#include "Docking/UIEditorDockHostInteractionInternal.h"

#include <algorithm>
#include <string_view>
#include <utility>
#include <vector>

namespace XCEngine::UI::Editor::Detail {

using ::XCEngine::UI::UIInputEvent;
using ::XCEngine::UI::UIInputEventType;
using ::XCEngine::UI::UIPoint;
using ::XCEngine::UI::UIRect;
using Widgets::HitTestUIEditorDockHost;
using Widgets::UIEditorDockHostHitTarget;
using Widgets::UIEditorDockHostHitTargetKind;
using Widgets::UIEditorDockHostTabItemLayout;
using Widgets::UIEditorDockHostTabStackLayout;
using Widgets::UIEditorTabStripHitTargetKind;
using Widgets::UIEditorTabStripItem;

bool ShouldUsePointerPosition(const UIInputEvent& event) {
    switch (event.type) {
    case UIInputEventType::PointerMove:
    case UIInputEventType::PointerEnter:
    case UIInputEventType::PointerButtonDown:
    case UIInputEventType::PointerButtonUp:
        return true;
    default:
        return false;
    }
}

bool ShouldDispatchTabStripEvent(
    const UIInputEvent& event,
    bool splitterActive) {
    if (splitterActive && event.type != UIInputEventType::FocusLost) {
        return false;
    }

    switch (event.type) {
    case UIInputEventType::FocusLost:
    case UIInputEventType::PointerMove:
    case UIInputEventType::PointerEnter:
    case UIInputEventType::PointerLeave:
    case UIInputEventType::PointerButtonDown:
    case UIInputEventType::PointerButtonUp:
    case UIInputEventType::KeyDown:
        return true;
    default:
        return false;
    }
}

UIEditorWorkspaceLayoutOperationResult ApplySplitRatio(
    UIEditorWorkspaceController& controller,
    std::string_view nodeId,
    float splitRatio) {
    return controller.SetSplitRatio(nodeId, splitRatio);
}

UIEditorWorkspaceCommandResult DispatchPanelCommand(
    UIEditorWorkspaceController& controller,
    UIEditorWorkspaceCommandKind kind,
    std::string panelId) {
    UIEditorWorkspaceCommand command = {};
    command.kind = kind;
    command.panelId = std::move(panelId);
    return controller.Dispatch(command);
}

UIEditorDockHostTabStripInteractionEntry& FindOrCreateTabStripInteractionEntry(
    UIEditorDockHostInteractionState& state,
    std::string_view nodeId) {
    for (UIEditorDockHostTabStripInteractionEntry& entry : state.tabStripInteractions) {
        if (entry.nodeId == nodeId) {
            return entry;
        }
    }

    state.tabStripInteractions.push_back({});
    UIEditorDockHostTabStripInteractionEntry& entry = state.tabStripInteractions.back();
    entry.nodeId = std::string(nodeId);
    return entry;
}

void PruneTabStripInteractionEntries(
    UIEditorDockHostInteractionState& state,
    const Widgets::UIEditorDockHostLayout& layout) {
    const auto isVisibleNodeId = [&layout](std::string_view nodeId) {
        return std::find_if(
                   layout.tabStacks.begin(),
                   layout.tabStacks.end(),
                   [nodeId](const UIEditorDockHostTabStackLayout& tabStack) {
                       return tabStack.nodeId == nodeId;
                   }) != layout.tabStacks.end();
    };

    state.tabStripInteractions.erase(
        std::remove_if(
            state.tabStripInteractions.begin(),
            state.tabStripInteractions.end(),
            [&isVisibleNodeId](const UIEditorDockHostTabStripInteractionEntry& entry) {
                return !isVisibleNodeId(entry.nodeId);
            }),
        state.tabStripInteractions.end());

    state.dockHostState.tabStripStates.erase(
        std::remove_if(
            state.dockHostState.tabStripStates.begin(),
            state.dockHostState.tabStripStates.end(),
            [&isVisibleNodeId](const Widgets::UIEditorDockHostTabStripVisualState& entry) {
                return !isVisibleNodeId(entry.nodeId);
            }),
        state.dockHostState.tabStripStates.end());

    if (!state.activeTabDragNodeId.empty() &&
        !isVisibleNodeId(state.activeTabDragNodeId)) {
        state.activeTabDragNodeId.clear();
        state.activeTabDragPanelId.clear();
        state.dockHostState.dropPreview = {};
    }
}

