EnvelopeGenerator/EnvelopeGenerator.Application/Common/Dto/DocReceiverElementDto.cs

using EnvelopeGenerator.Application.Common.Dto.Receiver;
using EnvelopeGenerator.Domain.Constants;
using EnvelopeGenerator.Domain.Interfaces;

namespace EnvelopeGenerator.Application.Common.Dto;

// TODO: Add the “Reason” property and integrate with UI and the digital signature process.
/// <summary>
/// Data Transfer Object representing a positioned element assigned to a document receiver.
/// </summary>
public class DocReceiverElementDto : IDocReceiverElement, ISignatureInkPayload
{
    /// <summary>
    /// Gets or sets the unique identifier of the element.
    /// </summary>
    public int Id { get; set; }

    /// <summary>
    /// Gets or sets the identifier of the associated document.
    /// </summary>
    public int DocumentId { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public virtual DocumentDto? Document { get; set; }

    /// <summary>
    /// Gets or sets the identifier of the receiver.
    /// </summary>
    public int ReceiverId { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public virtual ReceiverDto? Receiver { get; set; }

    /// <summary>
    /// Gets or sets the type of the element.
    /// </summary>
    public int ElementType { get; set; }

    /// <summary>
    /// Gets or sets the X coordinate of the element.
    /// </summary>
    public double X { get; set; }

    /// <summary>
    /// Gets or sets the Y coordinate of the element.
    /// </summary>
    public double Y { get; set; }

    /// <summary>
    /// Gets or sets the width of the element.
    /// </summary>
    public double Width { get; set; }

    /// <summary>
    /// Gets or sets the height of the element.
    /// </summary>
    public double Height { get; set; }

    /// <summary>
    /// Gets or sets the page number where the element appears.
    /// </summary>
    public int Page { get; set; }

    /// <summary>
    /// Gets or sets a value indicating whether the element is required.
    /// </summary>
    public bool Required { get; set; }

    /// <summary>
    /// Gets or sets the tooltip text for the element.
    /// </summary>
    public string? Tooltip { get; set; }

    /// <summary>
    /// Gets or sets a value indicating whether the element is read-only.
    /// </summary>
    public bool ReadOnly { get; set; }

    /// <summary>
    /// Gets or sets the annotation index for ordering or reference.
    /// </summary>
    public int AnnotationIndex { get; set; }

    /// <summary>
    /// Gets or sets the timestamp when the element was added.
    /// </summary>
    public DateTime AddedWhen { get; set; }

    /// <summary>
    /// Gets or sets the timestamp when the element was last changed, if applicable.
    /// </summary>
    public DateTime? ChangedWhen { get; set; }

    /// <summary>
    /// Gets or sets the top position of the element (in layout terms).
    /// </summary>
    public double Top => Y;

    /// <summary>
    /// Gets or sets the left position of the element (in layout terms).
    /// </summary>
    public double Left => X;

    /// <summary>
    /// 
    /// </summary>
    public IEnumerable<AnnotationDto>? Annotations { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public SenderAppType SenderAppType { get; set; } = SenderAppType.LegacyFormApp;

    /// <summary>
    /// 
    /// </summary>
    public string? FullName { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public string? Position { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public string? Place { get; set; }

    /// <summary>
    /// 
    /// </summary>
    public byte[]? Ink { get; set; }

    /// <summary>
    /// Returns the stored signature bytes as an image payload with detected MIME type.
    /// </summary>
    /// <exception cref="InvalidOperationException">Thrown when signature image bytes do not exist.</exception>
    public (byte[] Bytes, string ContentType, string FileExtension) ToImage()
    {
        if (Ink is not { Length: > 0 })
            throw new InvalidOperationException("Signature image (Ink) does not exist.");

        if (HasPrefix(Ink, 0x89, 0x50, 0x4E, 0x47))
            return (Ink, "image/png", ".png");

        if (HasPrefix(Ink, 0xFF, 0xD8, 0xFF))
            return (Ink, "image/jpeg", ".jpg");

        if (HasPrefix(Ink, 0x52, 0x49, 0x46, 0x46) &&
            Ink.Length >= 12 &&
            Ink[8] == 0x57 && Ink[9] == 0x45 && Ink[10] == 0x42 && Ink[11] == 0x50)
            return (Ink, "image/webp", ".webp");

        return (Ink, "application/octet-stream", ".bin");
    }

    private static bool HasPrefix(byte[] data, params byte[] prefix)
    {
        if (data.Length < prefix.Length)
            return false;

        for (var i = 0; i < prefix.Length; i++)
        {
            if (data[i] != prefix[i])
                return false;
        }

        return true;
    }
}