Duality/src/obj.c

/*
 * obj.c
 * Duality
 *
 * Copyright (C) 2025 Thomas Buck <thomas@xythobuz.de>
 *
 * 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.
 *
 * See <http://www.gnu.org/licenses/>.
 */

#include <gbdk/platform.h>
#include <string.h>
#include <stdlib.h>

#include "gb/hardware.h"
#include "sprites.h"
#include "game.h"
#include "obj.h"

/*
 * sprite budget:
 *
 * fixed:
 * ship: 4
 * thruster: 1
 * health: 4
 * power: 4
 * --> 13 fixed
 *
 * hardware tiles: 40 - 13 = 27
 *
 * dynamic:
 * shot: 1
 * light: 4
 * dark: 4
 * --> 2x dark & 2x light = 16
 * --> 5x shot & 6x small = 11
 * --> 16 + 11 = 27
 */
#define MAX_DARK 2
#define MAX_LIGHT 2
#define MAX_SHOT 5
#define MAX_SHOT_DARK 3
#define MAX_SHOT_LIGHT 3
#define MAX_OBJ ((4 * MAX_DARK) + (4 * MAX_LIGHT) + MAX_SHOT + MAX_SHOT_DARK + MAX_SHOT_LIGHT)

#define MAX_TRAVEL 32

struct obj {
    uint8_t active;
    enum SPRITES sprite;
    int16_t off_x;
    int16_t off_y;
    int16_t spd_x;
    int16_t spd_y;
    uint8_t travel;
};

static struct obj objs[MAX_OBJ];

void obj_init(void) {
    memset(objs, 0, sizeof(objs));
}

static uint8_t cnt_sprite(enum SPRITES sprite) {
    uint8_t cnt = 0;
    for (uint8_t i = 0; i < MAX_OBJ; i++) {
        if (!objs[i].active) {
            continue;
        }
        if (objs[i].sprite == sprite) {
            cnt++;
        }
    }
    return cnt;
}

enum OBJ_STATE obj_add(enum SPRITES sprite, int16_t off_x, int16_t off_y, int16_t spd_x, int16_t spd_y) {
    uint8_t obj_cnt = 0xFF;
    for (uint8_t i = 0; i < MAX_OBJ; i++) {
        if (!objs[i].active) {
            obj_cnt = i;
            break;
        }
    }
    if (obj_cnt >= MAX_OBJ) {
        return OBJ_LIST_FULL;
    }

    if (((sprite == SPR_DARK) && (cnt_sprite(sprite) >= MAX_DARK))
            || ((sprite == SPR_LIGHT) && (cnt_sprite(sprite) >= MAX_LIGHT))
            || ((sprite == SPR_SHOT) && (cnt_sprite(sprite) >= MAX_SHOT))
            || ((sprite == SPR_SHOT_DARK) && (cnt_sprite(sprite) >= MAX_SHOT_DARK))
            || ((sprite == SPR_SHOT_LIGHT) && (cnt_sprite(sprite) >= MAX_SHOT_LIGHT))) {
        return OBJ_TYPE_FULL;
    }

    objs[obj_cnt].active = 1;
    objs[obj_cnt].sprite = sprite;
    objs[obj_cnt].off_x = off_x << POS_SCALE_OBJS;
    objs[obj_cnt].off_y = off_y << POS_SCALE_OBJS;
    objs[obj_cnt].spd_x = spd_x;
    objs[obj_cnt].spd_y = spd_y;
    objs[obj_cnt].travel = 0;

    obj_cnt += 1;
    return OBJ_ADDED;
}

void obj_act(int16_t pos_x, int16_t pos_y, int16_t *spd_off_x, int16_t *spd_off_y) {
    pos_x += DEVICE_SPRITE_PX_OFFSET_X + (DEVICE_SCREEN_PX_WIDTH / 2) - 16;
    pos_y += DEVICE_SPRITE_PX_OFFSET_Y + (DEVICE_SCREEN_PX_HEIGHT / 2);

    for (uint8_t i = 0; i < MAX_OBJ; i++) {
        if (!objs[i].active) {
            continue;
        }

        switch (objs[i].sprite) {
            case SPR_DARK: {
                *spd_off_x += (objs[i].off_x - pos_x) >> 8;
                *spd_off_y += (objs[i].off_y - pos_y) >> 8;
            } break;

            default:
                break;
        }
    }
}

void obj_draw(int16_t spd_x, int16_t spd_y, uint8_t *hiwater) {
    for (uint8_t i = 0; i < MAX_OBJ; i++) {
        if (!objs[i].active) {
            continue;
        }

        // move objects by their speed and compensate for movement of the background / ship
        objs[i].off_x += objs[i].spd_x - spd_x;
        objs[i].off_y += objs[i].spd_y - spd_y;

        // only update travel time if we're actually moving
        if ((objs[i].spd_x != 0) || (objs[i].spd_y != 0)) {
            objs[i].travel += 1;
        }

        // remove objects that have traveled for too long
        if (objs[i].travel >= MAX_TRAVEL) {
            objs[i].active = 0;
        }

        spr_draw(objs[i].sprite, FLIP_NONE, objs[i].off_x >> POS_SCALE_OBJS, objs[i].off_y >> POS_SCALE_OBJS, hiwater);
    }
}