fix: add missing MapLeft

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

.github/workflows/build.yml

@@ -17,8 +17,8 @@ on:
 env:
   # Currently no way to detect automatically
   DEFAULT_BRANCH: main
-  GO_VERSION: 1.20.6 # renovate: datasource=golang-version depName=golang
-  NODE_VERSION: 18
+  GO_VERSION: 1.21.6 # renovate: datasource=golang-version depName=golang
+  NODE_VERSION: 20
   DRY_RUN: true
 
 jobs:
@@ -26,7 +26,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: [ '1.20.x', '1.21.x' ]
+        go-version: [ '1.20.x', '1.21.x']
     steps:
       # full checkout for semantic-release
       - uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4.1.1

array/monoid.go

@@ -24,10 +24,10 @@ import (
 func concat[T any](left, right []T) []T {
 	// some performance checks
 	ll := len(left)
-	lr := len(right)
 	if ll == 0 {
 		return right
 	}
+	lr := len(right)
 	if lr == 0 {
 		return left
 	}

context/readerioeither/http/builder/builder.go

@@ -0,0 +1,72 @@
+// Copyright (c) 2023 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 builder
+
+import (
+	"bytes"
+	"context"
+	"net/http"
+	"strconv"
+
+	RIOE "github.com/IBM/fp-go/context/readerioeither"
+	RIOEH "github.com/IBM/fp-go/context/readerioeither/http"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	R "github.com/IBM/fp-go/http/builder"
+	H "github.com/IBM/fp-go/http/headers"
+	LZ "github.com/IBM/fp-go/lazy"
+	O "github.com/IBM/fp-go/option"
+)
+
+func Requester(builder *R.Builder) RIOEH.Requester {
+
+	withBody := F.Curry3(func(data []byte, url string, method string) RIOE.ReaderIOEither[*http.Request] {
+		return RIOE.TryCatch(func(ctx context.Context) func() (*http.Request, error) {
+			return func() (*http.Request, error) {
+				req, err := http.NewRequestWithContext(ctx, method, url, bytes.NewReader(data))
+				if err == nil {
+					req.Header.Set(H.ContentLength, strconv.Itoa(len(data)))
+					H.Monoid.Concat(req.Header, builder.GetHeaders())
+				}
+				return req, err
+			}
+		})
+	})
+
+	withoutBody := F.Curry2(func(url string, method string) RIOE.ReaderIOEither[*http.Request] {
+		return RIOE.TryCatch(func(ctx context.Context) func() (*http.Request, error) {
+			return func() (*http.Request, error) {
+				req, err := http.NewRequestWithContext(ctx, method, url, nil)
+				if err == nil {
+					H.Monoid.Concat(req.Header, builder.GetHeaders())
+				}
+				return req, err
+			}
+		})
+	})
+
+	return F.Pipe5(
+		builder.GetBody(),
+		O.Fold(LZ.Of(E.Of[error](withoutBody)), E.Map[error](withBody)),
+		E.Ap[func(string) RIOE.ReaderIOEither[*http.Request]](builder.GetTargetUrl()),
+		E.Flap[error, RIOE.ReaderIOEither[*http.Request]](builder.GetMethod()),
+		E.GetOrElse(RIOE.Left[*http.Request]),
+		RIOE.Map(func(req *http.Request) *http.Request {
+			req.Header = H.Monoid.Concat(req.Header, builder.GetHeaders())
+			return req
+		}),
+	)
+}

context/readerioeither/http/builder/builder_test.go

@@ -0,0 +1,59 @@
+// Copyright (c) 2023 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 builder
+
+import (
+	"context"
+	"net/http"
+	"net/url"
+	"testing"
+
+	RIOE "github.com/IBM/fp-go/context/readerioeither"
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	R "github.com/IBM/fp-go/http/builder"
+	IO "github.com/IBM/fp-go/io"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuilderWithQuery(t *testing.T) {
+	// add some query
+	withLimit := R.WithQueryArg("limit")("10")
+	withUrl := R.WithUrl("http://www.example.org?a=b")
+
+	b := F.Pipe2(
+		R.Default,
+		withLimit,
+		withUrl,
+	)
+
+	req := F.Pipe3(
+		b,
+		Requester,
+		RIOE.Map(func(r *http.Request) *url.URL {
+			return r.URL
+		}),
+		RIOE.ChainFirstIOK(func(u *url.URL) IO.IO[any] {
+			return IO.FromImpure(func() {
+				q := u.Query()
+				assert.Equal(t, "10", q.Get("limit"))
+				assert.Equal(t, "b", q.Get("a"))
+			})
+		}),
+	)
+
+	assert.True(t, E.IsRight(req(context.Background())()))
+}

either/either.go

@@ -67,16 +67,17 @@ func MapTo[E, A, B any](b B) func(Either[E, A]) Either[E, B] {
 	return F.Bind2nd(MonadMapTo[E, A, B], b)
 }
 
-func MonadMapLeft[E, A, B any](fa Either[E, A], f func(E) B) Either[B, A] {
-	return MonadFold(fa, F.Flow2(f, Left[A, B]), Right[B, A])
+func MonadMapLeft[E1, A, E2 any](fa Either[E1, A], f func(E1) E2) Either[E2, A] {
+	return MonadFold(fa, F.Flow2(f, Left[A, E2]), Right[E2, A])
 }
 
 func Map[E, A, B any](f func(a A) B) func(fa Either[E, A]) Either[E, B] {
 	return Chain(F.Flow2(f, Right[E, B]))
 }
 
-func MapLeft[E, A, B any](f func(E) B) func(fa Either[E, A]) Either[B, A] {
-	return F.Bind2nd(MonadMapLeft[E, A, B], f)
+// MapLeft applies a mapping function to the error channel
+func MapLeft[A, E1, E2 any](f func(E1) E2) func(fa Either[E1, A]) Either[E2, A] {
+	return F.Bind2nd(MonadMapLeft[E1, A, E2], f)
 }
 
 func MonadChain[E, A, B any](fa Either[E, A], f func(a A) Either[E, B]) Either[E, B] {

endomorphism/generic/monoid.go

@@ -28,6 +28,16 @@ func Of[ENDO ~func(A) A, F ~func(A) A, A any](f F) ENDO {
 	}
 }
 
+// Wrap converts any function to an [Endomorphism]
+func Wrap[ENDO ~func(A) A, F ~func(A) A, A any](f F) ENDO {
+	return Of[ENDO](f)
+}
+
+// Unwrap converts any [Endomorphism] to a normal function
+func Unwrap[F ~func(A) A, ENDO ~func(A) A, A any](f ENDO) F {
+	return Of[F](f)
+}
+
 func Identity[ENDO ~func(A) A, A any]() ENDO {
 	return Of[ENDO](F.Identity[A])
 }

endomorphism/monoid.go

@@ -29,6 +29,16 @@ func Of[F ~func(A) A, A any](f F) Endomorphism[A] {
 	return G.Of[Endomorphism[A]](f)
 }
 
