// Copyright 2015 Google Inc. All Rights Reserved.
//
// 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 memfs_test

import (
	"io/ioutil"
	"log"
	"os"
	"os/user"
	"path"
	"strconv"
	"strings"
	"syscall"
	"testing"
	"time"

	"github.com/jacobsa/fuse"
	"github.com/jacobsa/fuse/samples/memfs"
	"github.com/jacobsa/gcsfuse/timeutil"
	. "github.com/jacobsa/oglematchers"
	. "github.com/jacobsa/ogletest"
	"golang.org/x/net/context"
)

func TestMemFS(t *testing.T) { RunTests(t) }

////////////////////////////////////////////////////////////////////////
// Helpers
////////////////////////////////////////////////////////////////////////

func currentUid() uint32 {
	user, err := user.Current()
	if err != nil {
		panic(err)
	}

	uid, err := strconv.ParseUint(user.Uid, 10, 32)
	if err != nil {
		panic(err)
	}

	return uint32(uid)
}

func currentGid() uint32 {
	user, err := user.Current()
	if err != nil {
		panic(err)
	}

	gid, err := strconv.ParseUint(user.Gid, 10, 32)
	if err != nil {
		panic(err)
	}

	return uint32(gid)
}

func timespecToTime(ts syscall.Timespec) time.Time {
	return time.Unix(ts.Sec, ts.Nsec)
}

////////////////////////////////////////////////////////////////////////
// Boilerplate
////////////////////////////////////////////////////////////////////////

type MemFSTest struct {
	clock timeutil.SimulatedClock
	mfs   *fuse.MountedFileSystem
}

var _ SetUpInterface = &MemFSTest{}
var _ TearDownInterface = &MemFSTest{}

func init() { RegisterTestSuite(&MemFSTest{}) }

func (t *MemFSTest) SetUp(ti *TestInfo) {
	var err error

	// Set up a fixed, non-zero time.
	t.clock.SetTime(time.Now())

	// Set up a temporary directory for mounting.
	mountPoint, err := ioutil.TempDir("", "memfs_test")
	if err != nil {
		panic("ioutil.TempDir: " + err.Error())
	}

	// Mount a file system.
	fs := memfs.NewMemFS(&t.clock)
	if t.mfs, err = fuse.Mount(mountPoint, fs); err != nil {
		panic("Mount: " + err.Error())
	}

	if err = t.mfs.WaitForReady(context.Background()); err != nil {
		panic("MountedFileSystem.WaitForReady: " + err.Error())
	}
}

func (t *MemFSTest) TearDown() {
	// Unmount the file system. Try again on "resource busy" errors.
	delay := 10 * time.Millisecond
	for {
		err := t.mfs.Unmount()
		if err == nil {
			break
		}

		if strings.Contains(err.Error(), "resource busy") {
			log.Println("Resource busy error while unmounting; trying again")
			time.Sleep(delay)
			delay = time.Duration(1.3 * float64(delay))
			continue
		}

		panic("MountedFileSystem.Unmount: " + err.Error())
	}

	if err := t.mfs.Join(context.Background()); err != nil {
		panic("MountedFileSystem.Join: " + err.Error())
	}
}

////////////////////////////////////////////////////////////////////////
// Test functions
////////////////////////////////////////////////////////////////////////

func (t *MemFSTest) ContentsOfEmptyFileSystem() {
	entries, err := ioutil.ReadDir(t.mfs.Dir())

	AssertEq(nil, err)
	ExpectThat(entries, ElementsAre())
}

func (t *MemFSTest) Mkdir_OneLevel() {
	var err error
	var fi os.FileInfo
	var stat *syscall.Stat_t
	var entries []os.FileInfo

	dirName := path.Join(t.mfs.Dir(), "dir")

	// Create a directory within the root.
	createTime := t.clock.Now()
	err = os.Mkdir(dirName, 0754)
	AssertEq(nil, err)

	// Simulate time advancing.
	t.clock.AdvanceTime(time.Second)

	// Stat the directory.
	fi, err = os.Stat(dirName)
	stat = fi.Sys().(*syscall.Stat_t)

	AssertEq(nil, err)
	ExpectEq("dir", fi.Name())
	ExpectEq(0, fi.Size())
	ExpectEq(os.ModeDir|0754, fi.Mode())
	ExpectEq(0, fi.ModTime().Sub(createTime))
	ExpectTrue(fi.IsDir())

