<?php

/**
 * Generate correct Format Information table with BCH error correction
 * Based on ISO/IEC 18004 specification
 */

echo "=== Generating Correct Format Information Table ===\n\n";

// EC Level encoding (ISO/IEC 18004)
$ecLevels = [
    'L' => 0b01,  // Level L
    'M' => 0b00,  // Level M
    'Q' => 0b11,  // Level Q
    'H' => 0b10,  // Level H
];

// BCH(15,5) generator polynomial: x^10 + x^8 + x^5 + x^4 + x^2 + x + 1
// Binary: 10100110111
$bchGenerator = 0b10100110111;

function calculateBCH(int $data): int
{
    global $bchGenerator;
    
    // Shift data left by 10 bits (for 10 BCH parity bits)
    $remainder = $data << 10;
    
    // Perform polynomial division
    for ($i = 4; $i >= 0; $i--) {
        if (($remainder >> (10 + $i)) & 1) {
            $remainder ^= ($bchGenerator << $i);
        }
    }
    
    return $remainder & 0b1111111111;  // 10 bits
}

function applyMask(int $formatBits): int
{
    // XOR mask: 101010000010010
    $mask = 0b101010000010010;
    return $formatBits ^ $mask;
}

echo "Generating format information for all EC levels and mask patterns:\n\n";

foreach ($ecLevels as $levelName => $ecBits) {
    echo "'{$levelName}' => [\n";
    
    for ($maskPattern = 0; $maskPattern <= 7; $maskPattern++) {
        // Combine EC level (2 bits) and mask pattern (3 bits) = 5 data bits
        $dataBits = ($ecBits << 3) | $maskPattern;
        
        // Calculate BCH error correction (10 bits)
        $bchBits = calculateBCH($dataBits);
        
        // Combine data and BCH (15 bits total)
        $formatBits = ($dataBits << 10) | $bchBits;
        
        // Apply XOR mask
        $maskedFormat = applyMask($formatBits);
        
        $binary = sprintf('%015b', $maskedFormat);
        $octal = sprintf('0b%015b', $maskedFormat);
        
        // Verify
        $ecPart = substr($binary, 0, 2);
        $maskPart = substr($binary, 2, 3);
        
        echo "    {$maskPattern} => {$octal},  // Level {$levelName}, Mask {$maskPattern} ";
        echo "(EC={$ecPart}, Mask={$maskPart})\n";
    }
    
    echo "],\n";
}