+// Wrap converts any function to an [Endomorphism]
+func Wrap[F ~func(A) A, A any](f F) Endomorphism[A] {
+	return G.Wrap[Endomorphism[A]](f)
+}
+
+// Unwrap converts any [Endomorphism] to a function
+func Unwrap[F ~func(A) A, A any](f Endomorphism[A]) F {
+	return G.Unwrap[F](f)
+}
+
 // Identity returns the identity [Endomorphism]
 func Identity[A any]() Endomorphism[A] {
 	return G.Identity[Endomorphism[A]]()

http/builder/builder.go

@@ -0,0 +1,311 @@
+// Copyright (c) 2023 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 builder
+
+import (
+	"net/http"
+	"net/url"
+
+	E "github.com/IBM/fp-go/either"
+	ENDO "github.com/IBM/fp-go/endomorphism"
+	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/http/content"
+	FM "github.com/IBM/fp-go/http/form"
+	H "github.com/IBM/fp-go/http/headers"
+	J "github.com/IBM/fp-go/json"
+	LZ "github.com/IBM/fp-go/lazy"
+	L "github.com/IBM/fp-go/optics/lens"
+	O "github.com/IBM/fp-go/option"
+	S "github.com/IBM/fp-go/string"
+	T "github.com/IBM/fp-go/tuple"
+)
+
+type (
+	Builder struct {
+		method  O.Option[string]
+		url     string
+		headers http.Header
+		body    O.Option[E.Either[error, []byte]]
+		query   url.Values
+	}
+
+	// Endomorphism returns an [ENDO.Endomorphism] that transforms a builder
+	Endomorphism = ENDO.Endomorphism[*Builder]
+)
+
+var (
+	// Default is the default builder
+	Default = &Builder{method: O.Some(defaultMethod()), headers: make(http.Header), body: noBody}
+
+	defaultMethod = F.Constant(http.MethodGet)
+
+	// Monoid is the [M.Monoid] for the [Endomorphism]
+	Monoid = ENDO.Monoid[*Builder]()
+
+	// Url is a [L.Lens] for the URL
+	Url = L.MakeLensRef((*Builder).GetUrl, (*Builder).SetUrl)
+	// Method is a [L.Lens] for the HTTP method
+	Method = L.MakeLensRef((*Builder).GetMethod, (*Builder).SetMethod)
+	// Body is a [L.Lens] for the request body
+	Body = L.MakeLensRef((*Builder).GetBody, (*Builder).SetBody)
+	// Headers is a [L.Lens] for the complete set of request headers
+	Headers = L.MakeLensRef((*Builder).GetHeaders, (*Builder).SetHeaders)
+	// Query is a [L.Lens] for the set of query parameters
+	Query = L.MakeLensRef((*Builder).GetQuery, (*Builder).SetQuery)
+
+	rawQuery = L.MakeLensRef(getRawQuery, setRawQuery)
+
+	getHeader = F.Bind2of2((*Builder).GetHeader)
+	delHeader = F.Bind2of2((*Builder).DelHeader)
+	setHeader = F.Bind2of3((*Builder).SetHeader)
+
+	noHeader   = O.None[string]()
+	noBody     = O.None[E.Either[error, []byte]]()
+	noQueryArg = O.None[string]()
+
+	parseUrl   = E.Eitherize1(url.Parse)
+	parseQuery = E.Eitherize1(url.ParseQuery)
+
+	// WithQuery creates a [Endomorphism] for a complete set of query parameters
+	WithQuery = Query.Set
+	// WithMethod creates a [Endomorphism] for a certain method
+	WithMethod = Method.Set
+	// WithUrl creates a [Endomorphism] for a certain method
+	WithUrl = Url.Set
+	// WithHeaders creates a [Endomorphism] for a set of headers
+	WithHeaders = Headers.Set
+	// WithBody creates a [Endomorphism] for a request body
+	WithBody = F.Flow2(
+		O.Of[E.Either[error, []byte]],
+		Body.Set,
+	)
+	// WithBytes creates a [Endomorphism] for a request body using bytes
+	WithBytes = F.Flow2(
+		E.Of[error, []byte],
+		WithBody,
+	)
+	// WithContentType adds the [H.ContentType] header
+	WithContentType = WithHeader(H.ContentType)
+	// WithAuthorization adds the [H.Authorization] header
+	WithAuthorization = WithHeader(H.Authorization)
+
+	// WithGet adds the [http.MethodGet] method
+	WithGet = WithMethod(http.MethodGet)
+	// WithPost adds the [http.MethodPost] method
+	WithPost = WithMethod(http.MethodPost)
+	// WithPut adds the [http.MethodPut] method
+	WithPut = WithMethod(http.MethodPut)
+	// WithDelete adds the [http.MethodDelete] method
+	WithDelete = WithMethod(http.MethodDelete)
+
+	// WithBearer creates a [Endomorphism] to add a Bearer [H.Authorization] header
+	WithBearer = F.Flow2(
+		S.Format[string]("Bearer %s"),
+		WithAuthorization,
+	)
+
+	// WithoutBody creates a [Endomorphism] to remove the body
+	WithoutBody = F.Pipe1(
+		noBody,
+		Body.Set,
+	)
+
+	// WithFormData creates a [Endomorphism] to send form data payload
+	WithFormData = F.Flow4(
+		url.Values.Encode,
+		S.ToBytes,
+		WithBytes,
+		ENDO.Chain(WithContentType(C.FormEncoded)),
+	)
+)
+
+func setRawQuery(u *url.URL, raw string) *url.URL {
+	u.RawQuery = raw
+	return u
+}
+
+func getRawQuery(u *url.URL) string {
+	return u.RawQuery
+}
+
+func (builder *Builder) clone() *Builder {
+	cpy := *builder
+	cpy.headers = cpy.headers.Clone()
+	return &cpy
+}
+
+// GetTargetUrl constructs a full URL with query parameters on top of the provided URL string
+func (builder *Builder) GetTargetUrl() E.Either[error, string] {
+	// construct the final URL
+	return F.Pipe3(
+		builder,
+		Url.Get,
+		parseUrl,
+		E.Chain(F.Flow4(
+			T.Replicate2[*url.URL],
+			T.Map2(
+				F.Flow2(
+					F.Curry2(setRawQuery),
+					E.Of[error, func(string) *url.URL],
+				),
+				F.Flow3(
+					rawQuery.Get,
+					parseQuery,
+					E.Map[error](F.Flow2(
+						F.Curry2(FM.ValuesMonoid.Concat)(builder.GetQuery()),
+						(url.Values).Encode,
+					)),
+				),
+			),
+			T.Tupled2(E.MonadAp[*url.URL, error, string]),
+			E.Map[error]((*url.URL).String),
+		)),
+	)
+}
+
+func (builder *Builder) GetUrl() string {
+	return builder.url
+}
+
+func (builder *Builder) GetMethod() string {
+	return F.Pipe1(
+		builder.method,
+		O.GetOrElse(defaultMethod),
+	)
+}
+
+func (builder *Builder) GetHeaders() http.Header {
+	return builder.headers
+}
+
+func (builder *Builder) GetQuery() url.Values {
+	return builder.query
+}
+
+func (builder *Builder) SetQuery(query url.Values) *Builder {
+	builder.query = query
+	return builder
+}
+
+func (builder *Builder) GetBody() O.Option[E.Either[error, []byte]] {
+	return builder.body
+}
+
+func (builder *Builder) SetMethod(method string) *Builder {
+	builder.method = O.Some(method)
+	return builder
+}
+
+func (builder *Builder) SetUrl(url string) *Builder {
+	builder.url = url
+	return builder
+}
+
+func (builder *Builder) SetHeaders(headers http.Header) *Builder {
+	builder.headers = headers
+	return builder
+}
+
+func (builder *Builder) SetBody(body O.Option[E.Either[error, []byte]]) *Builder {
+	builder.body = body
+	return builder
+}
+
+func (builder *Builder) SetHeader(name, value string) *Builder {
+	builder.headers.Set(name, value)
+	return builder
+}
+
+func (builder *Builder) DelHeader(name string) *Builder {
+	builder.headers.Del(name)
+	return builder
+}
+
+func (builder *Builder) GetHeader(name string) O.Option[string] {
+	return F.Pipe2(
+		name,
+		builder.headers.Get,
+		O.FromPredicate(S.IsNonEmpty),
+	)
+}
+
+func (builder *Builder) GetHeaderValues(name string) []string {
+	return builder.headers.Values(name)
+}
+
+// Header returns a [L.Lens] for a single header
+func Header(name string) L.Lens[*Builder, O.Option[string]] {
+	get := getHeader(name)
+	set := F.Bind1of2(setHeader(name))
+	del := F.Flow2(
+		LZ.Of[*Builder],
+		LZ.Map(delHeader(name)),
+	)
+
+	return L.MakeLens(get, func(b *Builder, value O.Option[string]) *Builder {
+		cpy := b.clone()
+		return F.Pipe1(
+			value,
+			O.Fold(del(cpy), set(cpy)),
+		)
+	})
+}
+
+// WithHeader creates a [Endomorphism] for a certain header
+func WithHeader(name string) func(value string) Endomorphism {
+	return F.Flow2(
+		O.Of[string],
+		Header(name).Set,
+	)
+}
+
+// WithoutHeader creates a [Endomorphism] to remove a certain header
+func WithoutHeader(name string) Endomorphism {
+	return Header(name).Set(noHeader)
+}
+
+// WithJson creates a [Endomorphism] to send JSON payload
+func WithJson[T any](data T) Endomorphism {
+	return Monoid.Concat(
+		F.Pipe2(
+			data,
+			J.Marshal[T],
+			WithBody,
+		),
+		WithContentType(C.Json),
+	)
+}
+
+// QueryArg is a [L.Lens] for the first value of a query argument
+func QueryArg(name string) L.Lens[*Builder, O.Option[string]] {
+	return F.Pipe1(
+		Query,
+		L.Compose[*Builder](FM.AtValue(name)),
+	)
+}
+
+// WithQueryArg creates a [Endomorphism] for a certain query argument
+func WithQueryArg(name string) func(value string) Endomorphism {
+	return F.Flow2(
+		O.Of[string],
+		QueryArg(name).Set,
+	)
+}
+
+// WithoutQueryArg creates a [Endomorphism] that removes a query argument
+func WithoutQueryArg(name string) Endomorphism {
+	return QueryArg(name).Set(noQueryArg)
+}

