HeadCommand with common flags

- Displays the first part of files.
- Implemented flags -n for specifying the number of lines and -c for specifying the number of bytes.
- Handles multiple file inputs with appropriate headers for each file.
- Defaults to 10 lines and error handling for mandatory arguments with flags.

Author: siddhant-vij

src/com/unixtools/command/filecontent/HeadCommand.java

@@ -1,5 +1,103 @@
 package com.unixtools.command.filecontent;
 
-public class HeadCommand {
-  
+import com.unixtools.core.Command;
+
+import java.io.*;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.util.ArrayList;
+import java.util.List;
+
+public class HeadCommand implements Command {
+  private static final String VALID_FLAGS = "nc";
+  private int numberOfLines = 10;
+  private int numberOfBytes = -1;
+  private boolean isBytesFlagUsed = false;
+
+  @Override
+  public void execute(String[] args) {
+    List<String> flags = new ArrayList<>();
+    List<String> filePaths = new ArrayList<>();
+    parseArguments(args, flags, filePaths);
+
+    if (!areFlagsValid(flags)) {
+      System.out.println("Invalid flags. Valid flags are: " + VALID_FLAGS);
+      return;
+    }
+
+    if (filePaths.isEmpty()) {
+      System.out.println("head: No file specified.");
+      return;
+    }
+
+    for (String filePath : filePaths) {
+      if (filePaths.size() > 1) {
+        System.out.println("==> " + filePath + " <==");
+      }
+      displayFileContents(normalizePath(filePath));
+    }
+  }
+
+  private void parseArguments(String[] args, List<String> flags, List<String> paths) {
+    for (int i = 0; i < args.length; i++) {
+      if (args[i].startsWith("-")) {
+        switch (args[i]) {
+          case "-n":
+            numberOfLines = Integer.parseInt(args[++i]);
+            break;
+          case "-c":
+            isBytesFlagUsed = true;
+            numberOfBytes = Integer.parseInt(args[++i]);
+            break;
+          default:
+            flags.add(args[i]);
+            break;
+        }
+      } else {
+        paths.add(args[i]);
+      }
+    }
+  }
+
+  private boolean areFlagsValid(List<String> flags) {
+    return flags.stream().allMatch(flag -> VALID_FLAGS.contains(flag.replace("-", "")));
+  }
+
+  private void displayFileContents(String filePath) {
+    try (BufferedReader reader = new BufferedReader(new FileReader(filePath))) {
+      if (isBytesFlagUsed) {
+        readBytes(reader, numberOfBytes);
+      } else {
+        readLines(reader, numberOfLines);
+      }
+    } catch (IOException e) {
+      System.out.println("Error reading file: " + e.getMessage());
+    }
+  }
+
+  private void readLines(BufferedReader reader, int numLines) throws IOException {
+    for (int i = 0; i < numLines; i++) {
+      String line = reader.readLine();
+      if (line == null) {
+        break;
+      }
+      System.out.println(line);
+    }
+  }
+
+  private void readBytes(BufferedReader reader, int numBytes) throws IOException {
+    int remainingBytes = numBytes;
+    int ch;
+    while (remainingBytes > 0 && (ch = reader.read()) != -1) {
+      System.out.print((char) ch);
+      remainingBytes--;
+    }
+    System.out.println();
+  }
+
+  private String normalizePath(String path) {
+    String normalizedPath = path.replace("\\", "/");
+    Path pathObj = Paths.get(normalizedPath).normalize();
+    return pathObj.toString();
+  }
 }

src/com/unixtools/core/CommandFactory.java

@@ -1,8 +1,8 @@
 package com.unixtools.core;
 
 import com.unixtools.command.filemanagement.*;
-import com.unixtools.command.filecontent.*;
 import com.unixtools.command.networking.*;
+import com.unixtools.command.filecontent.*;
 
 public class CommandFactory {
   public static Command getCommand(String commandName) {
@@ -52,6 +52,8 @@ public static Command getCommand(String commandName) {
         return new EchoCommand();
       case "cat":
         return new CatCommand();
+      case "head":
+        return new HeadCommand();
       default:
         return null;
     }