<?php
declare(strict_types=1);

namespace NeonBlog;

final class Shortcodes
{
    /** @var array<string, array<string, mixed>>|null */
    private static ?array $definitions = null;

    public static function render(string $source): string
    {
        $definitions = self::definitions();
        if ($definitions === [] || !str_contains($source, '[')) {
            return $source;
        }

        [$source, $placeholders] = self::protectCode($source);
        $source = preg_replace_callback('/(?<!\\\\)\[([A-Za-z][A-Za-z0-9_-]*)(?:=([^\]\s]+)|\s+([^\]]+))?\]/', static function (array $matches) use ($definitions): string {
            $name = strtolower($matches[1]);
            if (!isset($definitions[$name])) {
                return $matches[0];
            }

            $attributes = self::parseAttributes($matches[2] ?? '', $matches[3] ?? '');
            return self::renderDefinition($name, $definitions[$name], $attributes, $matches[0]);
        }, $source) ?? $source;

        return strtr($source, $placeholders);
    }

    /** @return array<string, array<string, mixed>> */
    private static function definitions(): array
    {
        if (self::$definitions !== null) {
            return self::$definitions;
        }

        $root = defined('BLOG_ROOT') ? BLOG_ROOT : dirname(__DIR__);
        $definitions = [];

        $phpFile = $root . '/config/shortcodes.php';
        if (is_file($phpFile)) {
            $loaded = require $phpFile;
            if (is_array($loaded)) {
                $definitions = $loaded;
            }
        }

        $jsonFile = $root . '/config/shortcodes.json';
        if (is_file($jsonFile)) {
            $decoded = json_decode((string) file_get_contents($jsonFile), true);
            if (is_array($decoded)) {
                $definitions = array_replace_recursive($definitions, $decoded);
            }
        }

        $normalized = [];
        foreach ($definitions as $name => $definition) {
            if (is_string($name) && is_array($definition)) {
                $normalized[strtolower($name)] = $definition;
            }
        }

        return self::$definitions = $normalized;
    }

    /** @return array{0: string, 1: array<string, string>} */
    private static function protectCode(string $source): array
    {
        $placeholders = [];
        $source = preg_replace_callback('/```[\s\S]*?```/', static function (array $matches) use (&$placeholders): string {
            $key = "\x1CSHORTCODE" . count($placeholders) . "\x1C";
            $placeholders[$key] = $matches[0];
            return $key;
        }, $source) ?? $source;
        $source = preg_replace_callback('/`[^`\n]*`/', static function (array $matches) use (&$placeholders): string {
            $key = "\x1CSHORTCODE" . count($placeholders) . "\x1C";
            $placeholders[$key] = $matches[0];
            return $key;
        }, $source) ?? $source;

        return [$source, $placeholders];
    }

    /** @return array<string, string> */
    private static function parseAttributes(string $value, string $arguments): array
    {
        $attributes = [];
        $value = trim($value);
        if ($value !== '') {
            $attributes['value'] = self::unquote($value);
        }

        if (trim($arguments) === '') {
            return $attributes;
        }

        preg_match_all('/([A-Za-z_][A-Za-z0-9_-]*)=(?:"([^"]*)"|\'([^\']*)\'|([^\s]+))|(?:"([^"]*)"|\'([^\']*)\'|([^\s]+))/', $arguments, $matches, PREG_SET_ORDER);
        foreach ($matches as $match) {
            if (($match[1] ?? '') !== '') {
                $attributes[strtolower($match[1])] = self::firstMatch($match, [2, 3, 4]);
                continue;
            }

            if (!isset($attributes['value'])) {
                $attributes['value'] = self::firstMatch($match, [5, 6, 7]);
            }
        }

        return $attributes;
    }

    /** @param array<int, string> $match @param array<int, int> $indexes */
    private static function firstMatch(array $match, array $indexes): string
    {
        foreach ($indexes as $index) {
            if (isset($match[$index]) && $match[$index] !== '') {
                return $match[$index];
            }
        }

        return '';
    }

    private static function unquote(string $value): string
    {
        if (strlen($value) >= 2) {
            $first = $value[0];
            $last = $value[strlen($value) - 1];
            if (($first === '"' && $last === '"') || ($first === "'" && $last === "'")) {
                return substr($value, 1, -1);
            }
        }

        return $value;
    }

    /** @param array<string, mixed> $definition @param array<string, string> $attributes */
    private static function renderDefinition(string $name, array $definition, array $attributes, string $fallback): string
    {
        $attributes = self::sanitizeAttributes($attributes, $definition['sanitize'] ?? []);
        foreach ((array) ($definition['required'] ?? []) as $required) {
            if ((string) ($attributes[(string) $required] ?? '') === '') {
                return '<!-- shortcode ' . self::e($name) . ' missing ' . self::e((string) $required) . ' -->';
            }
        }

