// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package fsys

import (
	"errors"
	"internal/testenv"
	"internal/txtar"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"slices"
	"strings"
	"sync"
	"testing"
)

func resetForTesting() {
	cwd = sync.OnceValue(cwdOnce)
	overlay = nil
	binds = nil
}

// initOverlay resets the overlay state to reflect the config.
// config should be a text archive string. The comment is the overlay config
// json, and the files, in the archive are laid out in a temp directory
// that cwd is set to.
func initOverlay(t *testing.T, config string) {
	t.Helper()
	t.Chdir(t.TempDir())
	resetForTesting()
	t.Cleanup(resetForTesting)
	cwd := cwd()

	a := txtar.Parse([]byte(config))
	for _, f := range a.Files {
		name := filepath.Join(cwd, f.Name)
		if err := os.MkdirAll(filepath.Dir(name), 0777); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(name, f.Data, 0666); err != nil {
			t.Fatal(err)
		}
	}

	if err := initFromJSON(a.Comment); err != nil {
		t.Fatal(err)
	}
}

var statInfoOverlay = `{"Replace": {
	"x": "replace/x",
	"a/b/c": "replace/c",
	"d/e": ""
}}`

var statInfoTests = []struct {
	path string
	info info
}{
	{"foo", info{abs: "/tmp/foo", actual: "foo"}},
	{"foo/bar/baz/quux", info{abs: "/tmp/foo/bar/baz/quux", actual: "foo/bar/baz/quux"}},
	{"x", info{abs: "/tmp/x", replaced: true, file: true, actual: "/tmp/replace/x"}},
	{"/tmp/x", info{abs: "/tmp/x", replaced: true, file: true, actual: "/tmp/replace/x"}},
	{"x/y", info{abs: "/tmp/x/y", deleted: true}},
	{"a", info{abs: "/tmp/a", replaced: true, dir: true, actual: "a"}},
	{"a/b", info{abs: "/tmp/a/b", replaced: true, dir: true, actual: "a/b"}},
	{"a/b/c", info{abs: "/tmp/a/b/c", replaced: true, file: true, actual: "/tmp/replace/c"}},
	{"d/e", info{abs: "/tmp/d/e", deleted: true}},
	{"d", info{abs: "/tmp/d", replaced: true, dir: true, actual: "d"}},
}

var statInfoChildrenTests = []struct {
	path     string
	children []info
}{
	{"foo", nil},
	{"foo/bar", nil},
	{"foo/bar/baz", nil},
	{"x", nil},
	{"x/y", nil},
	{"a", []info{{abs: "/tmp/a/b", replaced: true, dir: true, actual: ""}}},
	{"a/b", []info{{abs: "/tmp/a/b/c", replaced: true, actual: "/tmp/replace/c"}}},
	{"d", []info{{abs: "/tmp/d/e", deleted: true}}},
	{"d/e", nil},
	{".", []info{
		{abs: "/tmp/a", replaced: true, dir: true, actual: ""},
		// {abs: "/tmp/d", replaced: true, dir: true, actual: ""},
		{abs: "/tmp/x", replaced: true, actual: "/tmp/replace/x"},
	}},
}

func TestStatInfo(t *testing.T) {
	tmp := "/tmp"
	if runtime.GOOS == "windows" {
		tmp = `C:\tmp`
	}
	cwd = sync.OnceValue(func() string { return tmp })

	winFix := func(s string) string {
		if runtime.GOOS == "windows" {
			s = strings.ReplaceAll(s, `/tmp`, tmp) // fix tmp
			s = strings.ReplaceAll(s, `/`, `\`)    // use backslashes
		}
		return s
	}

	overlay := statInfoOverlay
	overlay = winFix(overlay)
	overlay = strings.ReplaceAll(overlay, `\`, `\\`) // JSON escaping
	if err := initFromJSON([]byte(overlay)); err != nil {
		t.Fatal(err)
	}

	for _, tt := range statInfoTests {
		tt.path = winFix(tt.path)
		tt.info.abs = winFix(tt.info.abs)
		tt.info.actual = winFix(tt.info.actual)
		info := stat(tt.path)
		if info != tt.info {
			t.Errorf("stat(%#q):\nhave %+v\nwant %+v", tt.path, info, tt.info)
		}
	}

	for _, tt := range statInfoChildrenTests {
		tt.path = winFix(tt.path)
		for i, info := range tt.children {
			info.abs = winFix(info.abs)
			info.actual = winFix(info.actual)
			tt.children[i] = info
		}
		parent := stat(winFix(tt.path))
		var children []info
		for name, child := range parent.children() {
			if name != filepath.Base(child.abs) {
				t.Errorf("stat(%#q): child %#q has inconsistent abs %#q", tt.path, name, child.abs)
			}
			children = append(children, child)
		}
		slices.SortFunc(children, func(x, y info) int { return cmp(x.abs, y.abs) })
		if !slices.Equal(children, tt.children) {
			t.Errorf("stat(%#q) children:\nhave %+v\nwant %+v", tt.path, children, tt.children)
		}
	}
}

func TestIsDir(t *testing.T) {
	initOverlay(t, `
{
	"Replace": {
		"subdir2/file2.txt":  "overlayfiles/subdir2_file2.txt",
		"subdir4":            "overlayfiles/subdir4",
		"subdir3/file3b.txt": "overlayfiles/subdir3_file3b.txt",
		"subdir5":            "",
		"subdir6":            ""
	}
}
-- subdir1/file1.txt --