http/builder/builder_test.go

@@ -0,0 +1,68 @@
+// Copyright (c) 2023 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 builder
+
+import (
+	"testing"
+
+	F "github.com/IBM/fp-go/function"
+	C "github.com/IBM/fp-go/http/content"
+	FD "github.com/IBM/fp-go/http/form"
+	H "github.com/IBM/fp-go/http/headers"
+	O "github.com/IBM/fp-go/option"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestBuilder(t *testing.T) {
+
+	name := H.ContentType
+	withContentType := WithHeader(name)
+	withoutContentType := WithoutHeader(name)
+
+	b1 := F.Pipe1(
+		Default,
+		withContentType(C.Json),
+	)
+
+	b2 := F.Pipe1(
+		b1,
+		withContentType(C.TextPlain),
+	)
+
+	b3 := F.Pipe1(
+		b2,
+		withoutContentType,
+	)
+
+	assert.Equal(t, O.None[string](), Default.GetHeader(name))
+	assert.Equal(t, O.Of(C.Json), b1.GetHeader(name))
+	assert.Equal(t, O.Of(C.TextPlain), b2.GetHeader(name))
+	assert.Equal(t, O.None[string](), b3.GetHeader(name))
+}
+
+func TestWithFormData(t *testing.T) {
+	data := F.Pipe1(
+		FD.Default,
+		FD.WithValue("a")("b"),
+	)
+
+	res := F.Pipe1(
+		Default,
+		WithFormData(data),
+	)
+
+	assert.Equal(t, C.FormEncoded, Headers.Get(res).Get(H.ContentType))
+}

io/generic/io.go

@@ -133,6 +133,29 @@ func Delay[GA ~func() A, A any](delay time.Duration) func(GA) GA {
 	}
 }
 
+func after(timestamp time.Time) func() {
+	return func() {
+		// check if we need to wait
+		current := time.Now()
+		if current.Before(timestamp) {
+			time.Sleep(timestamp.Sub(current))
+		}
+	}
+}
+
+// After creates an operation that passes after the given timestamp
+func After[GA ~func() A, A any](timestamp time.Time) func(GA) GA {
+	aft := after(timestamp)
+	return func(ga GA) GA {
+		return MakeIO[GA](func() A {
+			// wait as long as necessary
+			aft()
+			// execute after wait
+			return ga()
+		})
+	}
+}
+
 // Now returns the current timestamp
 func Now[GA ~func() time.Time]() GA {
 	return MakeIO[GA](time.Now)

io/io.go

@@ -146,3 +146,13 @@ func MonadFlap[B, A any](fab IO[func(A) B], a A) IO[B] {
 func Flap[FAB ~func(A) B, GFAB ~func() FAB, GB ~func() B, A, B any](a A) func(IO[func(A) B]) IO[B] {
 	return G.Flap[func(A) B, IO[func(A) B], IO[B], A, B](a)
 }
+
+// Delay creates an operation that passes in the value after some delay
+func Delay[A any](delay time.Duration) func(IO[A]) IO[A] {
+	return G.Delay[IO[A]](delay)
+}
+
+// After creates an operation that passes after the given timestamp
+func After[A any](timestamp time.Time) func(IO[A]) IO[A] {
+	return G.After[IO[A]](timestamp)
+}

ioeither/generic/ioeither.go

@@ -207,11 +207,16 @@ func MapLeft[GA1 ~func() ET.Either[E1, A], GA2 ~func() ET.Either[E2, A], E1, E2,
 	return F.Bind2nd(MonadMapLeft[GA1, GA2, E1, E2, A], f)
 }
 
