#include "application.h"

#include "rendering/render_api.h"    // RendererAPI
#include "settings_manager.h"
#include "hdri_manager.h"

#include "platform/opengl/opengl_device.h"
#include "platform/vulkan/vulkan_device.h"

#include <GLFW/glfw3.h>
#include <imgui.h>

#include <glm/gtc/matrix_transform.hpp>
#include <algorithm>
#include <cmath>
#include <numbers>

namespace Donut
{
    Application* Application::s_instance = nullptr;

    // Scroll is delivered through a GLFW callback; accumulate it here and drain it
    // once per frame in process_input (chaining ImGui's own scroll handler).
    static double        g_scroll_accum = 0.0;
    static GLFWscrollfun g_prev_scroll  = nullptr;
    static void donut_scroll_callback(GLFWwindow* w, double x, double y)
    {
        if (g_prev_scroll) g_prev_scroll(w, x, y);
        g_scroll_accum += y;
    }

    Application::Application(const std::string& name, int width, int height)
        : m_running(true), m_minimized(false)
    {
        s_instance = this;

        // Select the render API before the window is created: the window is built
        // differently for Vulkan (GLFW_NO_API) than for OpenGL.
        Logger::init();
        SettingsManager::initialize();
        {
            const auto& settings = SettingsManager::get_settings_const();
            RendererAPI::set_api(settings.graphics.render_api == "Vulkan"
                                ? RendererAPI::API::Vulkan : RendererAPI::API::OpenGL);
        }

        if (RendererAPI::get_api() == RendererAPI::API::Vulkan)
            RHI::vulkan_prepare_glfw(); // must precede glfwInit() inside the Window ctor

        m_window = create_scope<Window>(name, width, height);
        m_window->set_event_callback([this](Event& event) { on_event(event); });

        on_init();
    }

    Application::~Application()
    {
        on_shutdown();
        s_instance = nullptr;
    }

    auto Application::on_init() -> void
    {
        int w = 0, h = 0;
        glfwGetFramebufferSize((GLFWwindow*)m_window->get_native_window(), &w, &h);

        if (RendererAPI::get_api() == RendererAPI::API::Vulkan)
            m_device = RHI::create_vulkan_device();
        else
            m_device = RHI::create_opengl_device();

        RHI::NativeWindow native{ m_window->get_native_window(), w, h };
        if (!m_device->init(native))
        {
            DONUT_ERROR("RHI device initialization failed");
            return;
        }

        m_hdri_path = "assets/hdri/hdr_blue_nebulae_1.hdr";
        m_cubemap = m_device->create_cubemap_from_hdri(m_hdri_path);

        m_scene_renderer = create_scope<SceneRenderer>();
        m_scene_renderer->init(*m_device);
        m_black_hole_renderer = create_scope<BlackHoleRenderer>();
        m_black_hole_renderer->init(*m_device);

        // Black-hole camera: large-scale orbital viewer outside the disk.
        m_camera.set_camera_mode(CameraMode::Orbital);
        m_camera.set_orbital_target(glm::vec3(0.0f));
        m_camera.set_orbital_radius(4e11);          // ~31 r_s: outside the 12 r_s disk
        m_camera.set_orbital_limits(2.2e11, 1.5e12);
        m_camera.set_orbital_speed(0.01f);
        m_camera.set_zoom_speed(3e10);
        m_camera.set_azimuth(0.0f);
        m_camera.set_elevation(1.25f);

        // Scene camera: normal-scale orbital world-builder viewer.
        m_scene_camera.set_camera_mode(CameraMode::Orbital);
        m_scene_camera.set_orbital_target(glm::vec3(0.0f));
        m_scene_camera.set_orbital_radius(15.0);
        m_scene_camera.set_orbital_limits(2.0, 200.0);
        m_scene_camera.set_orbital_speed(0.01f);
        m_scene_camera.set_zoom_speed(2.0);
        m_scene_camera.set_azimuth(0.0f);
        m_scene_camera.set_elevation((float)std::numbers::pi / 3.0f);
        m_scene_camera.update_orbital();

