Build an in-memory file system

• A tree of directories and files rooted at /; paths are absolute, with . and .. segments resolved and repeated slashes ignored
• mkdir(path, { recursive }) creates directories; creating an existing directory or a path under a file is an error unless recursive makes the call idempotent
• ls(path) returns the sorted names inside a directory, or the file name itself if the path is a file
• writeFile(path, content), appendFile(path, content) and readFile(path) create or modify files, and reading a directory or a missing file raises a specific error
• rm(path, { recursive }) deletes a file, or a directory only if empty or when recursive is true; removing the root is rejected
• size(path) returns the size of a file, or the total size of a directory including descendants

Only after every requirement works.

• mv and cp for files and directories
• Symbolic links and cycle protection
• Permissions and a find with glob patterns