<?php

namespace app\common;

use think\Env;
use think\Exception;

/**
 * Turnitin Core API (TCA) REST 客户端封装。
 *
 * 适用 Crossref Similarity Check 通道（product_name=Crossref）以及标准 TCA 接入。
 *
 * 鉴权：Authorization: Bearer <API_KEY>
 *       X-Turnitin-Integration-Name / X-Turnitin-Integration-Version 用于审计
 *
 * .env 配置（[turnitin] 段）:
 *   BASE_URL              形如 https://crossref-12345.turnitin.com/api/v1（不带尾斜杠）
 *   API_KEY               生成的 Bearer token
 *   INTEGRATION_NAME      Scope Name（创建 integration 时填的名字）
 *   INTEGRATION_VERSION   自定义版本号，便于审计 e.g. 1.0.0
 *   SUBMISSION_INGEST_MAX_WAIT       上传后轮询 submission 就绪的最长秒数，默认 600（仅 waitAfterUploadForSimilarity 同步用）
 *   SUBMISSION_INGEST_POLL_INTERVAL  同步轮询间隔秒数，默认 3
 *   INGEST_CHAIN_FIRST_DELAY         上传后首次 ingest 检查延迟秒数，默认 10（队列链）
 *   INGEST_CHAIN_POLL_INTERVAL       ingest 链每步间隔秒数，默认 15
 *   INGEST_CHAIN_MAX_ATTEMPTS        ingest 链最大步数，默认 80
 *   EXCLUDE_QUOTES / EXCLUDE_BIBLIOGRAPHY / EXCLUDE_CITATIONS  0|1，默认 0（与 Crossref 网页手动查重更接近）
 *   VIEWER_DEFAULT_MODE           match_overview | all_sources（默认 all_sources，便于按来源库分类查看）
 *   ADD_TO_INDEX                     0|1，默认 1
 *
 * API 文档：https://developers.turnitin.com/docs/tca
 *
 * 注意：
 *   - 所有方法返回原始 decode 后的数组；HTTP 错误抛 Exception
 *   - 不做任何业务层逻辑（业务层在 PlagiarismService 里）
 *   - 不缓存 token（Bearer 不需要登录，每次请求自带）
 */
class TurnitinService
{
    private $baseUrl;
    private $apiKey;
    private $integrationName;
    private $integrationVersion;
    private $timeout = 60;

    public function __construct()
    {
        $this->baseUrl            = rtrim(trim((string)Env::get('turnitin.base_url', 'https://crossref-20794.turnitin.com/api/v1')), '/');
        $this->apiKey             = trim((string)Env::get('turnitin.api_key', 'c6315e8291a4433dae09ad5efdb8a89c'));
        $this->integrationName    = trim((string)Env::get('turnitin.integration_name', 'tmr'));
        $this->integrationVersion = trim((string)Env::get('turnitin.integration_version', '1.0.0'));

        if ($this->baseUrl === '' || $this->apiKey === '') {
            throw new Exception('Turnitin not configured: missing BASE_URL or API_KEY in .env [turnitin] section');
        }
    }

    // ==================== Public API ====================

    /**
     * 探活 / 拿账户能力
     * GET /features-enabled
     */
    public function featuresEnabled()
    {
        return $this->request('GET', '/features-enabled');
    }

    /**
     * 创建 submission（拿到 id 之后才能上传文件）
     * POST /submissions
     *
     * @param array $meta 必填字段:
     *   - title           论文标题
     *   - owner           submission owner 标识符（自定义字符串，比如投稿系统 user_id）
     *   - submitter       提交者标识符（同上）
     *   - eula            (可选) ['version' => '...', 'language' => 'en-US', 'accepted_timestamp' => ISO8601]
     *                     如果 features-enabled 返回 require_eula=false 可省略
     *   可选字段:
     *   - extract_text_only  bool
     *   - metadata           array  自定义键值，供后续追溯
     *
     * @return array 含 id（submission UUID）, status, owner, ...
     */
    public function createSubmission($meta)
    {
        return $this->request('POST', '/submissions', $meta);
    }

