#include <XCEditor/Shell/UIEditorViewportInputBridge.h>

#include <algorithm>

namespace XCEngine::UI::Editor {

namespace {

using ::XCEngine::UI::UIInputEvent;
using ::XCEngine::UI::UIInputEventType;
using ::XCEngine::UI::UIPoint;
using ::XCEngine::UI::UIPointerButton;
using ::XCEngine::UI::UIRect;

bool ContainsPoint(const UIRect& rect, const UIPoint& point) {
    return point.x >= rect.x &&
        point.x <= rect.x + rect.width &&
        point.y >= rect.y &&
        point.y <= rect.y + rect.height;
}

UIPoint ToLocalPoint(const UIRect& rect, const UIPoint& point) {
    return UIPoint(point.x - rect.x, point.y - rect.y);
}

std::uint8_t ButtonMask(UIPointerButton button) {
    switch (button) {
    case UIPointerButton::Left: return 1u << 0u;
    case UIPointerButton::Right: return 1u << 1u;
    case UIPointerButton::Middle: return 1u << 2u;
    case UIPointerButton::X1: return 1u << 3u;
    case UIPointerButton::X2: return 1u << 4u;
    case UIPointerButton::None:
    default:
        return 0u;
    }
}

bool AnyPointerButtonsDown(const UIEditorViewportInputBridgeState& state) {
    return state.pointerButtonsDownMask != 0u;
}

void ClearCapture(UIEditorViewportInputBridgeState& state) {
    state.captured = false;
    state.captureButton = UIPointerButton::None;
}

void ClearInputState(UIEditorViewportInputBridgeState& state) {
    state.pressedKeys.clear();
    state.pointerButtonsDownMask = 0u;
    ClearCapture(state);
    state.hovered = false;
}

void UpdatePointerPosition(
    UIEditorViewportInputBridgeState& state,
    UIEditorViewportInputBridgeFrame& frame,
    const UIRect& inputRect,
    const UIPoint& screenPosition,
    const ::XCEngine::UI::UIInputModifiers& modifiers) {
    if (state.hasPointerPosition) {
        frame.pointerDelta.x += screenPosition.x - state.lastScreenPointerPosition.x;
        frame.pointerDelta.y += screenPosition.y - state.lastScreenPointerPosition.y;
        frame.pointerMoved =
            frame.pointerMoved ||
            screenPosition.x != state.lastScreenPointerPosition.x ||
            screenPosition.y != state.lastScreenPointerPosition.y;
    }

    state.lastScreenPointerPosition = screenPosition;
    state.lastLocalPointerPosition = ToLocalPoint(inputRect, screenPosition);
    state.hasPointerPosition = true;
    state.modifiers = modifiers;

    frame.screenPointerPosition = state.lastScreenPointerPosition;
    frame.localPointerPosition = state.lastLocalPointerPosition;
    frame.modifiers = state.modifiers;
}

} // namespace

bool IsUIEditorViewportInputBridgeKeyDown(
    const UIEditorViewportInputBridgeState& state,
    std::int32_t keyCode) {
    return state.pressedKeys.contains(keyCode);
}

bool IsUIEditorViewportInputBridgePointerButtonDown(
    const UIEditorViewportInputBridgeState& state,
    UIPointerButton button) {
    const std::uint8_t mask = ButtonMask(button);
    return mask != 0u && (state.pointerButtonsDownMask & mask) != 0u;
}

UIEditorViewportInputBridgeFrame UpdateUIEditorViewportInputBridge(
    UIEditorViewportInputBridgeState& state,
    const UIRect& inputRect,
    const std::vector<UIInputEvent>& events,
    const UIEditorViewportInputBridgeConfig& config) {
    UIEditorViewportInputBridgeFrame frame = {};
    frame.screenPointerPosition = state.lastScreenPointerPosition;
    frame.localPointerPosition = state.lastLocalPointerPosition;
    frame.modifiers = state.modifiers;