-// Delay creates an operation that passes in the value after some delay
+// Delay creates an operation that passes in the value after some [time.Duration]
 func Delay[GA ~func() ET.Either[E, A], E, A any](delay time.Duration) func(GA) GA {
 	return IO.Delay[GA](delay)
 }
 
+// After creates an operation that passes after the given [time.Time]
+func After[GA ~func() ET.Either[E, A], E, A any](timestamp time.Time) func(GA) GA {
+	return IO.After[GA](timestamp)
+}
+
 func MonadBiMap[GA ~func() ET.Either[E1, A], GB ~func() ET.Either[E2, B], E1, E2, A, B any](fa GA, f func(E1) E2, g func(A) B) GB {
 	return eithert.MonadBiMap(IO.MonadMap[GA, GB, ET.Either[E1, A], ET.Either[E2, B]], fa, f, g)
 }

ioeither/generic/logging.go

@@ -0,0 +1,43 @@
+// Copyright (c) 2023 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 generic
+
+import (
+	"encoding/json"
+	"log"
+
+	B "github.com/IBM/fp-go/bytes"
+	ET "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+)
+
+// LogJson converts the argument to JSON and then logs it via the format string
+// Can be used with [ChainFirst]
+func LogJson[GA ~func() ET.Either[error, any], A any](prefix string) func(A) GA {
+	return func(a A) GA {
+		// log this
+		return F.Pipe3(
+			ET.TryCatchError(json.MarshalIndent(a, "", "  ")),
+			ET.Map[error](B.ToString),
+			FromEither[func() ET.Either[error, string]],
+			Chain[func() ET.Either[error, string], GA](func(data string) GA {
+				return FromImpure[GA](func() {
+					log.Printf(prefix, data)
+				})
+			}),
+		)
+	}
+}

ioeither/http/builder/builder.go

@@ -18,213 +18,26 @@ package builder
 import (
 	"bytes"
 	"net/http"
-	"net/url"
 	"strconv"
 
 	E "github.com/IBM/fp-go/either"
-	ENDO "github.com/IBM/fp-go/endomorphism"
 	F "github.com/IBM/fp-go/function"
-	C "github.com/IBM/fp-go/http/content"
-	FM "github.com/IBM/fp-go/http/form"
+	R "github.com/IBM/fp-go/http/builder"
 	H "github.com/IBM/fp-go/http/headers"
-	IOG "github.com/IBM/fp-go/io/generic"
 	IOE "github.com/IBM/fp-go/ioeither"
 	IOEH "github.com/IBM/fp-go/ioeither/http"
-	J "github.com/IBM/fp-go/json"
 	LZ "github.com/IBM/fp-go/lazy"
-	L "github.com/IBM/fp-go/optics/lens"
 	O "github.com/IBM/fp-go/option"
-	S "github.com/IBM/fp-go/string"
-	T "github.com/IBM/fp-go/tuple"
 )
 
