/*
   Copyright The containerd Authors.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.
*/

package mount

import (
	"fmt"
	"io/fs"
	"os"
	"os/exec"
	"path/filepath"
	"reflect"
	"syscall"
	"testing"

	kernel "github.com/containerd/containerd/v2/pkg/kernelversion"
	"github.com/stretchr/testify/assert"
	"github.com/stretchr/testify/require"

	"github.com/containerd/continuity/testutil"
	"golang.org/x/sys/unix"
)

func TestLongestCommonPrefix(t *testing.T) {
	tcases := []struct {
		in       []string
		expected string
	}{
		{[]string{}, ""},
		{[]string{"foo"}, "foo"},
		{[]string{"foo", "bar"}, ""},
		{[]string{"foo", "foo"}, "foo"},
		{[]string{"foo", "foobar"}, "foo"},
		{[]string{"foo", "", "foobar"}, ""},
	}

	for i, tc := range tcases {
		if got := longestCommonPrefix(tc.in); got != tc.expected {
			t.Fatalf("[%d case] expected (%s), but got (%s)", i+1, tc.expected, got)
		}
	}
}

func TestCompactLowerdirOption(t *testing.T) {
	tcases := []struct {
		opts      []string
		commondir string
		newopts   []string
	}{
		// no lowerdir or only one
		{
			[]string{"workdir=a"},
			"",
			[]string{"workdir=a"},
		},
		{
			[]string{"workdir=a", "lowerdir=b"},
			"",
			[]string{"workdir=a", "lowerdir=b"},
		},

		// >= 2 lowerdir
		{
			[]string{"lowerdir=/snapshots/1/fs:/snapshots/10/fs"},
			"/snapshots/",
			[]string{"lowerdir=1/fs:10/fs"},
		},
		{
			[]string{"lowerdir=/snapshots/1/fs:/snapshots/10/fs:/snapshots/2/fs"},
			"/snapshots/",
			[]string{"lowerdir=1/fs:10/fs:2/fs"},
		},

		// if common dir is /
		{
			[]string{"lowerdir=/snapshots/1/fs:/other_snapshots/1/fs"},
			"",
			[]string{"lowerdir=/snapshots/1/fs:/other_snapshots/1/fs"},
		},

		// if common dir is .
		{
			[]string{"lowerdir=a:aaa"},
			"",
			[]string{"lowerdir=a:aaa"},
		},
	}

	for i, tc := range tcases {
		dir, opts := compactLowerdirOption(tc.opts)
		if dir != tc.commondir {
			t.Fatalf("[%d case] expected common dir (%s), but got (%s)", i+1, tc.commondir, dir)
		}

		if !reflect.DeepEqual(opts, tc.newopts) {
			t.Fatalf("[%d case] expected options (%v), but got (%v)", i+1, tc.newopts, opts)
		}
	}
}

func TestFUSEHelper(t *testing.T) {
	testutil.RequiresRoot(t)
	const fuseoverlayfsBinary = "fuse-overlayfs"
	_, err := exec.LookPath(fuseoverlayfsBinary)
	if err != nil {
		t.Skip("fuse-overlayfs not installed")
	}
	td := t.TempDir()

	for _, dir := range []string{"lower1", "lower2", "upper", "work", "merged"} {
		if err := os.Mkdir(filepath.Join(td, dir), 0755); err != nil {
			t.Fatal(err)
		}
	}

	opts := fmt.Sprintf("lowerdir=%s:%s,upperdir=%s,workdir=%s", filepath.Join(td, "lower2"), filepath.Join(td, "lower1"), filepath.Join(td, "upper"), filepath.Join(td, "work"))
	m := Mount{
		Type:    "fuse3." + fuseoverlayfsBinary,
		Source:  "overlay",
		Options: []string{opts},
	}
	dest := filepath.Join(td, "merged")
	if err := m.Mount(dest); err != nil {
		t.Fatal(err)
	}
	if err := UnmountAll(dest, 0); err != nil {
		t.Fatal(err)
	}
}

