - bpp;
#endif
        iter.data = (const u8 *)image->data;
        iter.width = image->width;
        iter.i = 0;

        height = image->height;
        while (height--) {
                fb_bitblit(fb_bitmap_image, &iter, bpp, dst, reverse);
                fb_address_forward(dst, bits_per_line);
        }
}

/* one pixel per word, 64/32 bpp blitting */
static inline void fb_bitmap_1ppw(const struct fb_image *image, struct fb_address *dst,
                                  unsigned long fgcolor, unsigned long bgcolor,
                                  int words_per_line, struct fb_reverse reverse)
{
        unsigned long tab[2];
        const u8 *src = (u8 *)image->data;
        int width = image->width;
        int offset;
        u32 height;

        if (reverse.byte) {
                tab[0] = swab_long(bgcolor);
                tab[1] = swab_long(fgcolor);
        } else {
                tab[0] = bgcolor;
                tab[1] = fgcolor;
        }

        height = image->height;
        while (height--) {
                for (offset = 0; offset + 8 <= width; offset += 8) {
                        unsigned int srcbyte = *src++;

                        fb_write_offset(tab[(srcbyte >> 7) & 1], offset + 0, dst);
                        fb_write_offset(tab[(srcbyte >> 6) & 1], offset + 1, dst);
                        fb_write_offset(tab[(srcbyte >> 5) & 1], offset + 2, dst);
                        fb_write_offset(tab[(srcbyte >> 4) & 1], offset + 3, dst);
                        fb_write_offset(tab[(srcbyte >> 3) & 1], offset + 4, dst);
                        fb_write_offset(tab[(srcbyte >> 2) & 1], offset + 5, dst);
                        fb_write_offset(tab[(srcbyte >> 1) & 1], offset + 6, dst);
                        fb_write_offset(tab[(srcbyte >> 0) & 1], offset + 7, dst);
                }

                if (offset < width) {
                        unsigned int srcbyte = *src++;

                        while (offset < width) {
                                fb_write_offset(tab[(srcbyte >> 7) & 1], offset, dst);
                                srcbyte <<= 1;
                                offset++;
                        }
                }
                fb_address_move_long(dst, words_per_line);
        }
}

static inline unsigned long fb_pack(unsigned long left, unsigned long right, int bits)
{
#ifdef __LITTLE_ENDIAN
        return left | right << bits;
#else
        return right | left << bits;
#endif
}

/* aligned 32/16 bpp blitting */
static inline void fb_bitmap_2ppw(const struct fb_image *image, struct fb_address *dst,
                                  unsigned long fgcolor, unsigned long bgcolor,
                                  int words_per_line, struct fb_reverse reverse)
{
        unsigned long tab[4];
        const u8 *src = (u8 *)image->data;
        int width = image->width / 2;
        int offset;
        u32 height;

        tab[0] = fb_pack(bgcolor, bgcolor, BITS_PER_LONG/2);
        tab[1] = fb_pack(bgcolor, fgcolor, BITS_PER_LONG/2);
        tab[2] = fb_pack(fgcolor, bgcolor, BITS_PER_LONG/2);
        tab[3] = fb_pack(fgcolor, fgcolor, BITS_PER_LONG/2);

        if (reverse.byte) {
                tab[0] = swab_long(tab[0]);
                tab[1] = swab_long(tab[1]);
                tab[2] = swab_long(tab[2]);
                tab[3] = swab_long(tab[3]);
        }

        height = image->height;
        while (height--) {
                for (offset = 0; offset + 4 <= width; offset += 4) {
                        unsigned int srcbyte = *src++;

                        fb_write_offset(tab[(srcbyte >> 6) & 3], offset + 0, dst);
                        fb_write_offset(tab[(srcbyte >> 4) & 3], offset + 1, dst);
                        fb_write_offset(tab[(srcbyte >> 2) & 3], offset + 2, dst);
                        fb_write_offset(tab[(srcbyte >> 0) & 3], offset + 3, dst);
                }

                if (offset < width) {
                        unsigned int srcbyte = *src++;

                        while (offset < width) {
                                fb_write_offset(tab[(srcbyte >> 6) & 3], offset, dst);
                                srcbyte <<= 2;
                                offset++;
                        }
                }
                fb_address_move_long(dst, words_per_line);
        }
}

#define FB_PATP(a, b) (((a)<<((b)*BITS_PER_LONG/4))*((1UL<<BITS_PER_LONG/4)-1UL))
#define FB_PAT4(a) (FB_PATP((a)&1, 0)|FB_PATP(((a)&2)/2, 1)| \
        FB_PATP(((a)&4)/4, 2)|FB_PATP(((a)&8)/8, 3))

