michaelschiemer/tests/debug/test-data-placement-order.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 Order Verification ===\n\n";

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

echo "Test data: '{$testData}'\n";
echo "Expected: Should decode to 'HELLO WORLD'\n\n";

$matrix = QrCodeGenerator::generate($testData, $config);
$size = $matrix->getSize();

// Simulate reading data bits back in placement order
echo "Reading data bits from matrix (unmasking first)...\n";

// First, we need to know which mask was used
// Extract format info to determine mask
$formatCols = [0, 1, 2, 3, 4, 5, 7, 8, $size - 1, $size - 2, $size - 3, $size - 4, $size - 5, $size - 6, $size - 7];
$formatH = '';
foreach ($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 "Detected mask pattern: {$maskPattern}\n\n";

// Now read data bits in placement order and unmask them
use App\Framework\QrCode\Masking\MaskPattern as MaskPatternEnum;

$mask = match($maskPattern) {
    0 => MaskPatternEnum::PATTERN_0,
    1 => MaskPatternEnum::PATTERN_1,
    2 => MaskPatternEnum::PATTERN_2,
    3 => MaskPatternEnum::PATTERN_3,
    4 => MaskPatternEnum::PATTERN_4,
    5 => MaskPatternEnum::PATTERN_5,
    6 => MaskPatternEnum::PATTERN_6,
    7 => MaskPatternEnum::PATTERN_7,
};

$dataBits = [];
$bitIndex = 0;

// Read in same order as placement
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 >= 0 && $currentCol <= 5) || $currentCol === 7 || $currentCol === 8 || $currentCol >= $size - 8)) ||
                ($currentCol === 8 && (($row >= 0 && $row <= 5) || $row === 7 || $row === 8 || $row >= $size - 7)) ||
                ($row === 13 && $currentCol === 8)) {
                continue;
            }
            
            // Read bit
            $maskedBit = $matrix->getModuleAt($row, $currentCol)->isDark() ? 1 : 0;
            
            // Unmask
            $unmaskedBit = $mask->shouldInvert($row, $currentCol) ? (1 - $maskedBit) : $maskedBit;
            
            $dataBits[] = $unmaskedBit;
            $bitIndex++;
        }
    }
}

echo "Read {$bitIndex} data bits\n";

// Convert bits to codewords
$codewords = [];
for ($i = 0; $i < count($dataBits); $i += 8) {
    if ($i + 8 <= count($dataBits)) {
        $byte = '';
        for ($j = 0; $j < 8; $j++) {
            $byte .= (string)$dataBits[$i + $j];
        }
        $codewords[] = bindec($byte);
    }
}

echo "Extracted " . count($codewords) . " codewords\n";
echo "First 10 codewords: " . implode(', ', array_slice($codewords, 0, 10)) . "\n\n";

// Try to decode first few bytes
echo "=== Decoding Attempt ===\n";
if (count($codewords) >= 3) {
    // First byte should be mode indicator (0100 = 4)
    $mode = $codewords[0];
    echo "Mode indicator: {$mode} (expected: 4 for byte mode)\n";
    
    // Second byte should be character count
    $charCount = $codewords[1];
    echo "Character count: {$charCount} (expected: " . strlen($testData) . ")\n";
    
    // Next bytes should be data
    echo "First data bytes: ";
    for ($i = 2; $i < min(2 + strlen($testData), count($codewords)); $i++) {
        echo chr($codewords[$i]);
    }
    echo "\n";
}