<?php
/**
 * Compression Engine for TigerStyle Dash
 * Advanced Brotli + Gzip compression with cat-like speed
 */

// Prevent direct access
if (!defined('ABSPATH')) {
    exit;
}

class TigerStyle_Dash_Compression {
    
    /**
     * Compress content using the best available method
     */
    public static function compress($content, $method = 'auto', $level = 6) {
        $accept_encoding = $_SERVER['HTTP_ACCEPT_ENCODING'] ?? '';
        $original_size = strlen($content);
        
        // Determine compression method
        if ($method === 'auto') {
            if (strpos($accept_encoding, 'br') !== false && function_exists('brotli_compress')) {
                $method = 'brotli';
            } elseif (strpos($accept_encoding, 'gzip') !== false && function_exists('gzencode')) {
                $method = 'gzip';
            } else {
                return array(
                    'content' => $content,
                    'method' => 'none',
                    'original_size' => $original_size,
                    'compressed_size' => $original_size,
                    'ratio' => 0
                );
            }
        }
        
        // Compress based on method
        switch ($method) {
            case 'brotli':
                if (function_exists('brotli_compress')) {
                    $compressed = brotli_compress($content, $level);
                    if ($compressed !== false) {
                        return array(
                            'content' => $compressed,
                            'method' => 'brotli',
                            'original_size' => $original_size,
                            'compressed_size' => strlen($compressed),
                            'ratio' => round((($original_size - strlen($compressed)) / $original_size) * 100, 1),
                            'encoding' => 'br'
                        );
                    }
                }
                // Fall through to gzip if brotli fails
                
            case 'gzip':
                if (function_exists('gzencode')) {
                    $compressed = gzencode($content, $level);
                    if ($compressed !== false) {
                        return array(
                            'content' => $compressed,
                            'method' => 'gzip',
                            'original_size' => $original_size,
                            'compressed_size' => strlen($compressed),
                            'ratio' => round((($original_size - strlen($compressed)) / $original_size) * 100, 1),
                            'encoding' => 'gzip'
                        );
                    }
                }
                break;
                
            default:
                // No compression
                break;
        }
        
        // Return uncompressed if all methods fail
        return array(
            'content' => $content,
            'method' => 'none',
            'original_size' => $original_size,
            'compressed_size' => $original_size,
            'ratio' => 0
        );
    }
    
    /**
     * Check if content is suitable for compression
     */
    public static function should_compress($content, $content_type = '') {
        // Don't compress if content is too small
        if (strlen($content) < 1000) {
            return false;
        }
        
        // Don't compress if already compressed
        $compressed_types = array('image/', 'video/', 'audio/', 'application/zip', 'application/gzip');
        foreach ($compressed_types as $type) {
            if (strpos($content_type, $type) !== false) {
                return false;
            }
        }
        
        // Don't compress binary content
        if (!mb_check_encoding($content, 'UTF-8') && !self::is_text_content($content)) {
            return false;
        }
        
        return true;
    }
    
    /**
     * Check if content appears to be text-based
     */
    private static function is_text_content($content) {
        // Simple heuristic: if most bytes are printable ASCII or common UTF-8, it's probably text
        $text_chars = 0;
        $total_chars = min(strlen($content), 1000); // Sample first 1000 bytes
        
        for ($i = 0; $i < $total_chars; $i++) {
            $byte = ord($content[$i]);
            if (($byte >= 32 && $byte <= 126) || $byte == 9 || $byte == 10 || $byte == 13) {
                $text_chars++;
            }
        }
        
        return ($text_chars / $total_chars) > 0.7; // 70% text characters
    }
    
    /**
     * Get compression method capabilities
     */
    public static function get_capabilities() {
        return array(
            'brotli' => function_exists('brotli_compress'),
            'gzip' => function_exists('gzencode'),
            'auto' => function_exists('brotli_compress') || function_exists('gzencode')
        );
    }
    
    /**
     * Get recommended compression level for method
     */
    public static function get_recommended_level($method) {
        switch ($method) {
            case 'brotli':
                return 6; // Good balance for Brotli
            case 'gzip':
                return 6; // Standard for Gzip
            case 'auto':
                return 6; // Safe default
            default:
                return 6;
        }
    }
    
    /**
     * Estimate compression savings
     */
    public static function estimate_savings($content_size, $method = 'auto') {
        $estimates = array(
            'brotli' => 0.75, // 75% compression typically
            'gzip' => 0.65,   // 65% compression typically
            'auto' => 0.70    // Average of both
        );
        
        $ratio = $estimates[$method] ?? $estimates['auto'];
        return round($content_size * $ratio);
    }
}