allejo\stakx\FrontMatter\FrontMatterParser

Complexity

Total Complexity

31

Size/Duplication

Total Lines	314
Duplicated Lines	0 %

Coupling/Cohesion

Components	1
Dependencies	4

Test Coverage

Coverage

100%

Importance

Changes

0

10 Methods

Rating	Name	Duplication	Size	Complexity
A	__construct()	0	11	1
A	hasExpansion()	0	4	1
A	handleSpecialFrontMatter()	0	4	1
B	handleDateField()	0	32	5
B	evaluateBlock()	0	26	4
B	evaluateExpandableField()	0	26	4
C	evaluateArrayType()	0	35	7
B	evaluateBasicType()	0	20	5
A	getFrontMatterVariables()	0	10	1
A	getVariableValue()	0	9	2

<?php

/**
 * @copyright 2016 Vladimir Jimenez
 * @license   https://github.com/allejo/stakx/blob/master/LICENSE.md MIT
 */

namespace allejo\stakx\FrontMatter;

use allejo\stakx\Utilities\ArrayUtilities;

class FrontMatterParser
{
    /**
     * The RegEx used to identify Front Matter variables
     */
    const VARIABLE_DEF = '/(?<!\\\\)%([a-zA-Z]+)/';

    /**
     * A list of special fields in the Front Matter that will support expansion
     *
     * @var string[]
     */
    private static $expandableFields = array('permalink');

    /**
     * Whether or not an field was expanded into several values
     *
     * Only fields specified in $expandableFields will cause this value to be set to true
     *
     * @var bool
     */
    private $expansionUsed;

    /**
     * The current depth of the recursion for evaluating nested arrays in the Front Matter
     *
     * @var int
     */
    private $nestingLevel;

    /**
     * The current hierarchy of the keys that are being evaluated
     *
     * Since arrays can be nested, we'll keep track of the keys up until the current depth. This information is used for
     * error reporting
     *
     * @var array
     */
    private $yamlKeys;

    /**
     * The entire Front Matter block; evaluation will happen in place
     *
     * @var array
     */
    private $frontMatter;

    /**
     * FrontMatterParser constructor
     *
     * @param array $rawFrontMatter
     */
    public function __construct(&$rawFrontMatter)
    {
        $this->expansionUsed = false;
        $this->nestingLevel = 0;
        $this->yamlKeys = array();

        $this->frontMatter = &$rawFrontMatter;

        $this->handleSpecialFrontMatter();
        $this->evaluateBlock($this->frontMatter);
    }

    /**
     * True if any fields were expanded in the Front Matter block
     *
     * @return bool
     */
    public function hasExpansion ()
    {
        return $this->expansionUsed;
    }

    //
    // Special FrontMatter fields
    //

    /**
     * Special treatment for some FrontMatter variables
     */
    private function handleSpecialFrontMatter ()
    {
        $this->handleDateField();
    }

    /**
     * Special treatment for the `date` field in FrontMatter that creates three new variables: year, month, day
     */
    private function handleDateField ()
    {
        if (!isset($this->frontMatter['date'])) { return; }

        $date = &$this->frontMatter['date'];

        if (is_numeric($date))
        {
            // YAML has parsed them to Epoch time
            $itemDate = \DateTime::createFromFormat('U', $date);

            // Localize dates in FrontMatter based on the timezone set in the PHP configuration
            $timezone = new \DateTimeZone(date_default_timezone_get());
            $itemDate->setTimezone($timezone);
        }
        else
        {
            try
            {
                $itemDate = new \DateTime($date);
            }
            catch (\Exception $e) { return; }
        }

        if (!$itemDate === false)
        {
            $this->frontMatter['date']  = $itemDate->format('U');
            $this->frontMatter['year']  = $itemDate->format('Y');
            $this->frontMatter['month'] = $itemDate->format('m');
            $this->frontMatter['day']   = $itemDate->format('d');
        }
    }

    //
    // Evaluation
    //

    /**
     * Evaluate an array as Front Matter
     *
     * @param array $yaml
     */
    private function evaluateBlock (&$yaml)
    {
        $this->nestingLevel++;

        foreach ($yaml as $key => &$value)
        {
            $this->yamlKeys[$this->nestingLevel] = $key;
            $keys = implode('.', $this->yamlKeys);

            if (in_array($key, self::$expandableFields, true))
            {
                $value = $this->evaluateExpandableField($keys, $value);
            }
            else if (is_array($value))
            {
                $this->evaluateBlock($value);
            }
            else
            {
                $value = $this->evaluateBasicType($keys, $value);
            }
        }

