#include <stdio.h>

#include <SDL2/SDL.h>

#include "render.h"
#include "ppu.h"
#include "mapper.h"


static SDL_Color nes_palette[64] = {
   {0x80,0x80,0x80}, {0x00,0x00,0xBB}, {0x37,0x00,0xBF}, {0x84,0x00,0xA6},
   {0xBB,0x00,0x6A}, {0xB7,0x00,0x1E}, {0xB3,0x00,0x00}, {0x91,0x26,0x00},
   {0x7B,0x2B,0x00}, {0x00,0x3E,0x00}, {0x00,0x48,0x0D}, {0x00,0x3C,0x22},
   {0x00,0x2F,0x66}, {0x00,0x00,0x00}, {0x05,0x05,0x05}, {0x05,0x05,0x05},

   {0xC8,0xC8,0xC8}, {0x00,0x59,0xFF}, {0x44,0x3C,0xFF}, {0xB7,0x33,0xCC},
   {0xFF,0x33,0xAA}, {0xFF,0x37,0x5E}, {0xFF,0x37,0x1A}, {0xD5,0x4B,0x00},
   {0xC4,0x62,0x00}, {0x3C,0x7B,0x00}, {0x1E,0x84,0x15}, {0x00,0x95,0x66},
   {0x00,0x84,0xC4}, {0x11,0x11,0x11}, {0x09,0x09,0x09}, {0x09,0x09,0x09},

   {0xFF,0xFF,0xFF}, {0x00,0x95,0xFF}, {0x6F,0x84,0xFF}, {0xD5,0x6F,0xFF},
   {0xFF,0x77,0xCC}, {0xFF,0x6F,0x99}, {0xFF,0x7B,0x59}, {0xFF,0x91,0x5F},
   {0xFF,0xA2,0x33}, {0xA6,0xBF,0x00}, {0x51,0xD9,0x6A}, {0x4D,0xD5,0xAE},
   {0x00,0xD9,0xFF}, {0x66,0x66,0x66}, {0x0D,0x0D,0x0D}, {0x0D,0x0D,0x0D},

   {0xFF,0xFF,0xFF}, {0x84,0xBF,0xFF}, {0xBB,0xBB,0xFF}, {0xD0,0xBB,0xFF},
   {0xFF,0xBF,0xEA}, {0xFF,0xBF,0xCC}, {0xFF,0xC4,0xB7}, {0xFF,0xCC,0xAE},
   {0xFF,0xD9,0xA2}, {0xCC,0xE1,0x99}, {0xAE,0xEE,0xB7}, {0xAA,0xF7,0xEE},
   {0xB3,0xEE,0xFF}, {0xDD,0xDD,0xDD}, {0x11,0x11,0x11}, {0x11,0x11,0x11}
};


static inline uint8_t* chr_mem(const nes_ppu* ppu,
                               uint16_t addr) {
    return ppu->mapper->chr_addr(ppu->mapper, addr);
}


typedef struct {
    SDL_Window* window;
    SDL_Renderer* renderer;
    SDL_Surface* background;
    SDL_Surface* background_line;
    SDL_Surface* foreground;
    SDL_Surface* sprite;
    SDL_Surface* target;
} sdl_render_data;

static sdl_render_data the_render_data = {0};


static int sdl_render_init(nes_Renderer* rend) {
    sdl_render_data* data = &the_render_data;
    int status = SDL_Init(SDL_INIT_VIDEO);

    if (0 != status) {
        fprintf(stderr, "SDL: Failed to initialize\n");

    } else {
        SDL_DisplayMode mode = {0};

        SDL_GetCurrentDisplayMode(0, &mode);

        int yscale = (mode.h - 1) / nes_ppu_scan_h;
        int xscale = mode.w / nes_ppu_scan_w;
        int scale = (xscale < yscale ? xscale : yscale);

        data->window = SDL_CreateWindow(
                "NESe",
                SDL_WINDOWPOS_UNDEFINED,
                SDL_WINDOWPOS_UNDEFINED,
                nes_ppu_scan_w * scale,
                nes_ppu_scan_h * scale,
                0
            );
        if (NULL == data->window) {
            fprintf(stderr, "SDL: Failed to create window\n");
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        data->renderer = SDL_CreateRenderer(data->window, -1, 0);
        if (NULL == data->renderer) {
            fprintf(stderr, "SDL: Failed to create renderer\n");
            SDL_DestroyWindow(data->window);
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        data->background = SDL_CreateRGBSurfaceWithFormat(
                0, nes_ppu_render_w, nes_ppu_render_h,
                8, SDL_PIXELFORMAT_INDEX8
            );

