#include <iostream>
#include <thread>
#include <cstdint>

#include <GLFW/glfw3.h>
#include <sndio.h>
#include <math.h>

#include "imgui.h"
#include "imgui_impl_glfw.h"
#include "imgui_impl_opengl3.h"

static std::atomic<bool> shutdown_threads;
static std::atomic<float> frequency = 440.0f;

#define SND_SIG 1
#define SND_BITS 16
#define SND_PCHAN 2
#define SND_RATE 44100
#define SND_BUFLEN 4096

static void dsp_thread()
{
    struct sio_hdl *hdl;
    struct sio_par par;

    hdl = sio_open(SIO_DEVANY, SIO_PLAY, 0);
    if(hdl == nullptr) {
        std::cerr << "failed to open sound device" << std::endl;
        return;
    }
    sio_initpar(&par);
    par.sig = SND_SIG;
    par.bits = SND_BITS;
    par.pchan = SND_PCHAN;
    par.rate = SND_RATE;
    par.le = SIO_LE_NATIVE;
    if(!sio_setpar(hdl, &par)) {
        std::cerr << "failed to set sound device parameters" << std::endl;
        sio_close(hdl);
        return;
    }

    if(!sio_start(hdl)) {
        std::cerr << "failed to start sound device" << std::endl;
        sio_close(hdl);
        return;
    }

    uint32_t phase = 0;
    int16_t buf[SND_BUFLEN*SND_PCHAN];
    while(!shutdown_threads) {
        uint32_t ftw = frequency*(float)UINT32_MAX/SND_RATE;
        for(int i=0;i<SND_BUFLEN;i++) {
            buf[2*i] = buf[2*i+1] = (INT16_MAX-1)*sin(phase*2.0f*(float)M_PI/(float)UINT32_MAX);
            phase += ftw;
        }
        if(!sio_write(hdl, buf, SND_BUFLEN*(SND_BITS/8)*SND_PCHAN)) {
            std::cerr << "failed to write to sound device" << std::endl;
            sio_stop(hdl);
            sio_close(hdl);
            return;
        }
    }

    sio_stop(hdl);
    sio_close(hdl);
}

int main(int argc, char* argv[])
{
    if(!glfwInit()) {
        std::cerr << "failed to initialize GLFW" << std::endl;
        return 1;
    }
    std::atexit(glfwTerminate);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 0);
    static GLFWwindow* window = glfwCreateWindow(1024, 768, "sndlock", nullptr, nullptr);
    if(window == nullptr) {
        std::cerr << "failed to create GLFW window" << std::endl;
        return 1;
    }
    static auto DestroyWindow = []() {
        glfwDestroyWindow(window);
    };
    std::atexit(DestroyWindow);
    glfwMakeContextCurrent(window);
    glfwSwapInterval(1);

    IMGUI_CHECKVERSION();
    ImGui::CreateContext();
    static auto ImGuiDestroyContext = []() {
        ImGui::DestroyContext();
    };
    std::atexit(ImGuiDestroyContext);
    ImGuiIO& io = ImGui::GetIO();
    io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;
    ImGui::StyleColorsDark();
    ImGui_ImplGlfw_InitForOpenGL(window, true);
    std::atexit(ImGui_ImplGlfw_Shutdown);
    ImGui_ImplOpenGL3_Init("#version 130");
    std::atexit(ImGui_ImplOpenGL3_Shutdown);

    static std::thread dsp_thread_h = std::thread(dsp_thread);
    static auto JoinDSP = []() {
        dsp_thread_h.join();
    };
    std::atexit(JoinDSP);

    shutdown_threads = false;
    static auto SetShutdown = []() {
        shutdown_threads = true;
    };
    std::atexit(SetShutdown);

    bool exit = false;
    while(!exit && !glfwWindowShouldClose(window)) {
        glfwPollEvents();
        glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
        glClear(GL_COLOR_BUFFER_BIT);

        ImGui_ImplOpenGL3_NewFrame();
        ImGui_ImplGlfw_NewFrame();
        ImGui::NewFrame();

        ImGui::SetNextWindowPos(ImVec2(0.0f, 0.0f));
        ImGui::SetNextWindowSize(io.DisplaySize);
        ImGui::PushStyleVar(ImGuiStyleVar_WindowRounding, 0.0f);
        ImGui::Begin("sndlock", nullptr, ImGuiWindowFlags_NoDecoration | ImGuiWindowFlags_NoResize);

        float frequency_l = frequency;
        ImGui::SliderFloat("Frequency", &frequency_l, 50.0f, 8000.0f);
        frequency = frequency_l;
        if(ImGui::Button("Exit"))
            exit = true;

        ImGui::End();
        ImGui::PopStyleVar(1);

        ImGui::Render();
        ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
        int display_w, display_h;
        glfwGetFramebufferSize(window, &display_w, &display_h);
        glViewport(0, 0, display_w, display_h);
        glfwSwapBuffers(window);
    }

    return 0;
}