/* aligned 16/8 bpp blitting */
static inline void fb_bitmap_4ppw(const struct fb_image *image, struct fb_address *dst,
                                  unsigned long fgcolor, unsigned long bgcolor,
                                  int words_per_line, struct fb_reverse reverse)
{
        static const unsigned long tab16_be[] = {
                0, FB_PAT4(1UL), FB_PAT4(2UL), FB_PAT4(3UL),
                FB_PAT4(4UL), FB_PAT4(5UL), FB_PAT4(6UL), FB_PAT4(7UL),
                FB_PAT4(8UL), FB_PAT4(9UL), FB_PAT4(10UL), FB_PAT4(11UL),
                FB_PAT4(12UL), FB_PAT4(13UL), FB_PAT4(14UL), ~0UL
        };
        static const unsigned long tab16_le[] = {
                0, FB_PAT4(8UL), FB_PAT4(4UL), FB_PAT4(12UL),
                FB_PAT4(2UL), FB_PAT4(10UL), FB_PAT4(6UL), FB_PAT4(14UL),
                FB_PAT4(1UL), FB_PAT4(9UL), FB_PAT4(5UL), FB_PAT4(13UL),
                FB_PAT4(3UL), FB_PAT4(11UL), FB_PAT4(7UL), ~0UL
        };
        const unsigned long *tab;
        const u8 *src = (u8 *)image->data;
        int width = image->width / 4;
        int offset;
        u32 height;

        fgcolor = fgcolor | fgcolor << BITS_PER_LONG/4;
        bgcolor = bgcolor | bgcolor << BITS_PER_LONG/4;
        fgcolor = fgcolor | fgcolor << BITS_PER_LONG/2;
        bgcolor = bgcolor | bgcolor << BITS_PER_LONG/2;
        fgcolor ^= bgcolor;

        if (BITS_PER_LONG/4 > BITS_PER_BYTE && reverse.byte) {
                fgcolor = swab_long(fgcolor);
                bgcolor = swab_long(bgcolor);
        }

#ifdef __LITTLE_ENDIAN
        tab = reverse.byte ? tab16_be : tab16_le;
#else
        tab = reverse.byte ? tab16_le : tab16_be;
#endif

        height = image->height;
        while (height--) {
                for (offset = 0; offset + 2 <= width; offset += 2, src++) {
                        fb_write_offset((fgcolor & tab[*src >> 4]) ^ bgcolor, offset + 0, dst);
                        fb_write_offset((fgcolor & tab[*src & 0xf]) ^ bgcolor, offset + 1, dst);
                }

                if (offset < width)
                        fb_write_offset((fgcolor & tab[*src++ >> 4]) ^ bgcolor, offset, dst);

                fb_address_move_long(dst, words_per_line);
        }
}

static inline void fb_bitmap_imageblit(const struct fb_image *image, struct fb_address *dst,
                                       unsigned int bits_per_line, const u32 *palette, int bpp,
                                       struct fb_reverse reverse)
{
        unsigned long fgcolor, bgcolor;

        if (palette) {
                fgcolor = palette[image->fg_color];
                bgcolor = palette[image->bg_color];
        } else {
                fgcolor = image->fg_color;
                bgcolor = image->bg_color;
        }

        if (!dst->bits && !(bits_per_line & (BITS_PER_LONG-1))) {
                if (bpp == BITS_PER_LONG && BITS_PER_LONG == 32) {
                        fb_bitmap_1ppw(image, dst, fgcolor, bgcolor,
                                       bits_per_line / BITS_PER_LONG, reverse);
                        return;
                }
                if (bpp == BITS_PER_LONG/2 && !(image->width & 1)) {
                        fb_bitmap_2ppw(image, dst, fgcolor, bgcolor,
                                       bits_per_line / BITS_PER_LONG, reverse);
                        return;
                }
                if (bpp == BITS_PER_LONG/4 && !(image->width & 3)) {
                        fb_bitmap_4ppw(image, dst, fgcolor, bgcolor,
                                       bits_per_line / BITS_PER_LONG, reverse);
                        return;
                }
        }

        if (bpp > 0 && bpp <= BITS_PER_BYTE)
                fb_bitmap4x_imageblit(image, dst, fgcolor, bgcolor, bpp,
                                     bits_per_line, reverse);
        else if (bpp > BITS_PER_BYTE && bpp <= BITS_PER_LONG)
                fb_bitmap1x_imageblit(image, dst, fgcolor, bgcolor, bpp,
                                     bits_per_line, reverse);
}

static inline void fb_imageblit(struct fb_info *p, const struct fb_image *image)
{
        int bpp = p->var.bits_per_pixel;
        unsigned int bits_per_line = BYTES_TO_BITS(p->fix.line_length);
        struct fb_address dst = fb_address_init(p);
        struct fb_reverse reverse = fb_reverse_init(p);
        const u32 *palette = fb_palette(p);

        fb_address_forward(&dst, image->dy * bits_per_line + image->dx * bpp);

        if (image->depth == 1)
                fb_bitmap_imageblit(image, &dst, bits_per_line, palette, bpp, reverse);
        else
                fb_color_imageblit(image, &dst, bits_per_line, palette, bpp, reverse);
}