        if (NULL == data->background) {
            fprintf(stderr, "SDL: Failed to create background\n");
            SDL_DestroyRenderer(data->renderer);
            SDL_DestroyWindow(data->window);
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        data->background_line = SDL_CreateRGBSurfaceWithFormat(
                0, nes_ppu_render_w + 8, 8,
                8, SDL_PIXELFORMAT_INDEX8
            );

        if (NULL == data->background_line) {
            fprintf(stderr, "SDL: Failed to create block buffer\n");
            SDL_FreeSurface(data->background);
            SDL_DestroyRenderer(data->renderer);
            SDL_DestroyWindow(data->window);
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        data->foreground = SDL_CreateRGBSurfaceWithFormat(
                0, nes_ppu_render_w, nes_ppu_render_h,
                8, SDL_PIXELFORMAT_INDEX8
            );

        if (NULL == data->foreground) {
            fprintf(stderr, "SDL: Failed to create foreground\n");
            SDL_FreeSurface(data->background_line);
            SDL_FreeSurface(data->background);
            SDL_DestroyRenderer(data->renderer);
            SDL_DestroyWindow(data->window);
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        data->sprite = SDL_CreateRGBSurfaceWithFormat(
                0, 8, 16, 8, SDL_PIXELFORMAT_INDEX8
            );
        if (NULL == data->sprite) {
            fprintf(stderr, "SDL: Failed to create sprite\n");
            SDL_FreeSurface(data->foreground);
            SDL_FreeSurface(data->background_line);
            SDL_FreeSurface(data->background);
            SDL_DestroyRenderer(data->renderer);
            SDL_DestroyWindow(data->window);
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        data->target = SDL_CreateRGBSurfaceWithFormat(
                0U, nes_ppu_render_w, nes_ppu_render_h,
                24U, SDL_PIXELFORMAT_RGB888
            );
        if (NULL == data->target) {
            fprintf(stderr, "SDL: Failed to create target\n");
            SDL_FreeSurface(data->sprite);
            SDL_FreeSurface(data->foreground);
            SDL_FreeSurface(data->background_line);
            SDL_FreeSurface(data->background);
            SDL_DestroyRenderer(data->renderer);
            SDL_DestroyWindow(data->window);
            SDL_Quit();
            status = -1;
        }
    }

    if (0 == status) {
        SDL_SetPaletteColors(data->background->format->palette,
                             nes_palette, 0U, 64U);
        SDL_SetColorKey(data->background, SDL_TRUE, 0xFFU);

        SDL_SetPaletteColors(data->foreground->format->palette,
                             nes_palette, 0U, 64U);
        SDL_SetColorKey(data->foreground, SDL_TRUE, 0xFFU);

        SDL_SetPaletteColors(data->sprite->format->palette,
                             nes_palette, 0U, 64U);
        SDL_SetColorKey(data->sprite, SDL_TRUE, 0xFFU);

        rend->data = &the_render_data;
    }

    return status;
}

static void sdl_render_done(nes_Renderer* rend) {
    sdl_render_data* data = (sdl_render_data*)rend->data;
    SDL_FreeSurface(data->target);
    SDL_FreeSurface(data->sprite);
    SDL_FreeSurface(data->foreground);
    SDL_FreeSurface(data->background_line);
    SDL_FreeSurface(data->background);
    SDL_DestroyRenderer(data->renderer);
    SDL_DestroyWindow(data->window);
    SDL_Quit();
}

static inline void render_sprite_line(
        const nes_ppu* ppu, int index, int y, const uint8_t* pal,
        uint8_t* dst, int start, int end, const uint8_t* back) {
    uint8_t* sprite = chr_mem(ppu, index * 16U);
    uint8_t lo = sprite[0U + y] << start;
    uint8_t hi = sprite[8U + y] << start;
    for (int x = start; x < end; ++x) {
        if (back && *back != 0xFFU) {
            *dst = *back;
        } else {
            int pal_idx = (((hi & 0x80) >> 6) | ((lo & 0x80) >> 7));
            if (pal_idx) *dst = pal[pal_idx];
        }
        if (back) ++back;
        dst++;
        hi <<= 1;
        lo <<= 1;
    }
}

