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<?php |
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/** |
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* @copyright 2016 Vladimir Jimenez |
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* @license https://github.com/allejo/stakx/blob/master/LICENSE.md MIT |
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*/ |
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namespace allejo\stakx\FrontMatter; |
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use allejo\stakx\Utilities\ArrayUtilities; |
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class FrontMatterParser |
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{ |
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/** |
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* The RegEx used to identify Front Matter variables |
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*/ |
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const VARIABLE_DEF = '/(?<!\\\\)%([a-zA-Z]+)/'; |
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/** |
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* A list of special fields in the Front Matter that will support expansion |
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* |
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* @var string[] |
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*/ |
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private static $expandableFields = array('permalink'); |
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/** |
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* Whether or not an field was expanded into several values |
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* |
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* Only fields specified in $expandableFields will cause this value to be set to true |
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* |
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* @var bool |
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*/ |
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private $expansionUsed; |
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/** |
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* The current depth of the recursion for evaluating nested arrays in the Front Matter |
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* |
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* @var int |
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*/ |
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private $nestingLevel; |
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/** |
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* The current hierarchy of the keys that are being evaluated |
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* |
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* Since arrays can be nested, we'll keep track of the keys up until the current depth. This information is used for |
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* error reporting |
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* |
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* @var array |
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*/ |
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private $yamlKeys; |
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/** |
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* The entire Front Matter block; evaluation will happen in place |
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* |
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* @var array |
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*/ |
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private $frontMatter; |
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/** |
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* FrontMatterParser constructor |
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* |
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* @param array $rawFrontMatter |
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*/ |
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public function __construct(&$rawFrontMatter) |
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{ |
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$this->expansionUsed = false; |
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$this->nestingLevel = 0; |
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$this->yamlKeys = array(); |
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$this->frontMatter = &$rawFrontMatter; |
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$this->handleSpecialFrontMatter(); |
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$this->evaluateBlock($this->frontMatter); |
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} |
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/** |
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* True if any fields were expanded in the Front Matter block |
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* |
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* @return bool |
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*/ |
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public function hasExpansion () |
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{ |
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return $this->expansionUsed; |
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} |
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// |
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// Special FrontMatter fields |
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// |
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/** |
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* Special treatment for some FrontMatter variables |
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*/ |
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private function handleSpecialFrontMatter () |
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{ |
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$this->handleDateField(); |
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} |
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/** |
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* Special treatment for the `date` field in FrontMatter that creates three new variables: year, month, day |
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*/ |
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private function handleDateField () |
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{ |
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if (!isset($this->frontMatter['date'])) { return; } |
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$date = &$this->frontMatter['date']; |
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if (is_numeric($date)) |
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{ |
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// YAML has parsed them to Epoch time |
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$itemDate = \DateTime::createFromFormat('U', $date); |
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// Localize dates in FrontMatter based on the timezone set in the PHP configuration |
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$timezone = new \DateTimeZone(date_default_timezone_get()); |
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$itemDate->setTimezone($timezone); |
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} |
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else |
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{ |
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try |
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{ |
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$itemDate = new \DateTime($date); |
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} |
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catch (\Exception $e) { return; } |
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} |
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if (!$itemDate === false) |
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{ |
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$this->frontMatter['date'] = $itemDate->format('U'); |
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$this->frontMatter['year'] = $itemDate->format('Y'); |
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$this->frontMatter['month'] = $itemDate->format('m'); |
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$this->frontMatter['day'] = $itemDate->format('d'); |
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} |
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} |
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// |
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// Evaluation |
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// |
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/** |
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* Evaluate an array as Front Matter |
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* |
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* @param array $yaml |
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*/ |
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private function evaluateBlock (&$yaml) |
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{ |
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$this->nestingLevel++; |
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foreach ($yaml as $key => &$value) |
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{ |
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$this->yamlKeys[$this->nestingLevel] = $key; |
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$keys = implode('.', $this->yamlKeys); |
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if (in_array($key, self::$expandableFields, true)) |
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{ |
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$value = $this->evaluateExpandableField($keys, $value); |
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} |
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else if (is_array($value)) |
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{ |
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$this->evaluateBlock($value); |
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} |
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else |
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{ |
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$value = $this->evaluateBasicType($keys, $value); |
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} |
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} |
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$this->nestingLevel--; |
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$this->yamlKeys = array(); |
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} |
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/** |
