#include "HierarchyModel.h"

#include <algorithm>
#include <functional>
#include <optional>
#include <sstream>
#include <utility>

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

namespace {

const HierarchyNode* FindNodeRecursive(
    const std::vector<HierarchyNode>& nodes,
    std::string_view nodeId) {
    for (const HierarchyNode& node : nodes) {
        if (node.nodeId == nodeId) {
            return &node;
        }
        if (const HierarchyNode* child =
                FindNodeRecursive(node.children, nodeId);
            child != nullptr) {
            return child;
        }
    }
    return nullptr;
}

HierarchyNode* FindNodeRecursive(
    std::vector<HierarchyNode>& nodes,
    std::string_view nodeId) {
    for (HierarchyNode& node : nodes) {
        if (node.nodeId == nodeId) {
            return &node;
        }
        if (HierarchyNode* child =
                FindNodeRecursive(node.children, nodeId);
            child != nullptr) {
            return child;
        }
    }
    return nullptr;
}

bool FindNodeParentRecursive(
    const std::vector<HierarchyNode>& nodes,
    std::string_view nodeId,
    const HierarchyNode*& parent) {
    for (const HierarchyNode& node : nodes) {
        for (const HierarchyNode& child : node.children) {
            if (child.nodeId == nodeId) {
                parent = &node;
                return true;
            }
        }

        if (FindNodeParentRecursive(node.children, nodeId, parent)) {
            return true;
        }
    }
    return false;
}

bool ExtractNodeRecursive(
    std::vector<HierarchyNode>& nodes,
    std::string_view nodeId,
    HierarchyNode& extractedNode) {
    for (std::size_t index = 0u; index < nodes.size(); ++index) {
        if (nodes[index].nodeId == nodeId) {
            extractedNode = std::move(nodes[index]);
            nodes.erase(nodes.begin() + static_cast<std::ptrdiff_t>(index));
            return true;
        }

        if (ExtractNodeRecursive(nodes[index].children, nodeId, extractedNode)) {
            return true;
        }
    }
    return false;
}

HierarchyNode CloneNodeRecursive(
    const HierarchyNode& source,
    const std::function<std::string()>& allocateNodeId) {
    HierarchyNode duplicate = {};
    duplicate.nodeId = allocateNodeId();
    duplicate.label = source.label;
    duplicate.children.reserve(source.children.size());
    for (const HierarchyNode& child : source.children) {
        duplicate.children.push_back(CloneNodeRecursive(child, allocateNodeId));
    }
    return duplicate;
}

bool DuplicateNodeRecursive(
    std::vector<HierarchyNode>& nodes,
    std::string_view nodeId,
    const std::function<std::string()>& allocateNodeId,
    std::string& duplicatedNodeId) {
    for (std::size_t index = 0u; index < nodes.size(); ++index) {
        if (nodes[index].nodeId == nodeId) {
            HierarchyNode duplicate = CloneNodeRecursive(nodes[index], allocateNodeId);
            duplicatedNodeId = duplicate.nodeId;
            nodes.insert(
                nodes.begin() + static_cast<std::ptrdiff_t>(index + 1u),
                std::move(duplicate));
            return true;
        }

        if (DuplicateNodeRecursive(
                nodes[index].children,
                nodeId,
                allocateNodeId,
                duplicatedNodeId)) {
            return true;
        }
    }

    return false;
}

void BuildTreeItemsRecursive(
    const std::vector<HierarchyNode>& nodes,
    std::uint32_t depth,
    const ::XCEngine::UI::UITextureHandle& icon,
    std::vector<Widgets::UIEditorTreeViewItem>& items) {
    for (const HierarchyNode& node : nodes) {
        Widgets::UIEditorTreeViewItem item = {};
        item.itemId = node.nodeId;
        item.label = node.label;
        item.depth = depth;
        item.forceLeaf = node.children.empty();
        item.leadingIcon = icon;
        items.push_back(std::move(item));
        BuildTreeItemsRecursive(node.children, depth + 1u, icon, items);
    }
}

} // namespace

HierarchyModel HierarchyModel::BuildDefault() {
    HierarchyModel model = {};
    model.m_roots = {
        HierarchyNode{ "main_camera", "Main Camera", {} },
        HierarchyNode{ "directional_light", "Directional Light", {} },
        HierarchyNode{
            "player",
            "Player",
            {
                HierarchyNode{ "camera_pivot", "Camera Pivot", {} },
                HierarchyNode{ "player_mesh", "Mesh", {} }
            } },
        HierarchyNode{
            "environment",
            "Environment",
            {
                HierarchyNode{ "ground", "Ground", {} },
                HierarchyNode{
                    "props",
                    "Props",
                    {
                        HierarchyNode{ "crate_01", "Crate_01", {} },
                        HierarchyNode{ "barrel_01", "Barrel_01", {} }
                    } }
            } }
    };
    model.m_nextGeneratedNodeId = 1u;
    return model;
}

bool HierarchyModel::Empty() const {
    return m_roots.empty();
}

bool HierarchyModel::ContainsNode(std::string_view nodeId) const {
    return FindNode(nodeId) != nullptr;
}

const HierarchyNode* HierarchyModel::FindNode(std::string_view nodeId) const {
    return FindNodeRecursive(m_roots, nodeId);
}