    /**
     * 上传文件到 submission
     *
     * TCA 文档路径为 PUT /submissions/{id}/original（文件名仅通过 Content-Disposition 传递，
     * 不要再拼在 URL 末尾；否则网关会 404，错误里常见 path 形如 //v1/submissions/.../original/xxx.docx）。
     *
     * @param string $submissionId
     * @param string $filePath  本地 PDF/DOCX 路径
     * @param string $filename  传给 Turnitin 的展示文件名（默认取 basename）
     * @return array
     */
    public function uploadFile($submissionId, $filePath, $filename = '')
    {
        if (!is_file($filePath) || !is_readable($filePath)) {
            throw new Exception("File not found or not readable: {$filePath}");
        }
        if ($filename === '') {
            $filename = basename($filePath);
        }
        // Content-Disposition 里避免未转义的双引号
        $safeName = str_replace(['"', "\r", "\n"], '', $filename);
        if ($safeName === '') {
            $safeName = 'document.bin';
        }
        $body = file_get_contents($filePath);

        return $this->request(
            'PUT',
            '/submissions/' . rawurlencode($submissionId) . '/original',
            $body,
            [
                'Content-Type'        => 'application/octet-stream',
                'Content-Disposition' => 'attachment; filename="' . $safeName . '"',
            ]
        );
    }

    /**
     * 触发 similarity 比对
     * PUT /submissions/{id}/similarity
     *
     * @param string $submissionId
     * @param array  $opts
     *   - generation_settings.search_repositories  默认 ['INTERNET','PUBLICATION',...]
     *   - generation_settings.submission_auto_excludes  **字符串数组**（如 [] 或具体仓库键），不可传 boolean（否则会 400）
     *   - generation_settings.auto_exclude_self_matching_scope  可选，如 'GROUP_CONTEXT'
     *   - view_settings.exclude_*  布尔排除项（与 TCA 文档一致）
     *   - indexing_settings.add_to_index  bool 是否把本文加进 SUBMITTED_WORK 索引（一般 true）
     * @return array
     */
    public function triggerSimilarity($submissionId, $opts = [])
    {
        $body = array_merge($this->defaultSimilarityPayload(), $opts);

        return $this->request(
            'PUT',
            '/submissions/' . rawurlencode($submissionId) . '/similarity',
            $body
        );
    }

    /**
     * PUT /similarity 与 PDF 导出共用的默认参数。
     * 此前固定 exclude_*=true 时，总相似度会低于 Crossref 网页手动查重（与「匹配来源编号/类型」无关）。
     */
    public function defaultSimilarityPayload()
    {
        $scope = trim((string) Env::get('turnitin.auto_exclude_self_matching_scope', 'GROUP_CONTEXT'));
        if ($scope === '') {
            unset($scope);
        }

        $generation = [
            'search_repositories' => ['INTERNET', 'PUBLICATION', 'CROSSREF', 'CROSSREF_POSTED_CONTENT', 'SUBMITTED_WORK'],
            'submission_auto_excludes' => [],
        ];
        if (isset($scope)) {
            $generation['auto_exclude_self_matching_scope'] = $scope;
        }

        return [
            'generation_settings' => $generation,
            'view_settings'       => $this->defaultViewSettings(),
            'indexing_settings'   => [
                'add_to_index' => $this->envBool('turnitin.add_to_index', true),
            ],
        ];
    }

    public function defaultViewSettings()
    {
        return [
            'exclude_quotes'       => $this->envBool('turnitin.exclude_quotes', false),
            'exclude_bibliography' => $this->envBool('turnitin.exclude_bibliography', false),
            'exclude_citations'    => $this->envBool('turnitin.exclude_citations', false),
        ];
    }

    /**
     * 从 GET /similarity 响应解析总相似度（0–100）。
     * 兼容 overall_match_percentage 在 message 嵌套、以及 0–1 小数形式。
     */
    public static function extractOverallMatchPercentage(array $statusResp)
    {
        $candidates = [];

        $push = function ($v) use (&$candidates) {
            if ($v === null || $v === '') {
                return;
            }
            if (is_numeric($v)) {
                $candidates[] = floatval($v);
            }
        };

        $push($statusResp['overall_match_percentage'] ?? null);
        $push($statusResp['overall_match'] ?? null);
        $push($statusResp['similarity_percentage'] ?? null);

