/*
 * Copyright (c) 2020, Andreas Kling <andreas@ladybird.org>
 * Copyright (c) 2026, Jelle Raaijmakers <jelle@ladybird.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/Forward.h>
#include <AK/NonnullOwnPtr.h>
#include <AK/OwnPtr.h>
#include <AK/RefPtr.h>
#include <LibGC/Ptr.h>
#include <LibGC/Weak.h>
#include <LibJS/Heap/Cell.h>
#include <LibUnicode/Forward.h>
#include <LibWeb/CSS/Enums.h>
#include <LibWeb/Compositor/AsyncScrollingState.h>
#include <LibWeb/DOM/HoverEventData.h>
#include <LibWeb/Export.h>
#include <LibWeb/Forward.h>
#include <LibWeb/Gamepad/SDLGamepadForward.h>
#include <LibWeb/Page/EventResult.h>
#include <LibWeb/Page/InputEvent.h>
#include <LibWeb/Painting/Forward.h>
#include <LibWeb/PixelUnits.h>
#include <LibWeb/UIEvents/KeyCode.h>

namespace Web {

struct AsyncScrollOperation {
    GC::Ptr<HTML::Navigable> navigable;
    Compositor::AsyncScrollOperationID operation_id { 0 };
};

class WEB_API EventHandler {
    friend class AutoScrollHandler;

public:
    EventHandler(Badge<HTML::Navigable>, HTML::Navigable&);
    ~EventHandler();

    void visit_edges(JS::Cell::Visitor& visitor) const;

    EventResult handle_mousedown(CSSPixelPoint, CSSPixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, int click_count);
    EventResult handle_mousemove(CSSPixelPoint, CSSPixelPoint screen_position, unsigned buttons, unsigned modifiers);
    EventResult handle_mouseup(CSSPixelPoint, CSSPixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers);
    EventResult handle_mousewheel(CSSPixelPoint, CSSPixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, double wheel_delta_x, double wheel_delta_y, bool async_scroll_performed_default_action = false, Optional<AsyncScrollOperation>* async_scroll_operation = nullptr);
    EventResult handle_mouseleave();
    void update_hover_after_scroll();

    EventResult handle_keydown(UIEvents::KeyCode, unsigned modifiers, u32 code_point, bool repeat);
    EventResult handle_keyup(UIEvents::KeyCode, unsigned modifiers, u32 code_point, bool repeat);

    EventResult handle_drag_and_drop_event(DragEvent::Type, CSSPixelPoint, CSSPixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, Vector<HTML::SelectedFile> files);
    EventResult handle_pinch_event(CSSPixelPoint, double scale_delta);
    EventResult handle_paste(Utf16String const& text);
    void handle_sdl_input_events();

    void process_auto_scroll();

    enum class SelectionMode : u8 {
        None,
        Character,
        Word,
        Paragraph,
    };
    bool is_handling_mouse_selection() const { return m_selection_mode != SelectionMode::None; }

    Optional<MiddleButtonScrollHandler&> middle_button_scroll_handler() const
    {
        if (m_middle_button_scroll_handler)
            return *m_middle_button_scroll_handler;
        return {};
    }

    void clear_per_test_input_state(Badge<Internals::Internals>);

private:
    bool should_ignore_device_input_event() const;

    EventResult fire_keyboard_event(FlyString const& event_name, HTML::Navigable&, UIEvents::KeyCode, unsigned modifiers, u32 code_point, bool repeat);
    [[nodiscard]] EventResult input_event(FlyString const& event_name, FlyString const& input_type, HTML::Navigable&, Variant<u32, Utf16String> code_point_or_string);

    EventResult focus_next_element();
    EventResult focus_previous_element();

    struct MouseEventCoordinates {
        CSSPixelPoint page_offset;
        CSSPixelPoint visual_viewport_position;
        CSSPixelPoint viewport_position;
        CSSPixelPoint offset;
    };
    bool fire_click_events(GC::Ref<DOM::Node>, MouseEventCoordinates const&, CSSPixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers, int click_count);

    MouseEventCoordinates compute_mouse_event_coordinates(CSSPixelPoint visual_viewport_position, CSSPixelPoint viewport_position, Painting::Paintable const& paintable, Layout::Node const& layout_node) const;
    CSSPixelPoint compute_mouse_event_page_offset(CSSPixelPoint event_client_offset) const;
    CSSPixelPoint compute_mouse_event_movement(CSSPixelPoint screen_position) const;

    struct Target {
        RefPtr<Painting::Paintable> paintable;
        RefPtr<Painting::ChromeWidget> chrome_widget;
        Optional<int> index_in_node;
    };
    Optional<Target> target_for_mouse_position(CSSPixelPoint position);
    GC::Ptr<DOM::Node> focus_candidate_for_position(CSSPixelPoint) const;

