// 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 readerioeither import "github.com/IBM/fp-go/v2/ioeither" // WithResource constructs a function that creates a resource, operates on it, and then releases the resource. // This ensures proper resource cleanup even in the presence of errors, following the Resource Acquisition Is Initialization (RAII) pattern. // // The resource lifecycle is: // 1. onCreate: Acquires the resource // 2. use: Operates on the resource (provided as argument to the returned function) // 3. onRelease: Releases the resource (called regardless of success or failure) // // Type parameters: // - A: The type of the result produced by using the resource // - L: The context type // - E: The error type // - R: The resource type // - ANY: The type returned by the release function (typically ignored) // // Parameters: // - onCreate: A computation that acquires the resource // - onRelease: A function that releases the resource, called with the resource and executed regardless of errors // // Returns: // // A function that takes a resource-using function and returns a ReaderIOEither that manages the resource lifecycle // // Example: // // withFile := WithResource( // openFile("data.txt"), // func(f *File) ReaderIOEither[Config, error, int] { // return closeFile(f) // }, // ) // result := withFile(func(f *File) ReaderIOEither[Config, error, string] { // return readContent(f) // }) func WithResource[A, L, E, R, ANY any](onCreate ReaderIOEither[L, E, R], onRelease func(R) ReaderIOEither[L, E, ANY]) func(func(R) ReaderIOEither[L, E, A]) ReaderIOEither[L, E, A] { return func(f func(R) ReaderIOEither[L, E, A]) ReaderIOEither[L, E, A] { return func(l L) ioeither.IOEither[E, A] { // dispatch to the generic implementation return ioeither.WithResource[A]( onCreate(l), func(r R) ioeither.IOEither[E, ANY] { return onRelease(r)(l) }, )(func(r R) ioeither.IOEither[E, A] { return f(r)(l) }) } } }