dotnet-cqrs/Svrnty.Sample/Workflows/InviteUserWorkflow.cs

using System;
using Svrnty.Sample.Events;
using Svrnty.CQRS.Events.Abstractions.EventHandlers;
using Svrnty.CQRS.Events.Abstractions.Models;
using System.Threading;
using System.Threading.Tasks;
using FluentValidation;
using Svrnty.CQRS.Events.Abstractions;

namespace Svrnty.Sample.Workflows;

// ============================================================================
// STEP 1: Invite User Command
// ============================================================================

/// <summary>
/// Command to invite a user via email.
/// This is the first step in a multi-step workflow.
/// </summary>
public record InviteUserCommand
{
    public required string Email { get; init; }
    public required string InviterName { get; init; }
}

public class InviteUserCommandValidator : AbstractValidator<InviteUserCommand>
{
    public InviteUserCommandValidator()
    {
        RuleFor(x => x.Email)
            .NotEmpty()
            .EmailAddress()
            .WithMessage("Valid email is required");

        RuleFor(x => x.InviterName)
            .NotEmpty()
            .WithMessage("Inviter name is required");
    }
}

/// <summary>
/// Handler for inviting a user.
/// Phase 1: Creates a new workflow instance for each invitation.
/// </summary>
/// <remarks>
/// Future phases will support workflow continuation where Accept/Decline commands
/// can reference the same workflow instance using the workflow ID.
/// </remarks>
public class InviteUserCommandHandler : ICommandHandlerWithWorkflow<InviteUserCommand, string, InvitationWorkflow>
{
    public async Task<string> HandleAsync(
        InviteUserCommand command,
        InvitationWorkflow workflow,
        CancellationToken cancellationToken = default)
    {
        // Generate invitation ID
        var invitationId = Guid.NewGuid().ToString();

        // Emit event via workflow
        // Framework automatically assigns workflow.Id as CorrelationId
        workflow.EmitInvited(new UserInvitedEvent
        {
            InvitationId = invitationId,
            Email = command.Email,
            InviterName = command.InviterName
        });

        // Return invitation ID (client can use this to accept/decline)
        // Note: workflow.Id is the correlation ID, but for Phase 1 they're independent
        return await Task.FromResult(invitationId);
    }
}

// ============================================================================
// STEP 2: Accept/Decline Invite Commands
// ============================================================================

/// <summary>
/// Command to accept a user invitation.
/// Uses the same business data (email) as correlation key.
/// </summary>
public record AcceptInviteCommand
{
    public required string InvitationId { get; init; }
    public required string Email { get; init; } // Used for correlation
    public required string Name { get; init; }
}

public class AcceptInviteCommandValidator : AbstractValidator<AcceptInviteCommand>
{
    public AcceptInviteCommandValidator()
    {
        RuleFor(x => x.InvitationId)
            .NotEmpty()
            .WithMessage("Invitation ID is required");

        RuleFor(x => x.Name)
            .NotEmpty()
            .WithMessage("Name is required");
    }
}

/// <summary>
/// Handler for accepting an invitation.
/// Phase 1: Creates a new workflow instance for the acceptance.
/// </summary>
/// <remarks>
/// Future phases will support continuing the InvitationWorkflow from the invite command,
/// so all events (invite + accept) share the same workflow/correlation ID.
/// </remarks>
public class AcceptInviteCommandHandler : ICommandHandlerWithWorkflow<AcceptInviteCommand, int, InvitationWorkflow>
{
    public async Task<int> HandleAsync(
        AcceptInviteCommand command,
        InvitationWorkflow workflow,
        CancellationToken cancellationToken = default)
    {
        // Generate user ID
        var userId = new Random().Next(1000, 9999);

        // Emit acceptance event via workflow
        workflow.EmitAccepted(new UserInviteAcceptedEvent
        {
            InvitationId = command.InvitationId,
            UserId = userId,
            Name = command.Name
        });

        return await Task.FromResult(userId);
    }
}

/// <summary>
/// Command to decline a user invitation.
/// </summary>
public record DeclineInviteCommand
{
    public required string InvitationId { get; init; }
    public string? Reason { get; init; }
}

/// <summary>
/// Handler for declining an invitation.
/// Phase 1: Creates a new workflow instance for the decline action.
/// </summary>
/// <remarks>
/// Future phases will support continuing the InvitationWorkflow from the invite command,
/// so all events (invite + decline) share the same workflow/correlation ID.
/// </remarks>
public class DeclineInviteCommandHandler : ICommandHandlerWithWorkflow<DeclineInviteCommand, InvitationWorkflow>
{
    public async Task HandleAsync(
        DeclineInviteCommand command,
        InvitationWorkflow workflow,
        CancellationToken cancellationToken = default)
    {
        // Emit decline event via workflow
        workflow.EmitDeclined(new UserInviteDeclinedEvent
        {
            InvitationId = command.InvitationId,
            Reason = command.Reason
        });

        await Task.CompletedTask;
    }
}

// ============================================================================
// Events for the Workflow
// ============================================================================

public sealed record UserInvitedEvent : UserEvent
{
    public required string InvitationId { get; init; }
    public required string Email { get; init; }
    public required string InviterName { get; init; }
}

public sealed record UserInviteAcceptedEvent : UserEvent
{
    public required string InvitationId { get; init; }
    public required int UserId { get; init; }
    public required string Name { get; init; }
}

public sealed record UserInviteDeclinedEvent : UserEvent
{
    public required string InvitationId { get; init; }
    public string? Reason { get; init; }
}