#include <XCNewEditor/Editor/UIEditorPanelRegistry.h>
#include <XCNewEditor/Editor/UIEditorWorkspaceModel.h>

#include <cmath>
#include <unordered_set>
#include <utility>

namespace XCEngine::NewEditor {

namespace {

UIEditorWorkspaceValidationResult MakeValidationError(
    UIEditorWorkspaceValidationCode code,
    std::string message) {
    UIEditorWorkspaceValidationResult result = {};
    result.code = code;
    result.message = std::move(message);
    return result;
}

bool IsValidSplitRatio(float value) {
    return std::isfinite(value) && value > 0.0f && value < 1.0f;
}

const UIEditorPanelDescriptor& RequirePanelDescriptor(
    const UIEditorPanelRegistry& registry,
    std::string_view panelId) {
    if (const UIEditorPanelDescriptor* descriptor = FindUIEditorPanelDescriptor(registry, panelId);
        descriptor != nullptr) {
        return *descriptor;
    }

    static const UIEditorPanelDescriptor fallbackDescriptor = {};
    return fallbackDescriptor;
}

const UIEditorWorkspacePanelState* FindPanelRecursive(
    const UIEditorWorkspaceNode& node,
    std::string_view panelId) {
    if (node.kind == UIEditorWorkspaceNodeKind::Panel) {
        return node.panel.panelId == panelId ? &node.panel : nullptr;
    }

    for (const UIEditorWorkspaceNode& child : node.children) {
        if (const UIEditorWorkspacePanelState* found = FindPanelRecursive(child, panelId)) {
            return found;
        }
    }

    return nullptr;
}

bool TryActivateRecursive(
    UIEditorWorkspaceNode& node,
    std::string_view panelId) {
    switch (node.kind) {
    case UIEditorWorkspaceNodeKind::Panel:
        return node.panel.panelId == panelId;

    case UIEditorWorkspaceNodeKind::TabStack:
        for (std::size_t index = 0; index < node.children.size(); ++index) {
            UIEditorWorkspaceNode& child = node.children[index];
            if (child.kind == UIEditorWorkspaceNodeKind::Panel &&
                child.panel.panelId == panelId) {
                node.selectedTabIndex = index;
                return true;
            }
        }
        return false;

    case UIEditorWorkspaceNodeKind::Split:
        for (UIEditorWorkspaceNode& child : node.children) {
            if (TryActivateRecursive(child, panelId)) {
                return true;
            }
        }
        return false;
    }

    return false;
}

void CollectVisiblePanelsRecursive(
    const UIEditorWorkspaceNode& node,
    std::string_view activePanelId,
    std::vector<UIEditorWorkspaceVisiblePanel>& outPanels) {
    switch (node.kind) {
    case UIEditorWorkspaceNodeKind::Panel: {
        UIEditorWorkspaceVisiblePanel panel = {};
        panel.panelId = node.panel.panelId;
        panel.title = node.panel.title;
        panel.active = node.panel.panelId == activePanelId;
        panel.placeholder = node.panel.placeholder;
        outPanels.push_back(std::move(panel));
        return;
    }

    case UIEditorWorkspaceNodeKind::TabStack:
        if (node.selectedTabIndex < node.children.size()) {
            CollectVisiblePanelsRecursive(
                node.children[node.selectedTabIndex],
                activePanelId,
                outPanels);
        }
        return;

    case UIEditorWorkspaceNodeKind::Split:
        for (const UIEditorWorkspaceNode& child : node.children) {
            CollectVisiblePanelsRecursive(child, activePanelId, outPanels);
        }
        return;
    }
}

UIEditorWorkspaceValidationResult ValidateNodeRecursive(
    const UIEditorWorkspaceNode& node,
    std::unordered_set<std::string>& panelIds) {
    if (node.nodeId.empty()) {
        return MakeValidationError(
            UIEditorWorkspaceValidationCode::EmptyNodeId,
            "Workspace node id must not be empty.");
    }

    switch (node.kind) {
    case UIEditorWorkspaceNodeKind::Panel:
        if (!node.children.empty()) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::NonPanelTabChild,
                "Panel node '" + node.nodeId + "' must not contain child nodes.");
        }

        if (node.panel.panelId.empty()) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::EmptyPanelId,
                "Panel node '" + node.nodeId + "' must define a panelId.");
        }

        if (node.panel.title.empty()) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::EmptyPanelTitle,
                "Panel node '" + node.nodeId + "' must define a title.");
        }

        if (!panelIds.insert(node.panel.panelId).second) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::DuplicatePanelId,
                "Panel id '" + node.panel.panelId + "' is duplicated in the workspace tree.");
        }

        return {};

    case UIEditorWorkspaceNodeKind::TabStack:
        if (node.children.empty()) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::EmptyTabStack,
                "Tab stack '" + node.nodeId + "' must contain at least one panel.");
        }

        if (node.selectedTabIndex >= node.children.size()) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::InvalidSelectedTabIndex,
                "Tab stack '" + node.nodeId + "' selectedTabIndex is out of range.");
        }

        for (const UIEditorWorkspaceNode& child : node.children) {
            if (child.kind != UIEditorWorkspaceNodeKind::Panel) {
                return MakeValidationError(
                    UIEditorWorkspaceValidationCode::NonPanelTabChild,
                    "Tab stack '" + node.nodeId + "' may only contain panel leaf nodes.");
            }