func TestMountAt(t *testing.T) {
	testutil.RequiresRoot(t)

	dir1 := t.TempDir()
	dir2 := t.TempDir()

	defer unix.Unmount(filepath.Join(dir2, "bar"), unix.MNT_DETACH)

	if err := os.WriteFile(filepath.Join(dir1, "foo"), []byte("foo"), 0644); err != nil {
		t.Fatal(err)
	}

	if err := os.WriteFile(filepath.Join(dir2, "bar"), []byte{}, 0644); err != nil {
		t.Fatal(err)
	}

	wd, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}

	// mount ${dir1}/foo at ${dir2}/bar
	// But since we are using `mountAt` we only need to specify the relative path to dir2 as the target mountAt will chdir to there.
	if err := mountAt(dir2, filepath.Join(dir1, "foo"), "bar", "none", unix.MS_BIND, ""); err != nil {
		t.Fatal(err)
	}

	b, err := os.ReadFile(filepath.Join(dir2, "bar"))
	if err != nil {
		t.Fatal(err)
	}

	if string(b) != "foo" {
		t.Fatalf("unexpected file content: %s", b)
	}

	newWD, err := os.Getwd()
	if err != nil {
		t.Fatal(err)
	}
	if wd != newWD {
		t.Fatalf("unexpected working directory: %s", newWD)
	}
}

func TestUnmountMounts(t *testing.T) {
	testutil.RequiresRoot(t)

	target, mounts := setupMounts(t)
	if err := UnmountMounts(mounts, target, 0); err != nil {
		t.Fatal(err)
	}
}

func TestUnmountRecursive(t *testing.T) {
	testutil.RequiresRoot(t)

	target, _ := setupMounts(t)
	if err := UnmountRecursive(target, 0); err != nil {
		t.Fatal(err)
	}
}

func TestDoPrepareIDMappedOverlay(t *testing.T) {
	testutil.RequiresRoot(t)

	k512 := kernel.KernelVersion{Kernel: 5, Major: 12}
	ok, err := kernel.GreaterEqualThan(k512)
	require.NoError(t, err)
	if !ok {
		t.Skip("GetUsernsFD requires kernel >= 5.12")
	}

	usernsFD, err := getUsernsFD(testUIDMaps, testGIDMaps)
	require.NoError(t, err)
	defer usernsFD.Close()

	type testCase struct {
		name              string
		injectUmountFault bool
	}

	tcases := []testCase{
		{
			name:              "normal",
			injectUmountFault: false,
		},
		{
			name:              "umount-fault",
			injectUmountFault: true,
		},
	}

	for _, tc := range tcases {
		t.Run(tc.name, func(t *testing.T) {
			fakeLowerDirsDir := t.TempDir()
			if !supportsIDMap(fakeLowerDirsDir) {
				t.Skip("IDmapped mounts not supported on filesystem selected by t.TempDir()")
			}

			lowerDirs := []string{filepath.Join(fakeLowerDirsDir, "lower1"), filepath.Join(fakeLowerDirsDir, "lower2")}
			for _, dir := range lowerDirs {
				require.NoError(t, os.Mkdir(dir, 0755))
				require.NoError(t, os.WriteFile(filepath.Join(dir, filepath.Base(dir)), []byte("foo"), 0644))
			}

			remountsLocation := t.TempDir()

			tmpLowerDirs, cleanup, err := doPrepareIDMappedOverlay(remountsLocation, lowerDirs, int(usernsFD.Fd()))
			require.NoError(t, err)
			require.Len(t, tmpLowerDirs, len(lowerDirs))

			lowerContents := make([][]byte, len(lowerDirs))

			for i, dir := range lowerDirs {
				correspondingRemount := tmpLowerDirs[i]
				filename := filepath.Base(dir)

				expectedFile, err := os.ReadFile(filepath.Join(dir, filename))
				require.NoError(t, err, "reading comparison test fixture file")
				lowerContents[i] = expectedFile

				actualFile, err := os.ReadFile(filepath.Join(correspondingRemount, filename))
				require.NoError(t, err, "reading file in temporary remount")

				assert.Equal(t, expectedFile, actualFile, "file content in temporary remount")
			}

			var busyDh *os.File
			if tc.injectUmountFault {
				busyDh, err = os.Open(tmpLowerDirs[0])
				require.NoError(t, err)
				defer busyDh.Close()
			}

			cleanup()

