<?php

error_reporting(E_ALL);
ini_set('display_errors', 1);
ini_set('memory_limit', '512M');
set_time_limit(30);

header('Content-Type: application/json; charset=utf-8');
header('Access-Control-Allow-Origin: *');
header('Access-Control-Allow-Methods: GET, POST, OPTIONS');
header('Access-Control-Allow-Headers: Content-Type');

if ($_SERVER['REQUEST_METHOD'] === 'OPTIONS') {
    http_response_code(200);
    exit();
}

// Optimized similarity function
function fuzzyMatch($str1, $str2) {
    $str1 = strtolower($str1);
    $str2 = strtolower($str2);
    
    if ($str1 === $str2) return 100;
    
    // Similar text gives good results for typos
    similar_text($str1, $str2, $percent);
    
    return $percent;
}

$host = 'localhost';
$dbname = 'akinikpublication';
$username = 'akinikpublicatio';
$password = '2-xu&*3qAh%C';

$query = isset($_GET['q']) ? trim($_GET['q']) : '';

if (empty($query) || strlen($query) < 3) {
    echo json_encode(array(
        'success' => false,
        'message' => 'Minimum 3 characters required',
        'suggestions' => array()
    ));
    exit;
}

$mysqli = new mysqli($host, $username, $password, $dbname);

if ($mysqli->connect_error) {
    http_response_code(500);
    echo json_encode(array(
        'success' => false,
        'message' => 'Database connection failed',
        'suggestions' => array()
    ));
    exit;
}

$mysqli->set_charset('utf8mb4');

$results = array();
$queryLower = strtolower($query);
$queryLen = strlen($queryLower);

// Step 1: Direct exact search
$searchPattern = '%' . $mysqli->real_escape_string($query) . '%';
$sql = "SELECT bookname, volume, newlink 
        FROM bookchapters 
        WHERE bookname LIKE ? OR scope LIKE ? 
        ORDER BY bookname 
        LIMIT 10";

if ($stmt = $mysqli->prepare($sql)) {
    $stmt->bind_param('ss', $searchPattern, $searchPattern);
    $stmt->execute();
    $stmt->store_result();
    $stmt->bind_result($bookname, $volume, $newlink);
    
    while ($stmt->fetch()) {
        $results[] = array(
            'title' => $bookname . " (Volume - " . $volume . ")",
            'newlink' => $newlink,
            'source' => 'exact'
        );
    }
    $stmt->close();
}

// Step 2: Fuzzy search if no results
if (count($results) === 0) {
    
    // Get ALL distinct words from database (with length filtering in MySQL)
    $minLen = $queryLen - 3;
    $maxLen = $queryLen + 3;
    
    // More aggressive: get more records
    $wordSql = "SELECT DISTINCT bookname, scope 
                FROM bookchapters 
                LIMIT 2000";
    
    $candidateWords = array();
    
    if ($wordResult = $mysqli->query($wordSql)) {
        while ($row = $wordResult->fetch_assoc()) {
            
            // Process bookname
            if (!empty($row['bookname'])) {
                $words = preg_split('/[\s,\-_\.;:()\[\]]+/', $row['bookname'], -1, PREG_SPLIT_NO_EMPTY);
                foreach ($words as $word) {
                    $word = strtolower(trim($word));
                    $wlen = strlen($word);
                    
                    // Length-based filtering
                    if ($wlen >= $minLen && $wlen <= $maxLen && $wlen >= 4) {
                        if (!isset($candidateWords[$word])) {
                            $candidateWords[$word] = 0;
                        }
                        $candidateWords[$word]++;
                    }
                }
            }
            
            // Process scope
            if (!empty($row['scope'])) {
                $words = preg_split('/[\s,\-_\.;:()\[\]]+/', $row['scope'], -1, PREG_SPLIT_NO_EMPTY);
                foreach ($words as $word) {
                    $word = strtolower(trim($word));
                    $wlen = strlen($word);
                    
                    if ($wlen >= $minLen && $wlen <= $maxLen && $wlen >= 4) {
                        if (!isset($candidateWords[$word])) {
                            $candidateWords[$word] = 0;
                        }
                        $candidateWords[$word]++;
                    }
                }
            }
        }
        $wordResult->free();
    }
    
    // Find best matches
    $matches = array();
    
    foreach ($candidateWords as $word => $frequency) {
        $similarity = fuzzyMatch($queryLower, $word);
        
        // Accept anything above 50% similarity
        if ($similarity >= 50) {
            $matches[] = array(
                'word' => $word,
                'score' => $similarity,
                'frequency' => $frequency
            );
        }
    }
    
    // Sort by similarity first, then frequency
    usort($matches, function($a, $b) {
        if ($b['score'] != $a['score']) {
            return $b['score'] - $a['score'];
        }
        return $b['frequency'] - $a['frequency'];
    });
    
    // Try top 3 matches
    $topMatches = array_slice($matches, 0, 3);
    
    foreach ($topMatches as $match) {
        $correctedWord = $match['word'];
        $correctedPattern = '%' . $mysqli->real_escape_string($correctedWord) . '%';
        
        $sql2 = "SELECT bookname, volume, newlink 
                 FROM bookchapters 
                 WHERE bookname LIKE ? OR scope LIKE ? 
                 ORDER BY bookname 
                 LIMIT 20";
        
        if ($stmt2 = $mysqli->prepare($sql2)) {
            $stmt2->bind_param('ss', $correctedPattern, $correctedPattern);
            $stmt2->execute();
            $stmt2->store_result();
            $stmt2->bind_result($bookname, $volume, $newlink);
            
            while ($stmt2->fetch()) {
                // Avoid duplicates
                $isDuplicate = false;
                foreach ($results as $existing) {
                    if ($existing['newlink'] === $newlink) {
                        $isDuplicate = true;
                        break;
                    }
                }
                
                if (!$isDuplicate) {
                    $results[] = array(
                        'title' => $bookname . " (Volume - " . $volume . ")",
                        'newlink' => $newlink,
                        'source' => 'fuzzy',
                        'corrected_from' => $query,
                        'corrected_to' => $correctedWord,
                        'similarity' => round($match['score'], 1)
                    );
                }
            }
            $stmt2->close();
        }
        
        // Stop if we found results
        if (count($results) > 0) break;
    }
}

$mysqli->close();

// Limit final results
$results = array_slice($results, 0, 10);

echo json_encode(array(
    'success' => true,
    'message' => count($results) > 0 ? 'Books found' : 'No books found',
    'suggestions' => $results,
    'count' => count($results)
), JSON_UNESCAPED_UNICODE);