#include "ProductHierarchyPanel.h"

#include "Icons/ProductBuiltInIcons.h"
#include "Panels/ProductTreeViewStyle.h"

#include <XCEditor/Collections/UIEditorTreeView.h>

#include <algorithm>
#include <cmath>
#include <string>
#include <string_view>

namespace XCEngine::UI::Editor::App {

namespace {

using ::XCEngine::UI::UIColor;
using ::XCEngine::UI::UIDrawList;
using ::XCEngine::UI::UIInputEvent;
using ::XCEngine::UI::UIInputEventType;
using ::XCEngine::UI::UIPoint;
using ::XCEngine::UI::UIPointerButton;
using ::XCEngine::UI::UIRect;
using Widgets::AppendUIEditorTreeViewBackground;
using Widgets::AppendUIEditorTreeViewForeground;
using Widgets::DoesUIEditorTreeViewItemHaveChildren;
using Widgets::HitTestUIEditorTreeView;
using Widgets::IsUIEditorTreeViewPointInside;
using Widgets::UIEditorTreeViewHitTarget;
using Widgets::UIEditorTreeViewHitTargetKind;
using Widgets::UIEditorTreeViewInvalidIndex;

constexpr std::string_view kHierarchyPanelId = "hierarchy";
constexpr float kDragThreshold = 4.0f;
constexpr UIColor kDragPreviewColor(0.82f, 0.82f, 0.82f, 0.55f);

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;
}

float ComputeSquaredDistance(const UIPoint& lhs, const UIPoint& rhs) {
    const float dx = lhs.x - rhs.x;
    const float dy = lhs.y - rhs.y;
    return dx * dx + dy * dy;
}

::XCEngine::UI::UITextureHandle ResolveGameObjectIcon(
    const ProductBuiltInIcons* icons) {
    return icons != nullptr
        ? icons->Resolve(ProductBuiltInIconKind::GameObject)
        : ::XCEngine::UI::UITextureHandle {};
}

std::vector<UIInputEvent> FilterHierarchyInputEvents(
    const UIRect& bounds,
    const std::vector<UIInputEvent>& inputEvents,
    bool allowInteraction,
    bool panelActive,
    bool captureActive) {
    if (!allowInteraction && !captureActive) {
        return {};
    }

    std::vector<UIInputEvent> filteredEvents = {};
    filteredEvents.reserve(inputEvents.size());
    for (const UIInputEvent& event : inputEvents) {
        switch (event.type) {
        case UIInputEventType::PointerMove:
        case UIInputEventType::PointerButtonDown:
        case UIInputEventType::PointerButtonUp:
        case UIInputEventType::PointerWheel:
            if (captureActive || ContainsPoint(bounds, event.position)) {
                filteredEvents.push_back(event);
            }
            break;
        case UIInputEventType::PointerLeave:
            filteredEvents.push_back(event);
            break;
        case UIInputEventType::FocusGained:
        case UIInputEventType::FocusLost:
            if (panelActive || captureActive) {
                filteredEvents.push_back(event);
            }
            break;
        case UIInputEventType::KeyDown:
        case UIInputEventType::KeyUp:
        case UIInputEventType::Character:
            if (panelActive) {
                filteredEvents.push_back(event);
            }
            break;
        default:
            break;
        }
    }

    return filteredEvents;
}

const Widgets::UIEditorTreeViewItem* ResolveHitItem(
    const Widgets::UIEditorTreeViewLayout& layout,
    const std::vector<Widgets::UIEditorTreeViewItem>& items,
    const UIPoint& point,
    UIEditorTreeViewHitTarget* hitTargetOutput = nullptr) {
    const UIEditorTreeViewHitTarget hitTarget = HitTestUIEditorTreeView(layout, point);
    if (hitTargetOutput != nullptr) {
        *hitTargetOutput = hitTarget;
    }

    if (hitTarget.itemIndex >= items.size()) {
        return nullptr;
    }

    return &items[hitTarget.itemIndex];
}

std::size_t FindVisibleIndexForItemId(
    const Widgets::UIEditorTreeViewLayout& layout,
    const std::vector<Widgets::UIEditorTreeViewItem>& items,
    std::string_view itemId) {
    for (std::size_t visibleIndex = 0u; visibleIndex < layout.visibleItemIndices.size(); ++visibleIndex) {
        const std::size_t itemIndex = layout.visibleItemIndices[visibleIndex];
        if (itemIndex < items.size() && items[itemIndex].itemId == itemId) {
            return visibleIndex;
        }
    }

    return UIEditorTreeViewInvalidIndex;
}

} // namespace

void ProductHierarchyPanel::Initialize() {
    m_model = ProductHierarchyModel::BuildDefault();
    RebuildItems();
}

