<?php

declare(strict_types=1);

namespace app\common\service;

use think\facade\Log;

/**
 * 处方/诊单 AI 上游客户端。
 *
 * 兼容 Dify blocking chat-messages 与 OpenAI-compatible chat completions。
 * 地址和凭据只从服务端 prescription_ai 配置读取，不进入响应、日志或请求正文。
 */
class DifyChatService
{
    /** @var array<int,string> */
    private const ALLOWED_PROFILES = ['qwen', 'openai'];

    private const MIN_TIMEOUT = 1;

    private const MAX_TIMEOUT = 300;

    private const DEFAULT_MAX_FILES = 3;

    /**
     * 上游明确以“这批附件我处理不了”拒绝整次请求时使用的状态码。
     * 命中后会去掉附件重试一次，避免一张舌象图让整份病历分析失败。
     */
    private const FILE_REJECTION_CODES = [400, 413, 415, 422];

    /**
     * @param array<string,mixed> $inputs
     * @return array{ok:bool,content?:string,message_id?:string,latency_ms?:int,error_code?:string,error?:string}
     */
    public static function chat(
        string $profile,
        array $inputs,
        string $query,
        string $user,
        array $files = []
    ): array
    {
        $config = config('prescription_ai') ?: [];
        if (empty($config['enable'])) {
            return self::error('CONFIG_DISABLED', 'AI 报告功能未启用');
        }

        $modelConfig = self::resolveProfileConfig($config, $profile);
        if ($modelConfig === null) {
            return self::error('INVALID_PROFILE', '不支持的 AI 模型');
        }

        $baseUrl = trim((string) ($config['base_url'] ?? ''));
        $rawApiKey = (string) ($modelConfig['api_key'] ?? '');
        $apiKey = trim($rawApiKey);
        if ($baseUrl === '' || $apiKey === '') {
            return self::error('CONFIG_MISSING', '该模型服务尚未完整配置');
        }
        if (!self::isValidBaseUrl($baseUrl) || strpbrk($rawApiKey, "\r\n") !== false) {
            return self::error('CONFIG_INVALID', 'AI 服务配置无效');
        }

        $timeout = (int) ($config['timeout'] ?? 0);
        if (!self::isValidTimeout($timeout)) {
            return self::error('CONFIG_INVALID', 'AI 服务超时配置无效');
        }
        if (!function_exists('curl_init')) {
            return self::error('CURL_UNAVAILABLE', '服务器尚未启用 cURL 扩展');
        }

        $model = trim((string) ($modelConfig['name'] ?? ''));
        if ($model === '') {
            return self::error('CONFIG_INVALID', 'AI 模型配置无效');
        }

        $normalized = self::normalizeFiles($files, self::maxFiles($config));
        $startedAt = microtime(true);
        $formatted = null;

        foreach (self::buildAttemptPlan($normalized['kept'], $normalized['dropped']) as $attempt) {
            $requestSpecs = self::buildRequestSpecs(
                $baseUrl,
                $model,
                $inputs,
                $query,
                $user,
                false,
                $attempt['files'],
                $attempt['omitted']
            );
            $lastResponse = null;
            $lastSpec = [];
            // 协议回退会把最初的“附件被拒”换成另一协议的状态码，因此降级判断
            // 必须记住本轮出现过的附件拒绝信号，而不能只看最后一次响应。
            $fileRejected = false;

            foreach ($requestSpecs as $index => $requestSpec) {
                $elapsedSeconds = (int) floor(microtime(true) - $startedAt);
                $remainingTimeout = $timeout - $elapsedSeconds;
                if ($remainingTimeout < self::MIN_TIMEOUT) {
                    return self::error(
                        'UPSTREAM_TIMEOUT',
                        '模型响应超时，请稍后重试',
                        self::elapsedMilliseconds($startedAt)
                    );
                }

                $response = self::sendRequest(
                    $requestSpec['url'],
                    $requestSpec['payload'],
                    $apiKey,
                    $remainingTimeout
                );
                $lastResponse = $response;
                $lastSpec = $requestSpec;
                $fileRejected = $fileRejected || self::isFileRejection($response, $attempt['files']);

                // /v1 在两种协议中都是合法基址。仅在明确表示路径不存在时尝试另一协议，
                // 避免因业务参数错误而重复提交同一份临床数据。
                $hasFallback = isset($requestSpecs[$index + 1]);
                if ($hasFallback && self::shouldTryNextProtocol($response, false)) {
                    continue;
                }
                break;
            }