-- subdir3/file3a.txt --
33
-- subdir4/file4.txt --
444
-- overlayfiles/subdir2_file2.txt --
2
-- overlayfiles/subdir3_file3b.txt --
66666
-- overlayfiles/subdir4 --
x
-- subdir6/file6.txt --
six
`)

	cwd := cwd()
	testCases := []struct {
		path          string
		want, wantErr bool
	}{
		{"", true, true},
		{".", true, false},
		{cwd, true, false},
		{cwd + string(filepath.Separator), true, false},
		// subdir1 is only on disk
		{filepath.Join(cwd, "subdir1"), true, false},
		{"subdir1", true, false},
		{"subdir1" + string(filepath.Separator), true, false},
		{"subdir1/file1.txt", false, false},
		{"subdir1/doesntexist.txt", false, true},
		{"doesntexist", false, true},
		// subdir2 is only in overlay
		{filepath.Join(cwd, "subdir2"), true, false},
		{"subdir2", true, false},
		{"subdir2" + string(filepath.Separator), true, false},
		{"subdir2/file2.txt", false, false},
		{"subdir2/doesntexist.txt", false, true},
		// subdir3 has files on disk and in overlay
		{filepath.Join(cwd, "subdir3"), true, false},
		{"subdir3", true, false},
		{"subdir3" + string(filepath.Separator), true, false},
		{"subdir3/file3a.txt", false, false},
		{"subdir3/file3b.txt", false, false},
		{"subdir3/doesntexist.txt", false, true},
		// subdir4 is overlaid with a file
		{filepath.Join(cwd, "subdir4"), false, false},
		{"subdir4", false, false},
		{"subdir4" + string(filepath.Separator), false, false},
		{"subdir4/file4.txt", false, false},
		{"subdir4/doesntexist.txt", false, false},
		// subdir5 doesn't exist, and is overlaid with a "delete" entry
		{filepath.Join(cwd, "subdir5"), false, false},
		{"subdir5", false, false},
		{"subdir5" + string(filepath.Separator), false, false},
		{"subdir5/file5.txt", false, false},
		{"subdir5/doesntexist.txt", false, false},
		// subdir6 does exist, and is overlaid with a "delete" entry
		{filepath.Join(cwd, "subdir6"), false, false},
		{"subdir6", false, false},
		{"subdir6" + string(filepath.Separator), false, false},
		{"subdir6/file6.txt", false, false},
		{"subdir6/doesntexist.txt", false, false},
	}

	for _, tc := range testCases {
		got, err := IsDir(tc.path)
		if err != nil {
			if !tc.wantErr {
				t.Errorf("IsDir(%q): got error with string %q, want no error", tc.path, err.Error())
			}
			continue
		}
		if tc.wantErr {
			t.Errorf("IsDir(%q): got no error, want error", tc.path)
		}
		if tc.want != got {
			t.Errorf("IsDir(%q) = %v, want %v", tc.path, got, tc.want)
		}
	}
}

const readDirOverlay = `
{
	"Replace": {
		"subdir2/file2.txt":                 "overlayfiles/subdir2_file2.txt",
		"subdir4":                           "overlayfiles/subdir4",
		"subdir3/file3b.txt":                "overlayfiles/subdir3_file3b.txt",
		"subdir5":                           "",
		"subdir6/asubsubdir/afile.txt":      "overlayfiles/subdir6_asubsubdir_afile.txt",
		"subdir6/asubsubdir/zfile.txt":      "overlayfiles/subdir6_asubsubdir_zfile.txt",
		"subdir6/zsubsubdir/file.txt":       "overlayfiles/subdir6_zsubsubdir_file.txt",
		"subdir7/asubsubdir/file.txt":       "overlayfiles/subdir7_asubsubdir_file.txt",
		"subdir7/zsubsubdir/file.txt":       "overlayfiles/subdir7_zsubsubdir_file.txt",
		"subdir8/doesntexist":               "this_file_doesnt_exist_anywhere",
		"other/pointstodir":                 "overlayfiles/this_is_a_directory",
		"parentoverwritten/subdir1":         "overlayfiles/parentoverwritten_subdir1",
		"subdir9/this_file_is_overlaid.txt": "overlayfiles/subdir9_this_file_is_overlaid.txt",
		"subdir10/only_deleted_file.txt":    "",
		"subdir11/deleted.txt":              "",
		"subdir11":                          "overlayfiles/subdir11",
		"textfile.txt/file.go":              "overlayfiles/textfile_txt_file.go"
	}
}
-- subdir1/file1.txt --

-- subdir3/file3a.txt --
33
-- subdir4/file4.txt --
444
-- subdir6/file.txt --
-- subdir6/asubsubdir/file.txt --
-- subdir6/anothersubsubdir/file.txt --
-- subdir9/this_file_is_overlaid.txt --
-- subdir10/only_deleted_file.txt --
this will be deleted in overlay
-- subdir11/deleted.txt --
-- parentoverwritten/subdir1/subdir2/subdir3/file.txt --
-- textfile.txt --
this will be overridden by textfile.txt/file.go
-- overlayfiles/subdir2_file2.txt --
2
-- overlayfiles/subdir3_file3b.txt --
66666
-- overlayfiles/subdir4 --
x
-- overlayfiles/subdir6_asubsubdir_afile.txt --
-- overlayfiles/subdir6_asubsubdir_zfile.txt --
-- overlayfiles/subdir6_zsubsubdir_file.txt --
-- overlayfiles/subdir7_asubsubdir_file.txt --
-- overlayfiles/subdir7_zsubsubdir_file.txt --
-- overlayfiles/parentoverwritten_subdir1 --
x
-- overlayfiles/subdir9_this_file_is_overlaid.txt --
99999999
-- overlayfiles/subdir11 --
-- overlayfiles/this_is_a_directory/file.txt --
-- overlayfiles/textfile_txt_file.go --
x
`

