gui-cs.Terminal.Gui/Terminal.Gui/Configuration/ConfigProperty.cs

#nullable enable
using System.Reflection;
using System.Text.Json;
using System.Text.Json.Serialization;

namespace Terminal.Gui;

/// <summary>
///     Holds a property's value and the <see cref="PropertyInfo"/> that allows <see cref="ConfigurationManager"/> to
///     get and set the property's value.
/// </summary>
/// <remarks>
///     Configuration properties must be <see langword="public"/> and <see langword="static"/> and have the
///     <see cref="SerializableConfigurationProperty"/> attribute. If the type of the property requires specialized JSON
///     serialization, a <see cref="JsonConverter"/> must be provided using the <see cref="JsonConverterAttribute"/>
///     attribute.
/// </remarks>
public class ConfigProperty
{
    /// <summary>Describes the property.</summary>
    public PropertyInfo? PropertyInfo { get; set; }

    /// <summary>
    ///     Holds the property's value as it was either read from the class's implementation or from a config file. If the
    ///     property has not been set (e.g. because no configuration file specified a value), this will be
    ///     <see langword="null"/>.
    /// </summary>
    /// <remarks>
    ///     On <see langword="set"/>, performs a sparse-copy of the new value to the existing value (only copies elements
    ///     of the object that are non-null).
    /// </remarks>
    public object? PropertyValue { get; set; }

    /// <summary>Applies the <see cref="PropertyValue"/> to the property described by <see cref="PropertyInfo"/>.</summary>
    /// <returns></returns>
    public bool Apply ()
    {
        if (PropertyValue is { })
        {
            try
            {
                if (PropertyInfo?.GetValue (null) is { })
                {
                    PropertyInfo?.SetValue (null, DeepMemberWiseCopy (PropertyValue, PropertyInfo?.GetValue (null)));
                }
            }
            catch (TargetInvocationException tie)
            {
                // Check if there is an inner exception
                if (tie.InnerException is { })
                {
                    // Handle the inner exception separately without catching the outer exception
                    Exception? innerException = tie.InnerException;

                    // Handle the inner exception here
                    throw new JsonException (
                                             $"Error Applying Configuration Change: {innerException.Message}",
                                             innerException
                                            );
                }

                // Handle the outer exception or rethrow it if needed
                throw new JsonException ($"Error Applying Configuration Change: {tie.Message}", tie);
            }
            catch (ArgumentException ae)
            {
                throw new JsonException (
                                         $"Error Applying Configuration Change ({PropertyInfo?.Name}): {ae.Message}",
                                         ae
                                        );
            }
        }

        return PropertyValue != null;
    }

    /// <summary>
    ///     Helper to get either the Json property named (specified by [JsonPropertyName(name)] or the actual property
    ///     name.
    /// </summary>
    /// <param name="pi"></param>
    /// <returns></returns>
    public static string GetJsonPropertyName (PropertyInfo pi)
    {
        var attr = pi.GetCustomAttribute (typeof (JsonPropertyNameAttribute)) as JsonPropertyNameAttribute;

        return attr?.Name ?? pi.Name;
    }

    /// <summary>
    ///     Retrieves (using reflection) the value of the static property described in <see cref="PropertyInfo"/> into
    ///     <see cref="PropertyValue"/>.
    /// </summary>
    /// <returns></returns>
    public object? RetrieveValue () { return PropertyValue = PropertyInfo!.GetValue (null); }

    internal object? UpdateValueFrom (object source)
    {
        if (source is null)
        {
            return PropertyValue;
        }

        Type? ut = Nullable.GetUnderlyingType (PropertyInfo!.PropertyType);

        if (source.GetType () != PropertyInfo!.PropertyType && ut is { } && source.GetType () != ut)
        {
            throw new ArgumentException (
                                         $"The source object ({
                                             PropertyInfo!.DeclaringType
                                         }.{
                                             PropertyInfo!.Name
                                         }) is not of type {
                                             PropertyInfo!.PropertyType
                                         }."
                                        );
        }

        if (PropertyValue is { })
        {
            PropertyValue = DeepMemberWiseCopy (source, PropertyValue);
        }
        else
        {
            PropertyValue = source;
        }

        return PropertyValue;
    }
}