mirror of
https://github.com/IBM/fp-go.git
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342 lines
9.2 KiB
Go
342 lines
9.2 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 (
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"github.com/IBM/fp-go/v2/internal/apply"
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"github.com/IBM/fp-go/v2/internal/chain"
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"github.com/IBM/fp-go/v2/internal/functor"
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L "github.com/IBM/fp-go/v2/optics/lens"
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)
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// Do creates an empty context of type [S] to be used with the [Bind] operation.
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// This is the starting point for do-notation style composition.
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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// result := readerioeither.Do(State{})
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//
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//go:inline
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func Do[S any](
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empty S,
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) ReaderIOEither[S] {
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return Of(empty)
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}
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// Bind attaches the result of a computation to a context [S1] to produce a context [S2].
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// This enables sequential composition where each step can depend on the results of previous steps
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// and access the context.Context from the environment.
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//
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// The setter function takes the result of the computation and returns a function that
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// updates the context from S1 to S2.
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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//
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// result := F.Pipe2(
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// readerioeither.Do(State{}),
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// readerioeither.Bind(
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// func(user User) func(State) State {
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// return func(s State) State { s.User = user; return s }
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// },
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// func(s State) readerioeither.ReaderIOEither[User] {
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// return func(ctx context.Context) ioeither.IOEither[error, User] {
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// return ioeither.TryCatch(func() (User, error) {
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// return fetchUser(ctx)
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// })
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// }
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// },
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// ),
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// readerioeither.Bind(
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// func(cfg Config) func(State) State {
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// return func(s State) State { s.Config = cfg; return s }
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// },
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// func(s State) readerioeither.ReaderIOEither[Config] {
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// // This can access s.User from the previous step
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// return func(ctx context.Context) ioeither.IOEither[error, Config] {
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// return ioeither.TryCatch(func() (Config, error) {
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// return fetchConfigForUser(ctx, s.User.ID)
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// })
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// }
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// },
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// ),
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// )
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//
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//go:inline
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func Bind[S1, S2, T any](
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setter func(T) func(S1) S2,
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f Kleisli[S1, T],
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) Operator[S1, S2] {
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return chain.Bind(
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Chain[S1, S2],
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Map[T, S2],
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setter,
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f,
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)
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}
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// Let attaches the result of a computation to a context [S1] to produce a context [S2]
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//
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//go:inline
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func Let[S1, S2, T any](
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setter func(T) func(S1) S2,
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f func(S1) T,
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) Operator[S1, S2] {
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return functor.Let(
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Map[S1, S2],
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setter,
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f,
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)
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}
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// LetTo attaches the a value to a context [S1] to produce a context [S2]
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//
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//go:inline
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func LetTo[S1, S2, T any](
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setter func(T) func(S1) S2,
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b T,
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) Operator[S1, S2] {
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return functor.LetTo(
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Map[S1, S2],
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setter,
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b,
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)
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}
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// BindTo initializes a new state [S1] from a value [T]
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//
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//go:inline
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func BindTo[S1, T any](
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setter func(T) S1,
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) Operator[T, S1] {
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return chain.BindTo(
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Map[T, S1],
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setter,
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)
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}
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// ApS attaches a value to a context [S1] to produce a context [S2] by considering
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// the context and the value concurrently (using Applicative rather than Monad).
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// This allows independent computations to be combined without one depending on the result of the other.
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//
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// Unlike Bind, which sequences operations, ApS can be used when operations are independent
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// and can conceptually run in parallel.
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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//
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// // These operations are independent and can be combined with ApS
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// getUser := func(ctx context.Context) ioeither.IOEither[error, User] {
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// return ioeither.TryCatch(func() (User, error) {
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// return fetchUser(ctx)
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// })
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// }
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// getConfig := func(ctx context.Context) ioeither.IOEither[error, Config] {
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// return ioeither.TryCatch(func() (Config, error) {
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// return fetchConfig(ctx)
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// })
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// }
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//
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// result := F.Pipe2(
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// readerioeither.Do(State{}),
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// readerioeither.ApS(
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// func(user User) func(State) State {
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// return func(s State) State { s.User = user; return s }
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// },
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// getUser,
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// ),
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// readerioeither.ApS(
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// func(cfg Config) func(State) State {
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// return func(s State) State { s.Config = cfg; return s }
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// },
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// getConfig,
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// ),
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// )
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//
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//go:inline
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func ApS[S1, S2, T any](
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setter func(T) func(S1) S2,
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fa ReaderIOEither[T],
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) Operator[S1, S2] {
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return apply.ApS(
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Ap[S2, T],
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Map[S1, func(T) S2],
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setter,
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fa,
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)
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}
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// ApSL attaches a value to a context using a lens-based setter.