-type (
-	Builder struct {
-		method  O.Option[string]
-		url     string
-		headers http.Header
-		body    O.Option[IOE.IOEither[error, []byte]]
-		query   url.Values
-	}
-
-	// Endomorphism returns an [ENDO.Endomorphism] that transforms a builder
-	Endomorphism = ENDO.Endomorphism[*Builder]
-)
-
-var (
-	// Default is the default builder
-	Default = &Builder{method: O.Some(defaultMethod()), headers: make(http.Header), body: noBody}
-
-	defaultMethod = F.Constant(http.MethodGet)
-
-	// Monoid is the [M.Monoid] for the [Endomorphism]
-	Monoid = ENDO.Monoid[*Builder]()
-
-	// Url is a [L.Lens] for the URL
-	Url = L.MakeLensRef((*Builder).GetUrl, (*Builder).SetUrl)
-	// Method is a [L.Lens] for the HTTP method
-	Method = L.MakeLensRef((*Builder).GetMethod, (*Builder).SetMethod)
-	// Body is a [L.Lens] for the request body
-	Body = L.MakeLensRef((*Builder).GetBody, (*Builder).SetBody)
-	// Headers is a [L.Lens] for the complete set of request headers
-	Headers = L.MakeLensRef((*Builder).GetHeaders, (*Builder).SetHeaders)
-	// Query is a [L.Lens] for the set of query parameters
-	Query = L.MakeLensRef((*Builder).GetQuery, (*Builder).SetQuery)
-
-	rawQuery = L.MakeLensRef(getRawQuery, setRawQuery)
-
-	getHeader = F.Bind2of2((*Builder).GetHeader)
-	delHeader = F.Bind2of2((*Builder).DelHeader)
-	setHeader = F.Bind2of3((*Builder).SetHeader)
-
-	noHeader   = O.None[string]()
-	noBody     = O.None[IOE.IOEither[error, []byte]]()
-	noQueryArg = O.None[string]()
-
-	parseUrl   = E.Eitherize1(url.Parse)
-	parseQuery = E.Eitherize1(url.ParseQuery)
-
-	// WithQuery creates a [Endomorphism] for a complete set of query parameters
-	WithQuery = Query.Set
-	// WithMethod creates a [Endomorphism] for a certain method
-	WithMethod = Method.Set
-	// WithUrl creates a [Endomorphism] for a certain method
-	WithUrl = Url.Set
-	// WithHeaders creates a [Endomorphism] for a set of headers
-	WithHeaders = Headers.Set
-	// WithBody creates a [Endomorphism] for a request body
-	WithBody = F.Flow2(
-		O.Of[IOE.IOEither[error, []byte]],
-		Body.Set,
-	)
-	// WithBytes creates a [Endomorphism] for a request body using bytes
-	WithBytes = F.Flow2(
-		IOE.Of[error, []byte],
-		WithBody,
-	)
-	// WithContentType adds the [H.ContentType] header
-	WithContentType = WithHeader(H.ContentType)
-	// WithAuthorization adds the [H.Authorization] header
-	WithAuthorization = WithHeader(H.Authorization)
-
-	// WithGet adds the [http.MethodGet] method
-	WithGet = WithMethod(http.MethodGet)
-	// WithPost adds the [http.MethodPost] method
-	WithPost = WithMethod(http.MethodPost)
-	// WithPut adds the [http.MethodPut] method
-	WithPut = WithMethod(http.MethodPut)
-	// WithDelete adds the [http.MethodDelete] method
-	WithDelete = WithMethod(http.MethodDelete)
-
-	// WithBearer creates a [Endomorphism] to add a Bearer [H.Authorization] header
-	WithBearer = F.Flow2(
-		S.Format[string]("Bearer %s"),
-		WithAuthorization,
-	)
-
-	// Requester creates a requester from a builder
-	Requester = (*Builder).Requester
-
-	// WithoutBody creates a [Endomorphism] to remove the body
-	WithoutBody = F.Pipe1(
-		noBody,
-		Body.Set,
-	)
-)
-
-func setRawQuery(u *url.URL, raw string) *url.URL {
-	u.RawQuery = raw
-	return u
-}
-
-func getRawQuery(u *url.URL) string {
-	return u.RawQuery
-}
-
-func (builder *Builder) clone() *Builder {
-	cpy := *builder
-	cpy.headers = cpy.headers.Clone()
-	return &cpy
-}
-
-func (builder *Builder) GetUrl() string {
-	return builder.url
-}
-
-func (builder *Builder) GetMethod() string {
-	return F.Pipe1(
-		builder.method,
-		O.GetOrElse(defaultMethod),
-	)
-}
-
-func (builder *Builder) GetHeaders() http.Header {
-	return builder.headers
-}
-
-func (builder *Builder) GetQuery() url.Values {
-	return builder.query
-}
-
-func (builder *Builder) SetQuery(query url.Values) *Builder {
-	builder.query = query
-	return builder
-}
-
-func (builder *Builder) GetBody() O.Option[IOE.IOEither[error, []byte]] {
-	return builder.body
-}
-
-func (builder *Builder) SetMethod(method string) *Builder {
-	builder.method = O.Some(method)
-	return builder
-}
-
-func (builder *Builder) SetUrl(url string) *Builder {
-	builder.url = url
-	return builder
-}
-
-func (builder *Builder) SetHeaders(headers http.Header) *Builder {
-	builder.headers = headers
-	return builder
-}
-
-func (builder *Builder) SetBody(body O.Option[IOE.IOEither[error, []byte]]) *Builder {
-	builder.body = body
-	return builder
-}
-
-func (builder *Builder) SetHeader(name, value string) *Builder {
-	builder.headers.Set(name, value)
-	return builder
-}
-
-func (builder *Builder) DelHeader(name string) *Builder {
-	builder.headers.Del(name)
-	return builder
-}
-
-func (builder *Builder) GetHeader(name string) O.Option[string] {
-	return F.Pipe2(
-		name,
-		builder.headers.Get,
-		O.FromPredicate(S.IsNonEmpty),
-	)
-}
-
-func (builder *Builder) GetHeaderValues(name string) []string {
-	return builder.headers.Values(name)
-}
-
-func (builder *Builder) Requester() IOEH.Requester {
+func Requester(builder *R.Builder) IOEH.Requester {
 
 	withBody := F.Curry3(func(data []byte, url string, method string) IOE.IOEither[error, *http.Request] {
 		return IOE.TryCatchError(func() (*http.Request, error) {
 			req, err := http.NewRequest(method, url, bytes.NewReader(data))
 			if err == nil {
 				req.Header.Set(H.ContentLength, strconv.Itoa(len(data)))
-				H.Monoid.Concat(req.Header, builder.headers)
+				H.Monoid.Concat(req.Header, builder.GetHeaders())
 			}
 			return req, err
 		})
@@ -234,123 +47,21 @@ func (builder *Builder) Requester() IOEH.Requester {
 		return IOE.TryCatchError(func() (*http.Request, error) {
 			req, err := http.NewRequest(method, url, nil)
 			if err == nil {
-				H.Monoid.Concat(req.Header, builder.headers)
+				H.Monoid.Concat(req.Header, builder.GetHeaders())
 			}
 			return req, err
 		})
 	})
 
-	// construct the final URL
-	targetUrl := F.Pipe3(
-		builder,
-		Url.Get,
-		parseUrl,
-		E.Chain(F.Flow4(
-			T.Replicate2[*url.URL],
-			T.Map2(
-				F.Flow2(
-					F.Curry2(setRawQuery),
-					E.Of[error, func(string) *url.URL],
-				),
-				F.Flow3(
-					rawQuery.Get,
-					parseQuery,
-					E.Map[error](F.Flow2(
-						F.Curry2(FM.ValuesMonoid.Concat)(builder.GetQuery()),
-						(url.Values).Encode,
-					)),
-				),
-			),
-			T.Tupled2(E.MonadAp[*url.URL, error, string]),
-			E.Map[error]((*url.URL).String),
-		)),
-	)
-
 	return F.Pipe5(
-		builder,
-		Body.Get,
-		O.Fold(LZ.Of(IOE.Of[error](withoutBody)), IOE.Map[error](withBody)),
-		IOG.Map[IOE.IOEither[error, func(string) func(string) IOE.IOEither[error, *http.Request]], IOE.IOEither[error, func(string) IOE.IOEither[error, *http.Request]]](E.Ap[func(string) IOE.IOEither[error, *http.Request]](targetUrl)),
-		IOE.Flap[error, IOE.IOEither[error, *http.Request]](builder.GetMethod()),
-		IOE.Flatten[error, *http.Request],
+		builder.GetBody(),
+		O.Fold(LZ.Of(E.Of[error](withoutBody)), E.Map[error](withBody)),
+		E.Ap[func(string) IOE.IOEither[error, *http.Request]](builder.GetTargetUrl()),
+		E.Flap[error, IOE.IOEither[error, *http.Request]](builder.GetMethod()),
+		E.GetOrElse(IOE.Left[*http.Request, error]),
+		IOE.Map[error](func(req *http.Request) *http.Request {
+			req.Header = H.Monoid.Concat(req.Header, builder.GetHeaders())
+			return req
+		}),
 	)
 }
-
-// Header returns a [L.Lens] for a single header
-func Header(name string) L.Lens[*Builder, O.Option[string]] {
-	get := getHeader(name)
-	set := F.Bind1of2(setHeader(name))
-	del := F.Flow2(
-		LZ.Of[*Builder],
-		LZ.Map(delHeader(name)),
-	)
-
-	return L.MakeLens(get, func(b *Builder, value O.Option[string]) *Builder {
-		cpy := b.clone()
-		return F.Pipe1(
-			value,
-			O.Fold(del(cpy), set(cpy)),
-		)
-	})
-}
-
-// WithHeader creates a [Endomorphism] for a certain header
-func WithHeader(name string) func(value string) Endomorphism {
-	return F.Flow2(
-		O.Of[string],
-		Header(name).Set,
-	)
-}
-
-// WithoutHeader creates a [Endomorphism] to remove a certain header
-func WithoutHeader(name string) Endomorphism {
-	return Header(name).Set(noHeader)
-}
-
-// WithFormData creates a [Endomorphism] to send form data payload
-func WithFormData(value url.Values) Endomorphism {
-	return F.Flow2(
-		F.Pipe4(
-			value,
-			url.Values.Encode,
-			S.ToBytes,
-			IOE.Of[error, []byte],
-			WithBody,
-		),
-		WithContentType(C.FormEncoded),
-	)
-}
-
-// WithJson creates a [Endomorphism] to send JSON payload
-func WithJson[T any](data T) Endomorphism {
-	return F.Flow2(
-		F.Pipe3(
-			data,
-			J.Marshal[T],
-			IOE.FromEither[error, []byte],
-			WithBody,
-		),
-		WithContentType(C.Json),
-	)
-}
-
-// QueryArg is a [L.Lens] for the first value of a query argument
-func QueryArg(name string) L.Lens[*Builder, O.Option[string]] {
-	return F.Pipe1(
-		Query,
-		L.Compose[*Builder](FM.AtValue(name)),
-	)
-}
-
-// WithQueryArg creates a [Endomorphism] for a certain query argument
-func WithQueryArg(name string) func(value string) Endomorphism {
-	return F.Flow2(
-		O.Of[string],
-		QueryArg(name).Set,
-	)
-}
-
-// WithoutQueryArg creates a [Endomorphism] that removes a query argument
-func WithoutQueryArg(name string) Endomorphism {
-	return QueryArg(name).Set(noQueryArg)
-}

