using Avalonia.Controls;
using Avalonia.Controls.Templates;
using Avalonia_PC.ViewModels;
using System;
using System.Diagnostics.CodeAnalysis;

namespace Avalonia_PC
{
    /// <summary>
    /// Given a view model, returns the corresponding view if possible.
    /// </summary>
    [RequiresUnreferencedCode(
        "Default implementation of ViewLocator involves reflection which may be trimmed away.",
        Url = "https://docs.avaloniaui.net/docs/concepts/view-locator")]
    /// <summary>
    /// 视图定位器，根据 ViewModel 类型自动查找对应的 View，
    /// 实现 IDataTemplate 以支持 Avalonia 的数据模板机制。
    /// </summary>
    public class ViewLocator : IDataTemplate
    {
        /// <summary>
        /// 根据 ViewModel 实例构建对应的 View 控件。
        /// 约定：将 ViewModels 命名空间中的 ViewModel 替换为 Views 命名空间中的同名 View。
        /// </summary>
        /// <param name="param">ViewModel 实例。</param>
        /// <returns>对应的 View 控件；若未找到则返回 TextBlock 显示错误信息。</returns>
        public Control? Build(object? param)
        {
            if (param is null)
                return null;

            var name = param.GetType().FullName!.Replace("ViewModel", "View", StringComparison.Ordinal);
            var type = Type.GetType(name);

            if (type != null)
            {
                return (Control)Activator.CreateInstance(type)!;
            }

            return new TextBlock { Text = "Not Found: " + name };
        }

        /// <summary>
        /// 判断数据对象是否为 ViewModel 类型（以 "ViewModel" 结尾）。
        /// </summary>
        /// <param name="data">要判断的数据对象。</param>
        /// <returns>是否为 ViewModel。</returns>
        public bool Match(object? data)
        {
            return data is ViewModelBase;
        }
    }
}