        $this->nestingLevel--;
        $this->yamlKeys = array();
    }

    /**
     * Evaluate an expandable field
     *
     * @param  string $key
     * @param  string $fmStatement
     *
     * @return array
     */
    private function evaluateExpandableField ($key, $fmStatement)
    {
        if (!is_array($fmStatement))
        {
            $fmStatement = array($fmStatement);
        }

        $wip = array();

        foreach ($fmStatement as $statement)
        {
            $value = $this->evaluateBasicType($key, $statement, true);

            // Only continue expansion if there are Front Matter variables remain in the string, this means there'll be
            // Front Matter variables referencing arrays
            $expandingVars = $this->getFrontMatterVariables($value);
            if (!empty($expandingVars))
            {
                $value = $this->evaluateArrayType($key, $value, $expandingVars);
            }

            $wip[] = $value;
        }

        return $wip;
    }

    /**
     * Convert a string or an array into an array of ExpandedValue objects created through "value expansion"
     *
     * @param  string $frontMatterKey     The current hierarchy of the Front Matter keys being used
     * @param  string $expandableValue    The Front Matter value that will be expanded
     * @param  array  $arrayVariableNames The Front Matter variable names that reference arrays
     *
     * @return array
     *
     * @throws YamlUnsupportedVariableException If a multidimensional array is given for value expansion
     */
    private function evaluateArrayType ($frontMatterKey, $expandableValue, $arrayVariableNames)
    {
        if (!is_array($expandableValue))
        {
            $expandableValue = array($expandableValue);
        }

        $this->expansionUsed = true;

        foreach ($arrayVariableNames as $variable)
        {
            if (ArrayUtilities::is_multidimensional($this->frontMatter[$variable]))
            {
                throw new YamlUnsupportedVariableException("Yaml array expansion is not supported with multidimensional arrays with `$variable` for key `$frontMatterKey`");
            }

            $wip = array();

            foreach ($expandableValue as &$statement)
            {
                foreach ($this->frontMatter[$variable] as $value)
                {
                    $evaluatedValue = ($statement instanceof ExpandedValue) ? clone($statement) : new ExpandedValue($statement);
                    $evaluatedValue->setEvaluated(str_replace('%' . $variable, $value, $evaluatedValue->getEvaluated()));
                    $evaluatedValue->setIterator($variable, $value);

                    $wip[] = $evaluatedValue;
                }
            }

            $expandableValue = $wip;
        }

        return $expandableValue;
    }

    /**
     * Evaluate an string for FrontMatter variables and replace them with the corresponding values
     *
     * @param  string $key          The key of the Front Matter value
     * @param  string $string       The string that will be evaluated
     * @param  bool   $ignoreArrays When set to true, an exception won't be thrown when an array is found with the
     *                              interpolation
     *
     * @return string The final string with variables evaluated
     *
     * @throws YamlUnsupportedVariableException A FrontMatter variable is not an int, float, or string
     */
    private function evaluateBasicType ($key, $string, $ignoreArrays = false)
    {
        $variables = $this->getFrontMatterVariables($string);

        foreach ($variables as $variable)
        {
            $value = $this->getVariableValue($key, $variable);

            if (is_array($value) || is_bool($value))
            {
                if ($ignoreArrays) { continue; }

                throw new YamlUnsupportedVariableException("Yaml variable `$variable` for `$key` is not a supported data type.");
            }

            $string = str_replace('%' . $variable, $value, $string);
        }

        return $string;
    }

    //
    // Variable management
    //

    /**
     * Get an array of FrontMatter variables in the specified string that need to be interpolated
     *
     * @param  string $string
     *
     * @return string[]
     */
    private function getFrontMatterVariables ($string)
    {
        $variables = array();

        preg_match_all(self::VARIABLE_DEF, $string, $variables);

        // Default behavior causes $variables[0] is the entire string that was matched. $variables[1] will be each
        // matching result individually.
        return $variables[1];
    }

    /**
     * Get the value of a FM variable or throw an exception
     *
     * @param  string $key
     * @param  string $varName
     *
     * @return mixed
     * @throws YamlVariableUndefinedException
     */
    private function getVariableValue ($key, $varName)
    {
        if (!isset($this->frontMatter[$varName]))
        {
            throw new YamlVariableUndefinedException("Yaml variable `$varName` is not defined for: $key");
        }

        return $this->frontMatter[$varName];
    }
}