<?php

declare(strict_types=1);

function fix_encoding(string $str): string
{
    //return $str;
    return mb_convert_encoding($str, 'UTF-8', 'ISO-8859-1');
}

function parse_csv(string $csv, string $separator = ","): array
{
    $csv = strtr(
        $csv,
        [
            "\xEF\xBB\xBF" => "", // remove UTF-8 byte order masks, if present
            "\r\n" => "\n", // Windows CrLf=> Unix Lf
            "\r" => "\n" // old-MacOS Cr => Unix Lf
            // (both modern MacOS and Linux use Lf .. Windows is the only outlier)
        ]
    );
    $lines = explode("\n", $csv);
    $keys = str_getcsv(array_shift($lines), $separator);
    $ret = array();
    foreach ($lines as $lineno => $line) {
        if (strlen($line) < 1) {
            // ... probably malformed csv, but we'll allow it
            continue;
        }
        $parsed = str_getcsv($line, $separator);
        if (count($parsed) !== count($keys)) {
            throw new \RuntimeException("error on csv line #{$lineno}: count mismatch:" . count($parsed) . ' !== ' . count($keys) . ": " . var_export([
                'error' => 'count mismatch',
                'keys' => $keys,
                'parsed' => $parsed,
                'line' => $line
            ], true));
        }
        $ret[] = array_combine($keys, $parsed);
    }
    return $ret;
}
error_reporting(E_ALL);
ini_set('display_errors', '1');
set_error_handler(function ($errno, $errstr, $errfile, $errline) {
    if (error_reporting() & $errno) {
        throw new \ErrorException($errstr, 0, $errno, $errfile, $errline);
    }
});
if ($argc !== 3) {
    echo "Usage: php {$argv[0]} <file1.csv> <file2.csv>\n";
    exit(1);
}
$file1 = $argv[1];
$file2 = $argv[2];
$raw1 = file_get_contents($file1);
$raw2 = file_get_contents($file2);
$raw1 = fix_encoding($raw1);
$raw2 = fix_encoding($raw2);
$csv1 = parse_csv($raw1);
$csv2 = parse_csv($raw2);
$merged = [];


// Assuming both CSVs have the same headers and the merge is based on these headers.
$headers = array_keys($csv1[0] + $csv2[0]); // Combine and get unique headers from both CSVs
foreach ($csv1 as $index => $row) {
    foreach ($headers as $header) {
        // If the current header exists in both csv1 and csv2 rows
        if (isset($csv2[$index][$header], $row[$header])) {
            // If csv1's value is empty and csv2's value is not, take csv2's value
            if (empty($row[$header]) && !empty($csv2[$index][$header])) {
                $merged[$index][$header] = $csv2[$index][$header];
            } else {
                // Otherwise, use csv1's value (even if it's empty, since both are equal priority in this case)
                $merged[$index][$header] = $row[$header];
            }
        } elseif (isset($row[$header])) {
            // If the header exists only in csv1, take csv1's value
            $merged[$index][$header] = $row[$header];
        } elseif (isset($csv2[$index][$header])) {
            // If the header exists only in csv2, take csv2's value
            $merged[$index][$header] = $csv2[$index][$header];
        }
    }
}

// Handle the case where csv2 is longer than csv1
if (count($csv2) > count($csv1)) {
    for ($i = count($csv1); $i < count($csv2); $i++) {
        foreach ($headers as $header) {
            if (isset($csv2[$i][$header])) {
                $merged[$i][$header] = $csv2[$i][$header];
            }
        }
    }
}

function array_to_csv(array $data, string $delimiter = ",", string $enclosure = '"', string $escapeChar = "\\"): string {
    $fh = fopen('php://temp', 'rw'); // Write to a temporary file
    foreach ($data as $row) {
        fputcsv($fh, $row, $delimiter, $enclosure, $escapeChar);
    }
    rewind($fh);
    $csvString = stream_get_contents($fh);
    fclose($fh);
    return $csvString;
}

$mergedCsvString = array_to_csv($merged);
// For demonstration, let's just print the merged CSV string
echo mb_convert_encoding($mergedCsvString, 'ISO-8859-1', 'UTF-8');
//echo $mergedCsvString;