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// This is a convenience function that combines ApS with a lens, allowing you to use
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// optics to update nested structures in a more composable way.
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//
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// The lens parameter provides both the getter and setter for a field within the structure S.
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// This eliminates the need to manually write setter functions.
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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//
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// userLens := lens.MakeLens(
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// func(s State) User { return s.User },
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// func(s State, u User) State { s.User = u; return s },
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// )
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//
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// getUser := func(ctx context.Context) ioeither.IOEither[error, User] {
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// return ioeither.TryCatch(func() (User, error) {
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// return fetchUser(ctx)
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// })
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// }
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// result := F.Pipe2(
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// readerioeither.Of(State{}),
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// readerioeither.ApSL(userLens, getUser),
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// )
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//
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//go:inline
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func ApSL[S, T any](
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lens L.Lens[S, T],
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fa ReaderIOEither[T],
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) Operator[S, S] {
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return ApS(lens.Set, fa)
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}
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// BindL is a variant of Bind that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. The function f receives the current value of the focused field and
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// returns a ReaderIOEither computation that produces an updated value.
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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//
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// userLens := lens.MakeLens(
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// func(s State) User { return s.User },
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// func(s State, u User) State { s.User = u; return s },
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// )
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//
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// result := F.Pipe2(
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// readerioeither.Do(State{}),
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// readerioeither.BindL(userLens, func(user User) readerioeither.ReaderIOEither[User] {
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// return func(ctx context.Context) ioeither.IOEither[error, User] {
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// return ioeither.TryCatch(func() (User, error) {
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// return fetchUser(ctx)
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// })
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// }
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// }),
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// )
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//
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//go:inline
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func BindL[S, T any](
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lens L.Lens[S, T],
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f Kleisli[T, T],
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) Operator[S, S] {
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return Bind[S, S, T](lens.Set, func(s S) ReaderIOEither[T] {
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return f(lens.Get(s))
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})
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}
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// LetL is a variant of Let that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. The function f receives the current value of the focused field and
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// returns a new value (without wrapping in a ReaderIOEither).
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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//
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// userLens := lens.MakeLens(
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// func(s State) User { return s.User },
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// func(s State, u User) State { s.User = u; return s },
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// )
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//
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// result := F.Pipe2(
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// readerioeither.Do(State{User: User{Name: "Alice"}}),
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// readerioeither.LetL(userLens, func(user User) User {
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// user.Name = "Bob"
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// return user
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// }),
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// )
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//
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//go:inline
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func LetL[S, T any](
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lens L.Lens[S, T],
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f func(T) T,
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) Operator[S, S] {
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return Let[S, S, T](lens.Set, func(s S) T {
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return f(lens.Get(s))
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})
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}
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// LetToL is a variant of LetTo that uses a lens to focus on a specific part of the context.
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// This provides a more ergonomic API when working with nested structures, eliminating
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// the need to manually write setter functions.
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//
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// The lens parameter provides both a getter and setter for a field of type T within
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// the context S. The value b is set directly to the focused field.
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//
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// Example:
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//
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// type State struct {
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// User User
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// Config Config
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// }
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//
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// userLens := lens.MakeLens(
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// func(s State) User { return s.User },
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// func(s State, u User) State { s.User = u; return s },
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// )
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//
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// newUser := User{Name: "Bob", ID: 123}
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// result := F.Pipe2(
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// readerioeither.Do(State{}),
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// readerioeither.LetToL(userLens, newUser),
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// )
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//
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//go:inline
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func LetToL[S, T any](
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lens L.Lens[S, T],
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b T,
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) Operator[S, S] {
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return LetTo[S, S, T](lens.Set, b)
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}
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