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69 lines
2.5 KiB
Go
69 lines
2.5 KiB
Go
// Copyright (c) 2023 - 2025 IBM Corp.
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// All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package readerioeither
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import "github.com/IBM/fp-go/v2/ioeither"
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// WithResource constructs a function that creates a resource, operates on it, and then releases the resource.
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// This ensures proper resource cleanup even in the presence of errors, following the Resource Acquisition Is Initialization (RAII) pattern.
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//
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// The resource lifecycle is:
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// 1. onCreate: Acquires the resource
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// 2. use: Operates on the resource (provided as argument to the returned function)
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// 3. onRelease: Releases the resource (called regardless of success or failure)
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//
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// Type parameters:
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// - A: The type of the result produced by using the resource
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// - L: The context type
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// - E: The error type
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// - R: The resource type
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// - ANY: The type returned by the release function (typically ignored)
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//
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// Parameters:
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// - onCreate: A computation that acquires the resource
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// - onRelease: A function that releases the resource, called with the resource and executed regardless of errors
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//
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// Returns:
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//
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// A function that takes a resource-using function and returns a ReaderIOEither that manages the resource lifecycle
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//
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// Example:
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//
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// withFile := WithResource(
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// openFile("data.txt"),
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// func(f *File) ReaderIOEither[Config, error, int] {
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// return closeFile(f)
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// },
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// )
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// result := withFile(func(f *File) ReaderIOEither[Config, error, string] {
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// return readContent(f)
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// })
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func WithResource[A, L, E, R, ANY any](onCreate ReaderIOEither[L, E, R], onRelease Kleisli[L, E, R, ANY]) Kleisli[L, E, Kleisli[L, E, R, A], A] {
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return func(f func(R) ReaderIOEither[L, E, A]) ReaderIOEither[L, E, A] {
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return func(l L) ioeither.IOEither[E, A] {
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// dispatch to the generic implementation
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return ioeither.WithResource[A](
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onCreate(l),
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func(r R) ioeither.IOEither[E, ANY] {
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return onRelease(r)(l)
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},
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)(func(r R) ioeither.IOEither[E, A] {
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return f(r)(l)
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})
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}
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}
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}
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