package utils

import (
	"os"
	"path/filepath"
	"strings"
	"syscall"
)

// TreeSize walks a directory tree and returns its total size in bytes.
func TreeSize(dir string) (size int64, err error) {
	data := make(map[uint64]bool)
	err = filepath.Walk(dir, func(d string, fileInfo os.FileInfo, e error) error {
		// Ignore directory sizes
		if fileInfo == nil {
			return nil
		}

		s := fileInfo.Size()
		if fileInfo.IsDir() || s == 0 {
			return nil
		}

		// Check inode to handle hard links correctly
		inode := fileInfo.Sys().(*syscall.Stat_t).Ino
		if _, exists := data[inode]; exists {
			return nil
		}
		data[inode] = false

		size += s

		return nil
	})
	return
}

// FollowSymlink will follow an existing link and scope it to the root
// path provided.
func FollowSymlinkInScope(link, root string) (string, error) {
	prev := "."

	root, err := filepath.Abs(root)
	if err != nil {
		return "", err
	}
	root = filepath.Clean(root)
	link, err := filepath.Abs(link)
	if err != nil {
		return "", err
	}
	link = filepath.Clean(link)

	for _, p := range strings.Split(link, "/") {
		prev = filepath.Join(prev, p)
		prev = filepath.Clean(prev)

		stat, err := os.Lstat(prev)
		if err != nil {
			if os.IsNotExist(err) {
				continue
			}
			return "", err
		}
		if stat.Mode()&os.ModeSymlink == os.ModeSymlink {
			dest, err := os.Readlink(prev)
			if err != nil {
				return "", err
			}

			switch dest[0] {
			case '/':
				prev = filepath.Join(root, dest)
			case '.':
				if prev = filepath.Clean(filepath.Join(filepath.Dir(prev), dest)); len(prev) < len(root) {
					prev = filepath.Join(root, filepath.Base(dest))
				}
			}
		}
	}
	return prev, nil
}