closes #19: Add output option to diff.

* Added output option.

Author: w-martin

diff/src/main/java/diffr/diff/Main.java

@@ -1,17 +1,22 @@
 package diffr.diff;
 
+import com.google.common.base.Optional;
 import com.google.common.io.Files;
+import diffr.util.ArgumentsProcessor;
 import diffr.util.instruction.Instruction;
 import diffr.util.instruction.InstructionComposer;
+import diffr.util.instruction.Instructions;
 
+import java.io.BufferedWriter;
 import java.io.File;
+import java.io.FileWriter;
 import java.io.IOException;
 import java.nio.charset.Charset;
 import java.util.List;
 
 /**
  * Main entry point to diffr's DIFF tool.
- *
+ * <p/>
  * <p>
  * Expects two arguments:
  * <ul>
@@ -30,7 +35,9 @@ public final class Main {
      * Prints the usage of this tool.
      */
     private static void printUsage() {
-        System.out.println("Usage: diffr <original-file> <new-file>");
+        System.out.println("Usage: \n" +
+                "    diffr <original-file> <new-file>\n" +
+                "    diffr <original-file> <new-file> -o <output-file>");
     }
 
     /**
@@ -41,8 +48,9 @@ private static void printUsage() {
     public static void main(String... args) throws IOException {
 
         try {
-
-            if (args.length != 2) {
+            if (ArgumentsProcessor.containsHelpArgument(args)
+                    || (2 != args.length
+                    && 4 != args.length)) {
                 printUsage();
                 System.exit(-1);
             }
@@ -65,15 +73,26 @@ public static void main(String... args) throws IOException {
 
             final List<Instruction> instructions = new Diffr(originalFile, newFile).diff();
 
-            for (final Instruction instruction : instructions) {
-                System.out.println(InstructionComposer.composeString(instruction));
+            final Optional<String> outputFile = ArgumentsProcessor.extractOutputFile(args);
+
+            if (4 == args.length
+                    && outputFile.isPresent()) {
+
+                final File file = new File(outputFile.get());
+                final BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(file));
+                for (final Instruction instruction : instructions) {
+                    Instructions.writeInstruction(instruction, bufferedWriter);
+                }
+                bufferedWriter.close();
+            } else {
+                for (final Instruction instruction : instructions) {
+                    System.out.println(InstructionComposer.composeString(instruction));
+                }
+                System.out.flush();
             }
-            
-            System.out.flush();
 
             System.exit(0);
-        }
-        catch (final IOException io) {
+        } catch (final IOException io) {
             System.err.println("There was a problem reading the files: " + io);
         }
     }

patch/src/main/java/diffr/patch/Main.java

@@ -74,8 +74,10 @@ public static void main(final String... args) {
             final List<String> newFileStrings = patchr.patch();
 
             final Optional<String> outputFile = ArgumentsProcessor.extractOutputFile(args);
+
             if (4 == args.length
                     && outputFile.isPresent()) {
+
                 final File file = new File(outputFile.get());
                 final BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(file));
                 for (final String line : newFileStrings) {
@@ -87,6 +89,7 @@ public static void main(final String... args) {
                 for (final String line : newFileStrings) {
                     System.out.println(line);
                 }
+                System.out.flush();
             }
 
         } catch (final IOException io) {