#include <SDL2/SDL.h>

#include "render.h"
#include "ppu.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}
};


typedef struct {
    SDL_Window* window;
    SDL_Renderer* renderer;
    SDL_Surface* background;
    SDL_Surface* sprite8;
    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 {
        data->window = SDL_CreateWindow(
                "NESe",
                SDL_WINDOWPOS_UNDEFINED,
                SDL_WINDOWPOS_UNDEFINED,
                nes_ppu_scan_w * 4,
                nes_ppu_scan_h * 4,
                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 + 8, nes_ppu_render_h + 8,
                8, SDL_PIXELFORMAT_INDEX8
            );

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

    if (0 == status) {
        data->sprite8 = SDL_CreateRGBSurfaceWithFormat(
                0, 8, 8, 8, SDL_PIXELFORMAT_INDEX8
            );
        if (NULL == data->sprite8) {
            fprintf(stderr, "SDL: Failed to create sprite\n");
            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->sprite8);
            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->sprite8->format->palette,
                             nes_palette, 0U, 64U);
        SDL_SetColorKey(data->sprite8, 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->sprite8);
    SDL_FreeSurface(data->background);
    SDL_DestroyRenderer(data->renderer);
    SDL_DestroyWindow(data->window);
    SDL_Quit();
}

typedef enum {
    Render_Mode_Sprite      = 0b00000,
    Render_Mode_Background  = 0b00001,
    Render_Mode_Behind      = 0b00010,
//    Render_Mode_Collide     = 0b00100,
    Render_Mode_Flip_X      = 0b01000,
    Render_Mode_Flip_Y      = 0b10000,
} Render_Mode;


static void render_bg_sprite(const nes_ppu* ppu, int index,
                             const uint8_t* pal,
                             void* loc, int pitch) {
    uint8_t* sprite = &ppu->chr_mem[index * 16U];
    uint8_t* dst_line = (uint8_t*)loc;

    for (int y = 8; y > 0; --y) {
        uint8_t lo = sprite[0U];
        uint8_t hi = sprite[8U];
        uint8_t* dst = dst_line;
        for (int x = 8; x > 0; --x) {
            int pal_idx = ( ((hi & 0x80) >> 6) |
                            ((lo & 0x80) >> 7));
            *dst++ = (pal_idx ? pal[pal_idx] : 0xFFU);
            hi <<= 1;
            lo <<= 1;
        }
        dst_line += pitch;
        ++sprite;
    }
}

static void render_background_area(const nes_ppu* ppu, int page,
                                   void* buffer, int pitch,
                                   int xs, int ys, int w, int h) {
    int bank = (ppu->control & ppu_Control_Back_Bank) ? 0x100 : 0;
    const uint8_t* index_line = &ppu->vram[page * 0x400U];
    const uint8_t* attrs = index_line + 960U;
    index_line += xs + (ys * nes_ppu_blocks_w);
    uint8_t* dst_line = (uint8_t*)buffer;
    for (int y = ys; y < h + ys; ++y) {
        uint8_t* dst = dst_line;
        const uint8_t* index = index_line;
        for (int x = xs; x < w + xs; ++x) {
            int attr_idx = ((y / 4) * 8) + (x / 4);
            int shift = 2 * ((y & 0b10) | ((x & 0b10) >> 1));
            int pal_idx = (attrs[attr_idx] >> shift) & 3;
            const uint8_t* pal = &ppu->palette[pal_idx * 4];
            render_bg_sprite(ppu, bank + *index, pal,
                             dst, pitch);
            ++index;
            dst += 8;
        }
        dst_line += pitch * 8;
        index_line += nes_ppu_blocks_w;
    }
}

static void render_background_line(const nes_ppu* ppu, int line,
                                   void* buffer, int pitch) {
    // TODO: Handle vertical scrolling
    // TODO: Handle column 0 flag

    buffer += line * pitch * 8U;
    int page = (ppu->control & ppu_Control_Nametable_Mask);
    int x = ppu->scroll_x / 8;