void SyncDockHostTabStripVisualStates(UIEditorDockHostInteractionState& state) {
    state.dockHostState.tabStripStates.clear();
    state.dockHostState.tabStripStates.reserve(state.tabStripInteractions.size());
    for (const UIEditorDockHostTabStripInteractionEntry& entry :
         state.tabStripInteractions) {
        Widgets::UIEditorDockHostTabStripVisualState visualState = {};
        visualState.nodeId = entry.nodeId;
        visualState.state = entry.state.tabStripState;
        state.dockHostState.tabStripStates.push_back(std::move(visualState));
    }
}

bool HasFocusedTabStrip(const UIEditorDockHostInteractionState& state) {
    return std::find_if(
               state.tabStripInteractions.begin(),
               state.tabStripInteractions.end(),
               [](const UIEditorDockHostTabStripInteractionEntry& entry) {
                   return entry.state.tabStripState.focused;
               }) != state.tabStripInteractions.end();
}

const UIEditorDockHostTabStackLayout* FindTabStackLayoutByNodeId(
    const Widgets::UIEditorDockHostLayout& layout,
    std::string_view nodeId) {
    for (const UIEditorDockHostTabStackLayout& tabStack : layout.tabStacks) {
        if (tabStack.nodeId == nodeId) {
            return &tabStack;
        }
    }

    return nullptr;
}

bool IsPointInsideRect(
    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;
}

void ClearAllTabStripTransientInteractions(UIEditorDockHostInteractionState& state) {
    for (UIEditorDockHostTabStripInteractionEntry& entry : state.tabStripInteractions) {
        ClearUIEditorTabStripTransientInteraction(entry.state);
    }
    SyncDockHostTabStripVisualStates(state);
}

void ClearTabDockDragState(UIEditorDockHostInteractionState& state) {
    state.activeTabDragNodeId.clear();
    state.activeTabDragPanelId.clear();
    state.dockHostState.dropPreview = {};
}

std::vector<UIEditorTabStripItem> BuildTabStripItems(
    const UIEditorDockHostTabStackLayout& tabStack) {
    std::vector<UIEditorTabStripItem> items = {};
    items.reserve(tabStack.items.size());
    for (const UIEditorDockHostTabItemLayout& itemLayout : tabStack.items) {
        UIEditorTabStripItem item = {};
        item.tabId = itemLayout.panelId;
        item.title = itemLayout.title;
        item.closable = itemLayout.closable;
        items.push_back(std::move(item));
    }

    return items;
}

UIEditorDockHostHitTarget MapTabStripHitTarget(
    const UIEditorDockHostTabStackLayout& tabStack,
    const UIEditorTabStripInteractionResult& result) {
    UIEditorDockHostHitTarget target = {};
    target.nodeId = tabStack.nodeId;
    target.index = result.hitTarget.index;

    switch (result.hitTarget.kind) {
    case UIEditorTabStripHitTargetKind::HeaderBackground:
        target.kind = UIEditorDockHostHitTargetKind::TabStripBackground;
        break;
    case UIEditorTabStripHitTargetKind::Tab:
        target.kind = UIEditorDockHostHitTargetKind::Tab;
        if (result.hitTarget.index < tabStack.items.size()) {
            target.panelId = tabStack.items[result.hitTarget.index].panelId;
        }
        break;
    case UIEditorTabStripHitTargetKind::CloseButton:
        target.kind = UIEditorDockHostHitTargetKind::TabCloseButton;
        if (result.hitTarget.index < tabStack.items.size()) {
            target.panelId = tabStack.items[result.hitTarget.index].panelId;
        }
        break;
    default:
        break;
    }

    return target;
}

int ResolveTabStripPriority(const UIEditorTabStripInteractionResult& result) {
    if (result.reorderRequested ||
        result.dragStarted ||
        result.dragEnded ||
        result.dragCanceled) {
        return 5;
    }

    if (result.closeRequested) {
        return 4;
    }

    if (result.selectionChanged || result.keyboardNavigated) {
        return 3;
    }

    if (result.consumed ||
        result.hitTarget.kind != UIEditorTabStripHitTargetKind::None) {
        return 2;
    }

    return 0;
}

DockHostTabStripEventResult ProcessTabStripEvent(
    UIEditorDockHostInteractionState& state,
    const Widgets::UIEditorDockHostLayout& layout,
    const UIInputEvent& event,
    const Widgets::UIEditorDockHostMetrics& metrics) {
    DockHostTabStripEventResult resolved = {};

    for (const UIEditorDockHostTabStackLayout& tabStack : layout.tabStacks) {
        if (!state.activeTabDragNodeId.empty() &&
            tabStack.nodeId != state.activeTabDragNodeId) {
            continue;
        }