        $msg = $statusResp;
        if (isset($statusResp['message']) && is_array($statusResp['message'])) {
            $msg = $statusResp['message'];
        }
        $push($msg['overall_match_percentage'] ?? null);
        $push($msg['overall_match'] ?? null);
        if (isset($msg['similarity']) && is_array($msg['similarity'])) {
            $sim = $msg['similarity'];
            $push($sim['overall_match_percentage'] ?? null);
            $push($sim['overall_match'] ?? null);
        }

        foreach ($candidates as $n) {
            if ($n < 0) {
                continue;
            }
            // Turnitin TCA 的 overall_match_percentage 是 0–100 整数，"1" 即代表 1%。
            // 仅当值是「严格小于 1 的非整数」（真正的 0–1 小数比例，如 0.12=12%）时才 ×100，
            // 避免把整数 1（1%）误判成 100%。
            if ($n > 0 && $n < 1.0) {
                return round(min($n * 100, 100), 2);
            }
            return round(min($n, 100), 2);
        }

        return 0.0;
    }

    /**
     * 从 GET /similarity 响应中尽量提取「按来源」的摘要（供列表展示；完整明细仍在 Turnitin 在线报告里）。
     *
     * @return array{score:float,sources:array<int,array<string,mixed>>}
     */
    public static function parseSimilarityReportMeta(array $statusResp)
    {
        $meta = [
            'score'   => self::extractOverallMatchPercentage($statusResp),
            'sources' => [],
        ];

        $candidates = [];
        self::collectSimilaritySourceNodes($statusResp, $candidates, 0);
        if (isset($statusResp['message']) && is_array($statusResp['message'])) {
            self::collectSimilaritySourceNodes($statusResp['message'], $candidates, 0);
        }

        $seen = [];
        foreach ($candidates as $node) {
            if (!is_array($node)) {
                continue;
            }
            $pct = null;
            foreach (['percentage', 'match_percentage', 'overall_match_percentage', 'similarity_percentage'] as $k) {
                if (isset($node[$k]) && is_numeric($node[$k])) {
                    $pct = floatval($node[$k]);
                    break;
                }
            }
            $repo = '';
            foreach (['repository', 'repository_name', 'collection', 'source_type', 'type', 'database', 'category'] as $k) {
                if (!empty($node[$k])) {
                    $repo = strtoupper(trim((string) $node[$k]));
                    break;
                }
            }
            $words = isset($node['matched_word_count']) ? intval($node['matched_word_count'])
                : (isset($node['word_count']) ? intval($node['word_count']) : 0);
            $key = $repo . '|' . ($pct !== null ? $pct : '') . '|' . $words;
            if (isset($seen[$key])) {
                continue;
            }
            $seen[$key] = true;
            $meta['sources'][] = array_filter([
                'repository'         => $repo,
                'match_percentage'   => $pct,
                'matched_word_count' => $words > 0 ? $words : null,
            ], function ($v) {
                return $v !== null && $v !== '';
            });
        }

        return $meta;
    }

    /**
     * @param array<string,mixed> $node
     * @param array<int,mixed>    $out
     */
    private static function collectSimilaritySourceNodes($node, array &$out, $depth)
    {
        if ($depth > 8 || !is_array($node)) {
            return;
        }
        $hasRepo = false;
        foreach (['repository', 'repository_name', 'collection', 'source_type'] as $k) {
            if (!empty($node[$k])) {
                $hasRepo = true;
                break;
            }
        }
        if ($hasRepo) {
            $out[] = $node;
        }
        foreach ($node as $v) {
            if (is_array($v)) {
                if (isset($v[0]) && is_array($v[0])) {
                    foreach ($v as $item) {
                        self::collectSimilaritySourceNodes($item, $out, $depth + 1);
                    }
                } else {
                    self::collectSimilaritySourceNodes($v, $out, $depth + 1);
                }
            }
        }
    }

    /**
     * 在线 Similarity Report 默认视图（与 Crossref 后台「按来源查看」对齐）。
     */
    public function defaultViewerSimilarityBlock()
    {
        $mode = strtolower(trim((string) Env::get('turnitin.viewer_default_mode', 'all_sources')));
        if (!in_array($mode, ['match_overview', 'all_sources'], true)) {
            $mode = 'all_sources';
        }

        return [
            'default_mode' => $mode,
            'modes'        => [
                'match_overview' => true,
                'all_sources'    => true,
            ],
        ];
    }

    private function envBool($name, $default = false)
    {
        $v = Env::get($name, $default ? '1' : '0');
        if ($v === true) {
            return true;
        }
        if ($v === false) {
            return false;
        }
        $v = strtolower(trim((string) $v));
        return in_array($v, ['1', 'true', 'yes', 'on'], true);
    }

    /**
     * 查询 submission 详情（上传后用于轮询是否解析完成）。
     * GET /submissions/{id}
     *
     * @return array 解码后的 JSON（常见为 status=ok + message 内含 id/status）
     */
    public function getSubmission($submissionId)
    {
        return $this->request('GET', '/submissions/' . rawurlencode($submissionId));
    }

