// Copyright (c) 2023 - 2025 IBM Corp. // All rights reserved. // // Licensed under the Apache License, Version 2.0 (the "License"); // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // // http://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. // See the License for the specific language governing permissions and // limitations under the License. package either import ( F "github.com/IBM/fp-go/v2/function" ) // WithResource constructs a function that creates a resource, operates on it, and then releases it. // This ensures proper resource cleanup even if operations fail. // The resource is released immediately after the operation completes. // // Parameters: // - onCreate: Function to create/acquire the resource // - onRelease: Function to release/cleanup the resource // // Returns a function that takes an operation to perform on the resource. // // Example: // // withFile := either.WithResource( // func() either.Either[error, *os.File] { // return either.TryCatchError(os.Open("file.txt")) // }, // func(f *os.File) either.Either[error, any] { // return either.TryCatchError(f.Close()) // }, // ) // result := withFile(func(f *os.File) either.Either[error, string] { // // Use file here // return either.Right[error]("data") // }) func WithResource[E, R, A, ANY any](onCreate func() Either[E, R], onRelease Kleisli[E, R, 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), ) }) }, ) } }