package writefs

import (
	"errors"
	"fmt"
	"io/fs"
	"log"
	"os"
	"path"
	"syscall"
	"time"
)

func Main() {
	// Create a test directory
	dir := path.Join(os.TempDir(), "dir")
	dir1 := path.Join(os.TempDir(), "dir1")
	if err := os.Mkdir(dir, 0o700); err != nil {
		log.Panicln(err)
		return
	}
	defer os.Remove(dir)

	// Create a test file in that directory
	file := path.Join(dir, "file")
	file1 := path.Join(os.TempDir(), "file1")

	if err := os.WriteFile(file, []byte{}, 0o600); err != nil {
		log.Panicln(err)
		return
	}
	defer os.Remove(file)

	// Ensure stat works, particularly mode.
	for _, path := range []string{dir, file} {
		if stat, err := os.Stat(path); err != nil {
			log.Panicln(err)
		} else {
			fmt.Println(path, "mode", stat.Mode())
		}
	}

	// Now, test that syscall.WriteAt works
	f, err := os.OpenFile(file1, os.O_RDWR|os.O_CREATE, 0o600)
	if err != nil {
		log.Panicln(err)
	}
	defer f.Close()

	// Write segments to the file, noting map iteration isn't ordered.
	bytes := []byte("wazero")
	for o, b := range map[int][]byte{3: bytes[3:], 0: bytes[:3]} {
		n, err := f.WriteAt(b, int64(o))
		if err != nil {
			log.Panicln(err)
		} else if n != 3 {
			log.Panicln("expected 3, but wrote", n)
		}
	}

	// Now, use ReadAt (tested in testfs package) to verify everything wrote!
	if _, err = f.ReadAt(bytes, 0); err != nil {
		log.Panicln(err)
	} else if string(bytes) != "wazero" {
		log.Panicln("unexpected contents:", string(bytes))
	}

	// Next, truncate it.
	if err = f.Truncate(2); err != nil {
		log.Panicln(err)
	}
	// Next, sync it.
	if err = f.Sync(); err != nil {
		log.Panicln(err)
	}

	if stat, err := f.Stat(); err != nil {
		log.Panicln(err)
	} else if mode := stat.Mode() & fs.ModePerm; mode != 0o600 {
		log.Panicln("expected mode = 0o600", mode)
	}

	// Finally, close it.
	if err = f.Close(); err != nil {
		log.Panicln(err)
	}

	// Set to read-only
	if err = syscall.Chmod(file1, 0o400); err != nil {
		log.Panicln(err)
	}

	// Test stat
	stat, err := os.Stat(file1)
	if err != nil {
		log.Panicln(err)
	}

	if stat.Mode().Type() != 0 {
		log.Panicln("expected type = 0", stat.Mode().Type())
	}
	if stat.Mode().Perm() != 0o400 {
		log.Panicln("expected perm = 0o400", stat.Mode().Perm())
	}

	// Check the file was truncated.
	if bytes, err := os.ReadFile(file1); err != nil {
		log.Panicln(err)
	} else if string(bytes) != "wa" {
		log.Panicln("unexpected contents:", string(bytes))
	}

	// create a hard link
	link := file1 + "-link"
	if err = os.Link(file1, link); err != nil {
		log.Panicln(err)
	}

	// Ensure this is a hard link, so they have the same inode.
	file1Stat, err := os.Lstat(file1)
	if err != nil {
		log.Panicln(err)
	}
	linkStat, err := os.Lstat(link)
	if err != nil {
		log.Panicln(err)
	}
	if !os.SameFile(file1Stat, linkStat) {
		log.Panicln("expected file == link stat", file1Stat, linkStat)
	}

	// create a symbolic link
	symlink := file1 + "-symlink"
	if err = os.Symlink(file1, symlink); err != nil {
		log.Panicln(err)
	}

	// verify we can read the symbolic link back
	if dst, err := os.Readlink(symlink); err != nil {
		log.Panicln(err)
	} else if dst != dst {
		log.Panicln("expected link dst = old value", dst, dst)
	}