            $lastResponse = $lastResponse ?? ['body' => '', 'errno' => 0, 'http_code' => 0];
            $formatted = self::formatResponse($lastResponse, $startedAt);
            self::logUpstreamFailure($lastSpec, $lastResponse, $query, $attempt['files'], $formatted);
            if (!empty($formatted['ok'])) {
                return $formatted;
            }
            // 附件整体被拒时退回纯文本重试，附件清单已在下一轮尝试中补齐。
            if (!$fileRejected) {
                return $formatted;
            }
        }

        return $formatted ?? self::error('UPSTREAM_REJECTED', '模型未能处理本次请求', self::elapsedMilliseconds($startedAt));
    }

    /**
     * 流式调用 Dify / OpenAI-compatible 接口。上游原始响应与凭据不会进入返回值。
     *
     * @param array<string,mixed> $inputs
     * @param callable(string):mixed $onDelta
     * @param callable():bool|null $shouldAbort
     * @return array{ok:bool,content?:string,message_id?:string,latency_ms:int,error_code?:string,error?:string}
     */
    public static function streamChat(
        string $profile,
        array $inputs,
        string $query,
        string $user,
        callable $onDelta,
        ?callable $shouldAbort = null,
        array $files = []
    ): array {
        $config = config('prescription_ai') ?: [];
        if (empty($config['enable'])) {
            return self::error('CONFIG_DISABLED', 'AI 报告功能未启用');
        }

        $modelConfig = self::resolveProfileConfig($config, $profile);
        if ($modelConfig === null) {
            return self::error('INVALID_PROFILE', '不支持的 AI 模型');
        }

        $baseUrl = trim((string) ($config['base_url'] ?? ''));
        $rawApiKey = (string) ($modelConfig['api_key'] ?? '');
        $apiKey = trim($rawApiKey);
        if ($baseUrl === '' || $apiKey === '') {
            return self::error('CONFIG_MISSING', '该模型服务尚未完整配置');
        }
        if (!self::isValidBaseUrl($baseUrl) || strpbrk($rawApiKey, "\r\n") !== false) {
            return self::error('CONFIG_INVALID', 'AI 服务配置无效');
        }

        $timeout = (int) ($config['timeout'] ?? 0);
        if (!self::isValidTimeout($timeout)) {
            return self::error('CONFIG_INVALID', 'AI 服务超时配置无效');
        }
        if (!function_exists('curl_init')) {
            return self::error('CURL_UNAVAILABLE', '服务器尚未启用 cURL 扩展');
        }

        $model = trim((string) ($modelConfig['name'] ?? ''));
        if ($model === '') {
            return self::error('CONFIG_INVALID', 'AI 模型配置无效');
        }

        $normalized = self::normalizeFiles($files, self::maxFiles($config));
        $startedAt = microtime(true);
        $formatted = null;

        foreach (self::buildAttemptPlan($normalized['kept'], $normalized['dropped']) as $attempt) {
            $requestSpecs = self::buildRequestSpecs(
                $baseUrl,
                $model,
                $inputs,
                $query,
                $user,
                true,
                $attempt['files'],
                $attempt['omitted']
            );
            $lastResponse = null;
            $lastSpec = [];
            // 协议回退会把最初的“附件被拒”换成另一协议的状态码，因此降级判断
            // 必须记住本轮出现过的附件拒绝信号，而不能只看最后一次响应。
            $fileRejected = false;

            foreach ($requestSpecs as $index => $requestSpec) {
                $elapsedSeconds = (int) floor(microtime(true) - $startedAt);
                $remainingTimeout = $timeout - $elapsedSeconds;
                if ($remainingTimeout < self::MIN_TIMEOUT) {
                    return self::error(
                        'UPSTREAM_TIMEOUT',
                        '模型响应超时，请稍后重试',
                        self::elapsedMilliseconds($startedAt)
                    );
                }

                $response = self::sendStreamRequest(
                    $requestSpec['protocol'],
                    $requestSpec['url'],
                    $requestSpec['payload'],
                    $apiKey,
                    $remainingTimeout,
                    $onDelta,
                    $shouldAbort
                );
                $lastResponse = $response;
                $lastSpec = $requestSpec;
                $fileRejected = $fileRejected || self::isFileRejection($response, $attempt['files']);

                // 只在尚未向下游发送任何文本、且明确为路径不支持时尝试另一协议。
                $hasFallback = isset($requestSpecs[$index + 1]);
                if (
                    $hasFallback
                    && self::shouldTryNextProtocol($response, true)
                ) {
                    continue;
                }
                break;
            }

