<?php
/**
 * Minimal S3 client for Hetzner Object Storage (or any S3-compatible store).
 * Implements AWS Signature v4 in plain PHP — no SDK, no Composer.
 *
 * - Presigned GET  → visitors load gallery images directly from S3
 * - Signed PUT     → the webhost streams uploaded originals/thumbs to S3
 * - Signed DELETE  → server-side cleanup when images/galleries are removed
 *
 * Addressing style is configurable via s3.path_style:
 *   path-style (default)    → https://<endpoint-host>/<bucket>/<key>
 *   virtual-hosted-style    → https://<bucket>.<endpoint-host>/<key>
 * Hetzner Object Storage serves path-style reliably; virtual-hosted-style
 * requires the bucket to resolve as a TLS subdomain of the endpoint.
 */

declare(strict_types=1);

/** Percent-encode an object key, keeping the "/" separators. */
function s3_encode_key(string $key): string
{
    return implode('/', array_map('rawurlencode', explode('/', $key)));
}

/** Bare host of the configured endpoint, e.g. "fsn1.your-objectstorage.com". */
function s3_endpoint_host(): string
{
    return (string)parse_url(config('s3.endpoint'), PHP_URL_HOST);
}

/** ":port" suffix when the endpoint pins a non-default port, else "". */
function s3_endpoint_port_suffix(): string
{
    $port = parse_url(config('s3.endpoint'), PHP_URL_PORT);
    return $port ? ':' . $port : '';
}

/** Whether to address the bucket in the path (true) or as a subdomain (false). */
function s3_use_path_style(): bool
{
    return (bool)config('s3.path_style', true);
}

/**
 * Request host. Path-style keeps the bare endpoint host; virtual-hosted-style
 * prepends the bucket as a DNS label (never percent-encoded).
 */
function s3_host(): string
{
    $host = s3_endpoint_host();
    $host = s3_use_path_style() ? $host : config('s3.bucket') . '.' . $host;
    // The signed Host header and the request host must match, port included.
    return $host . s3_endpoint_port_suffix();
}

/** Base URL for object requests: scheme + host, no trailing slash. */
function s3_base_url(): string
{
    $scheme = parse_url(config('s3.endpoint'), PHP_URL_SCHEME) ?: 'https';
    return $scheme . '://' . s3_host();
}

/**
 * Canonical (and actual) request path for a key. Path-style prefixes the
 * bucket as the first, percent-encoded path segment; virtual-hosted-style
 * does not, because the bucket lives in the host instead.
 */
function s3_canonical_uri(string $key): string
{
    $path = '/' . s3_encode_key($key);
    return s3_use_path_style() ? '/' . rawurlencode(config('s3.bucket')) . $path : $path;
}

/**
 * Key prefix under which one gallery's objects live: "<prefix>/<slug>".
 * The prefix is configurable via s3.prefix (default "galleries"); an empty
 * prefix puts galleries at the bucket root.
 */
function s3_gallery_prefix(string $slug): string
{
    $prefix = trim((string)config('s3.prefix', 'galleries'), '/');
    return $prefix !== '' ? "$prefix/$slug" : $slug;
}

/** HMAC-SHA256 chain producing the SigV4 signing key. */
function s3_signing_key(string $date): string
{
    $k = hash_hmac('sha256', $date, 'AWS4' . config('s3.secret_key'), true);
    $k = hash_hmac('sha256', config('s3.region'), $k, true);
    $k = hash_hmac('sha256', 's3', $k, true);
    return hash_hmac('sha256', 'aws4_request', $k, true);
}

/**
 * SigV4 query-string signing core. Separated from s3_presign() so the
 * algorithm can be verified against the official AWS example vectors.
 * Returns the full query string including X-Amz-Signature.
 */
function s3_presign_query(
    string $method,
    string $host,
    string $canonicalUri,
    string $accessKey,
    string $secretKey,
    string $region,
    int $ttl,
    string $amzDate
): string {
    $date = substr($amzDate, 0, 8);
    $scope = $date . '/' . $region . '/s3/aws4_request';