            if (UIEditorWorkspaceValidationResult result = ValidateNodeRecursive(child, panelIds);
                !result.IsValid()) {
                return result;
            }
        }

        return {};

    case UIEditorWorkspaceNodeKind::Split:
        if (node.children.size() != 2u) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::InvalidSplitChildCount,
                "Split node '" + node.nodeId + "' must contain exactly two child nodes.");
        }

        if (!IsValidSplitRatio(node.splitRatio)) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::InvalidSplitRatio,
                "Split node '" + node.nodeId + "' must define a ratio in the open interval (0, 1).");
        }

        for (const UIEditorWorkspaceNode& child : node.children) {
            if (UIEditorWorkspaceValidationResult result = ValidateNodeRecursive(child, panelIds);
                !result.IsValid()) {
                return result;
            }
        }

        return {};
    }

    return {};
}

} // namespace

UIEditorWorkspaceModel BuildDefaultEditorShellWorkspaceModel() {
    const UIEditorPanelRegistry registry = BuildDefaultEditorShellPanelRegistry();
    const UIEditorPanelDescriptor& rootPanel =
        RequirePanelDescriptor(registry, "editor-foundation-root");

    UIEditorWorkspaceModel workspace = {};
    workspace.root = BuildUIEditorWorkspacePanel(
        "editor-foundation-root-node",
        rootPanel.panelId,
        rootPanel.defaultTitle,
        rootPanel.placeholder);
    workspace.activePanelId = rootPanel.panelId;
    return workspace;
}

UIEditorWorkspaceNode BuildUIEditorWorkspacePanel(
    std::string nodeId,
    std::string panelId,
    std::string title,
    bool placeholder) {
    UIEditorWorkspaceNode node = {};
    node.kind = UIEditorWorkspaceNodeKind::Panel;
    node.nodeId = std::move(nodeId);
    node.panel.panelId = std::move(panelId);
    node.panel.title = std::move(title);
    node.panel.placeholder = placeholder;
    return node;
}

UIEditorWorkspaceNode BuildUIEditorWorkspaceTabStack(
    std::string nodeId,
    std::vector<UIEditorWorkspaceNode> panels,
    std::size_t selectedTabIndex) {
    UIEditorWorkspaceNode node = {};
    node.kind = UIEditorWorkspaceNodeKind::TabStack;
    node.nodeId = std::move(nodeId);
    node.selectedTabIndex = selectedTabIndex;
    node.children = std::move(panels);
    return node;
}

UIEditorWorkspaceNode BuildUIEditorWorkspaceSplit(
    std::string nodeId,
    UIEditorWorkspaceSplitAxis axis,
    float splitRatio,
    UIEditorWorkspaceNode primary,
    UIEditorWorkspaceNode secondary) {
    UIEditorWorkspaceNode node = {};
    node.kind = UIEditorWorkspaceNodeKind::Split;
    node.nodeId = std::move(nodeId);
    node.splitAxis = axis;
    node.splitRatio = splitRatio;
    node.children.push_back(std::move(primary));
    node.children.push_back(std::move(secondary));
    return node;
}

UIEditorWorkspaceValidationResult ValidateUIEditorWorkspace(
    const UIEditorWorkspaceModel& workspace) {
    std::unordered_set<std::string> panelIds = {};
    UIEditorWorkspaceValidationResult result = ValidateNodeRecursive(workspace.root, panelIds);
    if (!result.IsValid()) {
        return result;
    }

    if (!workspace.activePanelId.empty()) {
        const UIEditorWorkspacePanelState* activePanel = FindUIEditorWorkspaceActivePanel(workspace);
        if (activePanel == nullptr) {
            return MakeValidationError(
                UIEditorWorkspaceValidationCode::InvalidActivePanelId,
                "Active panel id '" + workspace.activePanelId + "' is missing or hidden by the current tab selection.");
        }
    }

    return {};
}

std::vector<UIEditorWorkspaceVisiblePanel> CollectUIEditorWorkspaceVisiblePanels(
    const UIEditorWorkspaceModel& workspace) {
    std::vector<UIEditorWorkspaceVisiblePanel> visiblePanels = {};
    CollectVisiblePanelsRecursive(workspace.root, workspace.activePanelId, visiblePanels);
    return visiblePanels;
}

bool ContainsUIEditorWorkspacePanel(
    const UIEditorWorkspaceModel& workspace,
    std::string_view panelId) {
    return FindPanelRecursive(workspace.root, panelId) != nullptr;
}

const UIEditorWorkspacePanelState* FindUIEditorWorkspaceActivePanel(
    const UIEditorWorkspaceModel& workspace) {
    if (workspace.activePanelId.empty()) {
        return nullptr;
    }

    std::vector<UIEditorWorkspaceVisiblePanel> visiblePanels =
        CollectUIEditorWorkspaceVisiblePanels(workspace);
    for (const UIEditorWorkspaceVisiblePanel& panel : visiblePanels) {
        if (panel.panelId == workspace.activePanelId) {
            return FindPanelRecursive(workspace.root, workspace.activePanelId);
        }
    }

    return nullptr;
}

bool TryActivateUIEditorWorkspacePanel(
    UIEditorWorkspaceModel& workspace,
    std::string_view panelId) {
    if (!TryActivateRecursive(workspace.root, panelId)) {
        return false;
    }

    workspace.activePanelId = std::string(panelId);
    return true;
}

} // namespace XCEngine::NewEditor