<?php

declare(strict_types=1);

$root = dirname(__DIR__);
$catalogDir = $root . '/catalog';
$indexesDir = $root . '/indexes';

$upcIndex = [];
$skuIndex = [];
$manufacturerIndex = [];
$errors = [];
$checked = 0;

if (!is_dir($catalogDir)) {
    fwrite(STDERR, "Catalog directory not found: {$catalogDir}\n");
    exit(1);
}

if (!is_dir($indexesDir) && !mkdir($indexesDir, 0775, true) && !is_dir($indexesDir)) {
    fwrite(STDERR, "Unable to create indexes directory: {$indexesDir}\n");
    exit(1);
}

$iterator = new RecursiveIteratorIterator(
    new RecursiveDirectoryIterator(
        $catalogDir,
        FilesystemIterator::SKIP_DOTS
    )
);

foreach ($iterator as $file) {
    if (!$file->isFile() || strtolower($file->getExtension()) !== 'json') {
        continue;
    }

    $checked++;
    $path = $file->getPathname();
    $relativePath = substr($path, strlen($root) + 1);

    $raw = file_get_contents($path);

    if ($raw === false) {
        $errors[] = "{$relativePath}: unable to read file";
        continue;
    }

    try {
        $record = json_decode($raw, true, 512, JSON_THROW_ON_ERROR);
    } catch (JsonException $exception) {
        $errors[] = "{$relativePath}: invalid JSON: {$exception->getMessage()}";
        continue;
    }

    if (!is_array($record)) {
        $errors[] = "{$relativePath}: root value must be an object";
        continue;
    }

    $upc = $record['upc'] ?? null;
    $sku = $record['sku'] ?? null;
    $manufacturer = $record['manufacturer'] ?? null;

    if (is_string($upc) && $upc !== '') {
        if (isset($upcIndex[$upc])) {
            $errors[] = "{$relativePath}: duplicate UPC {$upc}, already used by {$upcIndex[$upc]}";
        } else {
            $upcIndex[$upc] = $relativePath;
        }
    }

    if (
        is_string($manufacturer) &&
        trim($manufacturer) !== ''
    ) {
        $manufacturerKey = strtolower(trim($manufacturer));

        if (!isset($manufacturerIndex[$manufacturerKey])) {
            $manufacturerIndex[$manufacturerKey] = [];
        }

        $manufacturerIndex[$manufacturerKey][] = $relativePath;

        if (is_string($sku) && trim($sku) !== '') {
            $skuKey = $manufacturerKey . ':' . strtolower(trim($sku));

            if (isset($skuIndex[$skuKey])) {
                $errors[] = "{$relativePath}: duplicate SKU key {$skuKey}, already used by {$skuIndex[$skuKey]}";
            } else {
                $skuIndex[$skuKey] = $relativePath;
            }
        }
    }
}

if ($errors !== []) {
    fwrite(STDERR, "Index build failed:\n\n");

    foreach ($errors as $error) {
        fwrite(STDERR, " - {$error}\n");
    }

    fwrite(STDERR, "\nChecked {$checked} product file(s).\n");
    exit(1);
}

ksort($upcIndex, SORT_STRING);
ksort($skuIndex, SORT_STRING);
ksort($manufacturerIndex, SORT_STRING);

foreach ($manufacturerIndex as &$paths) {
    sort($paths, SORT_STRING);
}
unset($paths);

$files = [
    $indexesDir . '/upc-index.json' => $upcIndex,
    $indexesDir . '/sku-index.json' => $skuIndex,
    $indexesDir . '/manufacturer-index.json' => $manufacturerIndex,
];

foreach ($files as $outputPath => $data) {
    $json = json_encode(
        $data,
        JSON_PRETTY_PRINT |
        JSON_UNESCAPED_SLASHES |
        JSON_THROW_ON_ERROR
    );

    if (file_put_contents($outputPath, $json . PHP_EOL) === false) {
        fwrite(STDERR, "Unable to write {$outputPath}\n");
        exit(1);
    }
}

echo "Index build complete.\n";
echo "Products checked: {$checked}\n";
echo "UPC entries: " . count($upcIndex) . "\n";
echo "SKU entries: " . count($skuIndex) . "\n";
echo "Manufacturers: " . count($manufacturerIndex) . "\n";