    $query = [
        'X-Amz-Algorithm'     => 'AWS4-HMAC-SHA256',
        'X-Amz-Credential'    => $accessKey . '/' . $scope,
        'X-Amz-Date'          => $amzDate,
        'X-Amz-Expires'       => (string)$ttl,
        'X-Amz-SignedHeaders' => 'host',
    ];
    ksort($query);
    $canonicalQuery = implode('&', array_map(
        fn($k, $v) => rawurlencode($k) . '=' . rawurlencode($v),
        array_keys($query),
        $query
    ));

    $canonicalRequest = implode("\n", [
        strtoupper($method),
        $canonicalUri,
        $canonicalQuery,
        'host:' . $host,
        '',
        'host',
        'UNSIGNED-PAYLOAD',
    ]);

    $stringToSign = implode("\n", [
        'AWS4-HMAC-SHA256',
        $amzDate,
        $scope,
        hash('sha256', $canonicalRequest),
    ]);

    $k = hash_hmac('sha256', $date, 'AWS4' . $secretKey, true);
    $k = hash_hmac('sha256', $region, $k, true);
    $k = hash_hmac('sha256', 's3', $k, true);
    $k = hash_hmac('sha256', 'aws4_request', $k, true);
    $signature = hash_hmac('sha256', $stringToSign, $k);

    return $canonicalQuery . '&X-Amz-Signature=' . $signature;
}

/**
 * Build a presigned URL for an object key. Only the Host header is signed.
 * Used for GET so visitors' browsers can load private images directly; uploads
 * go through the webhost (s3_put_file), never a presigned PUT.
 */
function s3_presign(string $method, string $key, ?int $ttl = null): string
{
    $ttl ??= (int)config('s3.url_ttl', 3600);
    $canonicalUri = s3_canonical_uri($key);
    $query = s3_presign_query(
        $method,
        s3_host(),
        $canonicalUri,
        config('s3.access_key'),
        config('s3.secret_key'),
        config('s3.region'),
        $ttl,
        gmdate('Ymd\THis\Z')
    );
    return s3_base_url() . $canonicalUri . '?' . $query;
}

function s3_presign_get(string $key, ?int $ttl = null): string
{
    return s3_presign('GET', $key, $ttl);
}

/**
 * Stream a local file to S3 with a signed PUT (header auth). The payload is sent
 * as UNSIGNED-PAYLOAD so the body is never hashed or buffered into memory — curl
 * streams it straight from the file handle, letting the webhost proxy originals
 * far larger than memory_limit. Content-Type is sent but not signed.
 * Returns [httpStatus, responseBody].
 */
function s3_put_file(string $key, string $filePath, string $contentType = 'application/octet-stream'): array
{
    $host = s3_host();
    $amzDate = gmdate('Ymd\THis\Z');
    $date = substr($amzDate, 0, 8);
    $scope = $date . '/' . config('s3.region') . '/s3/aws4_request';
    $canonicalUri = s3_canonical_uri($key);
    $payloadHash = 'UNSIGNED-PAYLOAD';

    $canonicalRequest = implode("\n", [
        'PUT',
        $canonicalUri,
        '',
        'host:' . $host,
        'x-amz-content-sha256:' . $payloadHash,
        'x-amz-date:' . $amzDate,
        '',
        'host;x-amz-content-sha256;x-amz-date',
        $payloadHash,
    ]);

    $stringToSign = implode("\n", [
        'AWS4-HMAC-SHA256',
        $amzDate,
        $scope,
        hash('sha256', $canonicalRequest),
    ]);

    $signature = hash_hmac('sha256', $stringToSign, s3_signing_key($date));
    $authorization = 'AWS4-HMAC-SHA256 Credential=' . config('s3.access_key') . '/' . $scope
        . ', SignedHeaders=host;x-amz-content-sha256;x-amz-date'
        . ', Signature=' . $signature;

