simplify ReadDocumentQuery

EnvelopeGenerator.Application/Documents/Queries/ReadDocumentQuery.cs

@@ -0,0 +1,58 @@
+using DigitalData.Core.Abstraction.Application.Repository;
+using EnvelopeGenerator.Application.Dto;
+using MediatR;
+using EnvelopeGenerator.Domain.Entities;
+
+namespace EnvelopeGenerator.Application.Documents.Queries;
+
+/// <summary>
+/// Represents a query to read a document based on its unique identifier or associated envelope identifier.
+/// </summary>
+/// <param name="Id">The unique identifier of the document. Optional.</param>
+/// <param name="EnvelopeId">The identifier of the envelope associated with the document. Optional.</param>
+public record ReadDocumentQuery(int? Id = null, int? EnvelopeId = null) : IRequest<EnvelopeDocumentDto?>
+{
+}
+
+/// <summary>
+/// Handles queries for reading <see cref="EnvelopeDocument"/> data based on either the document ID or the envelope ID.
+/// </summary>
+public class ReadDocumentQueryHandler : IRequestHandler<ReadDocumentQuery, EnvelopeDocumentDto?>
+{
+    /// <summary>
+    /// Repository for accessing <see cref="EnvelopeDocument"/> entities.
+    /// </summary>
+    private readonly IRepository<EnvelopeDocument> _repo;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="ReadDocumentQueryHandler"/> class.
+    /// </summary>
+    /// <param name="envelopeDocumentRepository">The repository used to access <see cref="EnvelopeDocument"/> entities.</param>
+    public ReadDocumentQueryHandler(IRepository<EnvelopeDocument> envelopeDocumentRepository)
+    {
+        _repo = envelopeDocumentRepository;
+    }
+
+    /// <summary>
+    /// Handles the <see cref="ReadDocumentQuery"/> and returns a <see cref="EnvelopeDocumentDto"/> based on the provided identifiers.
+    /// </summary>
+    /// <param name="query">The query containing the document ID or envelope ID to search for.</param>
+    /// <param name="cancellationToken">A token to monitor for cancellation requests.</param>
+    /// <returns>
+    /// A <see cref="EnvelopeDocumentDto"/> if a matching document is found; otherwise, <c>null</c>.
+    /// </returns>
+    /// <exception cref="InvalidOperationException">
+    /// Thrown when neither <see cref="ReadDocumentQuery.Id"/> nor <see cref="ReadDocumentQuery.EnvelopeId"/> is provided.
+    /// </exception>
+    [Obsolete("Use MediatR")]
+    public async Task<EnvelopeDocumentDto?> Handle(ReadDocumentQuery query, CancellationToken cancellationToken)
+    {
+        if (query.Id is not null)
+            return await _repo.ReadOrDefaultAsync<EnvelopeDocumentDto>(d => d.Id == query.Id);
+        else if (query.EnvelopeId is not null)
+            return await _repo.ReadOrDefaultAsync<EnvelopeDocumentDto>(d => d.EnvelopeId == query.EnvelopeId);
+
+        throw new InvalidOperationException(
+            $"Invalid {nameof(ReadDocumentQuery)}: either {nameof(query.Id)} or {nameof(query.EnvelopeId)} must be provided.");
+    }
+}