static inline void render_sprite_line_flip(
        const nes_ppu* ppu, int index, int y, const uint8_t* pal,
        uint8_t* dst, int start, int end, const uint8_t* back) {
    uint8_t* sprite = chr_mem(ppu, index * 16U);
    uint8_t lo = sprite[0U + y] >> start;
    uint8_t hi = sprite[8U + y] >> start;
    for (int x = start; x < end; ++x) {
        if (back && *back != 0xFFU) {
            *dst = *back;
        } else {
            int pal_idx = (((hi & 1) << 1) | (lo & 1));
            if (pal_idx) *dst = pal[pal_idx];
        }
        if (back) ++back;
        dst++;
        hi >>= 1;
        lo >>= 1;
    }
}

static inline void render_bg_sprite_line(
        const nes_ppu* ppu, int index, int y, const uint8_t* pal,
        uint8_t* dst, int start, int end) {
    uint8_t* sprite = chr_mem(ppu, index * 16U);
    uint8_t lo = sprite[0U + y] << (start % 8);
    uint8_t hi = sprite[8U + y] << (start % 8);
    for (int x = start; x < end; ++x) {
        int pal_idx = (((hi & 0x80) >> 6) | ((lo & 0x80) >> 7));
        *dst = (pal_idx ? pal[pal_idx] : 0xFFU);
        dst++;
        hi <<= 1;
        lo <<= 1;
    }
}

static inline void render_bg_scanline_area(
        const nes_ppu* ppu, int page,
        uint8_t* dst, int x, int y, int w) {
    int block_x = x / 8;
    int line_end = x + w;
    int block_y = y / 8;
    y = y % 8;
    int bank = (ppu->control & ppu_Control_Back_Bank) ? 0x100 : 0;
    const uint8_t* indexes = nes_map_vram_addr(ppu->mapper,
                                               page << 10);
    const uint8_t* attrs = indexes + 960U;
    const uint8_t* index = indexes +
                           (block_y * nes_ppu_blocks_w) +
                           block_x;

    while (x < line_end) {
        int attr_idx = ((block_y / 4) * 8) + (block_x / 4);
        int shift = 2 * ((block_y & 0b10) |
                        ((block_x & 0b10) >> 1));
        int pal_idx = (attrs[attr_idx] >> shift) & 3;
        const uint8_t* pal = &ppu->palette[pal_idx * 4];

        int end = (x + 8) & ~7;
        if (end > line_end) end = line_end;

        render_bg_sprite_line(ppu, bank + *index, y,
                              pal, dst, x, end);

        ++index;
        ++block_x;
        dst += (end - x);
        x = end;
    }
}

static void render_bg_scanline(const nes_ppu* ppu,/* int scanline,*/
                               uint8_t* dst) {
    int page = (ppu->control & ppu_Control_Nametable_Mask);
    int x = ppu->scroll_x;
    int y = ppu->scroll_y;
    int w = (nes_ppu_render_w - x);
    if (!(ppu->mask & ppu_Mask_Left_Back)) {
        // Handle column 0 flag - need to fill with transparency
        memset(dst, 0xFFU, 8);
        w -= 8;
        x += 8;
        dst += 8;
    }
    render_bg_scanline_area(ppu, page, dst, x, y, w);
    render_bg_scanline_area(ppu, page ^ 1, dst + w, 0, y,
                            nes_ppu_render_w - w);
}

static void render_line_sprites(nes_ppu* ppu, uint8_t* dst_line,
                                int scanline, const uint8_t* back,
                                const oam_sprite* sprites,
                                int n_sprites) {
    for (int i_sprite = n_sprites - 1; i_sprite >= 0; --i_sprite) {
        const oam_sprite* sprite = &sprites[i_sprite];

        int index = sprite->index;
        int bank = (ppu->control & ppu_Control_Sprite_Bank) ?
                   0x100 : 0;
        if (ppu->control & ppu_Control_Sprite_Size) {
            bank = (index & 1) ? 0x100 : 0;
            index &= 0xFEU;
        }
        index += bank;