ioeither/http/builder/builder_test.go

@@ -22,54 +22,26 @@ import (
 
 	E "github.com/IBM/fp-go/either"
 	F "github.com/IBM/fp-go/function"
-	C "github.com/IBM/fp-go/http/content"
-	H "github.com/IBM/fp-go/http/headers"
+	R "github.com/IBM/fp-go/http/builder"
 	IO "github.com/IBM/fp-go/io"
 	IOE "github.com/IBM/fp-go/ioeither"
-	O "github.com/IBM/fp-go/option"
 	"github.com/stretchr/testify/assert"
 )
 
-func TestBuilder(t *testing.T) {
-
-	name := H.ContentType
-	withContentType := WithHeader(name)
-	withoutContentType := WithoutHeader(name)
-
-	b1 := F.Pipe1(
-		Default,
-		withContentType(C.Json),
-	)
-
-	b2 := F.Pipe1(
-		b1,
-		withContentType(C.TextPlain),
-	)
-
-	b3 := F.Pipe1(
-		b2,
-		withoutContentType,
-	)
-
-	assert.Equal(t, O.None[string](), Default.GetHeader(name))
-	assert.Equal(t, O.Of(C.Json), b1.GetHeader(name))
-	assert.Equal(t, O.Of(C.TextPlain), b2.GetHeader(name))
-	assert.Equal(t, O.None[string](), b3.GetHeader(name))
-}
-
 func TestBuilderWithQuery(t *testing.T) {
 	// add some query
-	withLimit := WithQueryArg("limit")("10")
-	withUrl := WithUrl("http://www.example.org?a=b")
+	withLimit := R.WithQueryArg("limit")("10")
+	withUrl := R.WithUrl("http://www.example.org?a=b")
 
 	b := F.Pipe2(
-		Default,
+		R.Default,
 		withLimit,
 		withUrl,
 	)
 
-	req := F.Pipe2(
-		b.Requester(),
+	req := F.Pipe3(
+		b,
+		Requester,
 		IOE.Map[error](func(r *http.Request) *url.URL {
 			return r.URL
 		}),

ioeither/ioeither.go

@@ -16,6 +16,8 @@
 package ioeither
 
 import (
+	"time"
+
 	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
 	G "github.com/IBM/fp-go/ioeither/generic"
@@ -173,7 +175,7 @@ func MonadMapLeft[E1, E2, A any](fa IOEither[E1, A], f func(E1) E2) IOEither[E2,
 	return G.MonadMapLeft[IOEither[E1, A], IOEither[E2, A]](fa, f)
 }
 
-func MapLeft[E1, E2, A any](f func(E1) E2) func(IOEither[E1, A]) IOEither[E2, A] {
+func MapLeft[A, E1, E2 any](f func(E1) E2) func(IOEither[E1, A]) IOEither[E2, A] {
 	return G.MapLeft[IOEither[E1, A], IOEither[E2, A]](f)
 }
 
@@ -276,3 +278,13 @@ func Flap[E, B, A any](a A) func(IOEither[E, func(A) B]) IOEither[E, B] {
 func ToIOOption[E, A any](ioe IOEither[E, A]) IOO.IOOption[A] {
 	return G.ToIOOption[IOO.IOOption[A]](ioe)
 }
+
+// Delay creates an operation that passes in the value after some delay
+func Delay[E, A any](delay time.Duration) func(IOEither[E, A]) IOEither[E, A] {
+	return G.Delay[IOEither[E, A]](delay)
+}
+
+// After creates an operation that passes after the given [time.Time]
+func After[E, A any](timestamp time.Time) func(IOEither[E, A]) IOEither[E, A] {
+	return G.After[IOEither[E, A]](timestamp)
+}

ioeither/logging.go

@@ -0,0 +1,26 @@
+// Copyright (c) 2023 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 ioeither
+
+import (
+	G "github.com/IBM/fp-go/ioeither/generic"
+)
+
+// LogJson converts the argument to pretty printed JSON and then logs it via the format string
+// Can be used with [ChainFirst]
+func LogJson[A any](prefix string) func(A) IOEither[error, any] {
+	return G.LogJson[IOEither[error, any], A](prefix)
+}

ioeither/logging_test.go

@@ -0,0 +1,42 @@
+// Copyright (c) 2023 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 ioeither
+
+import (
+	"testing"
+
+	E "github.com/IBM/fp-go/either"
+	F "github.com/IBM/fp-go/function"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestLogging(t *testing.T) {
+
+	type SomeData struct {
+		Key   string `json:"key"`
+		Value string `json:"value"`
+	}
+
+	src := &SomeData{Key: "key", Value: "value"}
+
+	res := F.Pipe1(
+		Of[error](src),
+		ChainFirst(LogJson[*SomeData]("Data: \n%s")),
+	)
+
+	dst := res()
+	assert.Equal(t, E.Of[error](src), dst)
+}

iooption/generic/iooption.go

@@ -219,6 +219,11 @@ func Delay[GA ~func() O.Option[A], A any](delay time.Duration) func(GA) GA {
 	return IO.Delay[GA](delay)
 }
 