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* Evaluate an expandable field |
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* |
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* @param string $key |
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* @param string $fmStatement |
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* |
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* @return array |
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*/ |
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private function evaluateExpandableField ($key, $fmStatement) |
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{ |
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if (!is_array($fmStatement)) |
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{ |
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$fmStatement = array($fmStatement); |
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} |
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$wip = array(); |
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foreach ($fmStatement as $statement) |
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{ |
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$value = $this->evaluateBasicType($key, $statement, true); |
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// Only continue expansion if there are Front Matter variables remain in the string, this means there'll be |
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// Front Matter variables referencing arrays |
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$expandingVars = $this->getFrontMatterVariables($value); |
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if (!empty($expandingVars)) |
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{ |
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$value = $this->evaluateArrayType($key, $value, $expandingVars); |
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} |
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$wip[] = $value; |
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} |
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return $wip; |
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} |
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/** |
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* Convert a string or an array into an array of ExpandedValue objects created through "value expansion" |
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* |
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* @param string $frontMatterKey The current hierarchy of the Front Matter keys being used |
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* @param string $expandableValue The Front Matter value that will be expanded |
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* @param array $arrayVariableNames The Front Matter variable names that reference arrays |
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* |
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* @return array |
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* |
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* @throws YamlUnsupportedVariableException If a multidimensional array is given for value expansion |
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*/ |
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private function evaluateArrayType ($frontMatterKey, $expandableValue, $arrayVariableNames) |
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{ |
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if (!is_array($expandableValue)) |
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{ |
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$expandableValue = array($expandableValue); |
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} |
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$this->expansionUsed = true; |
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foreach ($arrayVariableNames as $variable) |
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{ |
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if (ArrayUtilities::is_multidimensional($this->frontMatter[$variable])) |
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{ |
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throw new YamlUnsupportedVariableException("Yaml array expansion is not supported with multidimensional arrays with `$variable` for key `$frontMatterKey`"); |
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} |
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$wip = array(); |
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foreach ($expandableValue as &$statement) |
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{ |
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foreach ($this->frontMatter[$variable] as $value) |
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{ |
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$evaluatedValue = ($statement instanceof ExpandedValue) ? clone($statement) : new ExpandedValue($statement); |
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$evaluatedValue->setEvaluated(str_replace('%' . $variable, $value, $evaluatedValue->getEvaluated())); |
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$evaluatedValue->setIterator($variable, $value); |
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$wip[] = $evaluatedValue; |
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} |
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} |
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$expandableValue = $wip; |
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} |
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return $expandableValue; |
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} |
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/** |
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* Evaluate an string for FrontMatter variables and replace them with the corresponding values |
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* |
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* @param string $key The key of the Front Matter value |
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* @param string $string The string that will be evaluated |
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* @param bool $ignoreArrays When set to true, an exception won't be thrown when an array is found with the |
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* interpolation |
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* |
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* @return string The final string with variables evaluated |
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* |
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* @throws YamlUnsupportedVariableException A FrontMatter variable is not an int, float, or string |
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*/ |
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private function evaluateBasicType ($key, $string, $ignoreArrays = false) |
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{ |
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$variables = $this->getFrontMatterVariables($string); |
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foreach ($variables as $variable) |
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{ |
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$value = $this->getVariableValue($key, $variable); |
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if (is_array($value) || is_bool($value)) |
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{ |
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if ($ignoreArrays) { continue; } |
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throw new YamlUnsupportedVariableException("Yaml variable `$variable` for `$key` is not a supported data type."); |
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} |
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$string = str_replace('%' . $variable, $value, $string); |
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} |
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return $string; |
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} |
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// |
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// Variable management |
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// |
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/** |
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* Get an array of FrontMatter variables in the specified string that need to be interpolated |
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* |
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* @param string $string |
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* |
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* @return string[] |
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*/ |
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private function getFrontMatterVariables ($string) |
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{ |
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$variables = array(); |
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preg_match_all(self::VARIABLE_DEF, $string, $variables); |
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// Default behavior causes $variables[0] is the entire string that was matched. $variables[1] will be each |
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// matching result individually. |
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return $variables[1]; |
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} |
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/** |
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* Get the value of a FM variable or throw an exception |
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* |
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* @param string $key |
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* @param string $varName |
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* |
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* @return mixed |
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* @throws YamlVariableUndefinedException |
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*/ |
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private function getVariableValue ($key, $varName) |
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{ |
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if (!isset($this->frontMatter[$varName])) |
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{ |
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throw new YamlVariableUndefinedException("Yaml variable `$varName` is not defined for: $key"); |
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} |
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return $this->frontMatter[$varName]; |
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} |
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} |