        int y = scanline - (sprite->y + 1);
        if (ppu->control & ppu_Control_Sprite_Size) {
            if (y >= 8) {
                index ^= 1;
                y -= 8;
            }
            if (sprite->attr & oam_Attr_Flip_Y) {
                index ^= 1;
            }
        }

        int pal_idx = (sprite->attr & oam_Attr_Pal_Mask);
        const uint8_t* pal = &ppu->palette[16 + (pal_idx * 4)];

        if (sprite->attr & oam_Attr_Flip_Y) y = 7 - y;
        int end = nes_ppu_render_w - sprite->x;
        if (end > 8) end = 8;
        int start = 0;
        if (    !(ppu->mask & ppu_Mask_Left_Sprite) &&
                sprite->x < 8) {
            start = 8 - sprite->x;
        }
        if (sprite->attr & oam_Attr_Flip_X) {
            render_sprite_line_flip(
                    ppu, index, y, pal,
                    dst_line + sprite->x + start, start, end,
                    (sprite->attr & oam_Attr_Background) ?
                        (back + sprite->x + start) : NULL
                );
        } else {
            render_sprite_line(
                    ppu, index, y, pal,
                    dst_line + sprite->x + start, start, end,
                    (sprite->attr & oam_Attr_Background) ?
                        (back + sprite->x + start) : NULL
                );
        }
    }
}

// Check sprite (0 only) collision on a scanline
// This assumes that we've verified that this sprite
// intersects with this scanline.
// Scanline is 0-239 from inside the rendering window
// (though we should never see this called with 0).
static int eval_sprite_line(const nes_ppu* ppu, int y,
                            const oam_sprite* sprite,
                            const uint8_t* chr,
                            const uint8_t* back) {
    int hit_pos = -1;

    // TODO: Handle Column 0 mask

    if (sprite->attr & oam_Attr_Flip_Y) y = 7 - y;
    uint8_t lo = chr[0U + y];
    uint8_t hi = chr[8U + y];

    back += sprite->x;
    int end = nes_ppu_render_w;
    if (end > sprite->x + 8) end = sprite->x + 8;
    for (int x = sprite->x; x < end; ++x) {
        int pal_idx = (sprite->attr & oam_Attr_Flip_X) ?
                      (((hi & 1) << 1) | (lo & 1)) :
                      (((hi & 0x80) >> 6) | ((lo & 0x80) >> 7));
        if (pal_idx && *back != 0xFFU) {
            hit_pos = x;
            break;
        }
        ++back;
        if (sprite->attr & oam_Attr_Flip_X) {
            hi >>= 1;
            lo >>= 1;
        } else {
            hi <<= 1;
            lo <<= 1;
        }
    }

    return hit_pos;
}

static void update_scanline_hit(nes_ppu* ppu, uint8_t* back_line,
                                int scanline) {
    const oam_sprite* sprite = &ppu->oam[0];
    int bank = (ppu->control & ppu_Control_Sprite_Bank) ?
               0x100 : 0;

    if (    !(ppu->mask & ppu_Mask_Left_Sprite) &&
            sprite->x < 8) {
        return;
    }
    int y_pos = (sprite->y + 1);
    int y = scanline - y_pos;
    if (0 > y) return;
    int h = (ppu->control & ppu_Control_Sprite_Size) ? 16 : 8;
    if (y >= h) return;

    int index = sprite->index;
    if (ppu->control & ppu_Control_Sprite_Size) {
        bank = (index & 1) ? 0x100 : 0;
        index &= 0xFEU;
    }
    index += bank;

    if (ppu->control & ppu_Control_Sprite_Size) {
        if (y >= 8) {
            index ^= 1;
            y -= 8;
        }
        if (sprite->attr & oam_Attr_Flip_Y) {
            index ^= 1;
        }
    }

    const uint8_t* chr = chr_mem(ppu, index * 16U);
    int hit = eval_sprite_line(ppu, y, sprite, chr, back_line);

    if (hit >= 0) {
        REND_LOG("Upcoming hit @ %d, %d\n", scanline + 1, hit);
        REND_LOG("(Currently @ %d, %d)\n", ppu->scanline, ppu->cycle);
        ppu->hit_line = scanline;
        ppu->hit_dot = hit;
    }
}

static int select_line_sprites(const nes_ppu* ppu, int scanline,
                               oam_sprite* sprites, int max) {
    int n_sprites = 0;

    for (   int i_sprite = 0;
            i_sprite < nes_ppu_oam_sprite_count && n_sprites < max;
            ++i_sprite) {
        const oam_sprite* sprite = &ppu->oam[i_sprite];
        int y_pos = (sprite->y + 1);
        int y = scanline - y_pos;
        if (0 > y) continue;
        int h = (ppu->control & ppu_Control_Sprite_Size) ? 16 : 8;
        if (y >= h) continue;

