filepath.go

package socker

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

type Filepath interface {
	Separator() uint8
	ListSeparator() uint8
	IsPathSeparator(c uint8) bool
	Clean(path string) string
	ToSlash(path string) string
	FromSlash(path string) string
	SplitList(path string) []string
	Split(path string) (dir, file string)
	Join(elem ...string) string
	Ext(path string) string
	Rel(basepath, targpath string) (string, error)
	Base(path string) string
	Dir(path string) string
	VolumeName(path string) string
	IsAbs(path string) bool
}

type localFilepath struct {
}

var _ Filepath = localFilepath{}

func (localFilepath) Separator() uint8                     { return filepath.Separator }
func (localFilepath) ListSeparator() uint8                 { return filepath.ListSeparator }
func (localFilepath) IsPathSeparator(c uint8) bool         { return os.IsPathSeparator(c) }
func (localFilepath) Clean(path string) string             { return filepath.Clean(path) }
func (localFilepath) ToSlash(path string) string           { return filepath.ToSlash(path) }
func (localFilepath) FromSlash(path string) string         { return filepath.FromSlash(path) }
func (localFilepath) SplitList(path string) []string       { return filepath.SplitList(path) }
func (localFilepath) Split(path string) (dir, file string) { return filepath.Split(path) }
func (localFilepath) Join(elem ...string) string           { return filepath.Join(elem...) }
func (localFilepath) Ext(path string) string               { return filepath.Ext(path) }
func (localFilepath) Rel(basepath, targpath string) (string, error) {
	return filepath.Rel(basepath, targpath)
}
func (localFilepath) Base(path string) string       { return filepath.Base(path) }
func (localFilepath) Dir(path string) string        { return filepath.Dir(path) }
func (localFilepath) VolumeName(path string) string { return filepath.VolumeName(path) }
func (localFilepath) IsAbs(path string) bool        { return filepath.IsAbs(path) }

type virtualFilepath struct {
	IsUnix            bool
	PathSeparator     uint8
	PathListSeparator uint8
	Getwd             func() (string, error)
}

var _ Filepath = virtualFilepath{}

func (f virtualFilepath) Separator() uint8 { return f.PathSeparator }

func (f virtualFilepath) ListSeparator() uint8 { return f.PathListSeparator }

func (f virtualFilepath) IsPathSeparator(c uint8) bool {
	return f.PathSeparator == c
}

func (f virtualFilepath) Clean(path string) string {
	return f.clean(path)
}

func (f virtualFilepath) ToSlash(path string) string {
	if f.PathSeparator == '/' {
		return path
	}
	return strings.Replace(path, string(f.PathSeparator), "/", -1)
}

func (f virtualFilepath) FromSlash(path string) string {
	if f.PathSeparator == '/' {
		return path
	}
	return strings.Replace(path, "/", string(f.PathSeparator), -1)
}

func (f virtualFilepath) SplitList(path string) []string {
	if f.IsUnix {
		return f.unixSplitList(path)
	}
	return f.windowsSplitList(path)
}

func (f virtualFilepath) Split(path string) (dir, file string) {
	vol := f.VolumeName(path)
	i := len(path) - 1
	for i >= len(vol) && !f.IsPathSeparator(path[i]) {
		i--
	}
	return path[:i+1], path[i+1:]
}

func (f virtualFilepath) Join(elem ...string) string {
	if f.IsUnix {
		return f.unixJoin(elem)
	}
	return f.windowsJoin(elem)
}

func (f virtualFilepath) Ext(path string) string {
	for i := len(path) - 1; i >= 0 && !f.IsPathSeparator(path[i]); i-- {
		if path[i] == '.' {
			return path[i:]
		}
	}
	return ""
}

func (f virtualFilepath) Rel(basepath, targpath string) (string, error) {
	baseVol := f.VolumeName(basepath)
	targVol := f.VolumeName(targpath)
	base := f.Clean(basepath)
	targ := f.Clean(targpath)
	if f.sameWord(targ, base) {
		return ".", nil
	}
	base = base[len(baseVol):]
	targ = targ[len(targVol):]
	if base == "." {
		base = ""
	}
	// Can't use IsAbs - `\a` and `a` are both relative in Windows.
	baseSlashed := len(base) > 0 && base[0] == f.PathSeparator
	targSlashed := len(targ) > 0 && targ[0] == f.PathSeparator
	if baseSlashed != targSlashed || !f.sameWord(baseVol, targVol) {
		return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
	}
	// Position base[b0:bi] and targ[t0:ti] at the first differing elements.
	bl := len(base)
	tl := len(targ)
	var b0, bi, t0, ti int
	for {
		for bi < bl && base[bi] != f.PathSeparator {
			bi++
		}
		for ti < tl && targ[ti] != f.PathSeparator {
			ti++
		}
		if !f.sameWord(targ[t0:ti], base[b0:bi]) {
			break
		}
		if bi < bl {
			bi++
		}
		if ti < tl {
			ti++
		}
		b0 = bi
		t0 = ti
	}
	if base[b0:bi] == ".." {
		return "", errors.New("Rel: can't make " + targpath + " relative to " + basepath)
	}
	if b0 != bl {
		// Base elements left. Must go up before going down.
		seps := strings.Count(base[b0:bl], string(f.PathSeparator))
		size := 2 + seps*3
		if tl != t0 {
			size += 1 + tl - t0
		}
		buf := make([]byte, size)
		n := copy(buf, "..")
		for i := 0; i < seps; i++ {
			buf[n] = f.PathSeparator
			copy(buf[n+1:], "..")
			n += 3
		}
		if t0 != tl {
			buf[n] = f.PathSeparator
			copy(buf[n+1:], targ[t0:])
		}
		return string(buf), nil
	}
	return targ[t0:], nil
}