        $type = strtolower((string) ($definition['type'] ?? 'html'));
        if ($type === 'iframe') {
            return self::renderIframe($definition, $attributes);
        }

        $template = (string) ($definition['template'] ?? '');
        if ($template === '') {
            return $fallback;
        }

        return self::replacePlaceholders($template, $attributes, true);
    }

    /** @param array<string, string> $attributes @param mixed $rules @return array<string, string> */
    private static function sanitizeAttributes(array $attributes, mixed $rules): array
    {
        $rules = is_array($rules) ? $rules : [];
        foreach ($attributes as $key => $value) {
            $rule = (string) ($rules[$key] ?? 'text');
            $attributes[$key] = self::sanitize($value, $rule);
        }

        return $attributes;
    }

    private static function sanitize(string $value, string $rule): string
    {
        $value = trim($value);
        if ($rule === 'youtube_id') {
            $parts = parse_url($value);
            if (isset($parts['query'])) {
                parse_str($parts['query'], $query);
                $value = (string) ($query['v'] ?? $value);
            } elseif (isset($parts['host'], $parts['path']) && str_contains($parts['host'], 'youtu.be')) {
                $value = trim($parts['path'], '/');
            } elseif (isset($parts['path']) && str_contains($parts['path'], '/embed/')) {
                $value = basename($parts['path']);
            }

            return substr(preg_replace('/[^A-Za-z0-9_-]/', '', $value) ?? '', 0, 80);
        }

        if ($rule === 'media_url' || $rule === 'url') {
            if (preg_match('/[\x00-\x1F\x7F]/', $value) || preg_match('/^\s*(javascript|data):/i', $value)) {
                return '';
            }
            return $value;
        }

        return preg_replace('/[\x00-\x08\x0B\x0C\x0E-\x1F\x7F]/', '', $value) ?? '';
    }

    /** @param array<string, mixed> $definition @param array<string, string> $attributes */
    private static function renderIframe(array $definition, array $attributes): string
    {
        $src = self::replacePlaceholders((string) ($definition['src'] ?? ''), $attributes, false);
        if ($src === '') {
            return '';
        }

        $query = [];
        foreach ((array) ($definition['query'] ?? []) as $key => $template) {
            $value = self::replacePlaceholders((string) $template, $attributes, false);
            if ($value !== '') {
                $query[(string) $key] = $value;
            }
        }

        if ($query !== []) {
            $src = self::isAbsoluteUrl($src) ? self::appendQuery($src, $query) : View::url($src, $query);
        } elseif (!self::isAbsoluteUrl($src) && !str_starts_with($src, '/')) {
            $src = View::url($src);
        }

        $iframeAttributes = ['src' => $src];
        foreach ((array) ($definition['attributes'] ?? []) as $key => $value) {
            $iframeAttributes[(string) $key] = is_string($value)
                ? self::replacePlaceholders($value, $attributes, false)
                : $value;
        }

        $htmlAttributes = [];
        foreach ($iframeAttributes as $key => $value) {
            if ($value === false || $value === null || $value === '') {
                continue;
            }
            if ($value === true) {
                $htmlAttributes[] = self::e((string) $key);
                continue;
            }
            $htmlAttributes[] = self::e((string) $key) . '="' . self::e((string) $value) . '"';
        }

        $class = (string) ($definition['class'] ?? 'shortcode-embed');
        return "\n\n" . '<div class="' . self::e($class) . '"><iframe ' . implode(' ', $htmlAttributes) . '></iframe></div>' . "\n\n";
    }

    /** @param array<string, string> $attributes */
    private static function replacePlaceholders(string $template, array $attributes, bool $escape): string
    {
        return preg_replace_callback('/\{([A-Za-z_][A-Za-z0-9_-]*)\}/', static function (array $matches) use ($attributes, $escape): string {
            $value = (string) ($attributes[strtolower($matches[1])] ?? '');
            return $escape ? self::e($value) : $value;
        }, $template) ?? $template;
    }

    /** @param array<string, string> $query */
    private static function appendQuery(string $url, array $query): string
    {
        return $url . (str_contains($url, '?') ? '&' : '?') . http_build_query($query);
    }

    private static function isAbsoluteUrl(string $url): bool
    {
        return (bool) preg_match('#^https?://#i', $url);
    }

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