    $fh = fopen($filePath, 'rb');
    if ($fh === false) {
        return [0, 'Cannot open upload for reading'];
    }
    $ch = curl_init(s3_base_url() . $canonicalUri);
    curl_setopt_array($ch, [
        CURLOPT_UPLOAD         => true,   // sets method to PUT and streams CURLOPT_INFILE
        CURLOPT_INFILE         => $fh,
        CURLOPT_INFILESIZE     => filesize($filePath),
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_CONNECTTIMEOUT => 30,
        CURLOPT_TIMEOUT        => 0,       // no cap: originals can be large
        CURLOPT_HTTPHEADER     => [
            'Authorization: ' . $authorization,
            'x-amz-content-sha256: ' . $payloadHash,
            'x-amz-date: ' . $amzDate,
            'Content-Type: ' . $contentType,
            'Expect:',                     // skip 100-continue round-trip
        ],
    ]);
    $body = curl_exec($ch);
    $status = (int)curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
    fclose($fh);
    return [$status, (string)$body];
}

/**
 * Server-side signed request (header auth). Used for DELETE.
 * Returns [httpStatus, responseBody].
 */
function s3_request(string $method, string $key): array
{
    $host = s3_host();
    $amzDate = gmdate('Ymd\THis\Z');
    $date = substr($amzDate, 0, 8);
    $scope = $date . '/' . config('s3.region') . '/s3/aws4_request';
    $canonicalUri = s3_canonical_uri($key);
    $payloadHash = hash('sha256', '');

    $canonicalRequest = implode("\n", [
        strtoupper($method),
        $canonicalUri,
        '', // no query string
        'host:' . $host,
        'x-amz-content-sha256:' . $payloadHash,
        'x-amz-date:' . $amzDate,
        '',
        'host;x-amz-content-sha256;x-amz-date',
        $payloadHash,
    ]);

    $stringToSign = implode("\n", [
        'AWS4-HMAC-SHA256',
        $amzDate,
        $scope,
        hash('sha256', $canonicalRequest),
    ]);

    $signature = hash_hmac('sha256', $stringToSign, s3_signing_key($date));
    $authorization = 'AWS4-HMAC-SHA256 Credential=' . config('s3.access_key') . '/' . $scope
        . ', SignedHeaders=host;x-amz-content-sha256;x-amz-date'
        . ', Signature=' . $signature;

    $ch = curl_init(s3_base_url() . $canonicalUri);
    curl_setopt_array($ch, [
        CURLOPT_CUSTOMREQUEST  => strtoupper($method),
        CURLOPT_RETURNTRANSFER => true,
        CURLOPT_TIMEOUT        => 30,
        CURLOPT_HTTPHEADER     => [
            'Authorization: ' . $authorization,
            'x-amz-content-sha256: ' . $payloadHash,
            'x-amz-date: ' . $amzDate,
        ],
    ]);
    $body = curl_exec($ch);
    $status = (int)curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
    return [$status, (string)$body];
}

/** Delete one object. S3 returns 204 for success and for already-gone keys. */
function s3_delete(string $key): bool
{
    [$status] = s3_request('DELETE', $key);
    return $status === 204 || $status === 200 || $status === 404;
}

/** Delete every S3 object referenced by a gallery (originals + thumbs). */
function s3_delete_gallery_objects(array $gallery): void
{
    foreach ($gallery['images'] ?? [] as $img) {
        if (!empty($img['key'])) {
            s3_delete($img['key']);
        }
        if (!empty($img['thumb'])) {
            s3_delete($img['thumb']);
        }
    }
}

