@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.
 *@

<style>
    .group-label {
        margin-top: 0.5rem;
        color: yellow;
    }

    .group {
        margin-left: 0.5rem;
    }

    .selected{
        background-color: @Night.ButtonBg;
    }

    .list-body{
        overflow-y: auto;
        max-height: 200px;
    }
</style>


<div class="@FormGroupClass">

    @if (!string.IsNullOrWhiteSpace(Name))
    {
        <div class="flex-stack-horizontal form-mw">
            <label for="@_id" class="input-group-text w-100">@Name</label>
        </div>
    }
    <div class="input-group mr-sm-2">
        @if (Icon != null)
        {
            <div class="input-group-prepend">
                <div class="input-group-text">
                    <div class="">
                        <span class="ui-icon-font ui-icon-sm @Icon"></span>
                    </div>
                </div>
            </div>
        }
        <div id="@_id" class="form-control d-flex flex-column" disabled="@(!Enabled)">
            <div class="list-body">
            @{
                var groupedValues = GetGroupedValues();
                if (groupedValues.Count == 1)
                {
                    foreach (var v in groupedValues[0].Values)
                    {
                        <div class="item @(Value?.Equals(v) ?? false ? "selected" : "")" @onclick="() => SelectItem(v)">
                            @RenderItem(v)
                        </div>
                    }
                }
                else
                {
                    foreach (var g in groupedValues)
                    {
                        <div class="group-label">@g.Name</div>
                        <div class="group">
                            @foreach (var v in g.Values)
                            {
                                <div class="item @(Value?.Equals(v) ?? false ? "selected" : "")" @onclick="() => SelectItem(v)">
                                    @RenderItem(v)
                                </div>
                            }
                        </div>
                    }
                }
            }
            </div>
        </div>
    </div>
</div>




@code {

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

    [Parameter]
    public T Value
    {
        get;
        set
        {
            if (value == null || (field?.Equals(value) ?? false))
                return;
            field = value;
            ValueChanged.InvokeAsync(value);
        }
    } = default!;

    [Parameter] public EventCallback<T>       ValueChanged           { get; set; }
    [Parameter] public IReadOnlyCollection<T> Values                 { get; set; } = [];
    [Parameter] public string?                Placeholder            { get; set; } = "";
    [Parameter] public string?                Icon                   { get; set; }
    [Parameter] public string                 Class                  { 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 string FormGroupClass => string.IsNullOrWhiteSpace(Name) ? Class : $"form-group {Class}";

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

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

        foreach (var v in Values)
        {
            if (!IsSelectable(v))
            {
                // Start a new group with this name
                currentGroup = new Group { Name = v?.ToString() ?? string.Empty };
                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 void SelectItem(T value)
    {
        if (Enabled && IsSelectable(value))
        {
            Value = value;
        }
    }

    private RenderFragment RenderItem(T value)
    {
        var selected = Value?.Equals(value) ?? false;
        if ( selected )
        {
            if (SelectedOptionTemplate != null)
            {
                return @<div>@SelectedOptionTemplate(value)</div>;
            }
            else if (OptionTemplate != null)
            {
                return @<div class="selected">@OptionTemplate(value)</div>;
            }
            else
            {
                return @<div class="selected">@GetText(value)</div>;
            }
        }

        if (OptionTemplate != null)
        {
            return @<div>@OptionTemplate(value)</div>;
        }
        else
        {
            return @<div>@GetText(value)</div>;
        }
    }
}
