using AutoMapper;
using AutoMapper.Internal;

namespace DigitalData.Core.Exceptions
{
    /// <summary>
    /// Represents errors that occur during mapping when the result is unexpectedly null.
    /// This exception is specifically used to indicate that an AutoMapper mapping operation
    /// resulted in a null object, which may suggest a misconfiguration or an issue with the source data.
    /// </summary>
    public class MappingResultNullException : AutoMapperMappingException
    {
        /// <summary>
        /// Initializes a new instance of the <see cref="MappingResultNullException"/> class with the source and destination types causing the error.
        /// </summary>
        /// <param name="sourceType">The source type of the mapping operation.</param>
        /// <param name="destinationType">The destination type of the mapping operation.</param>
        /// <param name="innerException">The exception that is the cause of the current exception, or a null reference if no inner exception is specified.</param>
        public MappingResultNullException(Type sourceType, Type destinationType, Exception? innerException = null)
            : base(FormatMessage(sourceType, destinationType), innerException, new TypePair(sourceType, destinationType))
        {
        }

        /// <summary>
        /// Formats the exception message to include detailed information about the mapping operation that failed.
        /// </summary>
        /// <param name="sourceType">The source type involved in the mapping operation.</param>
        /// <param name="destinationType">The destination type involved in the mapping operation.</param>
        /// <returns>A formatted string containing the error message.</returns>
        private static string FormatMessage(Type sourceType, Type destinationType)
        {
            return $"Mapping from {sourceType.FullName} to {destinationType.FullName} resulted in a null object. " +
                   "Hint: Ensure that the AutoMapper profile configuration for this mapping is correct.";
        }
    }
}