#include "../include/ImageViewer.hpp"
#include "../include/Notification.hpp"
#include "../include/Storage.hpp"
#include "../plugins/Manga.hpp"
#include <cmath>
#include <SFML/Window/Event.hpp>
#include <SFML/Graphics/RenderWindow.hpp>
#include <SFML/Graphics/RectangleShape.hpp>

namespace QuickMedia {
    ImageViewer::ImageViewer(MangaImagesPage *manga_images_page, const std::string &content_title, const std::string &chapter_title, int current_page, const Path &chapter_cache_dir, sf::Font *font) :
        current_page(current_page),
        num_pages(0),
        content_title(content_title),
        chapter_title(chapter_title),
        chapter_cache_dir(chapter_cache_dir),
        focused_page(current_page),
        font(font),
        page_text("", *font, 14)
    {
        if(manga_images_page->get_number_of_images(num_pages) != ImageResult::OK) {
            show_notification("QuickMedia", "Failed to get number of images", Urgency::CRITICAL);
            return;
        }
        current_page = std::min(current_page, num_pages);
        image_data.resize(num_pages);
        page_size.resize(num_pages);
        for(int i = 0; i < num_pages; ++i) {
            image_data[i] = nullptr;
            page_size[i].loaded = false;
        }
        page_text.setFillColor(sf::Color::White);

        has_default_cursor = default_cursor.loadFromSystem(sf::Cursor::Arrow);
        has_size_vertical_cursor = size_vertical_cursor.loadFromSystem(sf::Cursor::SizeVertical);
    }

    void ImageViewer::load_image_async(const Path &path, std::shared_ptr<ImageData> image_data) {
        image_data->image_status = ImageStatus::LOADING;
        image_data->texture.setSmooth(true);
        assert(!loading_image);
        loading_image = true;
        image_loader_thread = std::thread([this, image_data, path]() mutable {
            auto image = std::make_unique<sf::Image>();
            if(image->loadFromFile(path.data)) {
                image_data->image = std::move(image);
                image_data->image_status = ImageStatus::LOADED;
            } else {
                image_data->image_status = ImageStatus::FAILED_TO_LOAD;
            }
            loading_image = false;
        });
        image_loader_thread.detach();
    }

    bool ImageViewer::render_page(sf::RenderWindow &window, int page, double offset_y) {
        if(page < 0 || page >= (int)image_data.size())
            return false;

        std::shared_ptr<ImageData> &page_image_data = image_data[page];
        const sf::Vector2<double> image_size = get_page_size(page);
        sf::Vector2<double> render_pos(std::floor(window_size.x * 0.5 - image_size.x * 0.5), - image_size.y * 0.5 + scroll + offset_y);
        if(render_pos.y + image_size.y <= 0.0 || render_pos.y >= window_size.y) {
            if(page_image_data)
                page_image_data->visible_on_screen = false;
            return true;
        }

        bool scrolling = (std::abs(scroll_speed) > 0.01f);
        if(!scrolling)
            render_pos.y = std::floor(render_pos.y);

        double center_dist = std::abs(window_size.y * 0.5 - (render_pos.y + image_size.y * 0.5));
        if(center_dist < min_page_center_dist) {
            min_page_center_dist = center_dist;
            page_closest_to_center = page;
        }

        if(page_image_data) {
            page_image_data->visible_on_screen = true;

            if(page_image_data->image_status == ImageStatus::APPLIED_TO_TEXTURE) {
                page_image_data->sprite.setPosition(render_pos.x, render_pos.y);
                window.draw(page_image_data->sprite);
            } else {
                std::string page_str = std::to_string(1 + page);
                std::string msg;
                if(page_image_data->image_status == ImageStatus::WAITING) {
                    if(!loading_image) {
                        Path image_path = chapter_cache_dir;
                        image_path.join(page_str);
                        load_image_async(image_path, page_image_data);
                    }
                    msg = "Loading image for page " + page_str;
                } else if(page_image_data->image_status == ImageStatus::LOADING) {
                    msg = "Loading image for page " + page_str;
                } else if(page_image_data->image_status == ImageStatus::FAILED_TO_LOAD) {
                    msg = "Failed to load image for page " + page_str;
                }

                sf::Text error_message(std::move(msg), *font, 30);
                auto text_bounds = error_message.getLocalBounds();
                error_message.setFillColor(sf::Color::Black);
                sf::Vector2<double> render_pos_text(std::floor(window_size.x * 0.5 - text_bounds.width * 0.5), - text_bounds.height * 0.5 + scroll + offset_y);

                if(!scrolling)
                    render_pos_text.y = std::floor(render_pos_text.y);

                sf::RectangleShape background(sf::Vector2f(image_size.x, image_size.y));
                background.setFillColor(sf::Color::White);
                background.setPosition(render_pos.x, render_pos.y);
                window.draw(background);

