namespace EnvelopeGenerator.ReceiverUI.Models.Constants;

/// <summary>
/// Represents the unit of measurement for coordinate values in signature positioning.
/// Used for converting coordinates between different systems (GdPicture14, PDF.js, iText7).
/// </summary>
public enum UnitOfLength
{
    /// <summary>
    /// Inch unit (1 inch = 25.4 mm).
    /// This is the native unit used by GdPicture14 (EnvelopeGenerator.Form - Legacy VB.NET app).
    /// Database stores all coordinates (X, Y, Width, Height) in INCHES.
    /// </summary>
    /// <remarks>
    /// <b>Source:</b> GdPicture14.Annotations.AnnotationStickyNote uses INCHES natively.
    /// <br/>
    /// <b>Evidence:</b> VB.NET code directly assigns database values to annotation properties without conversion:
    /// <code>
    /// oAnnotation.Left = CSng(pElement.X)   ' Direct assignment → INCHES
    /// oAnnotation.Top = CSng(pElement.Y)
    /// </code>
    /// <b>Standard Page Dimensions:</b>
    /// <list type="bullet">
    ///   <item>A4: 8.27" × 11.69" (210mm × 297mm)</item>
    ///   <item>Letter: 8.5" × 11"</item>
    /// </list>
    /// </remarks>
    Inch = 0,

    /// <summary>
    /// PDF Point unit (1 point = 1/72 inch).
    /// This is the standard unit used by PDF specification and PDF.js viewer.
    /// </summary>
    /// <remarks>
    /// <b>Definition:</b> According to PDF specification and Microsoft documentation:
    /// <br/>
    /// <i>"PDF pages are sized in point units. 1 pt == 1/72 inch"</i>
    /// <br/><br/>
    /// <b>Conversion Formula:</b>
    /// <code>
    /// points = inches * 72.0
    /// inches = points / 72.0
    /// </code>
    /// <b>Important:</b> Point ≠ Pixel!
    /// <list type="bullet">
    ///   <item><b>Point (pt):</b> Device-independent unit (always 1/72 inch)</item>
    ///   <item><b>Pixel (px):</b> Device-dependent unit (varies with screen DPI)</item>
    ///   <item>At 72 DPI: 1 point = 1 pixel (coincidence)</item>
    ///   <item>At 96 DPI: 1 point ≈ 1.33 pixels</item>
    ///   <item>At 300 DPI: 1 point ≈ 4.17 pixels</item>
    /// </list>
    /// <b>Standard Page Dimensions (in points):</b>
    /// <list type="bullet">
    ///   <item>A4: 595 × 842 points (8.27" × 11.69" × 72)</item>
    ///   <item>Letter: 612 × 792 points (8.5" × 11" × 72)</item>
    /// </list>
    /// <b>Usage in EnvelopeGenerator:</b>
    /// <list type="bullet">
    ///   <item>PDF.js viewer expects coordinates in points</item>
    ///   <item>iText7 library uses points for PDF manipulation</item>
    ///   <item>PSPDFKit (Web) uses points for annotation placement</item>
    /// </list>
    /// </remarks>
    Point
}