DigitalData.MessagingService/src/presentation/DigitalData.MessagingService.API/Controllers/EmailController.cs

using DigitalData.MessagingService.Application.EmailSending.Commands;
using DigitalData.MessagingService.Application.EmailReceiving.Queries;
using DigitalData.MessagingService.Application.EmailReceiving.Commands;
using DigitalData.MessagingService.Application.EmailAccount.Queries;
using DigitalData.MessagingService.Abstraction;
using MediatR;
using Microsoft.AspNetCore.Mvc;

namespace DigitalData.MessagingService.API.Controllers;

/// <summary>
/// Email sending API controller.
/// Enqueues outgoing emails to RabbitMQ for async processing.
/// </summary>
[ApiController]
[Route("api/[controller]")]
public class EmailController(IMediator mediator) : ControllerBase
{
    /// <summary>
    /// 
    /// </summary>
    public enum OnlyFilter
    {
        /// <summary>
        /// 
        /// </summary>
        HtmlBody,
        /// <summary>
        /// 
        /// </summary>
        Uid,
    }

    #region Send
    /// <summary>
    /// Send an email, optionally with file attachments.
    /// Omit the <c>attachments</c> field for a plain send.
    /// </summary>
    /// <param name="command">Email fields as form values</param>
    /// <param name="attachments">Optional uploaded files</param>
    /// <param name="cancellationToken">Cancellation token</param>
    /// <returns>HTTP 202 Accepted with the queued event ID</returns>
    [HttpPost]
    [Consumes("multipart/form-data")]
    [ProducesResponseType(StatusCodes.Status202Accepted)]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    public async Task<IActionResult> SendEmail(
        [FromForm] PublishEmailCommand command,
        IFormFileCollection? attachments,
        CancellationToken cancellationToken)
    {
        var commandWithAttachments = command.WithAttachments(
            await BuildAttachmentsAsync(attachments, cancellationToken));

        var eventId = await mediator.Send(commandWithAttachments, cancellationToken);
        return Accepted(new { Id = eventId });
    }

    private static async Task<IEnumerable<EmailAttachmentContext>> BuildAttachmentsAsync(
        IFormFileCollection? files,
        CancellationToken cancellationToken)
    {
        if (files is null || files.Count == 0)
            return [];

        var result = new List<EmailAttachmentContext>(files.Count);

        foreach (var file in files)
        {
            using var ms = new MemoryStream();
            await file.CopyToAsync(ms, cancellationToken);

            result.Add(new EmailAttachmentContext
            {
                FileName    = file.FileName,
                Content     = ms.ToArray(),
                ContentType = file.ContentType
            });
        }

        return result;
    }
    #endregion Send

    #region Receive
    /// <summary>
    /// Fetch emails from an IMAP mailbox.
    /// </summary>
    /// <param name="query">Query parameters for filtering and fetching emails from the IMAP mailbox.</param>
    /// <param name="only"></param>
    /// <param name="cancellationToken">Cancellation token.</param>
    /// <returns>HTTP 200 with list of received emails.</returns>
    [HttpGet]
    [ProducesResponseType(StatusCodes.Status200OK)]
    [ProducesResponseType(StatusCodes.Status400BadRequest)]
    [ProducesResponseType(StatusCodes.Status404NotFound)]
    public async Task<IActionResult> FetchEmails([FromQuery] FetchEmailsQuery query, [FromQuery] OnlyFilter? only = null, CancellationToken cancellationToken = default)
    {
        var emails = await mediator.Send(query, cancellationToken);

        if(!emails.Any())
            return NotFound("No emails found matching the specified criteria.");

        if (only == OnlyFilter.HtmlBody)
        {
            if (emails.FirstOrDefault()?.HtmlBody is string htmlBody)
                return Content(htmlBody, "text/html");
            else
                return NotFound();
        }
        else if (only == OnlyFilter.Uid)
            return Ok(emails.Select(e => e.Uid).ToList());
        else
            return Ok(emails);
    }
    #endregion Receive
}