void ProductHierarchyPanel::SetBuiltInIcons(const ProductBuiltInIcons* icons) {
    m_icons = icons;
    RebuildItems();
}

const UIEditorPanelContentHostPanelState* ProductHierarchyPanel::FindMountedHierarchyPanel(
    const UIEditorPanelContentHostFrame& contentHostFrame) const {
    for (const UIEditorPanelContentHostPanelState& panelState : contentHostFrame.panelStates) {
        if (panelState.panelId == kHierarchyPanelId && panelState.mounted) {
            return &panelState;
        }
    }

    return nullptr;
}

void ProductHierarchyPanel::ResetTransientState() {
    m_frameEvents.clear();
    m_dragState.requestPointerCapture = false;
    m_dragState.requestPointerRelease = false;
}

void ProductHierarchyPanel::RebuildItems() {
    const auto icon = ResolveGameObjectIcon(m_icons);
    const std::string previousSelection =
        m_selection.HasSelection() ? m_selection.GetSelectedId() : std::string();

    m_treeItems = m_model.BuildTreeItems(icon);
    m_expansion.Expand("player");
    m_expansion.Expand("environment");
    m_expansion.Expand("props");

    if (!previousSelection.empty() && m_model.ContainsNode(previousSelection)) {
        m_selection.SetSelection(previousSelection);
        return;
    }

    if (!m_treeItems.empty()) {
        m_selection.SetSelection(m_treeItems.front().itemId);
    }
}

void ProductHierarchyPanel::EmitSelectionEvent() {
    if (!m_selection.HasSelection()) {
        return;
    }

    const ProductHierarchyNode* node = m_model.FindNode(m_selection.GetSelectedId());
    if (node == nullptr) {
        return;
    }

    Event event = {};
    event.kind = EventKind::SelectionChanged;
    event.itemId = node->nodeId;
    event.label = node->label;
    m_frameEvents.push_back(std::move(event));
}

void ProductHierarchyPanel::EmitReparentEvent(
    EventKind kind,
    std::string itemId,
    std::string targetItemId) {
    Event event = {};
    event.kind = kind;
    event.itemId = std::move(itemId);
    event.targetItemId = std::move(targetItemId);
    if (const ProductHierarchyNode* node = m_model.FindNode(event.itemId); node != nullptr) {
        event.label = node->label;
    }
    m_frameEvents.push_back(std::move(event));
}

std::vector<UIInputEvent> ProductHierarchyPanel::BuildInteractionInputEvents(
    const std::vector<UIInputEvent>& inputEvents,
    const UIRect& bounds,
    bool allowInteraction,
    bool panelActive) const {
    const std::vector<UIInputEvent> rawEvents = FilterHierarchyInputEvents(
        bounds,
        inputEvents,
        allowInteraction,
        panelActive,
        HasActivePointerCapture());

    struct DragPreviewState {
        std::string armedItemId = {};
        UIPoint pressPosition = {};
        bool armed = false;
        bool dragging = false;
    };

    const Widgets::UIEditorTreeViewLayout layout =
        m_treeFrame.layout.bounds.width > 0.0f ? m_treeFrame.layout : Widgets::BuildUIEditorTreeViewLayout(
            bounds,
            m_treeItems,
            m_expansion,
            BuildProductTreeViewMetrics());
    DragPreviewState preview = {};
    preview.armed = m_dragState.armed;
    preview.armedItemId = m_dragState.armedItemId;
    preview.pressPosition = m_dragState.pressPosition;
    preview.dragging = m_dragState.dragging;

    std::vector<UIInputEvent> filteredEvents = {};
    filteredEvents.reserve(rawEvents.size());
    for (const UIInputEvent& event : rawEvents) {
        bool suppress = false;

        switch (event.type) {
        case UIInputEventType::PointerButtonDown:
            if (event.pointerButton == UIPointerButton::Left) {
                UIEditorTreeViewHitTarget hitTarget = {};
                const Widgets::UIEditorTreeViewItem* hitItem =
                    ResolveHitItem(layout, m_treeItems, event.position, &hitTarget);
                if (hitItem != nullptr &&
                    hitTarget.kind == UIEditorTreeViewHitTargetKind::Row) {
                    preview.armed = true;
                    preview.armedItemId = hitItem->itemId;
                    preview.pressPosition = event.position;
                } else {
                    preview.armed = false;
                    preview.armedItemId.clear();
                }
            }
            if (preview.dragging) {
                suppress = true;
            }
            break;

        case UIInputEventType::PointerMove:
            if (preview.dragging) {
                suppress = true;
                break;
            }