HierarchyNode* HierarchyModel::FindNode(std::string_view nodeId) {
    return FindNodeRecursive(m_roots, nodeId);
}

std::optional<std::string> HierarchyModel::GetParentId(std::string_view nodeId) const {
    const HierarchyNode* parent = nullptr;
    if (!FindNodeParentRecursive(m_roots, nodeId, parent) || parent == nullptr) {
        return std::nullopt;
    }

    return parent->nodeId;
}

bool HierarchyModel::RenameNode(std::string_view nodeId, std::string label) {
    HierarchyNode* node = FindNode(nodeId);
    if (node == nullptr || label.empty() || node->label == label) {
        return false;
    }

    node->label = std::move(label);
    return true;
}

std::string HierarchyModel::CreateChild(
    std::string_view parentId,
    std::string_view label) {
    HierarchyNode* parent = FindNode(parentId);
    if (parent == nullptr) {
        return {};
    }

    HierarchyNode node = {};
    node.nodeId = AllocateNodeId();
    node.label = label.empty() ? std::string("GameObject") : std::string(label);
    parent->children.push_back(std::move(node));
    return parent->children.back().nodeId;
}

std::string HierarchyModel::DuplicateNode(std::string_view nodeId) {
    if (nodeId.empty() || !ContainsNode(nodeId)) {
        return {};
    }

    std::string duplicatedNodeId = {};
    const auto allocateNodeId = [this]() {
        return AllocateNodeId();
    };
    if (!DuplicateNodeRecursive(m_roots, nodeId, allocateNodeId, duplicatedNodeId)) {
        return {};
    }

    return duplicatedNodeId;
}

bool HierarchyModel::DeleteNode(std::string_view nodeId) {
    if (nodeId.empty()) {
        return false;
    }

    HierarchyNode removed = {};
    return ExtractNodeRecursive(m_roots, nodeId, removed);
}

bool HierarchyModel::CanReparent(
    std::string_view sourceNodeId,
    std::string_view targetParentId) const {
    if (sourceNodeId.empty()) {
        return false;
    }

    const HierarchyNode* source = FindNode(sourceNodeId);
    if (source == nullptr) {
        return false;
    }

    if (targetParentId.empty()) {
        return true;
    }

    const HierarchyNode* targetParent = FindNode(targetParentId);
    return CanAdopt(sourceNodeId, targetParent);
}

bool HierarchyModel::Reparent(
    std::string_view sourceNodeId,
    std::string_view targetParentId) {
    if (!CanReparent(sourceNodeId, targetParentId) || targetParentId.empty()) {
        return false;
    }

    const std::optional<std::string> currentParentId = GetParentId(sourceNodeId);
    if (currentParentId.has_value() && currentParentId.value() == targetParentId) {
        return false;
    }

    HierarchyNode movedNode = {};
    if (!ExtractNodeRecursive(m_roots, sourceNodeId, movedNode)) {
        return false;
    }

    HierarchyNode* targetParent = FindNode(targetParentId);
    if (targetParent == nullptr) {
        return false;
    }

    targetParent->children.push_back(std::move(movedNode));
    return true;
}

bool HierarchyModel::MoveToRoot(std::string_view sourceNodeId) {
    if (sourceNodeId.empty() || !ContainsNode(sourceNodeId)) {
        return false;
    }

    if (!GetParentId(sourceNodeId).has_value()) {
        return false;
    }

    HierarchyNode movedNode = {};
    if (!ExtractNodeRecursive(m_roots, sourceNodeId, movedNode)) {
        return false;
    }

    m_roots.push_back(std::move(movedNode));
    return true;
}

std::vector<Widgets::UIEditorTreeViewItem> HierarchyModel::BuildTreeItems(
    const ::XCEngine::UI::UITextureHandle& icon) const {
    std::vector<Widgets::UIEditorTreeViewItem> items = {};
    BuildTreeItemsRecursive(m_roots, 0u, icon, items);
    return items;
}

std::string HierarchyModel::AllocateNodeId() {
    std::ostringstream stream = {};
    stream << "generated_node_" << m_nextGeneratedNodeId++;
    return stream.str();
}

bool HierarchyModel::CanAdopt(
    std::string_view sourceNodeId,
    const HierarchyNode* targetParent) const {
    if (targetParent == nullptr || sourceNodeId == targetParent->nodeId) {
        return false;
    }

    const HierarchyNode* source = FindNode(sourceNodeId);
    if (source == nullptr) {
        return false;
    }

    return !ContainsDescendant(*source, targetParent->nodeId);
}

bool HierarchyModel::ContainsDescendant(
    const HierarchyNode& node,
    std::string_view candidateId) const {
    for (const HierarchyNode& child : node.children) {
        if (child.nodeId == candidateId || ContainsDescendant(child, candidateId)) {
            return true;
        }
    }
    return false;
}

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