michaelschiemer/tests/debug/test-data-placement-masking.php

<?php

declare(strict_types=1);

require_once __DIR__ . '/../../vendor/autoload.php';

use App\Framework\QrCode\QrCodeGenerator;
use App\Framework\QrCode\ValueObjects\ErrorCorrectionLevel;
use App\Framework\QrCode\ValueObjects\QrCodeConfig;
use App\Framework\QrCode\ValueObjects\QrCodeVersion;
use App\Framework\QrCode\ValueObjects\EncodingMode;

echo "=== Data Placement and Masking Test ===\n\n";

$testData = 'HELLO WORLD';
$config = new QrCodeConfig(
    version: QrCodeVersion::fromNumber(1),
    errorCorrectionLevel: ErrorCorrectionLevel::M,
    encodingMode: EncodingMode::BYTE
);

$matrix = QrCodeGenerator::generate($testData, $config);

// Decode format to get mask pattern
$formatCols = [0, 1, 2, 3, 4, 5, 7, 8, 20, 19, 18, 17, 16, 15, 14];
$formatH = '';
foreach ($formatCols as $col) {
    $formatH .= $matrix->getModuleAt(8, $col)->isDark() ? '1' : '0';
}

$xorMask = "101010000010010";
$unmasked = '';
for ($i = 0; $i < 15; $i++) {
    $unmasked .= (int)$formatH[$i] ^ (int)$xorMask[$i];
}

$maskBits = substr($unmasked, 2, 3);
$maskPattern = bindec($maskBits);

echo "Mask Pattern: {$maskPattern}\n";
echo "EC Level: M\n\n";

// Check if we can decode the data by reading it back
echo "=== Attempting to Decode Data ===\n";

// Read data bits in placement order (zig-zag, column pairs)
$size = $matrix->getSize();
$dataBits = '';
$bitCount = 0;
$maxBits = 26 * 8; // 26 codewords * 8 bits

// Remove mask first (unmask data area)
$unmaskedMatrix = $matrix;
for ($row = 0; $row < $size; $row++) {
    for ($col = 0; $col < $size; $col++) {
        // Skip function patterns
        if (
            ($row <= 8 && $col <= 8) ||
            ($row <= 7 && $col >= $size - 8) ||
            ($row >= $size - 8 && $col <= 7) ||
            $row === 6 || $col === 6 ||
            ($row === 8 && ($col <= 8 || $col >= $size - 8)) ||
            ($col === 8 && ($row <= 7 || $row >= 9)) ||
            ($row === 13 && $col === 8)
        ) {
            continue;
        }
        
        // Unmask using pattern 3: (row + column) % 3 == 0
        if (($row + $col) % 3 === 0) {
            $currentModule = $matrix->getModuleAt($row, $col);
            $invertedModule = $currentModule->isDark()
                ? \App\Framework\QrCode\ValueObjects\Module::light()
                : \App\Framework\QrCode\ValueObjects\Module::dark();
            $unmaskedMatrix = $unmaskedMatrix->setModuleAt($row, $col, $invertedModule);
        }
    }
}

// Now read data bits in placement order
// ISO/IEC 18004 Section 7.7.3: Column pairs, right-to-left, zig-zag
for ($col = $size - 1; $col >= 1; $col -= 2) {
    if ($col === 6) {
        $col--;
    }
    
    $upward = ((int) (($size - 1 - $col) / 2) % 2) === 0;
    
    for ($i = 0; $i < $size; $i++) {
        $row = $upward ? ($size - 1 - $i) : $i;
        
        for ($c = 0; $c < 2; $c++) {
            $currentCol = $col - $c;
            
            // Skip function patterns
            if (
                ($row <= 8 && $currentCol <= 8) ||
                ($row <= 7 && $currentCol >= $size - 8) ||
                ($row >= $size - 8 && $currentCol <= 7) ||
                $row === 6 || $currentCol === 6 ||
                ($row === 8 && ($currentCol <= 8 || $currentCol >= $size - 8)) ||
                ($currentCol === 8 && ($row <= 7 || $row >= 9)) ||
                ($row === 13 && $currentCol === 8)
            ) {
                continue;
            }
            
            if ($bitCount < $maxBits) {
                $isDark = $unmaskedMatrix->getModuleAt($row, $currentCol)->isDark();
                $dataBits .= $isDark ? '1' : '0';
                $bitCount++;
            }
        }
    }
}

echo "Read {$bitCount} bits from matrix\n";
echo "Expected: {$maxBits} bits\n\n";

if ($bitCount < $maxBits) {
    echo "⚠️ Not enough bits read - data placement might be wrong\n";
} else {
    echo "✅ Read all expected bits\n";
}

// Try to decode first few bits
echo "First 20 bits: " . substr($dataBits, 0, 20) . "\n";

// Mode indicator should be 0100 (Byte mode)
$modeBits = substr($dataBits, 0, 4);
echo "Mode indicator (first 4 bits): {$modeBits}\n";
if ($modeBits === '0100') {
    echo "✅ Correct (Byte mode)\n";
} else {
    echo "❌ Wrong! Expected 0100, got {$modeBits}\n";
}

// Character count should be 11 (00001011)
$countBits = substr($dataBits, 4, 8);
$count = bindec($countBits);
echo "Character count (bits 4-11): {$countBits} = {$count}\n";
if ($count === 11) {
    echo "✅ Correct (11 characters)\n";
} else {
    echo "❌ Wrong! Expected 11, got {$count}\n";
}

echo "\n";

// Check if data can be partially decoded
if (strlen($dataBits) >= 12) {
    echo "=== Partial Data Decode ===\n";
    $mode = bindec(substr($dataBits, 0, 4));
    $charCount = bindec(substr($dataBits, 4, 8));
    
    echo "Mode: {$mode}\n";
    echo "Character count: {$charCount}\n";
    
    if ($charCount === strlen($testData)) {
        echo "✅ Character count matches!\n";
    } else {
        echo "❌ Character count mismatch!\n";
    }
}