        UIEditorDockHostTabStripInteractionEntry& entry =
            FindOrCreateTabStripInteractionEntry(state, tabStack.nodeId);
        std::string selectedTabId = tabStack.selectedPanelId;
        const std::vector<UIEditorTabStripItem> items = BuildTabStripItems(tabStack);
        const UIEditorTabStripInteractionFrame frame = UpdateUIEditorTabStripInteraction(
            entry.state,
            selectedTabId,
            tabStack.bounds,
            items,
            { event },
            metrics.tabStripMetrics);

        const int priority = ResolveTabStripPriority(frame.result);
        if (priority < resolved.priority) {
            continue;
        }

        resolved.nodeId = tabStack.nodeId;
        resolved.hitTarget = MapTabStripHitTarget(tabStack, frame.result);
        resolved.requestPointerCapture = frame.result.requestPointerCapture;
        resolved.releasePointerCapture = frame.result.releasePointerCapture;
        resolved.dragStarted = frame.result.dragStarted;
        resolved.dragEnded = frame.result.dragEnded;
        resolved.dragCanceled = frame.result.dragCanceled;
        resolved.dropInsertionIndex = frame.result.dropInsertionIndex;
        resolved.draggedTabId = frame.result.draggedTabId;
        if ((frame.result.closeRequested && !frame.result.closedTabId.empty()) ||
            (event.type == UIInputEventType::PointerButtonUp &&
             frame.result.consumed &&
             resolved.hitTarget.kind == UIEditorDockHostHitTargetKind::TabCloseButton &&
             !resolved.hitTarget.panelId.empty())) {
            resolved.commandRequested = true;
            resolved.commandKind = UIEditorWorkspaceCommandKind::ClosePanel;
            resolved.panelId =
                !frame.result.closedTabId.empty()
                    ? frame.result.closedTabId
                    : resolved.hitTarget.panelId;
        } else if (frame.result.reorderRequested &&
                   !frame.result.draggedTabId.empty() &&
                   frame.result.dropInsertionIndex !=
                       Widgets::UIEditorTabStripInvalidIndex) {
            resolved.reorderRequested = true;
            resolved.panelId = frame.result.draggedTabId;
            resolved.dropInsertionIndex = frame.result.dropInsertionIndex;
        } else if ((frame.result.selectionChanged ||
                    frame.result.keyboardNavigated ||
                    (event.type == UIInputEventType::PointerButtonUp &&
                     frame.result.consumed &&
                     resolved.hitTarget.kind == UIEditorDockHostHitTargetKind::Tab)) &&
                   (!frame.result.selectedTabId.empty() ||
                    !resolved.hitTarget.panelId.empty())) {
            resolved.commandRequested = true;
            resolved.commandKind = UIEditorWorkspaceCommandKind::ActivatePanel;
            resolved.panelId =
                !frame.result.selectedTabId.empty()
                    ? frame.result.selectedTabId
                    : resolved.hitTarget.panelId;
        } else if (priority == 0) {
            continue;
        } else {
            resolved.commandRequested = false;
            resolved.reorderRequested = false;
            resolved.panelId.clear();
        }

        resolved.consumed = frame.result.consumed;
        resolved.priority = priority;
    }