    /**
     * 单次解析 GET /submissions/{id}，判断是否可调用 PUT /similarity（不 sleep，供队列链逐步轮询）。
     *
     * @return array{ready:bool, failed:bool, status:string, snippet:string, message:array}
     */
    public function parseSubmissionIngestState($submissionId)
    {
        $raw = $this->getSubmission($submissionId);
        $msg = self::unwrapSubmissionPayload($raw);
        $st  = strtoupper(trim((string) self::pickSubmissionStatus($msg)));
        $snippet = mb_substr(json_encode($msg, JSON_UNESCAPED_UNICODE), 0, 400);

        $ready = [
            'COMPLETE', 'COMPLETED', 'PROCESSED', 'READY', 'SUCCEEDED',
            'COMPLETE_PROCESSING',
        ];
        $failed = ['ERROR', 'FAILED', 'CANCELLED', 'CANCELED', 'DELETED'];

        $readyFlag = $st !== '' && in_array($st, $ready, true);
        $failedFlag = $st !== '' && in_array($st, $failed, true);

        return [
            'ready'   => $readyFlag,
            'failed'  => $failedFlag,
            'status'  => $st,
            'snippet' => $snippet,
            'message' => $msg,
        ];
    }

    /**
     * 上传完成后需等待 Turnitin 异步完成文本解析（同步阻塞版，仅 CLI/调试；线上请用队列链 PlagiarismWaitIngest）。
     *
     * @param string $submissionId
     * @param int    $maxWaitSec   最长等待秒数，默认 600（10 分钟）
     * @param int    $intervalSec  轮询间隔秒数，默认 3
     * @throws Exception 超时或终态为失败
     */
    public function waitAfterUploadForSimilarity($submissionId, $maxWaitSec = 600, $intervalSec = 3)
    {
        $deadline = time() + max(30, (int)$maxWaitSec);
        $intervalSec = max(1, (int)$intervalSec);
        $lastStatus = '';
        $lastSnippet = '';

        while (time() < $deadline) {
            $parsed = $this->parseSubmissionIngestState($submissionId);
            $lastStatus = $parsed['status'];
            $lastSnippet = $parsed['snippet'];

            if (!empty($parsed['ready'])) {
                return;
            }
            if (!empty($parsed['failed'])) {
                throw new Exception('Turnitin submission failed, status=' . $lastStatus . ' body=' . $lastSnippet);
            }

            sleep($intervalSec);
        }

        throw new Exception(
            'Timeout waiting for Turnitin submission ingest (last status=' . ($lastStatus ?: '(empty)') . ') snippet=' . $lastSnippet
        );
    }

    /**
     * @param mixed $decoded
     * @return array
     */
    private static function unwrapSubmissionPayload($decoded)
    {
        if (!is_array($decoded)) {
            return [];
        }
        if (isset($decoded['message']) && is_array($decoded['message'])) {
            return $decoded['message'];
        }
        return $decoded;
    }

    /**
     * @param array $msg
     * @return string
     */
    private static function pickSubmissionStatus(array $msg)
    {
        $candidates = [$msg];
        if (isset($msg['submission']) && is_array($msg['submission'])) {
            $candidates[] = $msg['submission'];
        }
        foreach ($candidates as $m) {
            foreach (['status', 'workflow_status', 'submission_status', 'processing_status', 'paper_status'] as $k) {
                if (!empty($m[$k])) {
                    return (string)$m[$k];
                }
            }
        }
        return '';
    }

    /**
     * 查询 similarity 状态
     * GET /submissions/{id}/similarity
     *
     * 返回 status: PROCESSING / COMPLETE / ERROR
     * COMPLETE 时返回 overall_match_percentage / time_requested / time_generated
     */
    public function getSimilarityStatus($submissionId)
    {
        return $this->request(
            'GET',
            '/submissions/' . rawurlencode($submissionId) . '/similarity'
        );
    }

    /**
     * 取在线查看报告的临时 URL
     * POST /submissions/{id}/viewer-url
     *
     * 返回 viewer_url（数小时有效）
     *
     * TCA 要求 default_mode 为小写（如 match_overview）；save_changes 等 LTI 字段会导致 400。
     * Crossref 通道常用 ADMINISTRATOR/USER，非 INSTRUCTOR。可在 .env 配置：
     *   turnitin.viewer_permission_set=ADMINISTRATOR
     *
     * @param array $viewer 可选：viewer_user_id、triggered_by（映射为 editor_{id}）、或完整请求体覆盖
     */
    public function getViewerUrl($submissionId, $viewer = [])
    {
        $submissionId = trim((string) $submissionId);
        if ($submissionId === '') {
            throw new Exception('submissionId required for viewer-url');
        }