        m_device->init_imgui();
        // Load the UI font into the device-created ImGui context (backend-agnostic;
        // the backend rebuilds the atlas on the next frame).
        ImGuiIO& io = ImGui::GetIO();
        if (!io.Fonts->AddFontFromFileTTF("assets/fonts/inter/static/Inter_18pt-Regular.ttf", 16.0f))
            io.Fonts->AddFontDefault();

        g_prev_scroll = glfwSetScrollCallback((GLFWwindow*)m_window->get_native_window(), donut_scroll_callback);

        m_start_time = glfwGetTime();
        DONUT_INFO("Application ready on {} backend", m_device->device_name());
    }

    auto Application::run() -> void
    {
        while (m_running)
        {
            glfwPollEvents();
            if (!m_minimized && m_device)
                render_frame();
        }
    }

    auto Application::render_frame() -> void
    {
        RHI::CommandList* cmd = m_device->begin_frame(glm::vec4(0.05f, 0.06f, 0.10f, 1.0f));
        if (!cmd) return;   // frame skipped (e.g. swapchain recreation)

        m_device->imgui_new_frame();
        build_ui();
        process_input();

        const glm::vec4 clear(0.05f, 0.06f, 0.10f, 1.0f);
        int w = 0, h = 0;
        glfwGetFramebufferSize((GLFWwindow*)m_window->get_native_window(), &w, &h);

        if (m_scene_mode)
        {
            float aspect = (float)w / (float)std::max(h, 1);
            m_scene_camera.set_projection(45.0f, aspect, 0.1f, 1000.0f);
            CameraView cv;
            cv.view       = m_scene_camera.get_view_matrix();
            cv.projection = m_scene_camera.get_projection_matrix();
            cv.position   = m_scene_camera.get_orbital_position();
            cv.fb_width   = w; cv.fb_height = h;

            cmd->begin_render_pass(nullptr, clear);
            m_scene_renderer->render(*cmd, cv, m_scene_objects, m_selected_object, m_cubemap.get());
            m_device->imgui_render(*cmd);
            cmd->end_render_pass();
        }
        else
        {
            GeodesicView gv;
            glm::vec3 pos, fwd;
            if (m_camera.get_camera_mode() == CameraMode::FPS)
            {
                pos = m_camera.get_position();
                fwd = m_camera.get_forward_direction();
            }
            else
            {
                pos = m_camera.get_orbital_position();
                fwd = glm::normalize(m_camera.get_orbital_target() - pos);
            }
            glm::vec3 right = glm::normalize(glm::cross(fwd, glm::vec3(0, 1, 0)));
            gv.position = pos; gv.right = right; gv.up = glm::cross(right, fwd); gv.forward = fwd;
            gv.tan_half_fov = (float)tan(glm::radians(m_bh_params.fov_degrees * 0.5f));
            gv.aspect = (float)BlackHoleRenderer::GEO_HI_W / (float)BlackHoleRenderer::GEO_HI_H;
            gv.moving = m_user_moving;
            gv.time = (float)(glfwGetTime() - m_start_time);

            m_black_hole_renderer->render_geodesic(*cmd, gv, m_bh_params, m_cubemap.get());
            cmd->begin_render_pass(nullptr, clear);
            m_black_hole_renderer->blit(*cmd, w, h);
            m_device->imgui_render(*cmd);
            cmd->end_render_pass();
        }

        m_device->end_frame();
    }

    auto Application::process_input() -> void
    {
        GLFWwindow* window = (GLFWwindow*)m_window->get_native_window();
        bool over_ui = ImGui::GetCurrentContext() && ImGui::GetIO().WantCaptureMouse;

        double now = glfwGetTime();
        float dt = m_last_frame_time > 0.0 ? (float)(now - m_last_frame_time) : 0.0f;
        m_last_frame_time = now;

        double mx = 0, my = 0;
        glfwGetCursorPos(window, &mx, &my);
        bool left_down = glfwGetMouseButton(window, GLFW_MOUSE_BUTTON_LEFT) == GLFW_PRESS;

