<TelerikTreeView @ref="@TreeViewRef"
                 Data="@FlatData"
                 @bind-ExpandedItems="@ExpandedItems"
                 SelectionMode="@TreeViewSelectionMode.Multiple"
                 SelectedItems="@SelectedItems"
                 SelectedItemsChanged="@((IEnumerable<object> items) => SelectedItemsHandler(items))" />

<TelerikButton OnClick="@ExpandAll">Expand All</TelerikButton>
<TelerikButton OnClick="@CollapseAll">Collapse All</TelerikButton>

@code {
    public TelerikTreeView TreeViewRef { get; set; }
    public IEnumerable<TreeItem> FlatData { get; set; }
    public IEnumerable<object> SelectedItems { get; set; } = new List<object>();
    public IEnumerable<object> ExpandedItems { get; set; } = new List<object>();

    async Task ExpandAll()
    {
        ExpandedItems = FlatData.Where(x => x.HasChildren == true);

        await Task.Delay(1);
        TreeViewRef.Rebind();
    }

    void CollapseAll()
    {
        ExpandedItems = new List<object>();
        SelectedItems = new List<object>();
    }

    void SelectedItemsHandler(IEnumerable<object> items)
    {
        SelectedItems = items;
    }
    protected override async void OnInitialized()
    {
        FlatData = LoadFlat();
    }

    int TreeLevels { get; set; } = 3;
    int ItemsPerLevel { get; set; } = 3;
    int IdCounter { get; set; } = 1;
    List<TreeItem> LoadFlat()
    {
        List<TreeItem> items = new List<TreeItem>();
        PopulateTreeItems(items, null, 1);
        return items;
    }
    void PopulateTreeItems(List<TreeItem> items, int? parentId, int level)
    {
        for (int i = 1; i <= ItemsPerLevel; i++)
        {
            var itemId = IdCounter++;
            items.Add(new TreeItem()
            {
                Id = itemId,
                Text = $"Level {level} Item {i} Id {itemId}",
                ParentId = parentId,
                HasChildren = level < TreeLevels
            });
            if (level < TreeLevels)
            {
                PopulateTreeItems(items, itemId, level + 1);
            }
        }
    }

    public class TreeItem
    {
        public int Id { get; set; }
        public string Text { get; set; }
        public int? ParentId { get; set; }
        public bool HasChildren { get; set; }
    }
}

<script suppress-error="BL9992">
    window.navigateToHref = (ev) => {
        if (ev.key === "Enter") {
            location.href = ev.target.href
        }
    };
</script>

@* This example shows how to create header and footer for the Drawer and select an item manually. *@
<TelerikDrawer @bind-Expanded="@DrawerExpanded"
               Data="@Data"
               MiniMode="true"
               Mode="@DrawerMode.Push"
               @bind-SelectedItem="@SelectedItem"
               @ref="@DrawerRef">
    <Template>
        @* the header *@
        <div>
            <TelerikButton OnClick="@(() => DrawerRef.ToggleAsync())" Icon="@FontIcon.Menu" />
            @if (DrawerExpanded)
            {
                <div class="text-info" style="border-bottom:solid; font-weight: bold; margin-bottom: 3em; white-space:nowrap">
                    <a href="https://google.com" onkeydown="navigateToHref(event)">
                        My Custom Navigation to Google
                    </a>
                </div>
            }
            else
            {
                <div class="text-info" style="border-bottom:solid; font-weight: bold;">
                    Nav
                </div>
            }
        </div>

        @* custom items rendering and item selection *@

        <div class="k-drawer-items">
            <ul>
                @if (SelectedItem != null && DrawerExpanded)
                {
                    <li class="k-drawer-item" style="white-space:nowrap">
                        <div>
                            <p><strong>@SelectedItem.Text</strong></p>
                            <p>@SelectedItem.Description</p>
                        </div>
                    </li>
                }

                @foreach (var item in Data)
                {
                    @* Use onclick to handle manual item selection *@
                    <li @onclick="@(() => SelectedItem = item)"
                    class="k-drawer-item @GetSelectedItemClass(item)" style="white-space:nowrap">
                        <TelerikFontIcon Icon="@item.Icon"></TelerikFontIcon>
                        @if (DrawerExpanded)
                        {
                            <div>
                                <div>@item.Text</div>
                            </div>
                        }
                    </li>
                }
            </ul>
        </div>

        @* the footer *@
        @if (DrawerExpanded)
        {
            <div style="text-align: center; margin-top: 3em; padding-top: 2em; border-top: 2px solid black; white-space:nowrap">
                <img src="user-avatar.png" alt="my avatar" style="border-radius: 50%; width: 50px; height: 50px;" />
                <br /><br />
                <TelerikButton Icon="@FontIcon.Logout" ThemeColor="primary">Log Out</TelerikButton>
            </div>
        }
    </Template>
    <DrawerContent>
        <div class="m-5">Content for @SelectedItem?.Text - @SelectedItem?.Description</div>
    </DrawerContent>
</TelerikDrawer>


@code {
    public TelerikDrawer<DrawerItem> DrawerRef { get; set; }
    public DrawerItem SelectedItem { get; set; }
    public bool DrawerExpanded { get; set; } = true;
    public IEnumerable<DrawerItem> Data { get; set; } = new List<DrawerItem>
    {
        new DrawerItem {Text = "Shopping Cart", Icon = FontIcon.Cart, Description = "Items in shopping cart"},
        new DrawerItem {Text = "Settings", Icon = FontIcon.Gear, Description = "My profile settings"},
        new DrawerItem {Text = "Notifications", Icon = FontIcon.ExclamationCircle, Description = "My profile notifications"},
        new DrawerItem {Text = "Calendar", Icon = FontIcon.Calendar, Description = "My events"},
    };

    public string GetSelectedItemClass(DrawerItem item)
    {
        if (SelectedItem == null) return string.Empty;
        return SelectedItem.Text.ToLowerInvariant().Equals(item.Text.ToLowerInvariant()) ? "text-info" : "";
    }

    public class DrawerItem
    {
        public string Text { get; set; }
        public FontIcon? Icon { get; set; }
        public string Description { get; set; }
    }
}