fp-go/either/resource.go

package either

import (
	F "github.com/IBM/fp-go/function"
)

// constructs a function that creates a resource, then operates on it and then releases the resource
func WithResource[E, R, A any](onCreate func() Either[E, R], onRelease func(R) Either[E, any]) func(func(R) Either[E, A]) Either[E, A] {

	return func(f func(R) Either[E, A]) Either[E, A] {
		return MonadChain(
			onCreate(), func(r R) Either[E, A] {
				// run the code and make sure to release as quickly as possible
				res := f(r)
				released := onRelease(r)
				// handle the errors
				return MonadFold(
					res,
					Left[A, E],
					func(a A) Either[E, A] {
						return F.Pipe1(
							released,
							MapTo[E, any](a),
						)
					})
			},
		)
	}
}