        if (!m_scene_mode && m_camera.get_camera_mode() == CameraMode::FPS)
        {
            if (left_down && !m_left_was_down) { m_fps_last_x = mx; m_fps_last_y = my; }
            if (left_down && !over_ui)
                m_camera.on_mouse_move(float(mx - m_fps_last_x), float(m_fps_last_y - my));
            m_fps_last_x = mx; m_fps_last_y = my;
            m_left_was_down = left_down;

            bool over_kb = ImGui::GetCurrentContext() && ImGui::GetIO().WantCaptureKeyboard;
            bool moved = false;
            if (!over_kb && dt > 0.0f)
            {
                float mdt = dt * (glfwGetKey(window, GLFW_KEY_LEFT_SHIFT) == GLFW_PRESS ? 4.0f : 1.0f);
                if (glfwGetKey(window, GLFW_KEY_W) == GLFW_PRESS) { m_camera.move_forward(mdt);  moved = true; }
                if (glfwGetKey(window, GLFW_KEY_S) == GLFW_PRESS) { m_camera.move_backward(mdt); moved = true; }
                if (glfwGetKey(window, GLFW_KEY_A) == GLFW_PRESS) { m_camera.move_left(mdt);     moved = true; }
                if (glfwGetKey(window, GLFW_KEY_D) == GLFW_PRESS) { m_camera.move_right(mdt);    moved = true; }
                if (glfwGetKey(window, GLFW_KEY_E) == GLFW_PRESS) { m_camera.move_up(mdt);       moved = true; }
                if (glfwGetKey(window, GLFW_KEY_Q) == GLFW_PRESS) { m_camera.move_down(mdt);     moved = true; }
            }
            g_scroll_accum = 0.0;
            m_user_moving = moved || (left_down && !over_ui);
        }
        else
        {
            Camera& cam = m_scene_mode ? m_scene_camera : m_camera;
            if (left_down && !m_left_was_down && !over_ui)
                cam.process_orbital_mouse_button(GLFW_MOUSE_BUTTON_LEFT, GLFW_PRESS, 0);
            else if (!left_down && m_left_was_down)
                cam.process_orbital_mouse_button(GLFW_MOUSE_BUTTON_LEFT, GLFW_RELEASE, 0);
            m_left_was_down = left_down;

            cam.process_orbital_mouse_move(mx, my);

            double scroll = g_scroll_accum; g_scroll_accum = 0.0;
            if (scroll != 0.0 && !over_ui)
                cam.process_orbital_scroll(0.0, scroll);

            m_user_moving = cam.is_dragging() || cam.is_panning();
        }
    }

    auto Application::set_free_fly(bool enabled) -> void
    {
        const bool is_fps = m_camera.get_camera_mode() == CameraMode::FPS;
        if (enabled == is_fps) return;
        if (enabled)
        {
            // Seed the fly pose from the current orbital framing so the view is continuous.
            glm::vec3 pos = m_camera.get_orbital_position();
            glm::vec3 fwd = glm::normalize(m_camera.get_orbital_target() - pos);
            float pitch = glm::degrees(asin(glm::clamp(fwd.y, -1.0f, 1.0f)));
            float yaw   = glm::degrees(atan2(fwd.z, fwd.x));
            m_camera.set_camera_mode(CameraMode::FPS);
            m_camera.set_movement_speed(2.0e10f);
            m_camera.set_mouse_sensitivity(0.15f);
            m_camera.set_position(pos);
            m_camera.set_rotation(glm::vec3(pitch, yaw, 0.0f));
        }
        else
        {
            m_camera.set_camera_mode(CameraMode::Orbital);  // orbital state was left intact
        }
    }

    auto Application::reset_camera() -> void
    {
        m_camera.set_camera_mode(CameraMode::Orbital);
        m_camera.set_orbital_radius(4e11);
        m_camera.set_azimuth(0.0f);
        m_camera.set_elevation(1.25f);
    }

    auto Application::set_hdri(const std::string& path) -> void
    {
        if (m_hdri_path == path || !m_device) return;
        m_device->wait_idle();
        m_cubemap = m_device->create_cubemap_from_hdri(path);   // old cube freed after idle
        m_hdri_path = path;
    }

