feat: add essential shell commands - pwd, uptime and clearhistory

.gitignore

@@ -0,0 +1 @@
+target/

src/main/java/com/mycmd/App.java

@@ -77,5 +77,8 @@ private static void registerCommands(Map<String, Command> commands) {
         commands.put("tree", new TreeCommand());
         commands.put("date", new DateCommand());
         commands.put("history", new HistoryCommand());
+        commands.put("pwd", new PwdCommand());
+        commands.put("uptime", new UptimeCommand());
+        commands.put("clearhistory", new ClearHistoryCommand());
     }
 }

src/main/java/com/mycmd/ShellContext.java

@@ -7,11 +7,13 @@
 public class ShellContext {
     private File currentDir;
     private List<String> commandHistory;
+    private final long startTime;
     private static final int MAX_HISTORY = 10;
 
     public ShellContext() {
         this.currentDir = new File(System.getProperty("user.dir"));
         this.commandHistory = new ArrayList<>();
+        this.startTime = System.currentTimeMillis();
     }
 
     public File getCurrentDir() {
@@ -22,6 +24,10 @@ public void setCurrentDir(File dir) {
         this.currentDir = dir;
     }
 
+    public long getStartTime() {
+        return startTime;
+    }
+
     public List<String> getCommandHistory() {
         return commandHistory;
     }
@@ -35,6 +41,10 @@ public void addToHistory(String command) {
         }
     }
 
+    public void clearHistory() {
+        commandHistory.clear();
+    }
+
     /**
      * Resolve the given path (absolute or relative) to a File using the current directory.
      * If the provided path is absolute, returns it directly; otherwise returns a File rooted at currentDir.

src/main/java/com/mycmd/commands/ClearHistoryCommand.java

@@ -0,0 +1,36 @@
+package com.mycmd.commands;
+
+import com.mycmd.Command;
+import com.mycmd.ShellContext;
+
+/**
+ * Clears the stored command history.
+ * 
+ * This command removes all previously executed commands from the shell's
+ * command history. After execution, the history list will be empty and
+ * the history command will show no previous commands.
+ * 
+ * Usage:
+ * - clearhistory : Clear all stored command history
+ * 
+ * This is useful for privacy purposes or when you want to start fresh
+ * with a clean command history. The history is cleared immediately
+ * and cannot be recovered.
+ */
+public class ClearHistoryCommand implements Command {
+    @Override
+    public void execute(String[] args, ShellContext context) {
+        context.clearHistory();
+        System.out.println("Command history cleared.");
+    }
+
+    @Override
+    public String description() {
+        return "Clear the stored command history.";
+    }
+
+    @Override
+    public String usage() {
+        return "clearhistory";
+    }
+}

src/main/java/com/mycmd/commands/HelpCommand.java

@@ -20,8 +20,8 @@ public HelpCommand(Map<String, Command> commands) {
     @Override
     public void execute(String[] args, ShellContext context) {
         // Detailed help for a specific command
-        if (args.length > 1) {
-            String cmdName = args[1];
+        if (args.length > 0) {
+            String cmdName = args[0];
             Command cmd = commands.get(cmdName);
 
             if (cmd != null) {

src/main/java/com/mycmd/commands/PwdCommand.java

@@ -0,0 +1,35 @@
+package com.mycmd.commands;
+
+import com.mycmd.Command;
+import com.mycmd.ShellContext;
+
+/**
+ * Prints the current working directory.
+ * 
+ * This command displays the absolute path of the current working directory
+ * stored in the shell context. It's equivalent to the Unix/Linux 'pwd' command
+ * and provides the same functionality as 'cd' without arguments.
+ * 
+ * Usage:
+ * - pwd : Print the current working directory path
+ * 
+ * The command always prints the absolute path of the current directory,
+ * making it useful for scripts and when you need to know your exact location
+ * in the file system.
+ */
+public class PwdCommand implements Command {
+    @Override
+    public void execute(String[] args, ShellContext context) {
+        System.out.println(context.getCurrentDir().getAbsolutePath());
+    }
+
+    @Override
+    public String description() {
+        return "Print the current working directory path.";
+    }
+
+    @Override
+    public String usage() {
+        return "pwd";
+    }
+}

src/main/java/com/mycmd/commands/UptimeCommand.java

@@ -0,0 +1,45 @@
+package com.mycmd.commands;
+
+import com.mycmd.Command;
+import com.mycmd.ShellContext;
+
+/**
+ * Displays how long the shell has been running since startup.
+ * 
+ * This command shows the uptime of the MyCMD shell session, displaying
+ * the time elapsed since the shell was started. The uptime is calculated
+ * from the shell start time stored in the ShellContext.
+ * 
+ * Usage:
+ * - uptime : Display shell uptime in hours, minutes, and seconds
+ * 
+ * The output format shows the uptime as "Up since Xh Ym Zs" where:
+ * - X is hours
+ * - Y is minutes  
+ * - Z is seconds
+ * 
+ * This is useful for monitoring how long a shell session has been active.
+ */
+public class UptimeCommand implements Command {
+    @Override
+    public void execute(String[] args, ShellContext context) {
+        long uptimeMillis = System.currentTimeMillis() - context.getStartTime();
+
+        long totalSeconds = uptimeMillis / 1000;
+        long hours = totalSeconds / 3600;
+        long minutes = (totalSeconds % 3600) / 60;
+        long seconds = totalSeconds % 60;
+
+        System.out.printf("Up since %dh %dm %ds%n", hours, minutes, seconds);
+    }
+
+    @Override
+    public String description() {
+        return "Display how long the shell has been running since startup.";
+    }
+
+    @Override
+    public String usage() {
+        return "uptime";
+    }
+}