        *sprites = *sprite;
        ++sprites;
        ++n_sprites;
    }

    return n_sprites;
}

static void dump_line_sprites(const nes_ppu* ppu, int line,
                              const oam_sprite* sprites, int n) {
    while (n-- > 0) {
        PPU_LOG("PPU: Line %3d: Sprite $%02x @ %3d, %3d (%02x)\n",
                line, sprites->index, sprites->x, sprites->y,
                sprites->attr);
        ++sprites;
    }
}

static void render_scanline(nes_ppu* ppu, int line,
                            sdl_render_data* data) {
    SDL_Rect dst_rect = {
        .x = 0,
        .y = line,
        .w = nes_ppu_render_w,
        .h = 1,
    };

    if (line >= 0) {
        // Emulate the happy part of the backdrop override quirk
        int pal_idx = (ppu->addr >= nes_ppu_mem_pal_start) ?
                      (ppu->addr & (nes_ppu_mem_pal_size - 1)) : 0;
        SDL_Color ext = nes_palette[ppu->palette[pal_idx]];
        SDL_FillRect(data->target, &dst_rect, ((int)ext.r << 16) |
                                              ((int)ext.g << 8) |
                                              ext.b);
    }

    if (!(ppu->mask & (ppu_Mask_Sprite | ppu_Mask_Back))) {
        // Do nothing if BOTH are disabled.
        return;
    }

    SDL_Rect src_rect = {
        .x = 0,
        .y = 0,
        .w = nes_ppu_render_w,
        .h = 1,
    };

    uint8_t* background = data->background->pixels;

    // We check for hits if EITHER layer is enabled.
    render_bg_scanline(ppu, background);
    if (ppu->hit_line <= 0) {
        update_scanline_hit(ppu, background, line);
    }

    oam_sprite line_sprites[8] = {0};
    int n_sprites = select_line_sprites(ppu, line,
                                        line_sprites, 8);

    dump_line_sprites(ppu, line, line_sprites, n_sprites);

    if (ppu->mask & ppu_Mask_Back) {
        SDL_BlitSurface(data->background, &src_rect,
                        data->target, &dst_rect);
    }

    if (ppu->mask & ppu_Mask_Sprite) {
        uint8_t* foreground = data->foreground->pixels;
        memset(foreground, 0xFFU, nes_ppu_render_w);

        render_line_sprites(ppu, foreground, line, background,
                            line_sprites, n_sprites);

        SDL_BlitSurface(data->foreground, &src_rect,
                        data->target, &dst_rect);
    }
}

static int sdl_render(nes_Renderer* rend, nes_ppu* ppu) {
    int status = 0;
    sdl_render_data* data = (sdl_render_data*)rend->data;

    if (ppu->scanline < nes_ppu_prerender) {
        REND_LOG("Scanline %3d -> Prerender\n", ppu->scanline);
        // TODO: Perform evaluations here?

    } else if (ppu->scanline < nes_ppu_prerender +
                               nes_ppu_height) {
        REND_LOG("Scanline %3d : N %d X %d Y %d\n",
                 ppu->scanline,
                 ppu->control & ppu_Control_Nametable_Mask,
                 ppu->scroll_x, ppu->scroll_y);
        int line = ppu->scanline - (int)nes_ppu_prerender;
        render_scanline(ppu, line, data);

    } else {
        REND_LOG("Scanline %3d -> Postrender\n", ppu->scanline);

        SDL_Texture* texture = SDL_CreateTextureFromSurface(
                data->renderer, data->target
            );
        SDL_RenderCopy(data->renderer, texture, NULL, NULL);
        SDL_RenderPresent(data->renderer);
        SDL_DestroyTexture(texture);

        status = 1;
    }

    return status;
}


nes_Renderer sdl_renderer = {
    .init = sdl_render_init,
    .done = sdl_render_done,
    .render = sdl_render,
};