func TestReadDir(t *testing.T) {
	initOverlay(t, readDirOverlay)

	type entry struct {
		name  string
		size  int64
		isDir bool
	}

	testCases := []struct {
		dir  string
		want []entry
	}{
		{
			".", []entry{
				{"other", 0, true},
				{"overlayfiles", 0, true},
				{"parentoverwritten", 0, true},
				{"subdir1", 0, true},
				{"subdir10", 0, true},
				{"subdir11", 0, false},
				{"subdir2", 0, true},
				{"subdir3", 0, true},
				{"subdir4", 2, false},
				// no subdir5.
				{"subdir6", 0, true},
				{"subdir7", 0, true},
				{"subdir8", 0, true},
				{"subdir9", 0, true},
				{"textfile.txt", 0, true},
			},
		},
		{
			"subdir1", []entry{
				{"file1.txt", 1, false},
			},
		},
		{
			"subdir2", []entry{
				{"file2.txt", 2, false},
			},
		},
		{
			"subdir3", []entry{
				{"file3a.txt", 3, false},
				{"file3b.txt", 6, false},
			},
		},
		{
			"subdir6", []entry{
				{"anothersubsubdir", 0, true},
				{"asubsubdir", 0, true},
				{"file.txt", 0, false},
				{"zsubsubdir", 0, true},
			},
		},
		{
			"subdir6/asubsubdir", []entry{
				{"afile.txt", 0, false},
				{"file.txt", 0, false},
				{"zfile.txt", 0, false},
			},
		},
		{
			"subdir8", []entry{
				{"doesntexist", 0, false}, // entry is returned even if destination file doesn't exist
			},
		},
		{
			// check that read dir actually redirects files that already exist
			// the original this_file_is_overlaid.txt is empty
			"subdir9", []entry{
				{"this_file_is_overlaid.txt", 9, false},
			},
		},
		{
			"subdir10", []entry{},
		},
		{
			"parentoverwritten", []entry{
				{"subdir1", 2, false},
			},
		},
		{
			"textfile.txt", []entry{
				{"file.go", 2, false},
			},
		},
	}

	for _, tc := range testCases {
		dir, want := tc.dir, tc.want
		infos, err := ReadDir(dir)
		if err != nil {
			t.Errorf("ReadDir(%q): %v", dir, err)
			continue
		}
		// Sorted diff of want and infos.
		for len(infos) > 0 || len(want) > 0 {
			switch {
			case len(want) == 0 || len(infos) > 0 && infos[0].Name() < want[0].name:
				t.Errorf("ReadDir(%q): unexpected entry: %s IsDir=%v", dir, infos[0].Name(), infos[0].IsDir())
				infos = infos[1:]
			case len(infos) == 0 || len(want) > 0 && want[0].name < infos[0].Name():
				t.Errorf("ReadDir(%q): missing entry: %s IsDir=%v", dir, want[0].name, want[0].isDir)
				want = want[1:]
			default:
				if infos[0].IsDir() != want[0].isDir {
					t.Errorf("ReadDir(%q): %s: IsDir=%v, want IsDir=%v", dir, want[0].name, infos[0].IsDir(), want[0].isDir)
				}
				infos = infos[1:]
				want = want[1:]
			}
		}
	}

	errCases := []string{
		"subdir1/file1.txt", // regular file on disk
		"subdir2/file2.txt", // regular file in overlay
		"subdir4",           // directory overlaid with regular file
		"subdir5",           // directory deleted in overlay
		"parentoverwritten/subdir1/subdir2/subdir3", // parentoverwritten/subdir1 overlaid with regular file
		"parentoverwritten/subdir1/subdir2",         // parentoverwritten/subdir1 overlaid with regular file
		"subdir11",                                  // directory with deleted child, overlaid with regular file
		"other/pointstodir",
	}

	for _, dir := range errCases {
		_, err := ReadDir(dir)
		if _, ok := err.(*fs.PathError); !ok {
			t.Errorf("ReadDir(%q): err = %T (%v), want fs.PathError", dir, err, err)
		}
	}
}

func TestGlob(t *testing.T) {
	initOverlay(t, readDirOverlay)

	testCases := []struct {
		pattern string
		match   []string
	}{
		{
			"*o*",
			[]string{
				"other",
				"overlayfiles",
				"parentoverwritten",
			},
		},
		{
			"subdir2/file2.txt",
			[]string{
				"subdir2/file2.txt",
			},
		},
		{
			"*/*.txt",
			[]string{
				"overlayfiles/subdir2_file2.txt",
				"overlayfiles/subdir3_file3b.txt",
				"overlayfiles/subdir6_asubsubdir_afile.txt",
				"overlayfiles/subdir6_asubsubdir_zfile.txt",
				"overlayfiles/subdir6_zsubsubdir_file.txt",
				"overlayfiles/subdir7_asubsubdir_file.txt",
				"overlayfiles/subdir7_zsubsubdir_file.txt",
				"overlayfiles/subdir9_this_file_is_overlaid.txt",
				"subdir1/file1.txt",
				"subdir2/file2.txt",
				"subdir3/file3a.txt",
				"subdir3/file3b.txt",
				"subdir6/file.txt",
				"subdir9/this_file_is_overlaid.txt",
			},
		},
	}