    void run_mousedown_default_actions(DOM::Document&, CSSPixelPoint visual_viewport_position, CSSPixelPoint viewport_position, unsigned button, unsigned modifiers, int click_count);
    void run_activation_behavior(GC::Ref<DOM::Node>, unsigned button, unsigned modifiers);

    void maybe_show_context_menu(GC::Ref<DOM::Node>, MouseEventCoordinates const&, CSSPixelPoint screen_position, CSSPixelPoint viewport_position, unsigned buttons, unsigned modifiers);
    bool maybe_request_paste_for_middle_click(DOM::Document&, CSSPixelPoint visual_viewport_position);

    bool initiate_character_selection(DOM::Document&, Painting::HitTestResult const&, CSS::UserSelect, bool shift_held);
    bool initiate_word_selection(DOM::Document&, Painting::HitTestResult const&, CSS::UserSelect);
    bool initiate_paragraph_selection(DOM::Document&, Painting::HitTestResult const&, CSS::UserSelect);

    void update_mouse_selection(CSSPixelPoint visual_viewport_position);
    void apply_mouse_selection(CSSPixelPoint visual_viewport_position);

    void clear_mousedown_tracking();
    void stop_updating_selection();

    void update_hover_after_scroll(CSSPixelPoint visual_viewport_position, CSSPixelPoint screen_position, unsigned button, unsigned buttons, unsigned modifiers);

    enum class PointerEventType : u8 {
        PointerDown,
        PointerUp,
        PointerMove,
        PointerCancel
    };
    bool dispatch_a_pointer_event_for_a_device_that_supports_hover(PointerEventType, GC::Ptr<DOM::Node>, RefPtr<Painting::ChromeWidget>, MouseEventCoordinates const&, CSSPixelPoint screen_position, CSSPixelPoint movement, unsigned button, unsigned buttons, unsigned modifiers, int click_count = 0);
    void track_the_effective_position_of_the_legacy_mouse_pointer(GC::Ptr<DOM::Node>, Optional<DOM::HoverEventData> = {});

    bool dispatch_chrome_widget_pointer_event(RefPtr<Painting::ChromeWidget>, FlyString const& type, unsigned button, CSSPixelPoint visual_viewport_position);
    void update_hovered_chrome_widget(RefPtr<Painting::ChromeWidget>);

    void update_cursor(RefPtr<Painting::Paintable> paintable, GC::Ptr<DOM::Node> host_element, RefPtr<Painting::ChromeWidget> chrome_widget);
    void record_last_known_mouse_position(CSSPixelPoint visual_viewport_position, CSSPixelPoint screen_position, unsigned buttons, unsigned modifiers);

    void handle_gamepad_connected(SDL_JoystickID);
    void handle_gamepad_updated(SDL_JoystickID);
    void handle_gamepad_disconnected(SDL_JoystickID);

    RefPtr<Painting::PaintableBox> paint_root();
    RefPtr<Painting::PaintableBox const> paint_root() const;
    Unicode::Segmenter& word_segmenter();

    GC::Ref<HTML::Navigable> m_navigable;

    SelectionMode m_selection_mode { SelectionMode::None };
    InputEventsTarget* m_mouse_selection_target { nullptr };
    GC::Ptr<DOM::Range> m_selection_origin;

    RefPtr<Painting::ChromeWidget> m_hovered_chrome_widget;
    RefPtr<Painting::ChromeWidget> m_captured_chrome_widget;

    GC::Weak<DOM::Node> m_effective_legacy_mouse_pointer_position;

    GC::Weak<DOM::Node> m_mousedown_target;
    Optional<CSSPixelPoint> m_mousedown_visual_viewport_position;
    int m_mousedown_click_count { 0 };
    bool m_mousedown_target_is_drag_candidate { false };

    // https://w3c.github.io/pointerevents/#the-pointerdown-event
    // The PREVENT MOUSE EVENT flag.
    // FIXME: This should be per-pointer, of which there can be multiple. Move it once multiple simultaneous pointer
    //        inputs are supported.
    bool m_prevent_mouse_event { false };

    Optional<CSSPixelPoint> m_mousemove_previous_screen_position;
    Optional<CSSPixelPoint> m_last_known_mouse_visual_viewport_position;
    CSSPixelPoint m_last_known_mouse_screen_position;
    unsigned m_last_known_mouse_buttons { 0 };
    unsigned m_last_known_mouse_modifiers { 0 };

    OwnPtr<Unicode::Segmenter> m_word_segmenter;

    OwnPtr<AutoScrollHandler> m_auto_scroll_handler;
    OwnPtr<MiddleButtonScrollHandler> m_middle_button_scroll_handler;
    NonnullOwnPtr<DragAndDropEventHandler> m_drag_and_drop_event_handler;
};

}
