using FluentValidation;
using FluentValidation.Results;
using Mccn.Common.Application.Exceptions;
using Mccn.Common.Domain.Abstractions;
using MediatR;
using ValidationException = Mccn.Common.Application.Exceptions.ValidationException;

namespace Mccn.Common.Application.Behaviors;

public sealed class ValidationBehavior<TRequest, TResponse> : IPipelineBehavior<TRequest, TResponse>
    where TRequest : IBaseRequest
    where TResponse : Result
{
    private readonly IEnumerable<IValidator<TRequest>> _validators;

    public ValidationBehavior(IEnumerable<IValidator<TRequest>> validators)
    {
        _validators = validators;
    }

    public async Task<TResponse> Handle(
        TRequest request,
        RequestHandlerDelegate<TResponse> next,
        CancellationToken cancellationToken)
    {
        ValidationContext<TRequest> context = new(request);

        ValidationResult[] validationFailures = await Task.WhenAll(
            _validators.Select(v => v.ValidateAsync(context, cancellationToken)));

        List<ValidationError> errors = validationFailures
            .Where(r => !r.IsValid)
            .SelectMany(r => r.Errors)
            .Select(f => new ValidationError(f.PropertyName, f.ErrorMessage))
            .ToList();

        if (errors.Count != 0) throw new ValidationException(errors);

        return await next();
    }
}