<?php
/*
 * Small explicit template renderer.
 *
 * Templates use escaped {{name}} placeholders and raw {{{name}}} placeholders.
 * Values are provided as an array, so templates do not depend on globals.
 */

final class RacketSandboxTemplate
{
    const DATA_DELIMITER = "\n===\n";

    public static function renderFile($template, $values)
    {
        $parts = self::readFile($template);

        return self::renderString($parts['html'], $values);
    }

    public static function dataFile($template)
    {
        $parts = self::readFile($template);
        $json = trim($parts['data']);

        if ($json === '') {
            return array();
        }

        $data = json_decode($json, true);

        if (!is_array($data)) {
            throw new RuntimeException('Template data is invalid JSON: ' . $template);
        }

        return $data;
    }

    public static function translationsFile($template)
    {
        $data = self::dataFile($template);
        $translations = $data['translations'] ?? array();

        if (!is_array($translations)) {
            throw new RuntimeException('Template translations must be an object: ' . $template);
        }

        return $translations;
    }

    public static function renderString($source, $values)
    {
        $source = preg_replace_callback('/\{\{\{\s*([A-Za-z0-9_.-]+)\s*\}\}\}/', function ($match) use ($values) {
            return self::value($values, $match[1]);
        }, $source);

        return preg_replace_callback('/\{\{\s*([A-Za-z0-9_.-]+)\s*\}\}/', function ($match) use ($values) {
            return self::escape(self::value($values, $match[1]));
        }, $source);
    }

    public static function escape($value)
    {
        return htmlspecialchars((string)$value, ENT_QUOTES | ENT_SUBSTITUTE, 'UTF-8');
    }

    private static function value($values, $name)
    {
        if (!is_array($values) || !array_key_exists($name, $values)) {
            return '';
        }

        return (string)$values[$name];
    }

    private static function readFile($template)
    {
        $file = __DIR__ . '/views/' . ltrim((string)$template, '/');

        if (!is_file($file)) {
            throw new RuntimeException('Template not found: ' . $template);
        }

        $source = file_get_contents($file);

        if ($source === false) {
            throw new RuntimeException('Template could not be read: ' . $template);
        }

        if (strpos($source, "===\n") === 0) {
            $chunks = array('', substr($source, 4));
        } else {
            $chunks = explode(self::DATA_DELIMITER, $source, 2);
        }

        return array(
            'html' => $chunks[0],
            'data' => $chunks[1] ?? '',
        );
    }
}