func (f virtualFilepath) Base(path string) string {
	if path == "" {
		return "."
	}
	// Strip trailing slashes.
	for len(path) > 0 && f.IsPathSeparator(path[len(path)-1]) {
		path = path[0 : len(path)-1]
	}
	// Throw away volume name
	path = path[len(f.VolumeName(path)):]
	// Find the last element
	i := len(path) - 1
	for i >= 0 && !f.IsPathSeparator(path[i]) {
		i--
	}
	if i >= 0 {
		path = path[i+1:]
	}
	// If empty now, it had only slashes.
	if path == "" {
		return string(f.PathSeparator)
	}
	return path
}

func (f virtualFilepath) Dir(path string) string {
	vol := f.VolumeName(path)
	i := len(path) - 1
	for i >= len(vol) && !f.IsPathSeparator(path[i]) {
		i--
	}
	dir := f.Clean(path[len(vol) : i+1])
	return vol + dir
}

func (f virtualFilepath) VolumeName(path string) string {
	return path[:f.volumeNameLen(path)]
}

func (f virtualFilepath) IsAbs(path string) bool {
	if f.IsUnix {
		return f.unixIsAbs(path)
	}
	return f.windowsIsAbs(path)
}

type lazybuf struct {
	path       string
	buf        []byte
	w          int
	volAndPath string
	volLen     int
}

func (b *lazybuf) index(i int) byte {
	if b.buf != nil {
		return b.buf[i]
	}
	return b.path[i]
}

func (b *lazybuf) append(c byte) {
	if b.buf == nil {
		if b.w < len(b.path) && b.path[b.w] == c {
			b.w++
			return
		}
		b.buf = make([]byte, len(b.path))
		copy(b.buf, b.path[:b.w])
	}
	b.buf[b.w] = c
	b.w++
}

func (b *lazybuf) string() string {
	if b.buf == nil {
		return b.volAndPath[:b.volLen+b.w]
	}
	return b.volAndPath[:b.volLen] + string(b.buf[:b.w])
}

func (f virtualFilepath) clean(path string) string {
	originalPath := path
	volLen := f.volumeNameLen(path)
	path = path[volLen:]
	if path == "" {
		if volLen > 1 && originalPath[1] != ':' {
			// should be UNC
			return f.FromSlash(originalPath)
		}
		return originalPath + "."
	}
	rooted := f.IsPathSeparator(path[0])

	// Invariants:
	//	reading from path; r is index of next byte to process.
	//	writing to buf; w is index of next byte to write.
	//	dotdot is index in buf where .. must stop, either because
	//		it is the leading slash or it is a leading ../../.. prefix.
	n := len(path)
	out := lazybuf{path: path, volAndPath: originalPath, volLen: volLen}
	r, dotdot := 0, 0
	if rooted {
		out.append(f.PathSeparator)
		r, dotdot = 1, 1
	}

	for r < n {
		switch {
		case f.IsPathSeparator(path[r]):
			// empty path element
			r++
		case path[r] == '.' && (r+1 == n || f.IsPathSeparator(path[r+1])):
			// . element
			r++
		case path[r] == '.' && path[r+1] == '.' && (r+2 == n || f.IsPathSeparator(path[r+2])):
			// .. element: remove to last separator
			r += 2
			switch {
			case out.w > dotdot:
				// can backtrack
				out.w--
				for out.w > dotdot && !f.IsPathSeparator(out.index(out.w)) {
					out.w--
				}
			case !rooted:
				// cannot backtrack, but not rooted, so append .. element.
				if out.w > 0 {
					out.append(f.PathSeparator)
				}
				out.append('.')
				out.append('.')
				dotdot = out.w
			}
		default:
			// real path element.
			// add slash if needed
			if rooted && out.w != 1 || !rooted && out.w != 0 {
				out.append(f.PathSeparator)
			}
			// copy element
			for ; r < n && !f.IsPathSeparator(path[r]); r++ {
				out.append(path[r])
			}
		}
	}

	// Turn empty string into "."
	if out.w == 0 {
		out.append('.')
	}

	return f.FromSlash(out.string())
}

func (f virtualFilepath) unixSplitList(path string) []string {
	if path == "" {
		return []string{}
	}
	return strings.Split(path, string(f.PathListSeparator))
}

func (f virtualFilepath) windowsSplitList(path string) []string {
	// The same implementation is used in LookPath in os/exec;
	// consider changing os/exec when changing this.

