<?php
/**
 * Gnieark’s TplBlock.
 *
 * PHP version 5
 *
 * @category Template
 * @package  TplBlock
 * @author   gnieark <gnieark@tinad.fr>
 * @license  GNU General Public License V3
 * @link     https://github.com/gnieark/tplBlock/
 */
namespace TplBlock;

/**
 * The TplBlock class.
 *
 * @category Template
 * @package  TplBlock
 * @author   gnieark <gnieark@tinad.fr>
 * @license  GNU General Public License V3
 * @link     https://github.com/gnieark/tplBlock/
 */
class TplBlock
{
    /**
     * The string starting a block start.
     *
     * @var string
     */
    const BLOCKSTARTSTART = '<!-- BEGIN ';

    /**
     * The string ending a block start.
     *
     * @var string
     */
    const BLOCKSTARTEND = ' -->';

    /**
     * The string starting a block end.
     *
     * @var string
     */
    const BLOCKENDSTART = '<!-- END ';

    /**
     * The string ending a block end.
     *
     * @var string
     */
    const BLOCKENDEND = ' -->';

    /**
     * The string starting an enclosure.
     *
     * @var string
     */
    const STARTENCLOSURE = '{{';

    /**
     * The string ending an enclosure.
     *
     * @var string
     */
    const ENDENCLOSURE = '}}';

    /**
     * The name of the block.
     *
     * @var string
     */
    public $name = '';

    /**
     * The array containing the variables used by TplBlock.
     *
     * @var array
     */
    private $vars = [];

    /**
     * The array containing the sub blocks.
     *
     * @var array
     */
    private $subBlocs = [];

    /**
     * The regex recognizing that a block is unused.
     *
     * @var string
     */
    private $unusedRegex = "";

    /**
     * Should we trim?
     *
     * @var boolean
     */
    private $trim = true;

    /**
     * Initialize TplBlock
     *
     * The name can be empty only for the top one block.
     *
     * @param string $name The template name
     */
    public function __construct($name = "")
    {
        // Checks that name is valid.
        if ($name !== "" and ! ctype_alnum($name)) {
            throw new \UnexpectedValueException(
                "Only alpha-numerics chars are allowed on the block name"
            );
        }

        $this->name = $name;

        // Build the unused regex.
        $this->unusedRegex = '/'
                           . self::BLOCKSTARTSTART
                           . ' *([a-z][a-z0-9.]*) *'
                           . self::BLOCKSTARTEND
                           . '(.*?)'
                           . self::BLOCKENDSTART
                           . ' *\1 *'
                           . self::BLOCKENDEND
                           . '/is'
                           ;
    }

    /**
     * Add simple variables
     *
     * The array must be structured like this:
     *
     *     [ "key" => "value", "key2" => "value2" ]
     *
     * @param array $vars Variables to add.
     *
     * @return TplBlock For chaining.
     */
    public function addVars(array $vars)
    {
        $this->vars = array_merge($this->vars, $vars);

        return $this;
    }

    /**
     * Add a sub block.
     *
     * @param TplBlock $bloc The block to add as a sub block.
     *
     * @return TplBlock For chaining.
     */
    public function addSubBlock(TplBlock $bloc)
    {
        // An unnamed block cannot be a sub block.
        if ($bloc->name === "") {
            throw new \UnexpectedValueException(
                "A sub tpl block can't have an empty name"
            );
        }

        $this->subBlocs[$bloc->name][] = $bloc;

        return $this;
    }

    /**
     * Generate the sub block regex.
     *
     * @param string $prefix   The prefix to add to the block name.
     * @param string $blocName The block name.
     *
     * @return string The regex.
     */
    private function subBlockRegex(string $prefix, string $blocName)
    {
        return '/'
             . self::BLOCKSTARTSTART
             . preg_quote($prefix . $blocName)
             . self::BLOCKSTARTEND
             . ($this->trim === false ? '' : '(?:\R|)?' )
             . '(.*?)'
             . ($this->trim === false ?  '' : '(?:\R|)?' )
             . self::BLOCKENDSTART
             . preg_quote($prefix . $blocName)
             . self::BLOCKENDEND
             . '/is';
    }

    /**
     * Shake the template string and input vars then returns the parsed text.
     *
     * @param string $str          containing the template to parse
     * @param string $subBlocsPath optional, for this class internal use.
     *                             The path should look like "bloc.subbloc".
     *
     * @return string The processed output.
     */
    public function applyTplStr(string $str, string $subBlocsPath = "")
    {
        // Replace all simple vars.
        $prefix = $subBlocsPath === "" ? "" : $subBlocsPath . ".";

        foreach ($this->vars as $key => $value) {
            $str = str_replace(
                self::STARTENCLOSURE . $prefix . $key . self::ENDENCLOSURE,
                $value,
                $str
            );
        }
    
        // Parse blocs.
        foreach ($this->subBlocs as $blocName => $blocsArr) {
            $str = preg_replace_callback(
                $this->subBlockRegex($prefix, $blocName),
                function ($m) use ($blocName, $blocsArr, $prefix) {
                    $out = "";
                    foreach ($blocsArr as $bloc) {
                        // Recursion.
                        $out .= $bloc->applyTplStr(
                            $m[1],
                            $prefix . $blocName
                        );
                    }

                    return $out;
                },
                $str
            );
        }

        // Delete unused blocs.
        $str = preg_replace($this->unusedRegex, "", $str);

        return $str;
    }

    /**
     * Load a file, and pass his content to applyTplStr function.
     *
     * @param string $file The file path of the template to load
     *
     * @return string The processed output.
     */
    public function applyTplFile(string $file)
    {
        if (! $tplStr = file_get_contents($file)) {
            throw new \UnexpectedValueException("Cannot read given file $file");
        }

        return $this->applyTplStr($tplStr, "");
    }

    /**
     * Enables trimming.
     *
     * @return TplBlock For chaining.
     */
    public function doTrim()
    {
        $this->trim = true;

        return $this;
    }

    /**
     * Disables trimming.
     *
     * @return TplBlock For chaining.
     */
    public function dontTrim()
    {
        $this->trim = false;

        return $this;
    }
}