    SyncDockHostTabStripVisualStates(state);
    return resolved;
}

std::size_t ResolveTabHeaderDropInsertionIndex(
    const UIEditorDockHostTabStackLayout& tabStack,
    const UIPoint& point) {
    if (!IsPointInsideRect(tabStack.tabStripLayout.headerRect, point)) {
        return Widgets::UIEditorTabStripInvalidIndex;
    }

    std::size_t insertionIndex = 0u;
    for (const UIRect& rect : tabStack.tabStripLayout.tabHeaderRects) {
        const float midpoint = rect.x + rect.width * 0.5f;
        if (point.x > midpoint) {
            ++insertionIndex;
        }
    }

    return insertionIndex;
}

UIEditorWorkspaceDockPlacement ResolveDockPlacement(
    const UIEditorDockHostTabStackLayout& tabStack,
    const UIPoint& point) {
    if (IsPointInsideRect(tabStack.tabStripLayout.headerRect, point)) {
        return UIEditorWorkspaceDockPlacement::Center;
    }

    const float leftDistance = point.x - tabStack.bounds.x;
    const float rightDistance =
        tabStack.bounds.x + tabStack.bounds.width - point.x;
    const float topDistance = point.y - tabStack.bounds.y;
    const float bottomDistance =
        tabStack.bounds.y + tabStack.bounds.height - point.y;
    const float minHorizontalThreshold = tabStack.bounds.width * 0.25f;
    const float minVerticalThreshold = tabStack.bounds.height * 0.25f;
    const float nearestEdge = (std::min)(
        (std::min)(leftDistance, rightDistance),
        (std::min)(topDistance, bottomDistance));

    if (nearestEdge == leftDistance && leftDistance <= minHorizontalThreshold) {
        return UIEditorWorkspaceDockPlacement::Left;
    }
    if (nearestEdge == rightDistance && rightDistance <= minHorizontalThreshold) {
        return UIEditorWorkspaceDockPlacement::Right;
    }
    if (nearestEdge == topDistance && topDistance <= minVerticalThreshold) {
        return UIEditorWorkspaceDockPlacement::Top;
    }
    if (nearestEdge == bottomDistance && bottomDistance <= minVerticalThreshold) {
        return UIEditorWorkspaceDockPlacement::Bottom;
    }

    return UIEditorWorkspaceDockPlacement::Center;
}

void SyncDockPreview(
    UIEditorDockHostInteractionState& state,
    const Widgets::UIEditorDockHostLayout& layout) {
    state.dockHostState.dropPreview = {};
    if (state.activeTabDragNodeId.empty() ||
        state.activeTabDragPanelId.empty() ||
        !state.hasPointerPosition) {
        return;
    }

    for (const UIEditorDockHostTabStackLayout& tabStack : layout.tabStacks) {
        if (!IsPointInsideRect(tabStack.bounds, state.pointerPosition)) {
            continue;
        }

        const UIEditorWorkspaceDockPlacement placement =
            ResolveDockPlacement(tabStack, state.pointerPosition);
        if (tabStack.nodeId == state.activeTabDragNodeId &&
            placement == UIEditorWorkspaceDockPlacement::Center) {
            return;
        }

        if (tabStack.nodeId == state.activeTabDragNodeId &&
            tabStack.items.size() <= 1u) {
            return;
        }

        Widgets::UIEditorDockHostDropPreviewState preview = {};
        preview.visible = true;
        preview.sourceNodeId = state.activeTabDragNodeId;
        preview.sourcePanelId = state.activeTabDragPanelId;
        preview.targetNodeId = tabStack.nodeId;
        preview.placement = placement;
        if (placement == UIEditorWorkspaceDockPlacement::Center) {
            preview.insertionIndex =
                ResolveTabHeaderDropInsertionIndex(tabStack, state.pointerPosition);
            if (preview.insertionIndex == Widgets::UIEditorTabStripInvalidIndex) {
                preview.insertionIndex = tabStack.items.size();
            }
        }
        state.dockHostState.dropPreview = std::move(preview);
        return;
    }
}

void SyncHoverTarget(
    UIEditorDockHostInteractionState& state,
    const Widgets::UIEditorDockHostLayout& layout) {
    if (state.splitterDragState.active) {
        state.dockHostState.hoveredTarget = {
            UIEditorDockHostHitTargetKind::SplitterHandle,
            state.dockHostState.activeSplitterNodeId,
            {},
            Widgets::UIEditorTabStripInvalidIndex
        };
        return;
    }

    if (!state.activeTabDragNodeId.empty()) {
        state.dockHostState.hoveredTarget = {};
        return;
    }

    if (!state.hasPointerPosition) {
        state.dockHostState.hoveredTarget = {};
        return;
    }

    state.dockHostState.hoveredTarget =
        HitTestUIEditorDockHost(layout, state.pointerPosition);
}

} // namespace XCEngine::UI::Editor::Detail