	if path == "" {
		return []string{}
	}

	// Split path, respecting but preserving quotes.
	list := []string{}
	start := 0
	quo := false
	for i := 0; i < len(path); i++ {
		switch c := path[i]; {
		case c == '"':
			quo = !quo
		case c == f.PathListSeparator && !quo:
			list = append(list, path[start:i])
			start = i + 1
		}
	}
	list = append(list, path[start:])

	// Remove quotes.
	for i, s := range list {
		if strings.Contains(s, `"`) {
			list[i] = strings.Replace(s, `"`, ``, -1)
		}
	}

	return list
}

func (f virtualFilepath) volumeNameLen(path string) int {
	if f.IsUnix {
		return f.unixVolumeNameLen(path)
	}
	return f.windowsVolumeNameLen(path)
}

func (f virtualFilepath) unixVolumeNameLen(path string) int {
	return 0
}

func (f virtualFilepath) windowsVolumeNameLen(path string) int {
	if len(path) < 2 {
		return 0
	}
	// with drive letter
	c := path[0]
	if path[1] == ':' && ('a' <= c && c <= 'z' || 'A' <= c && c <= 'Z') {
		return 2
	}
	// is it UNC? https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
	if l := len(path); l >= 5 && f.windowsIsSlash(path[0]) && f.windowsIsSlash(path[1]) &&
		!f.windowsIsSlash(path[2]) && path[2] != '.' {
		// first, leading `\\` and next shouldn't be `\`. its server name.
		for n := 3; n < l-1; n++ {
			// second, next '\' shouldn't be repeated.
			if f.windowsIsSlash(path[n]) {
				n++
				// third, following something characters. its share name.
				if !f.windowsIsSlash(path[n]) {
					if path[n] == '.' {
						break
					}
					for ; n < l; n++ {
						if f.windowsIsSlash(path[n]) {
							break
						}
					}
					return n
				}
				break
			}
		}
	}
	return 0
}

func (f virtualFilepath) windowsIsSlash(c uint8) bool {
	return c == '\\' || c == '/'
}

func (f virtualFilepath) isAbs(path string) bool {
	if f.IsUnix {
		return f.unixIsAbs(path)
	}
	return f.windowsIsAbs(path)
}

func (f virtualFilepath) unixIsAbs(path string) bool {
	return strings.HasPrefix(path, "/")
}

// IsAbs reports whether the path is absolute.
func (f virtualFilepath) windowsIsAbs(path string) (b bool) {
	l := f.windowsVolumeNameLen(path)
	if l == 0 {
		return false
	}
	path = path[l:]
	if path == "" {
		return false
	}
	return f.windowsIsSlash(path[0])
}

func (f virtualFilepath) join(elem []string) string {
	if f.IsUnix {
		return f.unixJoin(elem)
	}
	return f.windowsJoin(elem)
}

func (f virtualFilepath) unixJoin(elem []string) string {
	for i, e := range elem {
		if e != "" {
			return f.clean(strings.Join(elem[i:], string(f.PathSeparator)))
		}
	}
	return ""
}

func (f virtualFilepath) windowsJoin(elem []string) string {
	for i, e := range elem {
		if e != "" {
			return f.windowsJoinNonEmpty(elem[i:])
		}
	}
	return ""
}

// joinNonEmpty is like join, but it assumes that the first element is non-empty.
func (f virtualFilepath) windowsJoinNonEmpty(elem []string) string {
	if len(elem[0]) == 2 && elem[0][1] == ':' {
		// First element is drive letter without terminating slash.
		// Keep path relative to current directory on that drive.
		return f.clean(elem[0] + strings.Join(elem[1:], string(f.PathSeparator)))
	}
	// The following logic prevents Join from inadvertently creating a
	// UNC path on Windows. Unless the first element is a UNC path, Join
	// shouldn't create a UNC path. See golang.org/issue/9167.
	p := f.clean(strings.Join(elem, string(f.PathSeparator)))
	if !f.windowsIsUNC(p) {
		return p
	}
	// p == UNC only allowed when the first element is a UNC path.
	head := f.clean(elem[0])
	if f.windowsIsUNC(head) {
		return p
	}
	// head + tail == UNC, but joining two non-UNC paths should not result
	// in a UNC path. Undo creation of UNC path.
	tail := f.clean(strings.Join(elem[1:], string(f.PathSeparator)))
	if head[len(head)-1] == f.PathSeparator {
		return head + tail
	}
	return head + string(f.PathSeparator) + tail
}

func (f virtualFilepath) windowsIsUNC(path string) bool {
	return f.windowsVolumeNameLen(path) > 2
}

func (f virtualFilepath) sameWord(a, b string) bool {
	if f.IsUnix {
		return f.unixSameWord(a, b)
	}
	return f.windowsSameWord(a, b)
}

func (f virtualFilepath) windowsSameWord(a, b string) bool {
	return strings.EqualFold(a, b)
}

func (f virtualFilepath) unixSameWord(a, b string) bool {
	return a == b
}