Add simple templating support.

Templates use __name__ placeholders. A variant of the placeholder with a
capitalized first latter can be accessed using __Name__ (this is useful
for camel case identifiers, e.g. get__Name__).

Currently the implemention is not particularly clean, because the Template
instantiates a Lexer itself. Fixing this requires a major refactoring of
the lexer/parser interface.

lib/PHPParser/Template.php

@@ -0,0 +1,84 @@
+<?php
+
+class PHPParser_Template
+{
+    protected $parser;
+    protected $template;
+
+    /**
+     * Creates a new code template from a template string.
+     *
+     * @param PHPParser_Parser $parser   A parser instance
+     * @param string           $template The template string
+     */
+    public function __construct(PHPParser_Parser $parser, $template) {
+        $this->parser   = $parser;
+        $this->template = $template;
+    }
+
+    /**
+     * Get the statements of the template with the passed in placeholders
+     * replaced.
+     *
+     * @param array $placeholders Placeholders
+     *
+     * @return PHPParser_Node[] Statements
+     */
+    public function getStmts(array $placeholders) {
+        /*
+         * TODO This is evil.
+         * The lexer shouldn't be created in here, instead it should be a dependency, which
+         * basically means that we'd need to have a LexerFactory (which seems strange).
+         * An alternative solution would be to make the lexer work similar to how the parser
+         * works. I.e. one would instantiate the Lexer only once and then pass the results
+         * of ->lex() to the parser (which would then be the full tokens array). This design
+         * seems cleaner, but comes at the expense of higher memory consumption, as the token
+         * array can be quite large.
+         */
+        return $this->parser->parse(
+            new PHPParser_Lexer_Emulative(
+                $this->getTemplateWithPlaceholdersReplaced($placeholders)
+            )
+        );
+    }
+
+    protected function getTemplateWithPlaceholdersReplaced(array $placeholders) {
+        if (empty($placeholders)) {
+            return $this->template;
+        }
+
+        return strtr($this->template, $this->preparePlaceholders($placeholders));
+    }
+
+    /*
+     * Prepare the placeholders for replacement. This means that
+     * a) all placeholders will be surrounded with __.
+     * b) ucfirst/lcfirst variations of the placeholders are generated.
+     *
+     * E.g. for an input array of ['foo' => 'bar'] the result will be
+     * ['__foo__' => 'bar', '__Foo__' => 'Bar'].
+     */
+    protected function preparePlaceholders(array $placeholders) {
+        $preparedPlaceholders = array();
+
+        foreach ($placeholders as $name => $value) {
+            $preparedPlaceholders['__' . $name . '__'] = $value;
+
+            if (ctype_lower($name[0])) {
+                $ucfirstName = ucfirst($name);
+                if (!isset($placeholders[$ucfirstName])) {
+                    $preparedPlaceholders['__' . $ucfirstName . '__'] = ucfirst($value);
+                }
+            }
+
+            if (ctype_upper($name[0])) {
+                $lcfirstName = lcfirst($name);
+                if (!isset($placeholders[$lcfirstName])) {
+                    $preparedPlaceholders['__' . $lcfirstName . '__'] = lcfirst($value);
+                }
+            }
+        }
+
+        return $preparedPlaceholders;
+    }
+}

test/PHPParser/Tests/TemplateTest.php

@@ -0,0 +1,54 @@
+<?php
+
+class PHPParser_Tests_TemplateTest extends PHPUnit_Framework_TestCase
+{
+    /**
+     * @dataProvider provideTestPlaceholderReplacement
+     * @covers PHPParser_Template
+     */
+    public function testPlaceholderReplacement($templateCode, $placeholders, $expectedPrettyPrint) {
+        $parser = new PHPParser_Parser;
+        $prettyPrinter = new PHPParser_PrettyPrinter_Zend;
+
+        $template = new PHPParser_Template($parser, $templateCode);
+        $this->assertEquals(
+            $expectedPrettyPrint,
+            $prettyPrinter->prettyPrint($template->getStmts($placeholders))
+        );
+    }
+
+    public function provideTestPlaceholderReplacement() {
+        return array(
+            array(
+                '<?php $__name__ + $__Name__;',
+                array('name' => 'foo'),
+                '$foo + $Foo;'
+            ),
+            array(
+                '<?php $__name__ + $__Name__;',
+                array('Name' => 'Foo'),
+                '$foo + $Foo;'
+            ),
+            array(
+                '<?php $__name__ + $__Name__;',
+                array('name' => 'foo', 'Name' => 'Bar'),
+                '$foo + $Bar;'
+            ),
+            array(
+                '<?php $__name__ + $__Name__;',
+                array('Name' => 'Bar', 'name' => 'foo'),
+                '$foo + $Bar;'
+            ),
+            array(
+                '<?php $prefix__Name__Suffix;',
+                array('name' => 'infix'),
+                '$prefixInfixSuffix;'
+            ),
+            array(
+                '<?php $___name___;',
+                array('name' => 'foo'),
+                '$_foo_;'
+            )
+        );
+    }
+}