        $statusResp = $this->getSimilarityStatus($submissionId);
        $st = strtoupper(trim((string) ($statusResp['status'] ?? '')));
        if ($st !== '' && $st !== 'COMPLETE') {
            throw new Exception('similarity report not ready for viewer-url, status=' . $st);
        }

        $path = '/submissions/' . rawurlencode($submissionId) . '/viewer-url';
        $lastError = null;

        foreach ($this->buildViewerUrlBodies($viewer) as $body) {
            try {
                return $this->request('POST', $path, $body);
            } catch (Exception $e) {
                $lastError = $e;
                if (strpos($e->getMessage(), 'HTTP 400') === false) {
                    throw $e;
                }
            }
        }

        throw $lastError ?: new Exception('viewer-url failed');
    }

    /**
     * 按优先级生成若干合法请求体（前者失败且为 400 时尝试后者）。
     *
     * @return array<int,array>
     */
    private function buildViewerUrlBodies(array $viewerOverrides)
    {
        if (!empty($viewerOverrides) && isset($viewerOverrides['viewer_default_permission_set'])) {
            $body = $viewerOverrides;
            if (empty($body['viewer_user_id'])) {
                $body['viewer_user_id'] = $this->resolveViewerUserId($viewerOverrides);
            }
            return [$body];
        }

        $locale = trim((string) Env::get('turnitin.viewer_locale', 'en-US')) ?: 'en-US';
        $configured = trim((string) Env::get('turnitin.viewer_permission_set', ''));
        $permissionSets = $configured !== ''
            ? array_map('trim', explode(',', $configured))
            : $this->defaultViewerPermissionSets();
        $viewerUserId = $this->resolveViewerUserId($viewerOverrides);
        $saveChanges  = $this->envBool('turnitin.viewer_save_changes', false);
        $simModes     = $this->defaultViewerSimilarityBlock();

        $bodies = [];
        foreach ($permissionSets as $perm) {
            if ($perm === '') {
                continue;
            }
            // TCA 认证要求：必须带 viewer_user_id（此前缺失会导致 400 Bad request）
            $bodies[] = [
                'viewer_user_id'                => $viewerUserId,
                'locale'                        => $locale,
                'viewer_default_permission_set' => $perm,
                'similarity'                    => [
                    'view_settings' => ['save_changes' => $saveChanges],
                ],
            ];
            $bodies[] = [
                'viewer_user_id'                => $viewerUserId,
                'locale'                        => $locale,
                'viewer_default_permission_set' => $perm,
                'similarity'                    => array_merge($simModes, [
                    'view_settings' => ['save_changes' => $saveChanges],
                ]),
            ];
            $bodies[] = [
                'viewer_user_id'                => $viewerUserId,
                'locale'                        => $locale,
                'viewer_default_permission_set' => $perm,
            ];
        }

        return $bodies;
    }

    /**
     * viewer-url 必填：与 createSubmission 的 owner/submitter 同一命名空间（editor_{user_id}）。
     */
    public function resolveViewerUserId(array $opts = [])
    {
        if (!empty($opts['viewer_user_id'])) {
            return trim((string) $opts['viewer_user_id']);
        }
        // 打开报告的人（当前编辑）须与申请 viewer-url 时一致，否则易出现 session 认证失败
        $editorId = isset($opts['editor_id']) ? intval($opts['editor_id']) : 0;
        if ($editorId > 0) {
            return 'editor_' . $editorId;
        }
        $triggeredBy = isset($opts['triggered_by']) ? intval($opts['triggered_by']) : 0;
        if ($triggeredBy > 0) {
            return 'editor_' . $triggeredBy;
        }
        $custom = trim((string) Env::get('turnitin.viewer_user_id', ''));
        if ($custom !== '') {
            return $custom;
        }
        $name = trim((string) $this->integrationName);
        return ($name !== '' ? $name : 'tmr') . '_viewer';
    }

    /**
     * Crossref Similarity Check 通常不用 INSTRUCTOR；按常见可用角色排序尝试。
     *
     * @return array<int,string>
     */
    private function defaultViewerPermissionSets()
    {
        if (stripos($this->baseUrl, 'crossref') !== false) {
            return ['ADMINISTRATOR', 'USER', 'EDITOR', 'INSTRUCTOR'];
        }
        return ['INSTRUCTOR', 'ADMINISTRATOR', 'USER'];
    }

