using AutoMapper;
using EnvelopeGenerator.Domain.Interfaces.Auditing;
using System;

namespace EnvelopeGenerator.Application.Common.Extensions;

/// <summary>
/// Extension methods for applying auditing timestamps during AutoMapper mappings.
/// </summary>
public static class AutoMapperAuditingExtensions
{
    /// <summary>
    /// Maps <see cref="IHasAddedWhen.AddedWhen"/> to the current UTC time.
    /// </summary>
    public static IMappingExpression<TSource, TDestination> MapAddedWhen<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
        where TDestination : IHasAddedWhen
        => expression.ForMember(dest => dest.AddedWhen, opt => opt.MapFrom(_ => DateTime.Now));

    /// <summary>
    /// Maps <see cref="IHasChangedWhen.ChangedWhen"/> to the current UTC time.
    /// </summary>
    public static IMappingExpression<TSource, TDestination> MapChangedWhen<TSource, TDestination>(this IMappingExpression<TSource, TDestination> expression)
        where TDestination : IHasChangedWhen
        => expression.ForMember(dest => dest.ChangedWhen, opt => opt.MapFrom(_ => DateTime.Now));

    /// <summary>
    /// Converts a base64 data URL string to a byte array.
    /// Handles data URLs in the format: "data:image/png;base64,iVBORw0KG..."
    /// </summary>
    /// <param name="dataUrl">The base64 data URL string from Canvas.toDataURL()</param>
    /// <returns>The decoded byte array, or null if the input is null or empty</returns>
    public static byte[]? MapDataUrlToRequiredBytes(this string dataUrl)
    {
        // Remove data URL prefix (e.g., "data:image/png;base64,")
        var base64Index = dataUrl.IndexOf(',', StringComparison.Ordinal);
        if (base64Index == -1)
            throw new ArgumentException("Invalid data URL format. Unable to extract base64 data.", nameof(dataUrl));

        var base64Data = dataUrl[(base64Index + 1)..];
        return Convert.FromBase64String(base64Data);
    }
}