// 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 // 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[A, E, R, ANY any]( onCreate func() Either[E, R], onRelease Kleisli[E, R, ANY], ) Kleisli[E, Kleisli[E, R, A], A] { return func(f func(R) Either[E, A]) Either[E, A] { r := onCreate() if r.isLeft { return Left[A](r.l) } a := f(r.r) n := onRelease(r.r) if a.isLeft { return Left[A](a.l) } if n.isLeft { return Left[A](n.l) } return Of[E](a.r) } }