    // One-time ImGui theme: rounded, roomy, dark with a warm accretion-disk accent.
    static auto apply_donut_style() -> void
    {
        ImGuiStyle& s = ImGui::GetStyle();
        s.WindowRounding = 7.0f; s.ChildRounding = 5.0f; s.FrameRounding = 4.0f;
        s.GrabRounding = 4.0f; s.PopupRounding = 4.0f; s.ScrollbarRounding = 5.0f; s.TabRounding = 4.0f;
        s.WindowPadding = ImVec2(12, 12); s.FramePadding = ImVec2(9, 5);
        s.ItemSpacing = ImVec2(9, 8); s.ItemInnerSpacing = ImVec2(7, 5);
        s.WindowBorderSize = 0.0f; s.FrameBorderSize = 0.0f; s.WindowTitleAlign = ImVec2(0.02f, 0.5f);

        const ImVec4 amber   = ImVec4(0.98f, 0.62f, 0.20f, 1.00f);
        const ImVec4 amberHi = ImVec4(1.00f, 0.73f, 0.36f, 1.00f);
        ImVec4* c = s.Colors;
        c[ImGuiCol_WindowBg]        = ImVec4(0.07f, 0.08f, 0.10f, 0.97f);
        c[ImGuiCol_ChildBg]         = ImVec4(0.10f, 0.11f, 0.13f, 0.55f);
        c[ImGuiCol_PopupBg]         = ImVec4(0.09f, 0.10f, 0.12f, 0.98f);
        c[ImGuiCol_TitleBg]         = ImVec4(0.09f, 0.10f, 0.12f, 1.00f);
        c[ImGuiCol_TitleBgActive]   = ImVec4(0.13f, 0.14f, 0.17f, 1.00f);
        c[ImGuiCol_Text]            = ImVec4(0.90f, 0.91f, 0.93f, 1.00f);
        c[ImGuiCol_TextDisabled]    = ImVec4(0.48f, 0.50f, 0.54f, 1.00f);
        c[ImGuiCol_FrameBg]         = ImVec4(0.16f, 0.17f, 0.20f, 1.00f);
        c[ImGuiCol_FrameBgHovered]  = ImVec4(0.22f, 0.24f, 0.28f, 1.00f);
        c[ImGuiCol_FrameBgActive]   = ImVec4(0.26f, 0.28f, 0.33f, 1.00f);
        c[ImGuiCol_Header]          = ImVec4(0.17f, 0.19f, 0.23f, 1.00f);
        c[ImGuiCol_HeaderHovered]   = ImVec4(0.24f, 0.27f, 0.32f, 1.00f);
        c[ImGuiCol_HeaderActive]    = ImVec4(0.28f, 0.31f, 0.37f, 1.00f);
        c[ImGuiCol_Button]          = ImVec4(0.20f, 0.22f, 0.26f, 1.00f);
        c[ImGuiCol_ButtonHovered]   = ImVec4(0.27f, 0.30f, 0.35f, 1.00f);
        c[ImGuiCol_ButtonActive]    = amber;
        c[ImGuiCol_SliderGrab]      = amber;
        c[ImGuiCol_SliderGrabActive]= amberHi;
        c[ImGuiCol_CheckMark]       = amberHi;
        c[ImGuiCol_Separator]       = ImVec4(0.20f, 0.22f, 0.26f, 1.00f);
        c[ImGuiCol_ScrollbarGrab]   = ImVec4(0.24f, 0.26f, 0.30f, 1.00f);
    }

    auto Application::build_ui() -> void
    {
        static bool styled = false;
        if (!styled) { apply_donut_style(); styled = true; }
        if (!m_device) return;

        // Full-viewport dock space with a pass-through centre, so the panel can be
        // docked to any edge while the render shows through the middle.
        ImGui::DockSpaceOverViewport(0, ImGui::GetMainViewport(), ImGuiDockNodeFlags_PassthruCentralNode);