+// After creates an operation that passes after the given [time.Time]
+func After[GA ~func() O.Option[A], A any](timestamp time.Time) func(GA) GA {
+	return IO.After[GA](timestamp)
+}
+
 // Fold convers an IOOption into an IO
 func Fold[GA ~func() O.Option[A], GB ~func() B, A, B any](onNone func() GB, onSome func(A) GB) func(GA) GB {
 	return optiont.MatchE(IO.MonadChain[GA, GB, O.Option[A], B], onNone, onSome)

iooption/iooption.go

@@ -16,6 +16,8 @@
 package iooption
 
 import (
+	"time"
+
 	ET "github.com/IBM/fp-go/either"
 	I "github.com/IBM/fp-go/io"
 	IO "github.com/IBM/fp-go/io"
@@ -164,3 +166,13 @@ func MonadChainFirstIOK[A, B any](first IOOption[A], f func(A) IO.IO[B]) IOOptio
 func ChainFirstIOK[A, B any](f func(A) IO.IO[B]) func(IOOption[A]) IOOption[A] {
 	return G.ChainFirstIOK[IOOption[A], IO.IO[B]](f)
 }
+
+// Delay creates an operation that passes in the value after some delay
+func Delay[A any](delay time.Duration) func(IOOption[A]) IOOption[A] {
+	return G.Delay[IOOption[A]](delay)
+}
+
+// After creates an operation that passes after the given [time.Time]
+func After[A any](timestamp time.Time) func(IOOption[A]) IOOption[A] {
+	return G.After[IOOption[A]](timestamp)
+}

readereither/generic/reader.go

@@ -164,3 +164,12 @@ func MonadFlap[GEFAB ~func(E) ET.Either[L, func(A) B], GEB ~func(E) ET.Either[L,
 func Flap[GEFAB ~func(E) ET.Either[L, func(A) B], GEB ~func(E) ET.Either[L, B], L, E, A, B any](a A) func(GEFAB) GEB {
 	return FC.Flap(MonadMap[GEFAB, GEB], a)
 }
+
+func MonadMapLeft[GA1 ~func(C) ET.Either[E1, A], GA2 ~func(C) ET.Either[E2, A], C, E1, E2, A any](fa GA1, f func(E1) E2) GA2 {
+	return eithert.MonadMapLeft(R.MonadMap[GA1, GA2, C, ET.Either[E1, A], ET.Either[E2, A]], fa, f)
+}
+
+// MapLeft applies a mapping function to the error channel
+func MapLeft[GA1 ~func(C) ET.Either[E1, A], GA2 ~func(C) ET.Either[E2, A], C, E1, E2, A any](f func(E1) E2) func(GA1) GA2 {
+	return F.Bind2nd(MonadMapLeft[GA1, GA2, C, E1, E2, A], f)
+}

readereither/reader.go

@@ -151,3 +151,12 @@ func MonadFlap[L, E, A, B any](fab ReaderEither[L, E, func(A) B], a A) ReaderEit
 func Flap[L, E, B, A any](a A) func(ReaderEither[L, E, func(A) B]) ReaderEither[L, E, B] {
 	return G.Flap[ReaderEither[L, E, func(A) B], ReaderEither[L, E, B]](a)
 }
+
+func MonadMapLeft[C, E1, E2, A any](fa ReaderEither[C, E1, A], f func(E1) E2) ReaderEither[C, E2, A] {
+	return G.MonadMapLeft[ReaderEither[C, E1, A], ReaderEither[C, E2, A]](fa, f)
+}
+
+// MapLeft applies a mapping function to the error channel
+func MapLeft[C, E1, E2, A any](f func(E1) E2) func(ReaderEither[C, E1, A]) ReaderEither[C, E2, A] {
+	return G.MapLeft[ReaderEither[C, E1, A], ReaderEither[C, E2, A]](f)
+}

readerioeither/generic/reader.go

@@ -440,3 +440,12 @@ func MonadFlap[GREAB ~func(R) GEAB, GREB ~func(R) GEB, GEAB ~func() ET.Either[E,
 func Flap[GREAB ~func(R) GEAB, GREB ~func(R) GEB, GEAB ~func() ET.Either[E, func(A) B], GEB ~func() ET.Either[E, B], R, E, B, A any](a A) func(GREAB) GREB {
 	return FC.Flap(MonadMap[GREAB, GREB], a)
 }
+
+func MonadMapLeft[GREA1 ~func(R) GEA1, GREA2 ~func(R) GEA2, GEA1 ~func() ET.Either[E1, A], GEA2 ~func() ET.Either[E2, A], R, E1, E2, A any](fa GREA1, f func(E1) E2) GREA2 {
+	return eithert.MonadMapLeft(G.MonadMap[GREA1, GREA2], fa, f)
+}
+
+// MapLeft applies a mapping function to the error channel
+func MapLeft[GREA1 ~func(R) GEA1, GREA2 ~func(R) GEA2, GEA1 ~func() ET.Either[E1, A], GEA2 ~func() ET.Either[E2, A], R, E1, E2, A any](f func(E1) E2) func(GREA1) GREA2 {
+	return F.Bind2nd(MonadMapLeft[GREA1, GREA2], f)
+}

readerioeither/reader.go

@@ -280,3 +280,12 @@ func MonadFlap[R, E, B, A any](fab ReaderIOEither[R, E, func(A) B], a A) ReaderI
 func Flap[R, E, B, A any](a A) func(ReaderIOEither[R, E, func(A) B]) ReaderIOEither[R, E, B] {
 	return G.Flap[ReaderIOEither[R, E, func(A) B], ReaderIOEither[R, E, B]](a)
 }
+
+func MonadMapLeft[R, E1, E2, A any](fa ReaderIOEither[R, E1, A], f func(E1) E2) ReaderIOEither[R, E2, A] {
+	return G.MonadMapLeft[ReaderIOEither[R, E1, A], ReaderIOEither[R, E2, A]](fa, f)
+}
+
+// MapLeft applies a mapping function to the error channel
+func MapLeft[R, A, E1, E2 any](f func(E1) E2) func(ReaderIOEither[R, E1, A]) ReaderIOEither[R, E2, A] {
+	return G.MapLeft[ReaderIOEither[R, E1, A], ReaderIOEither[R, E2, A]](f)
+}

record/generic/record.go

@@ -19,6 +19,7 @@ import (
 	"sort"
 