	for _, tc := range testCases {
		pattern := tc.pattern
		match, err := Glob(pattern)
		if err != nil {
			t.Errorf("Glob(%q): %v", pattern, err)
			continue
		}
		want := tc.match
		for i, name := range want {
			if name != tc.pattern {
				want[i] = filepath.FromSlash(name)
			}
		}
		for len(match) > 0 || len(want) > 0 {
			switch {
			case len(match) == 0 || len(want) > 0 && want[0] < match[0]:
				t.Errorf("Glob(%q): missing match: %s", pattern, want[0])
				want = want[1:]
			case len(want) == 0 || len(match) > 0 && match[0] < want[0]:
				t.Errorf("Glob(%q): extra match: %s", pattern, match[0])
				match = match[1:]
			default:
				want = want[1:]
				match = match[1:]
			}
		}
	}
}

func TestActual(t *testing.T) {
	initOverlay(t, `
{
	"Replace": {
		"subdir2/file2.txt":                 "overlayfiles/subdir2_file2.txt",
		"subdir3/doesntexist":               "this_file_doesnt_exist_anywhere",
		"subdir4/this_file_is_overlaid.txt": "overlayfiles/subdir4_this_file_is_overlaid.txt",
		"subdir5/deleted.txt":               "",
		"parentoverwritten/subdir1":         ""
	}
}
-- subdir1/file1.txt --
file 1
-- subdir4/this_file_is_overlaid.txt --
these contents are replaced by the overlay
-- parentoverwritten/subdir1/subdir2/subdir3/file.txt --
-- subdir5/deleted.txt --
deleted
-- overlayfiles/subdir2_file2.txt --
file 2
-- overlayfiles/subdir4_this_file_is_overlaid.txt --
99999999
`)

	cwd := cwd()
	testCases := []struct {
		path     string
		wantPath string
		wantOK   bool
	}{
		{"subdir1/file1.txt", "subdir1/file1.txt", false},
		// Actual returns false for directories
		{"subdir2", "subdir2", false},
		{"subdir2/file2.txt", filepath.Join(cwd, "overlayfiles/subdir2_file2.txt"), true},
		// Actual doesn't stat a file to see if it exists, so it happily returns
		// the 'to' path and true even if the 'to' path doesn't exist on disk.
		{"subdir3/doesntexist", filepath.Join(cwd, "this_file_doesnt_exist_anywhere"), true},
		// Like the subdir2/file2.txt case above, but subdir4 exists on disk, but subdir2 does not.
		{"subdir4/this_file_is_overlaid.txt", filepath.Join(cwd, "overlayfiles/subdir4_this_file_is_overlaid.txt"), true},
		{"subdir5", "subdir5", false},
		{"subdir5/deleted.txt", "", true},
	}

	for _, tc := range testCases {
		path := Actual(tc.path)
		ok := Replaced(tc.path)

		if path != tc.wantPath {
			t.Errorf("Actual(%q) = %q, want %q", tc.path, path, tc.wantPath)
		}
		if ok != tc.wantOK {
			t.Errorf("Replaced(%q) = %v, want %v", tc.path, ok, tc.wantOK)
		}
	}
}

func TestOpen(t *testing.T) {
	initOverlay(t, `
{
    "Replace": {
		"subdir2/file2.txt":                  "overlayfiles/subdir2_file2.txt",
		"subdir3/doesntexist":                "this_file_doesnt_exist_anywhere",
		"subdir4/this_file_is_overlaid.txt":  "overlayfiles/subdir4_this_file_is_overlaid.txt",
		"subdir5/deleted.txt":                "",
		"parentoverwritten/subdir1":          "",
		"childoverlay/subdir1.txt/child.txt": "overlayfiles/child.txt",
		"subdir11/deleted.txt":               "",
		"subdir11":                           "overlayfiles/subdir11",
		"parentdeleted":                      "",
		"parentdeleted/file.txt":             "overlayfiles/parentdeleted_file.txt"
	}
}
-- subdir11/deleted.txt --
-- subdir1/file1.txt --
file 1
-- subdir4/this_file_is_overlaid.txt --
these contents are replaced by the overlay
-- parentoverwritten/subdir1/subdir2/subdir3/file.txt --
-- childoverlay/subdir1.txt --
this file doesn't exist because the path
childoverlay/subdir1.txt/child.txt is in the overlay
-- subdir5/deleted.txt --
deleted
-- parentdeleted --
this will be deleted so that parentdeleted/file.txt can exist
-- overlayfiles/subdir2_file2.txt --
file 2
-- overlayfiles/subdir4_this_file_is_overlaid.txt --
99999999
-- overlayfiles/child.txt --
-- overlayfiles/subdir11 --
11
-- overlayfiles/parentdeleted_file.txt --
this can exist because the parent directory is deleted
`)

	testCases := []struct {
		path         string
		wantContents string
		isErr        bool
	}{
		{"subdir1/file1.txt", "file 1\n", false},
		{"subdir2/file2.txt", "file 2\n", false},
		{"subdir3/doesntexist", "", true},
		{"subdir4/this_file_is_overlaid.txt", "99999999\n", false},
		{"subdir5/deleted.txt", "", true},
		{"parentoverwritten/subdir1/subdir2/subdir3/file.txt", "", true},
		{"childoverlay/subdir1.txt", "", true},
		{"subdir11", "11\n", false},
		{"parentdeleted/file.txt", "this can exist because the parent directory is deleted\n", false},
	}

