main.go

package main

import (
	"bufio"
	"fmt"
	"io"
	"log"
	"os"

	"github.com/davecgh/go-spew/spew"
)

func main() {
	if err := run(); err != nil {
		log.Printf("failed: %s", err)
		os.Exit(1)
	}
}

func run() error {
	file := "/tmp/test.txt"
	lines := []string{"one", "two", "three", "four"}

	if err := File(file).Write().Lines(lines); err != nil {
		return fmt.Errorf("write lines: %w", err)
	}

	got, err := File(file).Read().Lines()
	if err != nil {
		return fmt.Errorf("read lines: %w", err)
	}

	spew.Dump(got)

	return nil
}

type Reader struct {
	io.ReadCloser
	err error
}

func (r *Reader) Lines() ([]string, error) {
	if r.err != nil {
		return nil, r.err
	}

	scanner := bufio.NewScanner(r.ReadCloser)
	scanner.Split(bufio.ScanLines)

	var out []string

	for scanner.Scan() {
		out = append(out, scanner.Text())
	}

	if err := r.ReadCloser.Close(); err != nil {
		return nil, err
	}

	return out, nil
}

type Writer struct {
	io.WriteCloser
	err error
}

func (w *Writer) Lines(in []string) error {
	for i := range in {
		if _, err := w.Write([]byte(in[i])); err != nil {
			return err
		}
		if _, err := w.Write([]byte{'\n'}); err != nil {
			return err
		}
	}

	return nil
}


type FSAccessor struct {
	path string
}


func (fa FSAccessor) Read() *Reader {
	f, err := os.Open(fa.path)
	return &Reader{
		ReadCloser: f,
		err: err,
	}
}

func (fa FSAccessor) Write() *Writer {
	f, err := os.OpenFile(fa.path, os.O_WRONLY|os.O_CREATE, 0755)
	return &Writer{
		WriteCloser: f,
		err: err,
	}
}

func File(p string) FSAccessor {
	return FSAccessor{path: p}
}