    // Left
    render_background_area(
            ppu, page, buffer, pitch,
            x, line,
            nes_ppu_blocks_w - x, 1
        );

    // Right
    buffer += (nes_ppu_blocks_w - x) * 8U;
    render_background_area(
            ppu, page ^ 1, buffer, pitch,
            0, line,
            1U + x, 1
        );
}

static void render_sprite(nes_ppu* ppu, int index,
                          const uint8_t* pal, Render_Mode mode,
                          void* loc, int pitch,
                          const void* back_loc, int back_pitch) {
    uint8_t* sprite = &ppu->chr_mem[index * 16U];
    uint8_t* dst_line = (uint8_t*)loc;
    const uint8_t* back_line = (uint8_t*)back_loc;
    int dx = 1;
    if (mode & Render_Mode_Flip_X) {
        dst_line += 7;
        back_line += 7;
        dx = -dx;
    }
    if (mode & Render_Mode_Flip_Y) {
        dst_line += (7 * pitch);
        back_line += (7 * back_pitch);
        pitch = -pitch;
        back_pitch = -back_pitch;
    }

    for (int y = 8; y > 0; --y) {
        uint8_t lo = sprite[0U];
        uint8_t hi = sprite[8U];
        uint8_t* dst = dst_line;
        const uint8_t* back = back_line;
        for (int x = 8; x > 0; --x) {
            int pal_idx = ( ((hi & 0x80) >> 6) |
                            ((lo & 0x80) >> 7));
            int nes_pal_idx = (pal_idx ? pal[pal_idx] : 0xFFU);
            if ((mode & Render_Mode_Behind) && *back != 0xFFU) {
                nes_pal_idx = 0xFFU;
            }
            *dst = nes_pal_idx;
            dst += dx;
            back += dx;
            hi <<= 1;
            lo <<= 1;
        }
        dst_line += pitch;
        back_line += back_pitch;
        ++sprite;
    }
}

typedef struct {
    uint8_t y;
    uint8_t index;
    uint8_t attr;
    uint8_t x;
} oam_sprite;

typedef enum {
    oam_Attr_Pal_Mask   = 0b00000011,
    oam_Attr_Background = 0b00100000,
    oam_Attr_Flip_X     = 0b01000000,
    oam_Attr_Flip_Y     = 0b10000000,
} oam_Attribute;

typedef enum {
    oam_Index_Bank      = 0b00000001,
    oam_Index_Tile_Mask = 0b11111110,
} oam_Index;

// 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 line,
                            const oam_sprite* sprite,
                            const uint8_t* chr,
                            const uint8_t* back) {
    int hit_pos = -1;

    int y = line - (sprite->y + 1);

    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;
    for (int x = sprite->x; x < nes_ppu_render_w; ++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 const SDL_Rect sprite_rect = {
    .x = 0,
    .y = 0,
    .w = 8,
    .h = 8,
};

static void render_sprites(nes_ppu* ppu,
                           SDL_Surface* buffer,
                           SDL_Surface* target,
                           const void* back, int back_pitch) {
    int bank = (ppu->control & ppu_Control_Sprite_Bank) ?
               0x100 : 0;
    const oam_sprite* sprites = (const oam_sprite*)ppu->oam;
    uint8_t* dst_origin = (uint8_t*)buffer->pixels;
    int pitch = buffer->pitch;
    const uint8_t* back_origin = (uint8_t*)back;
    for (   int i_sprite = nes_ppu_oam_sprite_count - 1;
            i_sprite >= 0; --i_sprite) {
        const oam_sprite* sprite = &sprites[i_sprite];
        if (    !(ppu->mask & ppu_Mask_Left_Sprite) &&
                sprite->x < 8) {
            continue;
        }
        int y = (sprite->y + 1);
        if (y >= nes_ppu_render_h) continue;
        uint8_t* dst = dst_origin;
        int back_offset = sprite->x + (y * back_pitch);
        const uint8_t* dst_back = back_offset + back_origin;
        // TODO: Support 8x16 sprites
        int index = bank + sprite->index;
        int pal_idx = (sprite->attr & oam_Attr_Pal_Mask);
        const uint8_t* pal = &ppu->palette[16 + (pal_idx * 4)];
        Render_Mode mode = (sprite->attr & oam_Attr_Background) ?
                           Render_Mode_Behind :
                           Render_Mode_Sprite;
//        if (i_sprite == 0) mode |= Render_Mode_Collide;
        if (sprite->attr & oam_Attr_Flip_X) {
            mode |= Render_Mode_Flip_X;
        }
        if (sprite->attr & oam_Attr_Flip_Y) {
            mode |= Render_Mode_Flip_Y;
        }
        render_sprite(ppu, index, pal, mode, dst, pitch,
                      dst_back, back_pitch);