/** Human-readable reason for a PHP upload error code. */
function upload_error_message(int $code): string
{
    return match ($code) {
        UPLOAD_ERR_INI_SIZE, UPLOAD_ERR_FORM_SIZE => 'file exceeds the server upload size limit',
        UPLOAD_ERR_PARTIAL                        => 'upload was interrupted',
        UPLOAD_ERR_NO_FILE                        => 'no file received',
        UPLOAD_ERR_NO_TMP_DIR, UPLOAD_ERR_CANT_WRITE => 'server cannot store the upload',
        default                                   => 'upload error ' . $code,
    };
}

/**
 * Ingest one uploaded image into a gallery: stream the original (and optional
 * browser-generated thumbnail) to S3, then append it to the gallery's JSON file.
 *
 * Shared by admin/api.php (trusted admin) and upload-api.php (public guest link).
 * The gallery is re-loaded under a fresh read before appending to reduce lost
 * updates between concurrent uploads. Object keys are generated server-side
 * under the gallery's own prefix — never taken from the client.
 *
 * $original / $thumb are $_FILES entries (or null). When $imagesOnly is true the
 * original must have a recognised image extension and decode via getimagesize(),
 * so a public link cannot be used to store arbitrary file types.
 *
 * Returns [int $httpStatus, array $payload] for the caller to hand to
 * json_response(); a thumbnail failure is non-fatal (the grid falls back to the
 * original key).
 */
function gallery_store_s3_upload(array $gallery, ?array $original, ?array $thumb, bool $imagesOnly = false): array
{
    if (!is_array($original) || ($original['error'] ?? UPLOAD_ERR_NO_FILE) !== UPLOAD_ERR_OK) {
        return [400, ['error' => upload_error_message((int)($original['error'] ?? UPLOAD_ERR_NO_FILE))]];
    }
    if (!is_uploaded_file((string)$original['tmp_name'])) {
        return [400, ['error' => 'Invalid upload']];
    }

    if ($imagesOnly) {
        $ext = strtolower(pathinfo((string)($original['name'] ?? ''), PATHINFO_EXTENSION));
        if (!in_array($ext, MEDIA_EXTENSIONS, true) || getimagesize((string)$original['tmp_name']) === false) {
            return [400, ['error' => 'Only image files are allowed']];
        }
    }

    $slug  = $gallery['slug'];
    $name  = substr(safe_filename((string)($original['name'] ?? '')), 0, 120);
    $token = random_token(6);
    $base  = s3_gallery_prefix($slug);
    $key   = "$base/originals/$token-$name";

    // Stream the original to S3 byte-for-byte from the PHP upload temp file.
    $type = (string)($original['type'] ?? '') ?: 'application/octet-stream';
    [$status] = s3_put_file($key, (string)$original['tmp_name'], $type);
    if ($status < 200 || $status >= 300) {
        return [502, ['error' => "S3 rejected the original (HTTP $status)"]];
    }

    // Optional browser-generated thumbnail. A thumb failure is non-fatal: the
    // original stays, and the grid falls back to the original key.
    $thumbKey = null;
    if (is_array($thumb)
        && ($thumb['error'] ?? UPLOAD_ERR_NO_FILE) === UPLOAD_ERR_OK
        && is_uploaded_file((string)$thumb['tmp_name'])
    ) {
        $candidate = "$base/thumbs/$token-$name.jpg";
        [$tstatus] = s3_put_file($candidate, (string)$thumb['tmp_name'], 'image/jpeg');
        if ($tstatus >= 200 && $tstatus < 300) {
            $thumbKey = $candidate;
        } else {
            s3_delete($candidate);
        }
    }

    // Append under a fresh load to reduce lost updates between concurrent uploads.
    $gallery = gallery_load($slug);
    $gallery['images'][] = [
        'key'   => $key,
        'thumb' => $thumbKey,
        'name'  => substr((string)($original['name'] ?? basename($key)), 0, 200),
        'size'  => (int)($original['size'] ?? 0),
    ];
    gallery_save($gallery);

    return [200, ['ok' => true, 'key' => $key, 'thumb' => $thumbKey, 'count' => count($gallery['images'])]];
}