From 81ee3ec88048eb59924189afd82e81dee194d361 Mon Sep 17 00:00:00 2001
From: Kevin Pham <keevan.pham@gmail.com>
Date: Tue, 25 Jul 2023 15:43:44 +1000
Subject: [PATCH] feat: get dynamic vars with expression get_var()

Leverages the root variable tree.
---
 classes/local/provider/expression_provider.php | 15 +++++++++++++++
 classes/local/step/flow_transformer_filter.php |  6 ++----
 classes/local/variables/var_value.php          |  3 ++-
 lang/en/tool_dataflows.php                     |  2 +-
 version.php                                    |  4 ++--
 5 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/classes/local/provider/expression_provider.php b/classes/local/provider/expression_provider.php
index 097c268f..bcd64048 100644
--- a/classes/local/provider/expression_provider.php
+++ b/classes/local/provider/expression_provider.php
@@ -18,6 +18,7 @@
 
 use Symfony\Component\ExpressionLanguage\ExpressionFunction;
 use Symfony\Component\ExpressionLanguage\ExpressionFunctionProviderInterface;
+use tool_dataflows\parser;
 
 /**
  * Expression Provider
@@ -55,9 +56,23 @@ public function getFunctions(): array { // phpcs:ignore
             return isset($var);
         });
 
+        // Get variable (to handle dynamic variable names).
+        $getvar = new ExpressionFunction('get_var', function ($str)
+        {
+            return sprintf('get_var(%1$s)', $str);
+        }, function ($arguments, $var)
+        {
+            if (isset($arguments['root'])) {
+                $result = $arguments['root']->get($var);
+                return $result;
+            }
+            return $var;
+        });
+
         return [
             $fromjson,
             $isset,
+            $getvar,
             ExpressionFunction::fromPhp('count', 'count'),
             ExpressionFunction::fromPhp('format_time', 'format_time'),
             ExpressionFunction::fromPhp('round', 'round'),
diff --git a/classes/local/step/flow_transformer_filter.php b/classes/local/step/flow_transformer_filter.php
index 944cfb5b..88178405 100644
--- a/classes/local/step/flow_transformer_filter.php
+++ b/classes/local/step/flow_transformer_filter.php
@@ -16,10 +16,6 @@
 
 namespace tool_dataflows\local\step;
 
-use tool_dataflows\local\execution\flow_engine_step;
-use tool_dataflows\local\execution\iterators\dataflow_iterator;
-use tool_dataflows\local\execution\iterators\iterator;
-
 /**
  * Flow filter (transformer step) class
  *
@@ -80,10 +76,12 @@ public function form_add_custom_inputs(\MoodleQuickForm &$mform) {
      */
     public function execute($input = null) {
         $expr = $this->stepdef->config->filter;
+
         $result = (bool) $this->get_variables()->evaluate('${{ ' . $expr . ' }}');
         if (!$result) {
             return false;
         };
+
         return $input;
     }
 }
diff --git a/classes/local/variables/var_value.php b/classes/local/variables/var_value.php
index d5d819cb..d241ddb1 100644
--- a/classes/local/variables/var_value.php
+++ b/classes/local/variables/var_value.php
@@ -150,6 +150,7 @@ protected function get_resolved() {
      */
     public function evaluate(?callable $errorhandler = null) {
         $tree = $this->make_reference_tree();
+        $tree->root = $this->root;
         if (is_null($errorhandler)) {
             $this->resolved = parser::get_parser()->evaluate($this->raw, (array) $tree);
         } else {
@@ -191,7 +192,7 @@ private function make_reference_tree(): \stdClass {
         foreach ($this->references as $name => $obj) {
             $value = $obj->get_resolved(false);
 
-            // Do not add the value if it is not set. This shoudl result in the expression remaining unresolved in the evalutaion.
+            // Do not add the value if it is not set. This should result in the expression remaining unresolved in the evalutaion.
             if (is_null($value)) {
                 continue;
             }
diff --git a/lang/en/tool_dataflows.php b/lang/en/tool_dataflows.php
index dc231fc4..ccfe7b68 100644
--- a/lang/en/tool_dataflows.php
+++ b/lang/en/tool_dataflows.php
@@ -492,7 +492,7 @@
 
 // Flow transformer filter.
 $string['flow_transformer_filter:filter'] = 'Filter expression';
-$string['flow_transformer_filter:filter_help'] = "This expression must evaluate to a boolean. When the expression evaluates to false, the current value for the flow will not be passed on to later steps in the flow. There is no need for '\${{' and '}}'.";
+$string['flow_transformer_filter:filter_help'] = "This expression must evaluate to a boolean. When false, the current value will not be passed on to later flow steps. There is no need for '\${{' and '}}'.";
 
 // Flow tranformer regex.
 $string['flow_transformer_regex:pattern'] = 'Regex pattern';
diff --git a/version.php b/version.php
index d4882ea0..b05d18eb 100644
--- a/version.php
+++ b/version.php
@@ -25,8 +25,8 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version = 2023072600;
-$plugin->release = 2023072600;
+$plugin->version = 2023072601;
+$plugin->release = 2023072601;
 $plugin->requires = 2017051500;    // Our lowest supported Moodle (3.3.0).
 $plugin->supported = [35, 401];    // Available as of Moodle 3.9.0 or later.
 // TODO $plugin->incompatible = ;  // Available as of Moodle 3.9.0 or later.