			_, err = os.Stat(remountsLocation)

			if tc.injectUmountFault {
				// We should have failed to remove the remounts location if the unmount failed.
				assert.NoError(t, err, "expected remounts location to still exist after unmount failure")
			} else {
				pathErr, isPathErr := err.(*fs.PathError)
				require.True(t, isPathErr, "expected a PathError")
				assert.Equal(t, unix.ENOENT, pathErr.Err, "temporary remounts should be cleaned up")
			}

			// Original lowerdirs should be unaffected.
			for i, dir := range lowerDirs {
				filename := filepath.Base(dir)

				actualFile, err := os.ReadFile(filepath.Join(dir, filename))
				require.NoError(t, err, "reading file in original lowerdir")
				assert.Equal(t, lowerContents[i], actualFile, "file content in original lowerdir")
			}

			// If we blocked cleanup, allow it now so the test stays tidy.
			if tc.injectUmountFault {
				require.NoError(t, busyDh.Close())
				cleanup()
			}
		})
	}
}

func setupMounts(t *testing.T) (target string, mounts []Mount) {
	dir1 := t.TempDir()
	dir2 := t.TempDir()

	if err := os.Mkdir(filepath.Join(dir1, "foo"), 0755); err != nil {
		t.Fatal(err)
	}
	mounts = append(mounts, Mount{
		Type:   "bind",
		Source: dir1,
		Options: []string{
			"ro",
			"rbind",
		},
	})

	if err := os.WriteFile(filepath.Join(dir2, "bar"), []byte("bar"), 0644); err != nil {
		t.Fatal(err)
	}
	mounts = append(mounts, Mount{
		Type:   "bind",
		Source: dir2,
		Target: "foo",
		Options: []string{
			"ro",
			"rbind",
		},
	})

	target = t.TempDir()
	if err := All(mounts, target); err != nil {
		t.Fatal(err)
	}

	b, err := os.ReadFile(filepath.Join(target, "foo/bar"))
	if err != nil {
		t.Fatal(err)
	}

	if string(b) != "bar" {
		t.Fatalf("unexpected file content: %s", b)
	}

	return target, mounts
}

func supportsIDMap(path string) bool {
	treeFD, err := unix.OpenTree(-1, path, uint(unix.OPEN_TREE_CLONE|unix.OPEN_TREE_CLOEXEC))
	if err != nil {
		return false
	}
	defer unix.Close(treeFD)

	// We want to test if idmap mounts are supported.
	// So we use just some random mapping, it doesn't really matter which one.
	// For the helper command, we just need something that is alive while we
	// test this, a sleep 5 will do it.
	cmd := exec.Command("sleep", "5")
	cmd.SysProcAttr = &syscall.SysProcAttr{
		Cloneflags:  syscall.CLONE_NEWUSER,
		UidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
		GidMappings: []syscall.SysProcIDMap{{ContainerID: 0, HostID: 65536, Size: 65536}},
	}
	if err := cmd.Start(); err != nil {
		return false
	}
	defer func() {
		_ = cmd.Process.Kill()
		_ = cmd.Wait()
	}()

	usernsFD := fmt.Sprintf("/proc/%d/ns/user", cmd.Process.Pid)
	var usernsFile *os.File
	if usernsFile, err = os.Open(usernsFD); err != nil {
		return false
	}
	defer usernsFile.Close()

	attr := unix.MountAttr{
		Attr_set:  unix.MOUNT_ATTR_IDMAP,
		Userns_fd: uint64(usernsFile.Fd()),
	}
	if err := unix.MountSetattr(treeFD, "", unix.AT_EMPTY_PATH, &attr); err != nil {
		return false
	}

	return true
}