package files

import (
	"bufio"
	"fmt"
	"io"
	"os"
)

func Files() {
	Reading()
	Writing()
}

func check(err error) {
	if err != nil {
		panic(err)
	}
}

func Reading() {
	data, err := os.ReadFile("/etc/hosts")
	check(err)

	fmt.Println("Contents:")
	fmt.Println(string(data))

	f, err := os.Open("/etc/hosts")
	defer f.Close()
	check(err)

	bytes1 := make([]byte, 5)
	n1, err := f.Read(bytes1)
	check(err)

	fmt.Printf("Read %d bytes: %v\n", n1, string(bytes1[:n1]))

	o1, err := f.Seek(5, 0)
	check(err)
	bytes2 := make([]byte, 4)
	n2, err := f.Read(bytes2)
	check(err)
	fmt.Printf("Read %d bytes @ %d: %v\n", n2, o1, string(bytes2[:n2]))

	o2, err := f.Seek(5, 0)
	check(err)
	bytes3 := make([]byte, 4)
	n3, err := io.ReadAtLeast(f, bytes3, 2)
	check(err)
	fmt.Printf("Read %d bytes @ %d: %v\n", n3, o2, string(bytes3))

	o3, err := f.Seek(5, 0)
	check(err)
	br := bufio.NewReader(f)
	bytes4, err := br.Peek(4)
	check(err)
	fmt.Printf("Read @ %d: %v\n", o3, string(bytes4))
}

func Writing() {
	err := os.WriteFile("/tmp/go.files.write.txt", []byte("hello go!"), 0600)
	check(err)

	f, err := os.Create("/tmp/go.files.write2.txt")
	check(err)

	n1, err := f.Write([]byte{87, 73, 78})
	check(err)
	fmt.Printf("Wrote %d bytes\n", n1)

	n2, err := f.WriteString(" macOS")
	check(err)
	fmt.Printf("Wrote %d bytes\n", n2)

	f.Sync()

	bw := bufio.NewWriter(f)
	n3, err := bw.WriteString(" linux")
	check(err)
	fmt.Printf("Wrote %d bytes\n", n3)

	bw.Flush()
}