Fix 1-based index causing incorrect insertion of an empty word

Completing on a command line with a one-letter word at the end would
incorrectly cause an empty word to be inserted before that character:

         ↙ cursor immediately after "a" (character 5)
    cmd a
    -----
      \_ parsed to ['cmd', '', 'a'] instead of ['cmd', 'a']

This was due to `$this->charIndex` being zero-based, and `$cursor` being
one-based; the condition `$cursor >= $this->charIndex` was always off by
one. I'm have no idea what compelled me to write this with a one-based
index in the first place, but all the tests are passing and I've tested
this change in the console with a real application.

It took a while to understand this function again, so I've put a few
more helpful comments in for the next adventurer to pass by.

Fixes #65

Author: stecman

src/CompletionContext.php

@@ -196,7 +196,7 @@ protected function splitCommand()
     {
         $this->words = array();
         $this->wordIndex = null;
-        $cursor = 1;
+        $cursor = 0;
 
         $breaks = preg_quote($this->wordBreaks);
 
@@ -211,21 +211,23 @@ protected function splitCommand()
             // Determine which word the cursor is in
             $cursor += strlen($wholeMatch);
             $word = $matches[1][$index];
+            $breaks = $matches[2][$index];
 
             if ($this->wordIndex === null && $cursor >= $this->charIndex) {
                 $this->wordIndex = $index;
 
-                // Find the cursor position relative to the end of the word
-                $cursorWordOffset = $this->charIndex - ($cursor - strlen($matches[2][$index]) - 1);
+                // Find the user's cursor position relative to the end of this word
+                // The end of the word is the internal cursor minus any break characters that were captured
+                $cursorWordOffset = $this->charIndex - ($cursor - strlen($breaks));
 
                 if ($cursorWordOffset < 0) {
                     // Cursor is inside the word - truncate the word at the cursor
                     // (This emulates normal BASH completion behaviour I've observed, though I'm not entirely sure if it's useful)
                     $word = substr($word, 0, strlen($word) + $cursorWordOffset);
 
                 } elseif ($cursorWordOffset > 0) {
-                    // Cursor is in the break-space after the word
-                    // Push an empty word at the cursor
+                    // Cursor is in the break-space after a word
+                    // Push an empty word at the cursor to allow completion of new terms at the cursor, ignoring words ahead
                     $this->wordIndex++;
                     $this->words[] = $word;
                     $this->words[] = '';

src/CompletionHandler.php

@@ -152,7 +152,7 @@ protected function completeForOptions()
     {
         $word = $this->context->getCurrentWord();
 
-        if (strpos($word, '-') === 0) {
+        if (substr($word, 0, 2) === '--') {
             $options = array();
 
             foreach ($this->getAllOptions() as $opt) {

tests/Stecman/Component/Symfony/Console/BashCompletion/CompletionContextTest.php

@@ -31,7 +31,7 @@ public function testWordBreakSplit()
     public function testCursorPosition()
     {
         $context = new CompletionContext();
-        $context->setCommandLine('make horse --legs 4 --colour black');
+        $context->setCommandLine('make horse --legs 4 --colour black ');
 
         // Cursor at the start of the line
         $context->setCharIndex(0);
@@ -42,6 +42,11 @@ public function testCursorPosition()
         $this->assertEquals(5, $context->getWordIndex());
         $this->assertEquals('black', $context->getCurrentWord());
 
+        // Cursor after space at the end of the string
+        $context->setCharIndex(35);
+        $this->assertEquals(6, $context->getWordIndex());
+        $this->assertEquals('', $context->getCurrentWord());
+
         // Cursor in the middle of 'horse'
         $context->setCharIndex(8);
         $this->assertEquals(1, $context->getWordIndex());
@@ -53,6 +58,39 @@ public function testCursorPosition()
         $this->assertEquals('--legs', $context->getCurrentWord());
     }
 
+    public function testWordBreakingWithSmallInputs()
+    {
+        $context = new CompletionContext();
+
+        // Cursor at the end of a word and not in the following space has no effect
+        $context->setCommandLine('cmd a');
+        $context->setCharIndex(5);
+        $this->assertEquals(array('cmd', 'a'), $context->getWords());
+        $this->assertEquals(1, $context->getWordIndex());
+        $this->assertEquals('a', $context->getCurrentWord());
+
+        // As above, but in the middle of the command line string
+        $context->setCommandLine('cmd a');
+        $context->setCharIndex(3);
+        $this->assertEquals(array('cmd', 'a'), $context->getWords());
+        $this->assertEquals(0, $context->getWordIndex());
+        $this->assertEquals('cmd', $context->getCurrentWord());
+
+        // Cursor at the end of the command line with a space appends an empty word
+        $context->setCommandLine('cmd   a ');
+        $context->setCharIndex(8);
+        $this->assertEquals(array('cmd', 'a', ''), $context->getWords());
+        $this->assertEquals(2, $context->getWordIndex());
+        $this->assertEquals('', $context->getCurrentWord());
+
+        // Cursor in break space before a word appends an empty word in that position
+        $context->setCommandLine('cmd a');
+        $context->setCharIndex(4);
+        $this->assertEquals(array('cmd', '',  'a',), $context->getWords());
+        $this->assertEquals(1, $context->getWordIndex());
+        $this->assertEquals('', $context->getCurrentWord());
+    }
+
     public function testConfigureFromEnvironment()
     {
         putenv("CMDLINE_CONTENTS=beam up li");