using System.Collections.Generic;
using System.Linq;
using GB5Shared.Tree;
using FrameworkDAL.DTO.MenuGroup;
using Xunit;

namespace FrameworkTests;

/// <summary>
/// Covers the -1-sentinel-to-null-Parent translation MenuGroupBLL.GetMenuGroupTreeForSet
/// applies before calling TreeHelper.ConvertToTree (mirroring MenuBLL's existing MMENU
/// handling), plus the shared/private node-visibility mix and orphaned-parent handling
/// called out in the plan's Phase 4 test list. Pure C# — no DB involved, since
/// TreeHelper itself is DB-agnostic.
/// </summary>
public class MenuGroupTreeTests
{
    private static MenuGroupDTO Node(int id, string code, int parentGroupId, int? menuSetId = null) => new()
    {
        MenuGroupId = id,
        GroupCode = code,
        GroupName = code,
        ParentGroupId = parentGroupId,
        MenuSetId = menuSetId,
    };

    private static void ApplySentinelTranslation(IEnumerable<MenuGroupDTO> flat)
    {
        foreach (var node in flat)
            node.Parent = node.ParentGroupId == -1 ? null : new MenuGroupDTO { MenuGroupId = node.ParentGroupId };
    }

    [Fact]
    public void ConvertToTree_TranslatesMinusOneSentinelToRoot()
    {
        var flat = new List<MenuGroupDTO>
        {
            Node(1, "TOP", parentGroupId: -1),
            Node(2, "CHILD", parentGroupId: 1),
        };
        ApplySentinelTranslation(flat);

        var forest = flat.ConvertToTree();

        var top = Assert.Single(forest);
        Assert.Equal(1, top.MenuGroupId);
        var child = Assert.Single(top.children);
        Assert.Equal(2, child.MenuGroupId);
    }

    [Fact]
    public void ConvertToTree_SharedAndPrivateNodesCoexistInOneForest()
    {
        // MENUSETID IS NULL = shared bundle node; MENUSETID = 42 = private to that one set.
        var flat = new List<MenuGroupDTO>
        {
            Node(1, "SHARED_TOP", parentGroupId: -1, menuSetId: null),
            Node(2, "SHARED_CHILD", parentGroupId: 1, menuSetId: null),
            Node(3, "PRIVATE_CHILD", parentGroupId: 1, menuSetId: 42),
        };
        ApplySentinelTranslation(flat);

        var forest = flat.ConvertToTree();
        var top = forest.FindTreeNode(1)!;

        Assert.Equal(2, top.children.Count);
        Assert.Contains(top.children, c => c.MenuGroupId == 2);
        Assert.Contains(top.children, c => c.MenuGroupId == 3 && c.MenuSetId == 42);
    }

    [Fact]
    public void ConvertToTree_OrphanedParent_NodeIsSilentlyDropped()
    {
        // Node 2's parent (99) never made it into the flat list — e.g. a private group whose
        // parent was deleted, or simply not visible to this MenuSetId's filter. TreeHelper's
        // documented behavior is to drop the orphan rather than throw.
        var flat = new List<MenuGroupDTO>
        {
            Node(1, "TOP", parentGroupId: -1),
            Node(2, "ORPHAN", parentGroupId: 99),
        };
        ApplySentinelTranslation(flat);

        var forest = flat.ConvertToTree();

        Assert.Single(forest);
        Assert.Null(forest.FindTreeNode(2));
    }

    [Fact]
    public void FindTreeNode_ReturnsConfiguredRoot_AndDepthFirstTraversalCollectsAllDescendantIds()
    {
        var flat = new List<MenuGroupDTO>
        {
            Node(1, "ROOT", parentGroupId: -1),
            Node(2, "CHILD_A", parentGroupId: 1),
            Node(3, "CHILD_B", parentGroupId: 1),
            Node(4, "GRANDCHILD", parentGroupId: 2),
        };
        ApplySentinelTranslation(flat);

        var forest = flat.ConvertToTree();
        var root = forest.FindTreeNode(1);

        Assert.NotNull(root);
        var ids = root!.DepthFirstTraversal().Select(n => n.MenuGroupId).OrderBy(i => i).ToList();
        Assert.Equal(new[] { 1, 2, 3, 4 }, ids);
    }

    [Fact]
    public void FindTreeNode_MisconfiguredRoot_ReturnsNull()
    {
        // MMENUSET.MenuGroupId pointing at a group id that doesn't exist in the flat list
        // (e.g. a private node scoped to a different MenuSetId) must be detectable by the
        // BLL as "not found", not silently treated as an empty tree.
        var flat = new List<MenuGroupDTO> { Node(1, "TOP", parentGroupId: -1) };
        ApplySentinelTranslation(flat);

        var forest = flat.ConvertToTree();

        Assert.Null(forest.FindTreeNode(404));
    }
}