	ExpectNe(0, stat.Ino)
	ExpectEq(1, stat.Nlink)
	ExpectEq(currentUid(), stat.Uid)
	ExpectEq(currentGid(), stat.Gid)
	ExpectEq(0, stat.Size)
	ExpectEq(0, timespecToTime(stat.Atimespec).Sub(createTime))
	ExpectEq(0, timespecToTime(stat.Mtimespec).Sub(createTime))
	ExpectEq(0, timespecToTime(stat.Ctimespec).Sub(createTime))

	// Read the directory.
	entries, err = ioutil.ReadDir(dirName)

	AssertEq(nil, err)
	ExpectThat(entries, ElementsAre())

	// Read the root.
	entries, err = ioutil.ReadDir(t.mfs.Dir())

	AssertEq(nil, err)
	AssertEq(1, len(entries))

	fi = entries[0]
	ExpectEq("dir", fi.Name())
	ExpectEq(os.ModeDir|0754, fi.Mode())
}

func (t *MemFSTest) Mkdir_TwoLevels() {
	var err error
	var fi os.FileInfo
	var stat *syscall.Stat_t
	var entries []os.FileInfo

	// Create a directory within the root.
	err = os.Mkdir(path.Join(t.mfs.Dir(), "parent"), 0700)
	AssertEq(nil, err)

	// Create a child of that directory.
	createTime := t.clock.Now()
	err = os.Mkdir(path.Join(t.mfs.Dir(), "parent/dir"), 0754)
	AssertEq(nil, err)

	// Simulate time advancing.
	t.clock.AdvanceTime(time.Second)

	// Stat the directory.
	fi, err = os.Stat(path.Join(t.mfs.Dir(), "parent/dir"))
	stat = fi.Sys().(*syscall.Stat_t)

	AssertEq(nil, err)
	ExpectEq("dir", fi.Name())
	ExpectEq(0, fi.Size())
	ExpectEq(os.ModeDir|0754, fi.Mode())
	ExpectEq(0, fi.ModTime().Sub(createTime))
	ExpectTrue(fi.IsDir())

	ExpectNe(0, stat.Ino)
	ExpectEq(1, stat.Nlink)
	ExpectEq(currentUid(), stat.Uid)
	ExpectEq(currentGid(), stat.Gid)
	ExpectEq(0, stat.Size)
	ExpectEq(0, timespecToTime(stat.Atimespec).Sub(createTime))
	ExpectEq(0, timespecToTime(stat.Mtimespec).Sub(createTime))
	ExpectEq(0, timespecToTime(stat.Ctimespec).Sub(createTime))

	// Read the directory.
	entries, err = ioutil.ReadDir(path.Join(t.mfs.Dir(), "parent/dir"))

	AssertEq(nil, err)
	ExpectThat(entries, ElementsAre())

	// Read the parent.
	entries, err = ioutil.ReadDir(path.Join(t.mfs.Dir(), "parent"))

	AssertEq(nil, err)
	AssertEq(1, len(entries))

	fi = entries[0]
	ExpectEq("dir", fi.Name())
	ExpectEq(os.ModeDir|0754, fi.Mode())
}

func (t *MemFSTest) Mkdir_AlreadyExists() {
	var err error
	dirName := path.Join(t.mfs.Dir(), "dir")

	// Create the directory once.
	err = os.Mkdir(dirName, 0754)
	AssertEq(nil, err)

	// Attempt to create it again.
	err = os.Mkdir(dirName, 0754)

	AssertNe(nil, err)
	ExpectThat(err, Error(HasSubstr("exists")))
}

func (t *MemFSTest) Mkdir_IntermediateIsFile() {
	var err error

	// Create a file.
	fileName := path.Join(t.mfs.Dir(), "foo")
	err = ioutil.WriteFile(fileName, []byte{}, 0700)
	AssertEq(nil, err)

	// Attempt to create a directory within the file.
	dirName := path.Join(fileName, "dir")
	err = os.Mkdir(dirName, 0754)

	AssertNe(nil, err)
	ExpectThat(err, Error(HasSubstr("TODO")))
}

func (t *MemFSTest) Mkdir_IntermediateIsNonExistent() {
	var err error

	// Attempt to create a sub-directory of a non-existent sub-directory.
	dirName := path.Join(t.mfs.Dir(), "foo/dir")
	err = os.Mkdir(dirName, 0754)

