package system

import (
	"fmt"
	"io"
	"os"
	"strings"

	"golang.org/x/sys/unix"
)

func CopyFilePreferClone(sourcePath, targetPath string) error {
	source, err := os.Open(sourcePath)
	if err != nil {
		return err
	}
	defer source.Close()

	info, err := source.Stat()
	if err != nil {
		return err
	}

	target, err := os.OpenFile(targetPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, info.Mode().Perm())
	if err != nil {
		return err
	}
	defer target.Close()

	if err := unix.IoctlFileClone(int(target.Fd()), int(source.Fd())); err == nil {
		return nil
	}
	if _, err := source.Seek(0, io.SeekStart); err != nil {
		return err
	}
	if _, err := target.Seek(0, io.SeekStart); err != nil {
		return err
	}
	if _, err := io.Copy(target, source); err != nil {
		return err
	}
	if err := target.Sync(); err != nil {
		return err
	}
	if err := target.Chmod(info.Mode().Perm()); err != nil {
		return err
	}
	return nil
}

func ReadNormalizedLines(path string) ([]string, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	var out []string
	for _, line := range strings.Split(string(data), "\n") {
		if strings.HasSuffix(line, "\r") {
			line = strings.TrimSuffix(line, "\r")
		}
		if idx := strings.Index(line, "#"); idx >= 0 {
			line = line[:idx]
		}
		line = strings.TrimSpace(line)
		if line == "" {
			continue
		}
		out = append(out, line)
	}
	if len(out) == 0 {
		return nil, fmt.Errorf("file has no entries: %s", path)
	}
	return out, nil
}