<?php

declare(strict_types=1);

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

use App\Framework\QrCode\ErrorCorrection\ReedSolomonEncoder;

echo "=== Polynomial Division Step-by-Step ===\n\n";

// Test with simple data to trace the algorithm
$data = [1, 2, 3];
$ecCodewords = 3;

$rs = new ReedSolomonEncoder();
$reflection = new ReflectionClass($rs);

// Get generator polynomial
$getGeneratorMethod = $reflection->getMethod('getGeneratorPolynomial');
$getGeneratorMethod->setAccessible(true);
$generator = $getGeneratorMethod->invoke($rs, $ecCodewords);

echo "Data: " . implode(', ', $data) . "\n";
echo "EC codewords needed: {$ecCodewords}\n";
echo "Generator polynomial (degree {$ecCodewords}): " . implode(', ', $generator) . "\n\n";

// Manually trace the algorithm
echo "=== Algorithm Trace ===\n";

// Step 1: Create message polynomial
$messagePoly = array_merge($data, array_fill(0, $ecCodewords, 0));
echo "Step 1 - Message polynomial (data + zeros):\n";
echo "  [" . implode(', ', $messagePoly) . "]\n\n";

// Step 2: Polynomial division
echo "Step 2 - Polynomial division:\n";

$gfMultiplyMethod = $reflection->getMethod('gfMultiply');
$gfMultiplyMethod->setAccessible(true);

$traceMessagePoly = $messagePoly;

for ($i = 0; $i < count($data); $i++) {
    $coefficient = $traceMessagePoly[$i];
    
    if ($coefficient !== 0) {
        echo "  Iteration {$i}: coefficient = {$coefficient}\n";
        echo "    Before: [" . implode(', ', $traceMessagePoly) . "]\n";
        
        for ($j = 0; $j < count($generator); $j++) {
            $multiplied = $gfMultiplyMethod->invoke($rs, $generator[$j], $coefficient);
            $oldValue = $traceMessagePoly[$i + $j];
            $traceMessagePoly[$i + $j] ^= $multiplied;
            $newValue = $traceMessagePoly[$i + $j];
            
            if ($oldValue !== $newValue) {
                echo "      [{$i}+{$j}] = {$oldValue} XOR {$multiplied} = {$newValue}\n";
            }
        }
        
        echo "    After:  [" . implode(', ', $traceMessagePoly) . "]\n\n";
    } else {
        echo "  Iteration {$i}: coefficient = 0 (skip)\n\n";
    }
}

// Step 3: Extract EC codewords
$ec = array_slice($traceMessagePoly, count($data));
echo "Step 3 - EC codewords (last {$ecCodewords} coefficients):\n";
echo "  [" . implode(', ', $ec) . "]\n\n";

// Verify with actual implementation
$actualEC = $rs->encode($data, $ecCodewords);
echo "Actual EC codewords from implementation:\n";
echo "  [" . implode(', ', $actualEC) . "]\n\n";

if ($ec === $actualEC) {
    echo "✅ Traced algorithm matches implementation!\n";
} else {
    echo "❌ Traced algorithm doesn't match implementation!\n";
    echo "Differences:\n";
    for ($i = 0; $i < min(count($ec), count($actualEC)); $i++) {
        if ($ec[$i] !== $actualEC[$i]) {
            echo "  Position {$i}: traced={$ec[$i]}, actual={$actualEC[$i]}\n";
        }
    }
}

// Test with our actual QR code data
echo "\n=== Test with QR Code Data ===\n";
$qrData = [64, 180, 132, 84, 196, 196, 242, 5, 116, 245, 36, 196, 64, 236, 17, 236];
$qrEC = $rs->encode($qrData, 10);

echo "QR data codewords (16):\n";
echo "  " . implode(', ', $qrData) . "\n\n";
echo "QR EC codewords (10):\n";
echo "  " . implode(', ', $qrEC) . "\n\n";