game/main.cpp

#include "components/point.hpp"
#include "components/player.hpp"
#include "components/solid.hpp"
#include "components/texture.hpp"
#include "components/velocity.hpp"
#include "window.hpp"

#include <chrono>
#include <iostream>
#include <thread>

#include <entt/entt.hpp>
#include <SDL2/SDL.h>

constexpr std::chrono::microseconds FRAME_TIME (1'000'000 / 60);

static bool handleInputs(entt::registry& registry);

int main()
{
    if (auto err = sdl2Initialize(); err)
        return err;

    entt::registry registry;

    {
        const auto ent = registry.create();
        registry.emplace<Player>(ent);
        registry.emplace<Point>(ent, 0.f, WINDOW_HEIGHT - 200.f);
        registry.emplace<Velocity>(ent, 0.f, 0.f);
        registry.emplace<Texture>(ent, "img/player.png");
    }

    {
        const auto ent = registry.create();
        registry.emplace<Point>(ent, 0.f, 0.f);
        registry.emplace<Texture>(ent, "img/level.png");
        registry.emplace<Solid>(ent, "img/level.png");
    }

    do {
        const auto now = std::chrono::high_resolution_clock::now();

        SDL_RenderClear(renderer);
        registry.view<Texture, Point>().each([](auto& tex, auto& p) { tex(renderer, p); });
        SDL_RenderPresent(renderer);

        registry.view<Velocity, Point>().each([](auto& v, auto& p) { p += v; });

        registry.view<Solid, Point>().each(
            [&registry](auto& s, auto& p) {
                registry.view<Player, Point, Velocity, Texture>().each(
                    [&s, &p](auto& _, auto& pp, auto& pv, auto& t) {
                        const auto c = s.collision(pp + t.dim());

                        if (c) {
                            if (std::abs(c) > 1.f)
                                pv.y = c * 0.5f;
                            else
                                pv.y = 0.f;
                        } else {
                            pv.y += 0.1f;
                        }
                    });
            });

        std::this_thread::sleep_until(now + FRAME_TIME);
    } while (handleInputs(registry));
}

bool handleInputs(entt::registry& registry)
{
    bool quit = false;

    for (SDL_Event e; SDL_PollEvent(&e);) {
        if (e.type == SDL_QUIT) {
            quit = true;
        } else if (e.type == SDL_KEYDOWN && !e.key.repeat) {
            auto view = registry.view<Player, Velocity>();

            switch (e.key.keysym.sym) {
            case SDLK_d:
                view.each([](Player& p, Velocity& v) { v.x += 1.5f; });
                break;
            case SDLK_a:
                view.each([](Player& p, Velocity& v) { v.x -= 1.5f; });
                break;
            case SDLK_SPACE:
                view.each([](Player& p, Velocity& v) { if (v.y <= 0.f) v.y -= 3.f; });
                break;
            }
        } else if (e.type == SDL_KEYUP && !e.key.repeat) {
            auto view = registry.view<Player, Velocity>();

            switch (e.key.keysym.sym) {
            case SDLK_d:
                view.each([](Player& p, Velocity& v) { v.x -= 1.5f; });
                break;
            case SDLK_a:
                view.each([](Player& p, Velocity& v) { v.x += 1.5f; });
                break;
            }
        }
    }

    return !quit;
}