        ImGui::SetNextWindowSize(ImVec2(340, 580), ImGuiCond_FirstUseEver);
        ImGui::Begin("Donut  \xc2\xb7  Black Hole");

        ImGuiIO& io = ImGui::GetIO();
        ImGui::TextDisabled("%s", m_device->device_name().empty() ? "GPU" : m_device->device_name().c_str());
        ImGui::Text("%.0f FPS", io.Framerate);
        ImGui::SameLine(); ImGui::TextDisabled("%.1f ms/frame", io.Framerate > 0 ? 1000.0f / io.Framerate : 0.0f);
        ImGui::Spacing();

        if (ImGui::CollapsingHeader("Renderer", ImGuiTreeNodeFlags_DefaultOpen))
        {
            auto& s = SettingsManager::get_settings();
            const char* apis[] = { "OpenGL", "Vulkan" };
            int cur = (s.graphics.render_api == "Vulkan") ? 1 : 0;
            if (ImGui::Combo("Graphics API", &cur, apis, 2))
            {
                s.graphics.render_api = apis[cur];
                SettingsManager::save_settings();
            }
            const char* running = (RendererAPI::get_api() == RendererAPI::API::Vulkan) ? "Vulkan" : "OpenGL";
            if (s.graphics.render_api != running)
                ImGui::TextColored(ImVec4(0.98f, 0.62f, 0.20f, 1.0f), "Restart to apply (%s running)", running);
            else
                ImGui::TextDisabled("Active backend: %s", running);
        }

        ImGui::Spacing();
        ImGui::TextDisabled("VIEW");
        if (ImGui::RadioButton("Black hole", !m_scene_mode)) m_scene_mode = false;
        ImGui::SameLine();
        if (ImGui::RadioButton("Scene", m_scene_mode))       m_scene_mode = true;
        ImGui::Separator();

        if (m_scene_mode)
        {
            build_scene_ui();
        }
        else
        {
            BlackHoleParams& bh = m_bh_params;

            if (ImGui::CollapsingHeader("Camera", ImGuiTreeNodeFlags_DefaultOpen))
            {
                bool ff = m_camera.get_camera_mode() == CameraMode::FPS;
                if (ImGui::RadioButton("Orbital", !ff)) set_free_fly(false);
                ImGui::SameLine();
                if (ImGui::RadioButton("Free-fly", ff)) set_free_fly(true);
                ImGui::SameLine();
                if (ImGui::Button("Reset view")) reset_camera();
                ImGui::SliderFloat("FOV", &bh.fov_degrees, 20.0f, 90.0f, "%.0f\xc2\xb0");
                ImGui::TextDisabled(ff ? "WASD move | Q/E down-up | Shift boost | drag look"
                                       : "Drag to orbit | scroll to zoom");
            }

            if (ImGui::CollapsingHeader("Accretion disk", ImGuiTreeNodeFlags_DefaultOpen))
            {
                ImGui::SliderFloat("Temperature", &bh.temperature, 2000.0f, 15000.0f, "%.0f K");
                ImGui::SliderFloat("Brightness",  &bh.brightness, 0.0f, 3.0f, "%.2f");
                ImGui::SliderFloat("Inner radius", &bh.disk_inner_rs, 3.0f, 12.0f, "%.1f r_s");
                if (bh.disk_outer_rs < bh.disk_inner_rs + 0.5f) bh.disk_outer_rs = bh.disk_inner_rs + 0.5f;
                ImGui::SliderFloat("Outer radius", &bh.disk_outer_rs, bh.disk_inner_rs + 0.5f, 25.0f, "%.1f r_s");
                ImGui::SliderFloat("Turbulence",  &bh.turbulence, 0.0f, 2.0f, "%.2f");
                ImGui::TextDisabled("Inner edge is the ISCO (3 r_s). Novikov-Thorne profile.");
            }

            if (ImGui::CollapsingHeader("Quality"))
            {
                ImGui::SliderInt("Integration steps", &bh.quality_steps, 2000, 15000);
                ImGui::TextDisabled("Deeper lensing at higher cost. Settled frame is 4x supersampled.");
            }

