tiled_image.h

#ifndef TILED_IMAGE_H
#define TILED_IMAGE_H

#include <osbind.h>
#include <cstdint>
#include <utility>
#include <cstdio>
#include "degas_picture.h"

namespace AtariGraphics {
    
    struct SpriteDefinition {
        const uint16_t SPRITE_WIDTH;
        const uint16_t SPRITE_HEIGHT;

        SpriteDefinition(uint16_t w, uint16_t h) : SPRITE_WIDTH(w),
                                                   SPRITE_HEIGHT(h) {
        }
    };

    struct TiledImage {
        static constexpr int IMAGE_SIZE = sizeof(DegasPicture::picture_data);
        static constexpr int BITS_PER_PIXEL = 4;
        static constexpr int IMAGE_WDWIDTH = 320 * BITS_PER_PIXEL / sizeof(uint16_t) / 8;
    
        DegasPicture picture;
        SpriteDefinition defs;

        DegasPicture load(const char * const filename) {
            short fh;
            int32_t length = 0;
            DegasPicture picture;

            fh = Fopen(filename, 2);
            if (fh > 0) {
                length = Fread(fh, sizeof(DegasPicture), &picture);
                Fclose(fh);
            } 
        
            if (fh < 0 || length != sizeof(DegasPicture)) {
                (void) Cconws("Error: image ");
                (void) Cconws(filename);
                (void) Cconws(" not found\r\n");

                exit(1);
            }

            return picture;
        }

        TiledImage(const char * const filename, const SpriteDefinition& defs) : picture(load(filename)),
                                                                                defs(defs) {        
        }

        uint16_t* tile(const uint16_t tile_index) {
            // return start address of tile # tile_index
            // tiles are TILE_WIDTH pixels wide, image is IMAGE_WDWIDTH
            // words wide
            return picture.picture_data + tile_index * defs.SPRITE_WIDTH * BITS_PER_PIXEL / (sizeof(uint16_t) * 8);
        }
    };
}
#endif // TILED_IMAGE_H