using MediatR;
using Microsoft.EntityFrameworkCore;
using SequenceAuth.Example.Domain;
using SequenceAuth.Example.Infrastructure;

namespace SequenceAuth.Example.Features.Todos;

public enum ChangeTodoStatusOutcome { Success, NotFound, Unauthorized }

public record ChangeTodoStatusResult(ChangeTodoStatusOutcome Outcome, TodoItem? Item);

public record ChangeTodoStatusCommand(Guid TodoId, Guid UserId, TodoStatus NewStatus) : IRequest<ChangeTodoStatusResult>;

public class ChangeTodoStatusCommandHandler(AppDbContext dbContext) : IRequestHandler<ChangeTodoStatusCommand, ChangeTodoStatusResult>
{
    public async Task<ChangeTodoStatusResult> Handle(ChangeTodoStatusCommand request, CancellationToken cancellationToken)
    {
        var todo = await dbContext.Todos.FirstOrDefaultAsync(t => t.Id == request.TodoId, cancellationToken);
        
        return todo switch
        {
            null => new ChangeTodoStatusResult(ChangeTodoStatusOutcome.NotFound, null),
            { UserId: var userId } when userId != request.UserId => new ChangeTodoStatusResult(ChangeTodoStatusOutcome.Unauthorized, null),
            _ => await UpdateStatusAsync(todo, request.NewStatus, cancellationToken)
        };
    }

    private async Task<ChangeTodoStatusResult> UpdateStatusAsync(TodoItem todo, TodoStatus newStatus, CancellationToken cancellationToken)
    {
        var updatedTodo = todo with { Status = newStatus };
        
        dbContext.Entry(todo).CurrentValues.SetValues(updatedTodo);
        await dbContext.SaveChangesAsync(cancellationToken);
        
        return new ChangeTodoStatusResult(ChangeTodoStatusOutcome.Success, updatedTodo);
    }
}