            if (ImGui::CollapsingHeader("Environment", ImGuiTreeNodeFlags_DefaultOpen))
            {
                auto& hdri = HDRIManager::get();
                std::string preview = hdri.get_hdri_name(m_hdri_path);
                if (ImGui::BeginCombo("Starfield", preview.c_str()))
                {
                    for (const auto& path : hdri.get_available_hdri())
                    {
                        bool selected = (path == m_hdri_path);
                        if (ImGui::Selectable(hdri.get_hdri_name(path).c_str(), selected))
                            set_hdri(path);
                        if (selected) ImGui::SetItemDefaultFocus();
                    }
                    ImGui::EndCombo();
                }
                ImGui::TextDisabled("Switching rebuilds the cubemap (brief pause).");
            }
        }

        ImGui::End();
    }

    auto Application::build_scene_ui() -> void
    {
        if (!ImGui::CollapsingHeader("Objects", ImGuiTreeNodeFlags_DefaultOpen))
            return;

        ImGui::TextDisabled("Drag to orbit, scroll to zoom. HDRI skybox behind.");
        auto& objs = m_scene_objects;
        if (m_selected_object >= (int)objs.size()) m_selected_object = (int)objs.size() - 1;

        ImGui::Text("Spheres (%d)", (int)objs.size());
        if (ImGui::Button("Add") && objs.size() < 64)
        {
            SceneObject o;
            o.position = glm::vec3(((int)objs.size() % 5) * 5.0f - 10.0f, 2.0f, ((int)objs.size() / 5) * 5.0f);
            o.radius   = 1.5f;
            o.color    = glm::vec3(0.35f + 0.12f * (objs.size() % 5), 0.55f, 0.9f - 0.12f * (objs.size() % 4));
            objs.push_back(o);
            m_selected_object = (int)objs.size() - 1;
        }
        ImGui::SameLine();
        if (ImGui::Button("Delete") && !objs.empty())
        {
            objs.erase(objs.begin() + m_selected_object);
            if (m_selected_object >= (int)objs.size()) m_selected_object = (int)objs.size() - 1;
        }

        ImGui::BeginChild("obj_list", ImVec2(0, 90), true);
        for (int i = 0; i < (int)objs.size(); ++i)
        {
            std::string label = "Sphere " + std::to_string(i);
            if (ImGui::Selectable(label.c_str(), m_selected_object == i)) m_selected_object = i;
        }
        ImGui::EndChild();

        if (m_selected_object >= 0 && m_selected_object < (int)objs.size())
        {
            SceneObject& o = objs[m_selected_object];
            ImGui::DragFloat3("Position", &o.position.x, 0.1f);
            ImGui::DragFloat("Radius", &o.radius, 0.05f, 0.1f, 20.0f);
            ImGui::ColorEdit3("Color", &o.color.x);
        }
    }

    auto Application::close() -> void
    {
        m_running = false;
    }

    auto Application::on_event(Event& event) -> void
    {
        EventDispatcher dispatcher(event);
        dispatcher.dispatch<WindowCloseEvent>([this, &event](WindowCloseEvent& e)
        {
            m_running = false;
            event.handled = true;
            return true;
        });

        dispatcher.dispatch<WindowResizeEvent>([this, &event](WindowResizeEvent& e)
        {
            m_minimized = (e.get_width() == 0 || e.get_height() == 0);
            if (m_device) m_device->resize(e.get_width(), e.get_height());
            event.handled = true;
            return true;
        });
    }

    auto Application::on_shutdown() -> void
    {
        if (m_device)
        {
            m_device->wait_idle();
            m_scene_renderer.reset();
            m_black_hole_renderer.reset();
            m_cubemap.reset();
            // Free HDRIManager's cached GPU textures now, while the render context
            // is still alive. On OpenGL these are GL textures owned by a static
            // singleton; letting them destruct at program exit would call
            // glDeleteTextures after the GL context is gone and crash on close.
            HDRIManager::get().clear_cache();
            m_device->shutdown();
            m_device.reset();
        }
        SettingsManager::shutdown();
        Logger::shutdown();
    }
};