    /**
     * 触发生成 PDF 报告（异步，状态在另一个轮询里看）
     * POST /submissions/{id}/similarity/pdf
     *
     * 返回 id（pdf 报告 ID）
     */
    public function requestPdfReport($submissionId, $opts = [])
    {
        $body = array_merge([
            'locale'        => trim((string) Env::get('turnitin.viewer_locale', 'en-US')) ?: 'en-US',
            'view_settings' => $this->defaultViewSettings(),
        ], $opts);

        return $this->request(
            'POST',
            '/submissions/' . rawurlencode($submissionId) . '/similarity/pdf',
            $body
        );
    }

    /**
     * 查询 PDF 报告状态
     * GET /submissions/{id}/similarity/pdf/{pdf_id}/status
     *
     * status: PENDING / SUCCESS / FAILED
     */
    public function getPdfReportStatus($submissionId, $pdfId)
    {
        return $this->request(
            'GET',
            '/submissions/' . urlencode($submissionId) . '/similarity/pdf/' . urlencode($pdfId) . '/status'
        );
    }

    /**
     * 下载 PDF 报告内容（status=SUCCESS 后才可调用）
     * GET /submissions/{id}/similarity/pdf/{pdf_id}
     *
     * 返回 raw PDF binary 字符串；调用方负责落盘
     */
    public function downloadPdfReport($submissionId, $pdfId)
    {
        return $this->request(
            'GET',
            '/submissions/' . urlencode($submissionId) . '/similarity/pdf/' . urlencode($pdfId),
            null,
            [],
            true   // raw response (不 json_decode)
        );
    }

    // ==================== Internal HTTP layer ====================

    /**
     * 统一 HTTP 调用
     *
     * @param string      $method      GET/POST/PUT/DELETE
     * @param string      $path        以 / 开头的相对路径，会拼到 baseUrl 后
     * @param mixed       $body        array 时按 JSON 编码；string 时直接当 raw body
     * @param array       $extraHeaders 额外 header
     * @param bool        $rawResponse  true=返回 raw 字符串；false=json_decode
     * @return mixed
     * @throws Exception
     */
    private function request($method, $path, $body = null, $extraHeaders = [], $rawResponse = false)
    {
        $url = $this->baseUrl . $path;

        $headers = [
            'Authorization: Bearer ' . $this->apiKey,
            'X-Turnitin-Integration-Name: '    . $this->integrationName,
            'X-Turnitin-Integration-Version: ' . $this->integrationVersion,
        ];

        $payload = null;
        if ($body !== null) {
            if (is_array($body)) {
                $payload = json_encode($body, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
                $headers[] = 'Content-Type: application/json';
            } else {
                $payload = $body;
                if (!isset($extraHeaders['Content-Type'])) {
                    $headers[] = 'Content-Type: application/octet-stream';
                }
            }
        }
        foreach ($extraHeaders as $k => $v) {
            $headers[] = $k . ': ' . $v;
        }

        $ch = curl_init();
        curl_setopt_array($ch, [
            CURLOPT_URL            => $url,
            CURLOPT_CUSTOMREQUEST  => strtoupper($method),
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_HTTPHEADER     => $headers,
            CURLOPT_TIMEOUT        => $this->timeout,
            CURLOPT_CONNECTTIMEOUT => 15,
            CURLOPT_SSL_VERIFYPEER => true,
            CURLOPT_SSL_VERIFYHOST => 2,
        ]);
        if ($payload !== null) {
            curl_setopt($ch, CURLOPT_POSTFIELDS, $payload);
        }

        $resp     = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $err      = curl_error($ch);
        curl_close($ch);

        if ($resp === false) {
            throw new Exception("Turnitin curl error: {$err} (url={$url})");
        }
        if ($httpCode < 200 || $httpCode >= 300) {
            // 把响应体的前 1k 也带上方便排错
            $excerpt = mb_substr((string)$resp, 0, 1000);
            throw new Exception("Turnitin HTTP {$httpCode} {$method} {$path}: {$excerpt}");
        }

        if ($rawResponse) {
            return $resp;
        }
        // 部分响应可能是 204 No Content
        if ($resp === '' || $resp === null) {
            return [];
        }
        $data = json_decode($resp, true);
        if (json_last_error() !== JSON_ERROR_NONE) {
            // 不是 JSON 也直接抛回原文
            return $resp;
        }
        return $data;
    }
}