            if (preview.armed &&
                ComputeSquaredDistance(event.position, preview.pressPosition) >=
                    kDragThreshold * kDragThreshold) {
                preview.dragging = true;
                suppress = true;
            }
            break;

        case UIInputEventType::PointerButtonUp:
            if (event.pointerButton == UIPointerButton::Left) {
                if (preview.dragging) {
                    suppress = true;
                    preview.dragging = false;
                }
                preview.armed = false;
                preview.armedItemId.clear();
            } else if (preview.dragging) {
                suppress = true;
            }
            break;

        case UIInputEventType::PointerLeave:
            if (preview.dragging) {
                suppress = true;
            }
            break;

        case UIInputEventType::FocusLost:
            preview.armed = false;
            preview.dragging = false;
            preview.armedItemId.clear();
            break;

        default:
            break;
        }

        if (!suppress) {
            filteredEvents.push_back(event);
        }
    }

    return filteredEvents;
}

void ProductHierarchyPanel::ProcessDragAndFrameEvents(
    const std::vector<UIInputEvent>& inputEvents,
    const UIRect& bounds,
    bool allowInteraction,
    bool panelActive) {
    const std::vector<UIInputEvent> filteredEvents = FilterHierarchyInputEvents(
        bounds,
        inputEvents,
        allowInteraction,
        panelActive,
        HasActivePointerCapture());

    if (m_treeFrame.result.selectionChanged) {
        EmitSelectionEvent();
    }
    if (m_treeFrame.result.renameRequested &&
        !m_treeFrame.result.renameItemId.empty()) {
        Event event = {};
        event.kind = EventKind::RenameRequested;
        event.itemId = m_treeFrame.result.renameItemId;
        if (const ProductHierarchyNode* node = m_model.FindNode(event.itemId); node != nullptr) {
            event.label = node->label;
        }
        m_frameEvents.push_back(std::move(event));
    }

    for (const UIInputEvent& event : filteredEvents) {
        switch (event.type) {
        case UIInputEventType::PointerButtonDown:
            if (event.pointerButton == UIPointerButton::Left) {
                UIEditorTreeViewHitTarget hitTarget = {};
                const Widgets::UIEditorTreeViewItem* hitItem =
                    ResolveHitItem(m_treeFrame.layout, m_treeItems, event.position, &hitTarget);
                if (hitItem != nullptr &&
                    hitTarget.kind == UIEditorTreeViewHitTargetKind::Row) {
                    m_dragState.armed = true;
                    m_dragState.armedItemId = hitItem->itemId;
                    m_dragState.pressPosition = event.position;
                } else {
                    m_dragState.armed = false;
                    m_dragState.armedItemId.clear();
                }
            }
            break;

        case UIInputEventType::PointerMove:
            if (m_dragState.armed && !m_dragState.dragging &&
                ComputeSquaredDistance(event.position, m_dragState.pressPosition) >=
                    kDragThreshold * kDragThreshold) {
                m_dragState.dragging = !m_dragState.armedItemId.empty();
                m_dragState.draggedItemId = m_dragState.armedItemId;
                m_dragState.dropTargetItemId.clear();
                m_dragState.dropToRoot = false;
                m_dragState.validDropTarget = false;
                if (m_dragState.dragging) {
                    m_dragState.requestPointerCapture = true;
                    if (!m_selection.IsSelected(m_dragState.draggedItemId)) {
                        m_selection.SetSelection(m_dragState.draggedItemId);
                        EmitSelectionEvent();
                    }
                }
            }

            if (m_dragState.dragging) {
                UIEditorTreeViewHitTarget hitTarget = {};
                const Widgets::UIEditorTreeViewItem* hitItem =
                    ResolveHitItem(m_treeFrame.layout, m_treeItems, event.position, &hitTarget);

                m_dragState.dropTargetItemId.clear();
                m_dragState.dropToRoot = false;
                m_dragState.validDropTarget = false;

                if (hitItem != nullptr &&
                    (hitTarget.kind == UIEditorTreeViewHitTargetKind::Row ||
                     hitTarget.kind == UIEditorTreeViewHitTargetKind::Disclosure)) {
                    m_dragState.dropTargetItemId = hitItem->itemId;
                    m_dragState.validDropTarget =
                        m_model.CanReparent(
                            m_dragState.draggedItemId,
                            m_dragState.dropTargetItemId);
                } else if (ContainsPoint(bounds, event.position)) {
                    m_dragState.dropToRoot = true;
                    m_dragState.validDropTarget =
                        m_model.GetParentId(m_dragState.draggedItemId).has_value();
                }
            }
            break;

        case UIInputEventType::PointerButtonUp:
            if (event.pointerButton != UIPointerButton::Left) {
                break;
            }