	AssertNe(nil, err)
	ExpectThat(err, Error(HasSubstr("no such file or directory")))
}

func (t *MemFSTest) Mkdir_PermissionDenied() {
	var err error

	// Create a directory within the root without write permissions.
	err = os.Mkdir(path.Join(t.mfs.Dir(), "parent"), 0500)
	AssertEq(nil, err)

	// Attempt to create a child of that directory.
	err = os.Mkdir(path.Join(t.mfs.Dir(), "parent/dir"), 0754)

	AssertNe(nil, err)
	ExpectThat(err, Error(HasSubstr("permission denied")))
}

func (t *MemFSTest) CreateNewFile_InRoot() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) CreateNewFile_InSubDir() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) ModifyExistingFile_InRoot() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) ModifyExistingFile_InSubDir() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) UnlinkFile_Exists() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) UnlinkFile_NotAFile() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) UnlinkFile_NonExistent() {
	AssertTrue(false, "TODO")
}

func (t *MemFSTest) Rmdir_NonEmpty() {
	var err error

	// Create two levels of directories.
	err = os.MkdirAll(path.Join(t.mfs.Dir(), "foo/bar"), 0754)
	AssertEq(nil, err)

	// Attempt to remove the parent.
	err = os.Remove(path.Join(t.mfs.Dir(), "foo"))

	AssertNe(nil, err)
	ExpectThat(err, Error(HasSubstr("not empty")))
}

func (t *MemFSTest) Rmdir_Empty() {
	var err error
	var entries []os.FileInfo

	// Create two levels of directories.
	err = os.MkdirAll(path.Join(t.mfs.Dir(), "foo/bar"), 0754)
	AssertEq(nil, err)

	// Remove the leaf.
	err = os.Remove(path.Join(t.mfs.Dir(), "foo/bar"))
	AssertEq(nil, err)

	// There should be nothing left in the parent.
	entries, err = ioutil.ReadDir(path.Join(t.mfs.Dir(), "foo"))

	AssertEq(nil, err)
	ExpectThat(entries, ElementsAre())

	// Remove the parent.
	err = os.Remove(path.Join(t.mfs.Dir(), "foo"))
	AssertEq(nil, err)

	// Now the root directory should be empty, too.
	entries, err = ioutil.ReadDir(t.mfs.Dir())

	AssertEq(nil, err)
	ExpectThat(entries, ElementsAre())
}

func (t *MemFSTest) Rmdir_NonExistent() {
	err := os.Remove(path.Join(t.mfs.Dir(), "blah"))

	AssertNe(nil, err)
	ExpectThat(err, Error(HasSubstr("no such file or directory")))
}

func (t *MemFSTest) Rmdir_OpenedForReading() {
	var err error

	// Create a directory.
	createTime := t.clock.Now()
	err = os.Mkdir(path.Join(t.mfs.Dir(), "dir"), 0700)
	AssertEq(nil, err)

	// Simulate time advancing.
	t.clock.AdvanceTime(time.Second)

	// Open the directory for reading.
	f, err := os.Open(path.Join(t.mfs.Dir(), "dir"))
	defer func() {
		if f != nil {
			ExpectEq(nil, f.Close())
		}
	}()

	AssertEq(nil, err)

	// Remove the directory.
	err = os.Remove(path.Join(t.mfs.Dir(), "dir"))
	AssertEq(nil, err)

	// Create a new directory, with the same name even, and add some contents
	// within it.
	err = os.MkdirAll(path.Join(t.mfs.Dir(), "dir/foo"), 0700)
	AssertEq(nil, err)

	err = os.MkdirAll(path.Join(t.mfs.Dir(), "dir/bar"), 0700)
	AssertEq(nil, err)

	err = os.MkdirAll(path.Join(t.mfs.Dir(), "dir/baz"), 0700)
	AssertEq(nil, err)

	// We should still be able to stat the open file handle. It should show up as
	// unlinked.
	fi, err := f.Stat()

	ExpectEq("dir", fi.Name())
	ExpectEq(0, fi.ModTime().Sub(createTime))

	// TODO(jacobsa): Re-enable this assertion if the following issue is fixed:
	//     https://github.com/bazillion/fuse/issues/66
	// ExpectEq(0, fi.Sys().(*syscall.Stat_t).Nlink)

	// Attempt to read from the directory. This should succeed even though it has
	// been unlinked, and we shouldn't see any junk from the new directory.
	entries, err := f.Readdir(0)

	AssertEq(nil, err)
	ExpectThat(entries, ElementsAre())
}