	for _, tc := range testCases {
		f, err := Open(tc.path)
		if tc.isErr {
			if err == nil {
				f.Close()
				t.Errorf("Open(%q): got no error, but want error", tc.path)
			}
			continue
		}
		if err != nil {
			t.Errorf("Open(%q): got error %v, want nil", tc.path, err)
			continue
		}
		contents, err := io.ReadAll(f)
		if err != nil {
			t.Errorf("unexpected error reading contents of file: %v", err)
		}
		if string(contents) != tc.wantContents {
			t.Errorf("contents of file opened with Open(%q): got %q, want %q",
				tc.path, contents, tc.wantContents)
		}
		f.Close()
	}
}

func TestIsGoDir(t *testing.T) {
	initOverlay(t, `
{
	"Replace": {
		"goinoverlay/file.go":       "dummy",
		"directory/removed/by/file": "dummy",
		"directory_with_go_dir/dir.go/file.txt": "dummy",
		"otherdirectory/deleted.go": "",
		"nonexistentdirectory/deleted.go": "",
		"textfile.txt/file.go": "dummy"
	}
}
-- dummy --
a destination file for the overlay entries to point to
contents don't matter for this test
-- nogo/file.txt --
-- goondisk/file.go --
-- goinoverlay/file.txt --
-- directory/removed/by/file/in/overlay/file.go --
-- otherdirectory/deleted.go --
-- textfile.txt --
`)

	testCases := []struct {
		dir     string
		want    bool
		wantErr bool
	}{
		{"nogo", false, false},
		{"goondisk", true, false},
		{"goinoverlay", true, false},
		{"directory/removed/by/file/in/overlay", false, false},
		{"directory_with_go_dir", false, false},
		{"otherdirectory", false, false},
		{"nonexistentdirectory", false, false},
		{"textfile.txt", true, false},
	}

	for _, tc := range testCases {
		got, gotErr := IsGoDir(tc.dir)
		if tc.wantErr {
			if gotErr == nil {
				t.Errorf("IsGoDir(%q): got %v, %v; want non-nil error", tc.dir, got, gotErr)
			}
			continue
		}
		if gotErr != nil {
			t.Errorf("IsGoDir(%q): got %v, %v; want nil error", tc.dir, got, gotErr)
		}
		if got != tc.want {
			t.Errorf("IsGoDir(%q) = %v; want %v", tc.dir, got, tc.want)
		}
	}
}

func TestWalk(t *testing.T) {
	// The root of the walk must be a name with an actual basename, not just ".".
	// Walk uses Lstat to obtain the name of the root, and Lstat on platforms
	// other than Plan 9 reports the name "." instead of the actual base name of
	// the directory. (See https://golang.org/issue/42115.)

	type file struct {
		path  string
		name  string
		size  int64
		mode  fs.FileMode
		isDir bool
	}
	testCases := []struct {
		name      string
		overlay   string
		root      string
		wantFiles []file
	}{
		{"no overlay", `
{}
-- dir/file.txt --
`,
			"dir",
			[]file{
				{"dir", "dir", 0, fs.ModeDir | 0700, true},
				{"dir/file.txt", "file.txt", 0, 0600, false},
			},
		},
		{"overlay with different file", `
{
	"Replace": {
		"dir/file.txt": "dir/other.txt"
	}
}
-- dir/file.txt --
-- dir/other.txt --
contents of other file
`,
			"dir",
			[]file{
				{"dir", "dir", 0, fs.ModeDir | 0500, true},
				{"dir/file.txt", "file.txt", 23, 0600, false},
				{"dir/other.txt", "other.txt", 23, 0600, false},
			},
		},
		{"overlay with new file", `
{
	"Replace": {
		"dir/file.txt": "dir/other.txt"
	}
}
-- dir/other.txt --
contents of other file
`,
			"dir",
			[]file{
				{"dir", "dir", 0, fs.ModeDir | 0500, true},
				{"dir/file.txt", "file.txt", 23, 0600, false},
				{"dir/other.txt", "other.txt", 23, 0600, false},
			},
		},
		{"overlay with new directory", `
{
	"Replace": {
		"dir/subdir/file.txt": "dir/other.txt"
	}
}
-- dir/other.txt --
contents of other file
`,
			"dir",
			[]file{
				{"dir", "dir", 0, fs.ModeDir | 0500, true},
				{"dir/other.txt", "other.txt", 23, 0600, false},
				{"dir/subdir", "subdir", 0, fs.ModeDir | 0500, true},
				{"dir/subdir/file.txt", "file.txt", 23, 0600, false},
			},
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			initOverlay(t, tc.overlay)

			var got []file
			WalkDir(tc.root, func(path string, d fs.DirEntry, err error) error {
				info, err := d.Info()
				if err != nil {
					t.Fatal(err)
				}
				if info.Name() != d.Name() {
					t.Errorf("walk %s: d.Name() = %q, but info.Name() = %q", path, d.Name(), info.Name())
				}
				if info.IsDir() != d.IsDir() {
					t.Errorf("walk %s: d.IsDir() = %v, but info.IsDir() = %v", path, d.IsDir(), info.IsDir())
				}
				if info.Mode().Type() != d.Type() {
					t.Errorf("walk %s: d.Type() = %v, but info.Mode().Type() = %v", path, d.Type(), info.Mode().Type())
				}
				got = append(got, file{path, d.Name(), info.Size(), info.Mode(), d.IsDir()})
				return nil
			})