 	F "github.com/IBM/fp-go/function"
+	RAG "github.com/IBM/fp-go/internal/array"
 	FC "github.com/IBM/fp-go/internal/functor"
 	G "github.com/IBM/fp-go/internal/record"
 	Mg "github.com/IBM/fp-go/magma"
@@ -334,6 +335,62 @@ func ToEntries[M ~map[K]V, GT ~[]T.Tuple2[K, V], K comparable, V any](r M) GT {
 	return ToArray[M, GT](r)
 }
 
+// FromFoldableMap uses the reduce method for a higher kinded type to transform
+// its values into a tuple. The key and value are then used to populate the map. Duplicate
+// values are resolved via the provided [Mg.Magma]
+func FromFoldableMap[
+	FCT ~func(A) T.Tuple2[K, V],
+	HKTA any,
+	FOLDABLE ~func(func(M, A) M, M) func(HKTA) M,
+	M ~map[K]V,
+	A any,
+	K comparable,
+	V any](m Mg.Magma[V], fld FOLDABLE) func(f FCT) func(fa HKTA) M {
+	return func(f FCT) func(fa HKTA) M {
+		return fld(func(dst M, a A) M {
+			if IsEmpty(dst) {
+				dst = make(M)
+			}
+			e := f(a)
+			k := T.First(e)
+			old, ok := dst[k]
+			if ok {
+				dst[k] = m.Concat(old, T.Second(e))
+			} else {
+				dst[k] = T.Second(e)
+			}
+			return dst
+		}, Empty[M]())
+	}
+}
+
+func FromFoldable[
+	HKTA any,
+	FOLDABLE ~func(func(M, T.Tuple2[K, V]) M, M) func(HKTA) M,
+	M ~map[K]V,
+	K comparable,
+	V any](m Mg.Magma[V], red FOLDABLE) func(fa HKTA) M {
+	return FromFoldableMap[func(T.Tuple2[K, V]) T.Tuple2[K, V], HKTA, FOLDABLE](m, red)(F.Identity[T.Tuple2[K, V]])
+}
+
+func FromArrayMap[
+	FCT ~func(A) T.Tuple2[K, V],
+	GA ~[]A,
+	M ~map[K]V,
+	A any,
+	K comparable,
+	V any](m Mg.Magma[V]) func(f FCT) func(fa GA) M {
+	return FromFoldableMap[FCT](m, F.Bind23of3(RAG.Reduce[GA, A, M]))
+}
+
+func FromArray[
+	GA ~[]T.Tuple2[K, V],
+	M ~map[K]V,
+	K comparable,
+	V any](m Mg.Magma[V]) func(fa GA) M {
+	return FromFoldable[GA](m, F.Bind23of3(RAG.Reduce[GA, T.Tuple2[K, V], M]))
+}
+
 func FromEntries[M ~map[K]V, GT ~[]T.Tuple2[K, V], K comparable, V any](fa GT) M {
 	m := make(M)
 	for _, t := range fa {

record/record.go

@@ -16,6 +16,7 @@
 package record
 
 import (
+	EM "github.com/IBM/fp-go/endomorphism"
 	Mg "github.com/IBM/fp-go/magma"
 	Mo "github.com/IBM/fp-go/monoid"
 	O "github.com/IBM/fp-go/option"
@@ -291,6 +292,44 @@ func Copy[K comparable, V any](m map[K]V) map[K]V {
 }
 
 // Clone creates a deep copy of the map using the provided endomorphism to clone the values
-func Clone[K comparable, V any](f func(V) V) func(m map[K]V) map[K]V {
+func Clone[K comparable, V any](f EM.Endomorphism[V]) EM.Endomorphism[map[K]V] {
 	return G.Clone[map[K]V](f)
 }
+
+// FromFoldableMap converts from a reducer to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromFoldableMap[
+	FOLDABLE ~func(func(map[K]V, A) map[K]V, map[K]V) func(HKTA) map[K]V, // the reduce function
+	A any,
+	HKTA any,
+	K comparable,
+	V any](m Mg.Magma[V], red FOLDABLE) func(f func(A) T.Tuple2[K, V]) func(fa HKTA) map[K]V {
+	return G.FromFoldableMap[func(A) T.Tuple2[K, V]](m, red)
+}
+
+// FromArrayMap converts from an array to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromArrayMap[
+	A any,
+	K comparable,
+	V any](m Mg.Magma[V]) func(f func(A) T.Tuple2[K, V]) func(fa []A) map[K]V {
+	return G.FromArrayMap[func(A) T.Tuple2[K, V], []A, map[K]V](m)
+}
+
+// FromFoldable converts from a reducer to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromFoldable[
+	HKTA any,
+	FOLDABLE ~func(func(map[K]V, T.Tuple2[K, V]) map[K]V, map[K]V) func(HKTA) map[K]V, // the reduce function
+	K comparable,
+	V any](m Mg.Magma[V], red FOLDABLE) func(fa HKTA) map[K]V {
+	return G.FromFoldable[HKTA, FOLDABLE](m, red)
+}
+
+// FromArray converts from an array to a map
+// Duplicate keys are resolved by the provided [Mg.Magma]
+func FromArray[
+	K comparable,
+	V any](m Mg.Magma[V]) func(fa []T.Tuple2[K, V]) map[K]V {
+	return G.FromArray[[]T.Tuple2[K, V], map[K]V](m)
+}

record/record_test.go

@@ -1,5 +1,5 @@
-// Copyright (c) 2023 IBM Corp.
 // All rights reserved.
+// Copyright (c) 2023 IBM Corp.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
@@ -23,8 +23,10 @@ import (
 
 	A "github.com/IBM/fp-go/array"
 	"github.com/IBM/fp-go/internal/utils"
+	Mg "github.com/IBM/fp-go/magma"
 	O "github.com/IBM/fp-go/option"
 	S "github.com/IBM/fp-go/string"
+	T "github.com/IBM/fp-go/tuple"
 	"github.com/stretchr/testify/assert"
 )
 
@@ -149,3 +151,28 @@ func TestCopyVsClone(t *testing.T) {
 	assert.NotEqual(t, cpy, cln)
 	assert.Equal(t, src, cpy)
 }
+
+func TestFromArrayMap(t *testing.T) {
+	src1 := A.From("a", "b", "c", "a")
+	frm := FromArrayMap[string, string](Mg.Second[string]())
+
+	f := frm(T.Replicate2[string])
+
+	res1 := f(src1)
+
+	assert.Equal(t, map[string]string{
+		"a": "a",
+		"b": "b",
+		"c": "c",
+	}, res1)
+
+	src2 := A.From("A", "B", "C", "A")
+
+	res2 := f(src2)
+
+	assert.Equal(t, map[string]string{
+		"A": "A",
+		"B": "B",
+		"C": "C",
+	}, res2)
+}