                error_message.setPosition(render_pos_text.x, render_pos_text.y);
                window.draw(error_message);
            }
        } else {
            std::string page_str = std::to_string(1 + page);

            sf::Text error_message("Downloading page " + page_str, *font, 30);
            auto text_bounds = error_message.getLocalBounds();
            error_message.setFillColor(sf::Color::Black);
            sf::Vector2<double> render_pos_text(std::floor(window_size.x * 0.5 - text_bounds.width * 0.5), - text_bounds.height * 0.5 + scroll + offset_y);

            if(!scrolling)
                render_pos_text.y = std::floor(render_pos_text.y);

            sf::RectangleShape background(sf::Vector2f(image_size.x, image_size.y));
            background.setFillColor(sf::Color::White);
            background.setPosition(render_pos.x, render_pos.y);
            window.draw(background);

            error_message.setPosition(render_pos_text.x, render_pos_text.y);
            window.draw(error_message);

            Path image_path = chapter_cache_dir;
            image_path.join(page_str);

            if(get_file_type(image_path) == FileType::REGULAR) {
                fprintf(stderr, "ImageViewer: Loaded page %d\n", 1 + page);

                page_image_data = std::make_shared<ImageData>();
                page_image_data->visible_on_screen = true;
                
                page_image_data->image_status = ImageStatus::WAITING;
                page_image_data->texture.setSmooth(true);
            }
        }

        return true;
    }

    static double sign(double value) {
        return value >= 0.0 ? 1.0 : -1.0;
    }

    ImageViewerAction ImageViewer::draw(sf::RenderWindow &window) {
        const double frame_delta = frame_timer.restart().asSeconds();
        const double scroll_speed_key_input = 50.0;
        const double scroll_speed_mouse_wheel = 600.0;
        const double scroll_speed_autoscroll = 10.0;
        const double scroll_deaccel = 0.96;

        if(!window_size_set) {
            auto window_size_i = window.getSize();
            window_size.x = window_size_i.x;
            window_size.y = window_size_i.y;
            window_size_set = true;
        }

        // TODO: Only redraw when scrolling and when image has finished downloading
        sf::Event event;
        while(window.pollEvent(event)) {
            if (event.type == sf::Event::Closed) {
                if(has_default_cursor)
                    window.setMouseCursor(default_cursor);
                window.close();
                return ImageViewerAction::RETURN;
            } else if(event.type == sf::Event::Resized) {
                window_size.x = event.size.width;
                window_size.y = event.size.height;
                sf::FloatRect visible_area(0, 0, window_size.x, window_size.y);
                window.setView(sf::View(visible_area));
                //redraw = true;
            } else if(event.type == sf::Event::GainedFocus) {
                //redraw = true;
            } else if(event.type == sf::Event::KeyPressed) {
                if(event.key.code == sf::Keyboard::Up)
                    up_pressed = true;
                if(event.key.code == sf::Keyboard::Down)
                    down_pressed = true;

                if(event.key.code == sf::Keyboard::Escape) {
                    if(has_default_cursor)
                        window.setMouseCursor(default_cursor);
                    return ImageViewerAction::RETURN;
                }
                
                if(event.key.code == sf::Keyboard::I)
                    return ImageViewerAction::SWITCH_TO_SINGLE_IMAGE_MODE;
            } else if(event.type == sf::Event::KeyReleased) {
                if(event.key.code == sf::Keyboard::Up)
                    up_pressed = false;
                if(event.key.code == sf::Keyboard::Down)
                    down_pressed = false;
            } else if(event.type == sf::Event::MouseWheelScrolled && event.mouseWheelScroll.wheel == sf::Mouse::VerticalWheel) {
                scroll_speed += scroll_speed_mouse_wheel * event.mouseWheelScroll.delta * frame_delta;
            } else if(event.type == sf::Event::MouseButtonPressed && event.mouseButton.button == sf::Mouse::Button::Middle) {
                middle_mouse_scrolling = true;
                autoscroll_start_y = sf::Mouse::getPosition(window).y;
                if(has_size_vertical_cursor)
                    window.setMouseCursor(size_vertical_cursor);

            } else if(event.type == sf::Event::MouseButtonReleased && event.mouseButton.button == sf::Mouse::Button::Middle) {
                middle_mouse_scrolling = false;
                scroll_speed = 0.0;
                if(has_default_cursor)
                    window.setMouseCursor(default_cursor);
            }
        }

        if(up_pressed)
            scroll_speed += scroll_speed_key_input * frame_delta;
        if(down_pressed)
            scroll_speed -= scroll_speed_key_input * frame_delta;