			if len(got) != len(tc.wantFiles) {
				t.Errorf("Walk: saw %#v in walk; want %#v", got, tc.wantFiles)
			}
			for i := 0; i < len(got) && i < len(tc.wantFiles); i++ {
				wantPath := filepath.FromSlash(tc.wantFiles[i].path)
				if got[i].path != wantPath {
					t.Errorf("walk #%d: path = %q, want %q", i, got[i].path, wantPath)
				}
				if got[i].name != tc.wantFiles[i].name {
					t.Errorf("walk %s: Name = %q, want %q", got[i].path, got[i].name, tc.wantFiles[i].name)
				}
				if got[i].mode&(fs.ModeDir|0700) != tc.wantFiles[i].mode {
					t.Errorf("walk %s: Mode = %q, want %q", got[i].path, got[i].mode&(fs.ModeDir|0700), tc.wantFiles[i].mode)
				}
				if got[i].isDir != tc.wantFiles[i].isDir {
					t.Errorf("walk %s: IsDir = %v, want %v", got[i].path, got[i].isDir, tc.wantFiles[i].isDir)
				}
			}
		})
	}
}

func TestWalkSkipDir(t *testing.T) {
	initOverlay(t, `
{
	"Replace": {
		"dir/skip/file.go": "dummy.txt",
		"dir/dontskip/file.go": "dummy.txt",
		"dir/dontskip/skip/file.go": "dummy.txt"
	}
}
-- dummy.txt --
`)

	var seen []string
	WalkDir("dir", func(path string, d fs.DirEntry, err error) error {
		seen = append(seen, filepath.ToSlash(path))
		if d.Name() == "skip" {
			return filepath.SkipDir
		}
		return nil
	})

	wantSeen := []string{"dir", "dir/dontskip", "dir/dontskip/file.go", "dir/dontskip/skip", "dir/skip"}

	if len(seen) != len(wantSeen) {
		t.Errorf("paths seen in walk: got %v entries; want %v entries", len(seen), len(wantSeen))
	}

	for i := 0; i < len(seen) && i < len(wantSeen); i++ {
		if seen[i] != wantSeen[i] {
			t.Errorf("path #%v seen walking tree: want %q, got %q", i, seen[i], wantSeen[i])
		}
	}
}

func TestWalkSkipAll(t *testing.T) {
	initOverlay(t, `
{
	"Replace": {
		"dir/subdir1/foo1": "dummy.txt",
		"dir/subdir1/foo2": "dummy.txt",
		"dir/subdir1/foo3": "dummy.txt",
		"dir/subdir2/foo4": "dummy.txt",
		"dir/zzlast": "dummy.txt"
	}
}
-- dummy.txt --
`)

	var seen []string
	WalkDir("dir", func(path string, d fs.DirEntry, err error) error {
		seen = append(seen, filepath.ToSlash(path))
		if d.Name() == "foo2" {
			return filepath.SkipAll
		}
		return nil
	})

	wantSeen := []string{"dir", "dir/subdir1", "dir/subdir1/foo1", "dir/subdir1/foo2"}

	if len(seen) != len(wantSeen) {
		t.Errorf("paths seen in walk: got %v entries; want %v entries", len(seen), len(wantSeen))
	}

	for i := 0; i < len(seen) && i < len(wantSeen); i++ {
		if seen[i] != wantSeen[i] {
			t.Errorf("path %#v seen walking tree: got %q, want %q", i, seen[i], wantSeen[i])
		}
	}
}

func TestWalkError(t *testing.T) {
	initOverlay(t, "{}")

	alreadyCalled := false
	err := WalkDir("foo", func(path string, d fs.DirEntry, err error) error {
		if alreadyCalled {
			t.Fatal("expected walk function to be called exactly once, but it was called more than once")
		}
		alreadyCalled = true
		return errors.New("returned from function")
	})
	if !alreadyCalled {
		t.Fatal("expected walk function to be called exactly once, but it was never called")

	}
	if err == nil {
		t.Fatalf("Walk: got no error, want error")
	}
	if err.Error() != "returned from function" {
		t.Fatalf("Walk: got error %v, want \"returned from function\" error", err)
	}
}

func TestWalkSymlink(t *testing.T) {
	testenv.MustHaveSymlink(t)

	initOverlay(t, `{
	"Replace": {"overlay_symlink/file": "symlink/file"}
}
-- dir/file --`)

	// Create symlink
	if err := os.Symlink("dir", "symlink"); err != nil {
		t.Error(err)
	}

	testCases := []struct {
		name      string
		dir       string
		wantFiles []string
	}{
		{"control", "dir", []string{"dir", filepath.Join("dir", "file")}},
		// ensure Walk doesn't walk into the directory pointed to by the symlink
		// (because it's supposed to use Lstat instead of Stat).
		{"symlink_to_dir", "symlink", []string{"symlink"}},
		{"overlay_to_symlink_to_dir", "overlay_symlink", []string{"overlay_symlink", filepath.Join("overlay_symlink", "file")}},

		// However, adding filepath.Separator should cause the link to be resolved.
		{"symlink_with_slash", "symlink" + string(filepath.Separator), []string{"symlink" + string(filepath.Separator), filepath.Join("symlink", "file")}},
		{"overlay_to_symlink_to_dir", "overlay_symlink" + string(filepath.Separator), []string{"overlay_symlink" + string(filepath.Separator), filepath.Join("overlay_symlink", "file")}},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			var got []string

			err := WalkDir(tc.dir, func(path string, d fs.DirEntry, err error) error {
				t.Logf("walk %q", path)
				got = append(got, path)
				if err != nil {
					t.Errorf("walkfn: got non nil err argument: %v, want nil err argument", err)
				}
				return nil
			})
			if err != nil {
				t.Errorf("Walk: got error %q, want nil", err)
			}

			if !reflect.DeepEqual(got, tc.wantFiles) {
				t.Errorf("files examined by walk: got %v, want %v", got, tc.wantFiles)
			}
		})
	}