	// Test lstat which should be about the link not its target.
	symlinkStat, err := os.Lstat(symlink)
	if err != nil {
		log.Panicln(err)
	}

	if symlinkStat.Mode().Type() != fs.ModeSymlink {
		log.Panicln("expected type = symlink", symlinkStat.Mode().Type())
	}
	if size := int64(len(file1)); symlinkStat.Size() != size {
		log.Panicln("unexpected symlink size", symlinkStat.Size(), size)
	}
	// A symbolic link isn't the same file as what it points to.
	if os.SameFile(file1Stat, symlinkStat) {
		log.Panicln("expected file != link stat", file1Stat, symlinkStat)
	}

	// Test removing a non-empty empty directory
	if err = syscall.Rmdir(dir); err != syscall.ENOTEMPTY {
		log.Panicln("unexpected error", err)
	}

	// Test updating the mod time of a file, noting JS has millis precision.
	atime := time.Unix(123, 4*1e6)
	mtime := time.Unix(567, 8*1e6)

	// Ensure errors propagate
	if err = os.Chtimes("noexist", atime, mtime); !errors.Is(err, syscall.ENOENT) {
		log.Panicln("unexpected error", err)
	}

	// Now, try a real update.
	if err = os.Chtimes(dir, atime, mtime); err != nil {
		log.Panicln("unexpected error", err)
	}

	// Ensure the times translated properly.
	dirAtimeNsec, dirMtimeNsec, dirDev, dirInode := statFields(dir)
	fmt.Println("dir times:", dirAtimeNsec, dirMtimeNsec)

	// Ensure we were able to read the dev and inode.
	//
	// Note: The size of syscall.Stat_t.Dev (32-bit) in js is smaller than
	// linux (64-bit), so we can't compare its real value against the host.
	if dirDev == 0 {
		log.Panicln("expected dir dev != 0", dirDev)
	}
	if dirInode == 0 {
		log.Panicln("expected dir inode != 0", dirInode)
	}

	// Test renaming a file, noting we can't verify error numbers as they
	// vary per operating system.
	if err = syscall.Rename(file, dir); err == nil {
		log.Panicln("expected error")
	}
	if err = syscall.Rename(file, file1); err != nil {
		log.Panicln("unexpected error", err)
	}

	// Test renaming a directory
	if err = syscall.Rename(dir, file1); err == nil {
		log.Panicln("expected error")
	}
	if err = syscall.Rename(dir, dir1); err != nil {
		log.Panicln("unexpected error", err)
	}

	// Compare stat after renaming.
	atimeNsec, mtimeNsec, dev, inode := statFields(dir1)
	// atime shouldn't change as we didn't access (re-open) the directory.
	if atimeNsec != dirAtimeNsec {
		log.Panicln("expected dir atimeNsec = previous value", atimeNsec, dirAtimeNsec)
	}
	// mtime should change because we renamed the directory.
	if mtimeNsec <= dirMtimeNsec {
		log.Panicln("expected dir mtimeNsec > previous value", mtimeNsec, dirMtimeNsec)
	}
	// dev/inode shouldn't change during rename.
	if dev != dirDev {
		log.Panicln("expected dir dev = previous value", dev, dirDev)
	}
	if inode != dirInode {
		log.Panicln("expected dir inode = previous value", dev, dirInode)
	}

	// Test unlinking a file
	if err = syscall.Rmdir(file1); err != syscall.ENOTDIR {
		log.Panicln("unexpected error", err)
	}
	if err = syscall.Unlink(file1); err != nil {
		log.Panicln("unexpected error", err)
	}

	// Test removing an empty directory
	if err = syscall.Unlink(dir1); err != syscall.EISDIR {
		log.Panicln("unexpected error", err)
	}
	if err = syscall.Rmdir(dir1); err != nil {
		log.Panicln("unexpected error", err)
	}

	// shouldn't fail
	if err = os.RemoveAll(dir1); err != nil {
		log.Panicln(err)
		return
	}

	// ensure we can use zero as is used in TestRemoveReadOnlyDir
	if err = os.Mkdir(dir1, 0); err != nil {
		log.Panicln(err)
		return
	}
	defer os.Remove(dir)

	// Symlink and Readlink tests.
	s := "0123456789abcdef0123456789abcdef0123456789abcdef0123456789abcdef"
	from := "/symlink.txt"
	err = os.Symlink(s, from)
	if err != nil {
		log.Panicln(err)
	}

	r, err := os.Readlink(from)
	if err != nil {
		log.Fatalf("readlink %q failed: %v", from, err)
	}
	if r != s {
		log.Fatalf("after symlink %q != %q", r, s)
	}
}