using EnvelopeGenerator.ReceiverUI.Models.Constants;

namespace EnvelopeGenerator.ReceiverUI.Models;

/// <summary>
/// Represents a signature position on a PDF page.
/// Coordinates stored in INCHES (GdPicture14 native unit).
/// Origin: Top-left corner, X increases right, Y increases down.
/// </summary>
public class SignatureDto
{
    /// <summary>Unique identifier.</summary>
    public int Id { get; init; }

    private double _x;
    private double _y;

    /// <summary>Horizontal position in INCHES from left edge.</summary>
    public double X 
    { 
        get => _x * Factor;
        init => _x = value; 
    }

    /// <summary>Vertical position in INCHES from top edge.</summary>
    public double Y 
    { 
        get => _y * Factor;
        init => _y = value; 
    }

    /// <summary>1-based page number.</summary>
    public int Page { get; init; }

    /// <summary>Sender application type that created this signature.</summary>
    public SenderAppType SenderAppType { get; init; }

    private UnitOfLength _unitOfLength;

    public SignatureDto Convert(UnitOfLength unitOfLength)
    {
        _unitOfLength = unitOfLength;
        return this;
    }

    public double Factor
    {
        get
        {
            if (SenderAppType != SenderAppType.LegacyFormApp)
            {
                throw new NotImplementedException(
                    $"SenderAppType '{SenderAppType}' is not yet implemented. " +
                    $"Currently, only '{nameof(SenderAppType.LegacyFormApp)}' is supported. " +
                    $"Future implementations will handle '{nameof(SenderAppType.ReceiverUIBlazorApp)}' and other types.");
            }

            // LegacyFormApp uses GdPicture14 with INCHES
            return _unitOfLength switch
            {
                UnitOfLength.Inch => 1.0,   // No conversion needed: INCHES → INCHES
                UnitOfLength.Point => 72.0, // INCHES → PDF Points: 1 inch = 72 points (PDF standard, NOT pixels!)
                _ => throw new InvalidOperationException(
                    $"Unknown UnitOfLength: {_unitOfLength}. Expected '{nameof(UnitOfLength.Inch)}' or '{nameof(UnitOfLength.Point)}'.")
            };
        }
    }
}

public static class SignatureDtoExtensions
{
    /// <summary>
    /// Converts all signatures in the collection to the specified unit of length.
    /// </summary>
    /// <typeparam name="T">Type of the collection (IEnumerable, List, etc.)</typeparam>
    /// <param name="signatures">Collection of SignatureDto objects to convert.</param>
    /// <param name="unitOfLength">Target unit of measurement (Inch or Point).</param>
    /// <returns>The same collection with all signatures converted to the specified unit.</returns>
    /// <exception cref="ArgumentNullException">Thrown when signatures collection is null.</exception>
    /// <remarks>
    /// <b>Usage:</b>
    /// <code>
    /// var signatures = await SignatureService.GetAsync(envelopeKey);
    /// var convertedSignatures = signatures.ConvertAll(UnitOfLength.Point);
    /// </code>
    /// <b>Note:</b> This method modifies each SignatureDto object in place and returns the same collection.
    /// </remarks>
    public static T Convert<T>(this T signatures, UnitOfLength unitOfLength) 
        where T : IEnumerable<SignatureDto>
    {
        if (signatures == null)
            throw new ArgumentNullException(nameof(signatures));

        foreach (var signature in signatures)
        {
            signature.Convert(unitOfLength);
        }

        return signatures;
    }
}