        if(middle_mouse_scrolling) {
            double distance_to_start_y = (double)sf::Mouse::getPosition(window).y - autoscroll_start_y;
            double dist_abs = std::abs(distance_to_start_y);
            dist_abs -= 20.0;
            if(dist_abs < 0.0)
                dist_abs = 0.0;
            scroll_speed = -(dist_abs * sign(distance_to_start_y)) * scroll_speed_autoscroll * frame_delta;
            const double max_speed = 100.0;
            if(scroll_speed > max_speed)
                scroll_speed = max_speed;
            if(scroll_speed < -max_speed)
                scroll_speed = -max_speed;
            scroll += scroll_speed;
        } else {
            const double max_speed = 100.0;
            if(scroll_speed > max_speed)
                scroll_speed = max_speed;
            if(scroll_speed < -max_speed)
                scroll_speed = -max_speed;

            scroll_speed *= scroll_deaccel;
            if(std::abs(scroll_speed) < 0.01) {
                scroll_speed = 0.0;
                scroll = std::round(scroll); /* Better image quality! */
            } else {
                scroll += scroll_speed;
            }
        }

        min_page_center_dist = 9999999.0;
        page_closest_to_center = -1;

        int page_i = 0;
        for(auto &page_data : image_data) {
            if(page_data) {
                if(page_data->image_status == ImageStatus::LOADED && page_data->image->getSize().x > 0 && page_data->image->getSize().y > 0) {
                    if(page_data->texture.loadFromImage(*page_data->image)) {
                        //page_data->texture.setSmooth(true);
                        //page_data->texture.generateMipmap();
                        double height_before = get_page_size(page_i).y;
                        page_data->image_status = ImageStatus::APPLIED_TO_TEXTURE;
                        page_data->sprite.setTexture(page_data->texture, true);
                        page_size[page_i].size = get_page_size(page_i);
                        page_size[page_i].loaded = true;
                        double height_after = page_size[page_i].size.y;

                        double height_diff = height_before - height_after;
                        if(scroll_speed <= 0.0 && page_i < current_page) {
                            scroll -= height_diff;
                        }
                    } else {
                        page_data->image_status = ImageStatus::FAILED_TO_LOAD;
                    }
                    page_data->image.reset();
                }
                page_data->visible_on_screen = false;
            }
            ++page_i;
        }

        const sf::Vector2<double> selected_page_size = get_page_size(current_page);
        render_page(window, current_page, window_size.y*0.5);
        //if(!focused_page_rendered)
        //    return;

        // Render previous pages
        double page_offset = window_size.y*0.5 - selected_page_size.y*0.5;
        int page = current_page - 1;
        while(true) {
            const sf::Vector2<double> image_size = get_page_size(page);
            page_offset -= image_size.y*0.5;
            if(!render_page(window, page, page_offset))
                break;
            --page;
            page_offset -= image_size.y*0.5;
        }

        // Render next pages
        page_offset = window_size.y*0.5 + selected_page_size.y*0.5;
        page = current_page + 1;
        while(true) {
            const sf::Vector2<double> image_size = get_page_size(page);
            page_offset += image_size.y*0.5;
            if(!render_page(window, page, page_offset))
                break;
            ++page;
            page_offset += image_size.y*0.5;
        }

        if(page_closest_to_center != -1) {
            focused_page = page_closest_to_center;
        }

        if(focused_page != prev_focused_page) {
            prev_focused_page = focused_page;
            page_text.setString(content_title + " | " + chapter_title + " | Page " + std::to_string(1 + focused_page) + "/" + std::to_string(num_pages));
        }

        const float font_height = page_text.getCharacterSize() + 8.0f;
        const float background_height = font_height + 6.0f;

        sf::RectangleShape page_text_background(sf::Vector2f(window_size.x, background_height));
        page_text_background.setFillColor(sf::Color(0, 0, 0, 150));
        page_text_background.setPosition(0.0f, window_size.y - background_height);
        window.draw(page_text_background);

        auto page_text_bounds = page_text.getLocalBounds();
        page_text.setPosition(std::floor(window_size.x * 0.5f - page_text_bounds.width * 0.5f), std::floor(window_size.y - background_height * 0.5f - font_height * 0.5f));
        window.draw(page_text);

        // Free pages that are not visible on the screen
        int i = 0;
        for(auto &page_data : image_data) {
            if(page_data && !page_data->visible_on_screen) {
                fprintf(stderr, "ImageViewer: Unloaded page %d\n", 1 + i);
                page_data.reset();
            }
            ++i;
        }

        return ImageViewerAction::NONE;
    }

    int ImageViewer::get_focused_page() const {
        return 1 + focused_page;
    }

    sf::Vector2<double> ImageViewer::get_page_size(int page) {
        const sf::Vector2<double> no_image_page_size(720.0, 1280.0);

        if(page < 0 || page >= (int)image_data.size())
            return no_image_page_size;

        if(page_size[page].loaded)
            return page_size[page].size;

        if(!image_data[page] || image_data[page]->image_status != ImageStatus::APPLIED_TO_TEXTURE)
            return no_image_page_size;

        sf::Vector2u texture_size = image_data[page]->texture.getSize();
        return sf::Vector2<double>(texture_size.x, texture_size.y);
    }
}