fix: automate eitherize methods

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

cli/reader.go

@@ -0,0 +1,163 @@
+// 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 cli
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"path/filepath"
+	"time"
+
+	C "github.com/urfave/cli/v2"
+)
+
+func generateReaderFrom(f, fg *os.File, i int) {
+	// non generic version
+	fmt.Fprintf(f, "\n// From%d converts a function with %d parameters returning a [R] into a function with %d parameters returning a [Reader[C, R]]\n// The first parameter is considered to be the context [C] of the reader\n", i, i+1, i)
+	fmt.Fprintf(f, "func From%d[F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ") R")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(f, ", T%d", j)
+	}
+	fmt.Fprintf(f, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(f, ", ")
+		}
+		fmt.Fprintf(f, "T%d", j)
+	}
+	fmt.Fprintf(f, ") Reader[C, R] {\n")
+	fmt.Fprintf(f, "  return G.From%d[Reader[C, R]](f)\n", i)
+	fmt.Fprintln(f, "}")
+
+	// generic version
+	fmt.Fprintf(fg, "\n// From%d converts a function with %d parameters returning a [R] into a function with %d parameters returning a [GRA]\n// The first parameter is considered to be the context [C].\n", i, i+1, i)
+	fmt.Fprintf(fg, "func From%d[GRA ~func(C) R, F ~func(C", i)
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ") R")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", T%d", j)
+	}
+	fmt.Fprintf(fg, ", C, R any](f F) func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "T%d", j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+
+	fmt.Fprintf(fg, "  return func(")
+	for j := 0; j < i; j++ {
+		if j > 0 {
+			fmt.Fprintf(fg, ", ")
+		}
+		fmt.Fprintf(fg, "t%d T%d", j, j)
+	}
+	fmt.Fprintf(fg, ") GRA {\n")
+	fmt.Fprintf(fg, "    return MakeReader[GRA](func(r C) R {\n")
+	fmt.Fprintf(fg, "      return f(r")
+	for j := 0; j < i; j++ {
+		fmt.Fprintf(fg, ", t%d", j)
+	}
+	fmt.Fprintf(fg, ")\n")
+	fmt.Fprintf(fg, "    })\n")
+	fmt.Fprintf(fg, "  }\n")
+	fmt.Fprintf(fg, "}\n")
+}
+
+func generateReaderHelpers(filename string, count int) error {
+	dir, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+	absDir, err := filepath.Abs(dir)
+	if err != nil {
+		return err
+	}
+	pkg := filepath.Base(absDir)
+	f, err := os.Create(filepath.Clean(filename))
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+	// construct subdirectory
+	genFilename := filepath.Join("generic", filename)
+	err = os.MkdirAll("generic", os.ModePerm)
+	if err != nil {
+		return err
+	}
+	fg, err := os.Create(filepath.Clean(genFilename))
+	if err != nil {
+		return err
+	}
+	defer fg.Close()
+
+	// log
+	log.Printf("Generating code in [%s] for package [%s] with [%d] repetitions ...", filename, pkg, count)
+
+	// some header
+	fmt.Fprintln(f, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(f, "// This file was generated by robots at")
+	fmt.Fprintf(f, "// %s\n", time.Now())
+
+	fmt.Fprintf(f, "package %s\n\n", pkg)
+
+	fmt.Fprintf(f, `
+import (
+	G "github.com/ibm/fp-go/%s/generic"	
+)
+`, pkg)
+
+	// some header
+	fmt.Fprintln(fg, "// Code generated by go generate; DO NOT EDIT.")
+	fmt.Fprintln(fg, "// This file was generated by robots at")
+	fmt.Fprintf(fg, "// %s\n", time.Now())
+
+	fmt.Fprintf(fg, "package generic\n\n")
+
+	// from
+	generateReaderFrom(f, fg, 0)
+
+	for i := 1; i <= count; i++ {
+		// from
+		generateReaderFrom(f, fg, i)
+	}
+
+	return nil
+}
+
+func ReaderCommand() *C.Command {
+	return &C.Command{
+		Name:  "reader",
+		Usage: "generate code for Reader",
+		Flags: []C.Flag{
+			flagCount,
+			flagFilename,
+		},
+		Action: func(ctx *C.Context) error {
+			return generateReaderHelpers(
+				ctx.String(keyFilename),
+				ctx.Int(keyCount),
+			)
+		},
+	}
+}