    for (const UIInputEvent& event : events) {
        const bool inside = ContainsPoint(inputRect, event.position);
        switch (event.type) {
        case UIInputEventType::PointerEnter:
        case UIInputEventType::PointerMove:
            UpdatePointerPosition(state, frame, inputRect, event.position, event.modifiers);
            state.hovered = inside;
            break;
        case UIInputEventType::PointerLeave:
            state.hovered = false;
            state.lastScreenPointerPosition = event.position;
            state.lastLocalPointerPosition = ToLocalPoint(inputRect, event.position);
            frame.screenPointerPosition = state.lastScreenPointerPosition;
            frame.localPointerPosition = state.lastLocalPointerPosition;
            frame.modifiers = state.modifiers;
            break;
        case UIInputEventType::PointerButtonDown:
            UpdatePointerPosition(state, frame, inputRect, event.position, event.modifiers);
            state.hovered = inside;
            state.pointerButtonsDownMask |= ButtonMask(event.pointerButton);
            frame.changedPointerButton = event.pointerButton;
            if (inside) {
                frame.pointerPressedInside = true;
                if (config.focusOnPointerDownInside && !state.focused) {
                    state.focused = true;
                    frame.focusGained = true;
                }
                if (config.capturePointerOnPointerDownInside && !state.captured) {
                    state.captured = true;
                    state.captureButton = event.pointerButton;
                    frame.captureStarted = true;
                }
            } else if (config.clearFocusOnPointerDownOutside) {
                if (state.focused) {
                    state.focused = false;
                    frame.focusLost = true;
                }
                if (state.captured) {
                    ClearCapture(state);
                    frame.captureEnded = true;
                }
            }
            break;
        case UIInputEventType::PointerButtonUp:
            UpdatePointerPosition(state, frame, inputRect, event.position, event.modifiers);
            state.hovered = inside;
            state.pointerButtonsDownMask &= static_cast<std::uint8_t>(~ButtonMask(event.pointerButton));
            frame.changedPointerButton = event.pointerButton;
            if (inside) {
                frame.pointerReleasedInside = true;
            }
            if (state.captured &&
                state.captureButton == event.pointerButton &&
                !AnyPointerButtonsDown(state)) {
                ClearCapture(state);
                frame.captureEnded = true;
            }
            break;
        case UIInputEventType::PointerWheel:
            UpdatePointerPosition(state, frame, inputRect, event.position, event.modifiers);
            state.hovered = inside;
            if (inside || state.captured) {
                frame.wheelDelta += event.wheelDelta;
            }
            break;
        case UIInputEventType::KeyDown:
            state.modifiers = event.modifiers;
            frame.modifiers = state.modifiers;
            if (state.focused) {
                state.pressedKeys.insert(event.keyCode);
                frame.pressedKeyCodes.push_back(event.keyCode);
            }
            break;
        case UIInputEventType::KeyUp:
            state.modifiers = event.modifiers;
            frame.modifiers = state.modifiers;
            if (state.focused) {
                state.pressedKeys.erase(event.keyCode);
                frame.releasedKeyCodes.push_back(event.keyCode);
            }
            break;
        case UIInputEventType::Character:
            if (state.focused) {
                frame.characters.push_back(event.character);
            }
            break;
        case UIInputEventType::FocusLost:
            if (state.focused) {
                frame.focusLost = true;
            }
            if (state.captured) {
                frame.captureEnded = true;
            }
            state.focused = false;
            ClearInputState(state);
            break;
        case UIInputEventType::FocusGained:
            state.modifiers = event.modifiers;
            frame.modifiers = state.modifiers;
            break;
        case UIInputEventType::None:
        default:
            break;
        }
    }

    frame.pointerInside = ContainsPoint(inputRect, state.lastScreenPointerPosition);
    frame.hovered = state.hovered;
    frame.focused = state.focused;
    frame.captured = state.captured;
    frame.screenPointerPosition = state.lastScreenPointerPosition;
    frame.localPointerPosition = state.lastLocalPointerPosition;
    frame.modifiers = state.modifiers;
    return frame;
}

} // namespace XCEngine::UI::Editor