Smart File System Simulator

A robust, in-memory file system simulator written in Java. This project mimics the core functionality of a Unix-like file system, providing a rich command-line interface (CLI) for file management, navigation, and diagnostics.

It is designed to demonstrate advanced data structures and system design concepts, including Inode-based architecture, Command Pattern for Undo/Redo, and Graph traversal algorithms.

Key Features

Core File Operations

• File & Directory Management: mkdir, touch, rm (recursive), mv, cp.
• Navigation: cd, pwd, ls (with detailed view), tree (visual structure).
• Content Manipulation: write, read, cat, grep (text search).

Advanced Linking

• Hard Links: Create multiple directory entries pointing to the same Inode (ln).
• Symbolic Links: Create soft links to other paths with cycle detection (ln -s).
• Path Resolution: Robust engine handling absolute/relative paths, .., ., and symlink traversal.

System Integrity & Diagnostics

• Inode Architecture: Separation of file metadata (Inode) from directory entries (FileNode).
• Consistency Checker (fsck): Detects orphaned nodes, broken symlinks, and reference count mismatches.
• Disk Usage (du): Calculates directory sizes while handling cycles gracefully.
• Permissions: Basic r (read) and w (write) permission system (chmod).

History & Persistence

• Undo/Redo: Full support for undoing and redoing file operations.
• Snapshots: Save and restore the entire file system state to disk (snapshot, restore).
• Access History: Tracks navigation history and recently accessed files (history, mru).

Getting Started

Prerequisites

• Java SE 22 or higher.

Running the Simulator

1. Compile the project:

   javac Main.java core/*.java history/*.java model/*.java

2. Run the application:

   java Main

Command Reference

Command	Description
ls [-l]	List files in current directory (use -l for details).
cd <path>	Change directory. Supports .. and symlinks.
mkdir <name>	Create a new directory.
touch <name>	Create a new empty file.
write <file> "<text>"	Write text content to a file.
cat <file>	Display file content.
ln [-s] <src> <dst>	Create a hard link or symbolic link (-s).
rm [-r] <name>	Remove a file or directory (recursively with -r).
cp <src> <dst>	Copy a file or directory.
mv <src> <dst>	Move or rename a file or directory.
find <name>	Search for files or directories by name.
grep <text> <file>	Search for text within a file.
chmod <perm> <file>	Change permissions (e.g., chmod rw file.txt).
fsck	Run file system consistency check.
undo / redo	Undo or redo the last operation.
tree	Display the directory structure as a tree.
stat <name>	Show detailed inode statistics.
snapshot / restore	Save or load the file system state.
exit	Quit the simulator.

Architecture

• core/FileSystem.java: The main controller handling commands and logic.
• core/FileNode.java: Represents a directory entry (name + pointer to Inode).
• model/Inode.java: Stores actual file data, metadata, and reference counts.
• history/UndoManager.java: Implements the Command Pattern for operation history.