}

func TestLstat(t *testing.T) {
	type file struct {
		name  string
		size  int64
		mode  fs.FileMode // mode & (fs.ModeDir|0x700): only check 'user' permissions
		isDir bool
	}

	testCases := []struct {
		name    string
		overlay string
		path    string

		want    file
		wantErr bool
	}{
		{
			"regular_file",
			`{}
-- file.txt --
contents`,
			"file.txt",
			file{"file.txt", 9, 0600, false},
			false,
		},
		{
			"new_file_in_overlay",
			`{"Replace": {"file.txt": "dummy.txt"}}
-- dummy.txt --
contents`,
			"file.txt",
			file{"file.txt", 9, 0600, false},
			false,
		},
		{
			"file_replaced_in_overlay",
			`{"Replace": {"file.txt": "dummy.txt"}}
-- file.txt --
-- dummy.txt --
contents`,
			"file.txt",
			file{"file.txt", 9, 0600, false},
			false,
		},
		{
			"file_cant_exist",
			`{"Replace": {"deleted": "dummy.txt"}}
-- deleted/file.txt --
-- dummy.txt --
`,
			"deleted/file.txt",
			file{},
			true,
		},
		{
			"deleted",
			`{"Replace": {"deleted": ""}}
-- deleted --
`,
			"deleted",
			file{},
			true,
		},
		{
			"dir_on_disk",
			`{}
-- dir/foo.txt --
`,
			"dir",
			file{"dir", 0, 0700 | fs.ModeDir, true},
			false,
		},
		{
			"dir_in_overlay",
			`{"Replace": {"dir/file.txt": "dummy.txt"}}
-- dummy.txt --
`,
			"dir",
			file{"dir", 0, 0500 | fs.ModeDir, true},
			false,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			initOverlay(t, tc.overlay)
			got, err := Lstat(tc.path)
			if tc.wantErr {
				if err == nil {
					t.Errorf("lstat(%q): got no error, want error", tc.path)
				}
				return
			}
			if err != nil {
				t.Fatalf("lstat(%q): got error %v, want no error", tc.path, err)
			}
			if got.Name() != tc.want.name {
				t.Errorf("lstat(%q).Name(): got %q, want %q", tc.path, got.Name(), tc.want.name)
			}
			if got.Mode()&(fs.ModeDir|0700) != tc.want.mode {
				t.Errorf("lstat(%q).Mode()&(fs.ModeDir|0700): got %v, want %v", tc.path, got.Mode()&(fs.ModeDir|0700), tc.want.mode)
			}
			if got.IsDir() != tc.want.isDir {
				t.Errorf("lstat(%q).IsDir(): got %v, want %v", tc.path, got.IsDir(), tc.want.isDir)
			}
			if tc.want.isDir {
				return // don't check size for directories
			}
			if got.Size() != tc.want.size {
				t.Errorf("lstat(%q).Size(): got %v, want %v", tc.path, got.Size(), tc.want.size)
			}
		})
	}
}

func TestStat(t *testing.T) {
	testenv.MustHaveSymlink(t)

	type file struct {
		name  string
		size  int64
		mode  os.FileMode // mode & (os.ModeDir|0x700): only check 'user' permissions
		isDir bool
	}

	testCases := []struct {
		name    string
		overlay string
		path    string

		want    file
		wantErr bool
	}{
		{
			"regular_file",
			`{}
-- file.txt --
contents`,
			"file.txt",
			file{"file.txt", 9, 0600, false},
			false,
		},
		{
			"new_file_in_overlay",
			`{"Replace": {"file.txt": "dummy.txt"}}
-- dummy.txt --
contents`,
			"file.txt",
			file{"file.txt", 9, 0600, false},
			false,
		},
		{
			"file_replaced_in_overlay",
			`{"Replace": {"file.txt": "dummy.txt"}}
-- file.txt --
-- dummy.txt --
contents`,
			"file.txt",
			file{"file.txt", 9, 0600, false},
			false,
		},
		{
			"file_cant_exist",
			`{"Replace": {"deleted": "dummy.txt"}}
-- deleted/file.txt --
-- dummy.txt --
`,
			"deleted/file.txt",
			file{},
			true,
		},
		{
			"deleted",
			`{"Replace": {"deleted": ""}}
-- deleted --
`,
			"deleted",
			file{},
			true,
		},
		{
			"dir_on_disk",
			`{}
-- dir/foo.txt --
`,
			"dir",
			file{"dir", 0, 0700 | os.ModeDir, true},
			false,
		},
		{
			"dir_in_overlay",
			`{"Replace": {"dir/file.txt": "dummy.txt"}}
-- dummy.txt --
`,
			"dir",
			file{"dir", 0, 0500 | os.ModeDir, true},
			false,
		},
	}