        SDL_Rect target_rect = {
            .x = sprite->x,
            .y = y,
            .w = 8,
            .h = 8,
        };
        SDL_BlitSurface(buffer, &sprite_rect,
                        target, &target_rect);
    }
}

static void update_sprite_hit(nes_ppu* ppu,
                              const void* back_line,
                              int back_pitch) {
    const oam_sprite* sprite = (oam_sprite*)ppu->oam;
    int block_line = (ppu->scanline - nes_ppu_prerender) / 8U;
    int x_fine = ppu->scroll_x % 8;
    int index = sprite->index;
    if (ppu->control & ppu_Control_Sprite_Bank) {
        index += 0x100U;
    }
    const uint8_t* chr = &ppu->chr_mem[index * 16U];
    int render_line = block_line * 8U;
    int start_y = (sprite->y + 1) - render_line;
    int end_y = start_y + 8;
    if (start_y < 8 && end_y > 0) {
        if (start_y < 0) start_y = 0;
        if (end_y > 8) end_y = 8;
        int hit = -1;
        const uint8_t* back = (uint8_t*)back_line + x_fine;
        back += (render_line + start_y) * back_pitch;
        for (int y = start_y; y < end_y; ++y) {
            hit = eval_sprite_line(
                    ppu, render_line + y,
                    sprite, chr, back
                );
            if (hit >= 0) {
                ppu->hit_line = y + render_line;
                ppu->hit_dot = hit;
                break;
            }
            back += back_pitch;
        }
    }
}

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) {
//        printf("Scanline %3d -> Prerender\n", ppu->scanline);

        // 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, NULL, ((int)ext.r << 16) |
                                         ((int)ext.g << 8) |
                                         ext.b);

    } else if (ppu->scanline < nes_ppu_prerender +
                               nes_ppu_height) {
        int line = (ppu->scanline - (int)nes_ppu_prerender) / 8;

//        printf("Scanline %3d -> Line %2d @ X %d\n", ppu->scanline, line, ppu->scroll_x);

        if (ppu->mask & ppu_Mask_Back) {
            // TODO: Only re-render if VRAM/scroll changes
            render_background_line(ppu, line,
                                   data->background->pixels,
                                   data->background->pitch);

            // TODO: Y scroll support

            int x_fine = ppu->scroll_x % 8;

            // Check for Sprite 0 Hit
            if (    0 >= ppu->hit_line &&
                    (ppu->mask & ppu_Mask_Sprite)) {
                update_sprite_hit(ppu,
                                  data->background->pixels,
                                  data->background->pitch);
            }

            // Gotta render it now while scroll is set

            SDL_Rect back_rect = {
                .x = x_fine,
                .y = line * 8U,
                .w = nes_ppu_render_w,
                .h = 8U,
            };

            SDL_Rect render_rect = {
                .x = 0,
                .y = line * 8U,
                .w = nes_ppu_render_w,
                .h = 8U,
            };

            SDL_BlitSurface(data->background, &back_rect,
                            data->target, &render_rect);
        }

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

        if (ppu->mask & ppu_Mask_Sprite) {
            render_sprites(ppu, data->sprite8, data->target,
                           data->background->pixels,
                           data->background->pitch);
        }
        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,
};