            if (m_dragState.dragging) {
                if (m_dragState.validDropTarget) {
                    const std::string draggedItemId = m_dragState.draggedItemId;
                    const std::string dropTargetItemId = m_dragState.dropTargetItemId;
                    const bool changed =
                        m_dragState.dropToRoot
                            ? m_model.MoveToRoot(draggedItemId)
                            : m_model.Reparent(draggedItemId, dropTargetItemId);
                    if (changed) {
                        RebuildItems();
                        EmitReparentEvent(
                            m_dragState.dropToRoot ? EventKind::MovedToRoot : EventKind::Reparented,
                            draggedItemId,
                            dropTargetItemId);
                    }
                }

                m_dragState.armed = false;
                m_dragState.dragging = false;
                m_dragState.armedItemId.clear();
                m_dragState.draggedItemId.clear();
                m_dragState.dropTargetItemId.clear();
                m_dragState.dropToRoot = false;
                m_dragState.validDropTarget = false;
                m_dragState.requestPointerRelease = true;
            } else {
                m_dragState.armed = false;
                m_dragState.armedItemId.clear();
            }
            break;

        case UIInputEventType::FocusLost:
            if (m_dragState.dragging) {
                m_dragState.requestPointerRelease = true;
            }
            m_dragState = {};
            break;

        default:
            break;
        }
    }
}

void ProductHierarchyPanel::Update(
    const UIEditorPanelContentHostFrame& contentHostFrame,
    const std::vector<UIInputEvent>& inputEvents,
    bool allowInteraction,
    bool panelActive) {
    ResetTransientState();

    const UIEditorPanelContentHostPanelState* panelState =
        FindMountedHierarchyPanel(contentHostFrame);
    if (panelState == nullptr) {
        m_visible = false;
        m_treeFrame = {};
        m_dragState = {};
        return;
    }

    if (m_treeItems.empty()) {
        RebuildItems();
    }

    m_visible = true;
    const std::vector<UIInputEvent> interactionEvents =
        BuildInteractionInputEvents(
            inputEvents,
            panelState->bounds,
            allowInteraction,
            panelActive);
    m_treeFrame = UpdateUIEditorTreeViewInteraction(
        m_treeInteractionState,
        m_selection,
        m_expansion,
        panelState->bounds,
        m_treeItems,
        interactionEvents,
        BuildProductTreeViewMetrics());
    ProcessDragAndFrameEvents(
        inputEvents,
        panelState->bounds,
        allowInteraction,
        panelActive);
}

void ProductHierarchyPanel::Append(UIDrawList& drawList) const {
    if (!m_visible || m_treeFrame.layout.bounds.width <= 0.0f || m_treeFrame.layout.bounds.height <= 0.0f) {
        return;
    }

    const Widgets::UIEditorTreeViewPalette palette = BuildProductTreeViewPalette();
    const Widgets::UIEditorTreeViewMetrics metrics = BuildProductTreeViewMetrics();
    AppendUIEditorTreeViewBackground(
        drawList,
        m_treeFrame.layout,
        m_treeItems,
        m_selection,
        m_treeInteractionState.treeViewState,
        palette,
        metrics);
    AppendUIEditorTreeViewForeground(
        drawList,
        m_treeFrame.layout,
        m_treeItems,
        palette,
        metrics);

    if (!m_dragState.dragging || !m_dragState.validDropTarget) {
        return;
    }

    if (m_dragState.dropToRoot) {
        drawList.AddRectOutline(
            m_treeFrame.layout.bounds,
            kDragPreviewColor,
            1.0f,
            0.0f);
        return;
    }

    const std::size_t visibleIndex = FindVisibleIndexForItemId(
        m_treeFrame.layout,
        m_treeItems,
        m_dragState.dropTargetItemId);
    if (visibleIndex == UIEditorTreeViewInvalidIndex ||
        visibleIndex >= m_treeFrame.layout.rowRects.size()) {
        return;
    }

    drawList.AddRectOutline(
        m_treeFrame.layout.rowRects[visibleIndex],
        kDragPreviewColor,
        1.0f,
        0.0f);
}

bool ProductHierarchyPanel::WantsHostPointerCapture() const {
    return m_dragState.requestPointerCapture;
}

bool ProductHierarchyPanel::WantsHostPointerRelease() const {
    return m_dragState.requestPointerRelease;
}

bool ProductHierarchyPanel::HasActivePointerCapture() const {
    return m_dragState.dragging;
}

const std::vector<ProductHierarchyPanel::Event>& ProductHierarchyPanel::GetFrameEvents() const {
    return m_frameEvents;
}

} // namespace XCEngine::UI::Editor::App