	for _, tc := range testCases {
		t.Run(tc.name, func(t *testing.T) {
			initOverlay(t, tc.overlay)
			got, err := Stat(tc.path)
			if tc.wantErr {
				if err == nil {
					t.Errorf("Stat(%q): got no error, want error", tc.path)
				}
				return
			}
			if err != nil {
				t.Fatalf("Stat(%q): got error %v, want no error", tc.path, err)
			}
			if got.Name() != tc.want.name {
				t.Errorf("Stat(%q).Name(): got %q, want %q", tc.path, got.Name(), tc.want.name)
			}
			if got.Mode()&(os.ModeDir|0700) != tc.want.mode {
				t.Errorf("Stat(%q).Mode()&(os.ModeDir|0700): got %v, want %v", tc.path, got.Mode()&(os.ModeDir|0700), tc.want.mode)
			}
			if got.IsDir() != tc.want.isDir {
				t.Errorf("Stat(%q).IsDir(): got %v, want %v", tc.path, got.IsDir(), tc.want.isDir)
			}
			if tc.want.isDir {
				return // don't check size for directories
			}
			if got.Size() != tc.want.size {
				t.Errorf("Stat(%q).Size(): got %v, want %v", tc.path, got.Size(), tc.want.size)
			}
		})
	}
}

func TestStatSymlink(t *testing.T) {
	testenv.MustHaveSymlink(t)

	initOverlay(t, `{
	"Replace": {"file.go": "symlink"}
}
-- to.go --
0123456789
`)

	// Create symlink
	if err := os.Symlink("to.go", "symlink"); err != nil {
		t.Error(err)
	}

	f := "file.go"
	fi, err := Stat(f)
	if err != nil {
		t.Errorf("Stat(%q): got error %q, want nil error", f, err)
	}

	if !fi.Mode().IsRegular() {
		t.Errorf("Stat(%q).Mode(): got %v, want regular mode", f, fi.Mode())
	}

	if fi.Size() != 11 {
		t.Errorf("Stat(%q).Size(): got %v, want 11", f, fi.Size())
	}
}

func TestBindOverlay(t *testing.T) {
	initOverlay(t, `{"Replace": {"mtpt/x.go": "xx.go"}}
-- mtpt/x.go --
mtpt/x.go
-- mtpt/y.go --
mtpt/y.go
-- mtpt2/x.go --
mtpt/x.go
-- replaced/x.go --
replaced/x.go
-- replaced/x/y/z.go --
replaced/x/y/z.go
-- xx.go --
xx.go
`)

	testReadFile(t, "mtpt/x.go", "xx.go\n")

	Bind("replaced", "mtpt")
	testReadFile(t, "mtpt/x.go", "replaced/x.go\n")
	testReadDir(t, "mtpt/x", "y/")
	testReadDir(t, "mtpt/x/y", "z.go")
	testReadFile(t, "mtpt/x/y/z.go", "replaced/x/y/z.go\n")
	testReadFile(t, "mtpt/y.go", "ERROR")

	Bind("replaced", "mtpt2/a/b")
	testReadDir(t, "mtpt2", "a/", "x.go")
	testReadDir(t, "mtpt2/a", "b/")
	testReadDir(t, "mtpt2/a/b", "x/", "x.go")
	testReadFile(t, "mtpt2/a/b/x.go", "replaced/x.go\n")
}

var badOverlayTests = []struct {
	json string
	err  string
}{
	{`{`,
		"parsing overlay JSON: unexpected end of JSON input"},
	{`{"Replace": {"":"a"}}`,
		"empty string key in overlay map"},
	{`{"Replace": {"/tmp/x": "y", "x": "y"}}`,
		`duplicate paths /tmp/x and x in overlay map`},
	{`{"Replace": {"/tmp/x/z": "z", "x":"y"}}`,
		`inconsistent files /tmp/x and /tmp/x/z in overlay map`},
	{`{"Replace": {"/tmp/x/z/z2": "z", "x":"y"}}`,
		`inconsistent files /tmp/x and /tmp/x/z/z2 in overlay map`},
	{`{"Replace": {"/tmp/x": "y", "x/z/z2": "z"}}`,
		`inconsistent files /tmp/x and /tmp/x/z/z2 in overlay map`},
}

func TestBadOverlay(t *testing.T) {
	tmp := "/tmp"
	if runtime.GOOS == "windows" {
		tmp = `C:\tmp`
	}
	cwd = sync.OnceValue(func() string { return tmp })
	defer resetForTesting()

	for i, tt := range badOverlayTests {
		if runtime.GOOS == "windows" {
			tt.json = strings.ReplaceAll(tt.json, `/tmp`, tmp) // fix tmp
			tt.json = strings.ReplaceAll(tt.json, `/`, `\`)    // use backslashes
			tt.json = strings.ReplaceAll(tt.json, `\`, `\\`)   // JSON escaping
			tt.err = strings.ReplaceAll(tt.err, `/tmp`, tmp)   // fix tmp
			tt.err = strings.ReplaceAll(tt.err, `/`, `\`)      // use backslashes
		}
		err := initFromJSON([]byte(tt.json))
		if err == nil || err.Error() != tt.err {
			t.Errorf("#%d: err=%v, want %q", i, err, tt.err)
		}
	}
}

func testReadFile(t *testing.T, name string, want string) {
	t.Helper()
	data, err := ReadFile(name)
	if want == "ERROR" {
		if data != nil || err == nil {
			t.Errorf("ReadFile(%q) = %q, %v, want nil, error", name, data, err)
		}
		return
	}
	if string(data) != want || err != nil {
		t.Errorf("ReadFile(%q) = %q, %v, want %q, nil", name, data, err, want)
	}
}

func testReadDir(t *testing.T, name string, want ...string) {
	t.Helper()
	dirs, err := ReadDir(name)
	var names []string
	for _, d := range dirs {
		name := d.Name()
		if d.IsDir() {
			name += "/"
		}
		names = append(names, name)
	}
	if !slices.Equal(names, want) || err != nil {
		t.Errorf("ReadDir(%q) = %q, %v, want %q, nil", name, names, err, want)
	}
}