type CompositeFS struct {
	UnimplementedFS
	// contains filtered or unexported fields
}

type FS interface {
	// String should return a human-readable format of the filesystem
	//
	// For example, if this filesystem is backed by the real directory
	// "/tmp/wasm", the expected value is "/tmp/wasm".
	//
	// When the host filesystem isn't a real filesystem, substitute a symbolic,
	// human-readable name. e.g. "virtual"
	String() string

	// OpenFile is similar to os.OpenFile, except the path is relative to this
	// file system, and syscall.Errno are returned instead of a os.PathError.
	//
	// # Errors
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `path` or `flag` is invalid.
	//   - syscall.ENOENT: `path` doesn't exist and `flag` doesn't contain
	//     os.O_CREATE.
	//
	// # Constraints on the returned file
	//
	// Implementations that can read flags should enforce them regardless of
	// the type returned. For example, while os.File implements io.Writer,
	// attempts to write to a directory or a file opened with os.O_RDONLY fail
	// with a syscall.EBADF.
	//
	// Some implementations choose whether to enforce read-only opens, namely
	// fs.FS. While fs.FS is supported (Adapt), wazero cannot runtime enforce
	// open flags. Instead, we encourage good behavior and test our built-in
	// implementations.
	OpenFile(path string, flag int, perm fs.FileMode) (fs.File, error)

	// Mkdir is similar to os.Mkdir, except the path is relative to this file
	// system, and syscall.Errno are returned instead of a os.PathError.
	//
	// # Errors
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `path` is invalid.
	//   - syscall.EEXIST: `path` exists and is a directory.
	//   - syscall.ENOTDIR: `path` exists and is a file.
	//
	Mkdir(path string, perm fs.FileMode) error

	// Rename is similar to syscall.Rename, except the path is relative to this
	// file system.
	//
	// # Errors
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `from` or `to` is invalid.
	//   - syscall.ENOENT: `from` or `to` don't exist.
	//   - syscall.ENOTDIR: `from` is a directory and `to` exists, but is a file.
	//   - syscall.EISDIR: `from` is a file and `to` exists, but is a directory.
	//   - syscall.ENOTEMPTY: `both from` and `to` are existing directory, but `to` is not empty.
	//
	// # Notes
	//
	//   -  Windows doesn't let you overwrite an existing directory.
	Rename(from, to string) error

	// Rmdir is similar to syscall.Rmdir, except the path is relative to this
	// file system.
	//
	// # Errors
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `path` is invalid.
	//   - syscall.ENOENT: `path` doesn't exist.
	//   - syscall.ENOTDIR: `path` exists, but isn't a directory.
	//   - syscall.ENOTEMPTY: `path` exists, but isn't empty.
	//
	// # Notes
	//
	//   - As of Go 1.19, Windows maps syscall.ENOTDIR to syscall.ENOENT.
	Rmdir(path string) error

	// Unlink is similar to syscall.Unlink, except the path is relative to this
	// file system.
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `path` is invalid.
	//   - syscall.ENOENT: `path` doesn't exist.
	//   - syscall.EISDIR: `path` exists, but is a directory.
	Unlink(path string) error

	// Truncate is similar to syscall.Truncate, except the path is relative to
	// this file system.
	//
	// # Errors
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `path` is invalid or size is negative.
	//   - syscall.ENOENT: `path` doesn't exist
	Truncate(name string, size int64) error

	// Utimes is similar to syscall.UtimesNano, except the path is relative to
	// this file system.
	//
	// # Errors
	//
	// The following errors are expected:
	//   - syscall.EINVAL: `path` is invalid.
	//   - syscall.ENOENT: `path` doesn't exist
	//
	// # Notes
	//
	//   - To set wall clock time, retrieve it first from sys.Walltime.
	//   - syscall.UtimesNano cannot change the ctime. Also, neither WASI nor
	//     runtime.GOOS=js support changing it. Hence, ctime it is absent here.
	Utimes(path string, atimeNsec, mtimeNsec int64) error
}

type UnimplementedFS struct{}