@typeparam T

@*
 *                                dbMango
 *
 * Copyright 2025 Deutsche Bank AG
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *@

<div class="form-group @Class">
    <style>
        .opt-group{
            font-weight: bold;
            margin-top: 0.5rem;
            margin-bottom: 0.5rem;
            color: greenyellow
        }
    </style>

    @if (!string.IsNullOrWhiteSpace(Name))
    {
        <div class="flex-stack-horizontal form-mw">
            <label for="@_id" class="input-group-text w-100">@Name</label>
        </div>
    }

    <div id="@_id" class="form-control h-auto flex-stack-vertical @ListClass">
        @{
            var groupedValues = GetGroupedValues();
            foreach ( var g in groupedValues )
            {
                if ( groupedValues.Count > 1)
                {
                    <div class="opt-group">@g.Name</div>
                }
                @foreach (var v in g.Values)
                {
                    if (v.Value?.Equals(v) ?? false)
                    {
                        @GetSelectedOption(v)
                    }
                    else
                    {
                        @GetOption(v)
                    }
                }
            }
         }
    </div>
</div>




@code {

    public class SelectableItem(T val)
    {
        public bool                Selected
        {
            get;
            set
            {
                if (field == value)
                    return;
                field = value;
                SelectedChanged.InvokeAsync(field);
            }
        }
        public T                   Value           { get; } = val;
        public EventCallback<bool> SelectedChanged { get; set; }
    }

    [Parameter] public string Name { get; set; } = "";

    [Parameter]
    public List<SelectableItem> Values
    {
        get;
        set
        {
            if (field?.Equals(value) ?? false)
                return;
            field = value;
            InvokeAsync(StateHasChanged);
        }
    } = [];

    [Parameter] public string?            Icon                   { get; set; }
    [Parameter] public string             Class                  { get; set; } = "";
    [Parameter] public string             ListClass              { get; set; } = "";
    [Parameter] public bool               Enabled                { get; set; } = true;
    [Parameter] public Func<T,bool>       IsSelectable           { get; set; } = _ => true;
    [Parameter] public Func<T, string>    GetText                { get; set; } = x => x?.ToString() ?? "<null>";
    [Parameter] public RenderFragment<T>? OptionTemplate         { get; set; }
    [Parameter] public RenderFragment<T>? SelectedOptionTemplate { get; set; }

    private string _id = $"h{Random.Shared.Next():X8}";

    private class Group
    {
        public string  Name   { get; set; } = string.Empty;
        public List<SelectableItem> Values { get; set; } = new ();
    }

    private List<Group> GetGroupedValues()
    {
        var    groups       = new List<Group>();
        Group? currentGroup = null;

        foreach (var v in Values)
        {
            if (!IsSelectable(v.Value))
            {
                // Start a new group with this name
                currentGroup = new () { Name = GetText(v.Value) };
                groups.Add(currentGroup);
            }
            else
            {
                if (currentGroup == null)
                {
                    // If no group has been started, create a default group
                    currentGroup = new () { Name = "Not grouped" };
                    groups.Add(currentGroup);
                }
                currentGroup.Values.Add(v);
            }
        }

        return groups;
    }

    private RenderFragment GetOption(SelectableItem v)
    {
        if (OptionTemplate != null)
        {
            return 
               @<div class="flex-stack-horizontal">
                    <FormItemCheckBox @bind-Value="v.Selected" />
                    @OptionTemplate(v.Value)
                </div>;
        }
        else
        {
            return 
               @<div class="flex-stack-horizontal">
                    <FormItemCheckBox @bind-Value="v.Selected" />
                    <div>@GetText(v.Value)</div>
                </div>;
        }
    }

    private RenderFragment GetSelectedOption(SelectableItem v) => GetOption(v);

}