package util

import (
	"io/fs"
	"os"
	"strings"
	"syscall"

	"codeberg.org/gruf/go-fastpath"
)

// IsDirTraversal will check if rootPlusPath is a dir traversal outside of root,
// assuming that both are cleaned and that rootPlusPath is path.Join(root, somePath)
func IsDirTraversal(root string, rootPlusPath string) bool {
	switch {
	// Root is $PWD, check for traversal out of
	case root == ".":
		return strings.HasPrefix(rootPlusPath, "../")

	// The path MUST be prefixed by root
	case !strings.HasPrefix(rootPlusPath, root):
		return true

	// In all other cases, check not equal
	default:
		return len(root) == len(rootPlusPath)
	}
}

// WalkDir traverses the dir tree of the supplied path, performing the supplied walkFn on each entry
func WalkDir(pb *fastpath.Builder, path string, walkFn func(string, fs.DirEntry)) error {
	// Read supplied dir path
	dirEntries, err := os.ReadDir(path)
	if err != nil {
		return err
	}

	// Iter entries
	for _, entry := range dirEntries {
		// Pass to walk fn
		walkFn(path, entry)

		// Recurse dir entries
		if entry.IsDir() {
			err = WalkDir(pb, pb.Join(path, entry.Name()), walkFn)
			if err != nil {
				return err
			}
		}
	}

	return nil
}

// CleanDirs traverses the dir tree of the supplied path, removing any folders with zero children
func CleanDirs(path string) error {
	// Acquire builder
	pb := GetPathBuilder()
	defer PutPathBuilder(pb)

	// Get dir entries
	entries, err := os.ReadDir(path)
	if err != nil {
		return err
	}

	// Recurse dirs
	for _, entry := range entries {
		if entry.IsDir() {
			err := cleanDirs(pb, pb.Join(path, entry.Name()))
			if err != nil {
				return err
			}
		}
	}
	return nil
}

// cleanDirs performs the actual dir cleaning logic for the exported version
func cleanDirs(pb *fastpath.Builder, path string) error {
	// Get dir entries
	entries, err := os.ReadDir(path)
	if err != nil {
		return err
	}

	// If no entries, delete
	if len(entries) < 1 {
		return os.Remove(path)
	}

	// Recurse dirs
	for _, entry := range entries {
		if entry.IsDir() {
			err := cleanDirs(pb, pb.Join(path, entry.Name()))
			if err != nil {
				return err
			}
		}
	}
	return nil
}

// RetryOnEINTR is a low-level filesystem function for retrying syscalls on O_EINTR received
func RetryOnEINTR(do func() error) error {
	for {
		err := do()
		if err == syscall.EINTR {
			continue
		}
		return err
	}
}