            $lastResponse = $lastResponse ?? self::emptyStreamResponse(0);
            $formatted = self::formatStreamResponse($lastResponse, $startedAt);
            self::logUpstreamFailure($lastSpec, $lastResponse, $query, $attempt['files'], $formatted);
            if (!empty($formatted['ok'])) {
                return $formatted;
            }
            // 已经推给医生的文本不能重复输出，因此只在一个字都没发出去时才降级重试。
            if (!empty($lastResponse['emitted']) || !$fileRejected) {
                return $formatted;
            }
        }

        return $formatted ?? self::error('UPSTREAM_REJECTED', '模型未能处理本次请求', self::elapsedMilliseconds($startedAt));
    }

    /**
     * @param array<string,mixed> $config
     * @return array<string,mixed>|null
     */
    private static function resolveProfileConfig(array $config, string $profile): ?array
    {
        if (!in_array($profile, self::ALLOWED_PROFILES, true)) {
            return null;
        }
        $modelConfig = $config['models'][$profile] ?? null;
        return is_array($modelConfig) ? $modelConfig : null;
    }

    /**
     * @param array<string,mixed> $inputs
     * @param array<int,array<string,string>> $files 随请求送达的附件
     * @param array<int,array<string,string>> $omitted 超出上游数量上限、只能写进清单的附件
     * @return array<int,array{protocol:string,url:string,payload:array<string,mixed>}>
     */
    private static function buildRequestSpecs(
        string $baseUrl,
        string $model,
        array $inputs,
        string $query,
        string $user,
        bool $streaming = false,
        array $files = [],
        array $omitted = []
    ): array {
        $baseUrl = rtrim($baseUrl, '/');
        $path = strtolower((string) (parse_url($baseUrl, PHP_URL_PATH) ?? ''));

        // Dify 能承载全部附件类型，只需补上被数量上限截断的清单。
        // inputs 必须是 JSON 对象：空数组会被 json_encode 成 []，Dify 直接
        // 以 invalid_param 拒绝整单，因此这里强制对象语义。
        $difySpec = [
            'protocol' => 'dify',
            'url' => self::buildEndpoint($baseUrl, 'chat-messages'),
            'payload' => [
                'inputs' => (object) $inputs,
                'query' => self::withAttachmentManifest($query, $omitted),
                'response_mode' => $streaming ? 'streaming' : 'blocking',
                'user' => $user,
            ],
        ];
        if ($files !== []) {
            $difySpec['payload']['files'] = $files;
        }

        // Chat Completions 只能内联图片，非图片附件与被截断的附件一并进清单。
        $openAiContent = self::buildOpenAiContent(
            self::withAttachmentManifest(
                $query,
                array_merge(self::nonImageFiles($files), $omitted)
            ),
            $files
        );
        $openAiSpec = [
            'protocol' => 'openai',
            'url' => self::buildEndpoint($baseUrl, 'chat/completions'),
            'payload' => [
                'model' => $model,
                'messages' => [
                    ['role' => 'user', 'content' => $openAiContent],
                ],
                'stream' => $streaming,
            ],
        ];

        if (!$streaming) {
            unset($openAiSpec['payload']['stream']);
        }

        if (str_ends_with($path, '/chat-messages')) {
            return [$difySpec];
        }
        if (str_ends_with($path, '/chat/completions')) {
            return [$openAiSpec];
        }

        // 保持既有 /v1 Dify 配置优先，同时让 OpenAI-compatible 服务在 404/405 后透明回退。
        // 早期实现只在“无附件或全是图片”时提供回退，患者带检查报告/录像附件时
        // Dify 路径 404 会直接变成“模型未能处理本次请求”，因此这里始终保留回退，
        // 非图片附件改为在正文中以清单形式随请求送达，绝不静默丢弃。
        return [$difySpec, $openAiSpec];
    }

    /**
     * 构造 OpenAI-compatible 正文。图片走多模态 image_url；非图片附件已由调用方
     * 写进 $query 末尾的清单，这里只负责内联图片。
     *
     * @param array<int,array<string,string>> $files
     * @return string|array<int,array<string,mixed>>
     */
    private static function buildOpenAiContent(string $query, array $files)
    {
        $content = [['type' => 'text', 'text' => $query]];
        foreach ($files as $file) {
            $url = (string) ($file['url'] ?? '');
            if ($url === '' || ($file['type'] ?? '') !== 'image') {
                continue;
            }
            $content[] = [
                'type' => 'image_url',
                'image_url' => ['url' => $url],
            ];
        }
        return count($content) === 1 ? $query : $content;
    }

    /**
     * @param array<int,array<string,string>> $files
     * @return array<int,array<string,string>>
     */
    private static function nonImageFiles(array $files): array
    {
        return array_values(array_filter(
            $files,
            static fn (array $file): bool => ($file['type'] ?? '') !== 'image'
        ));
    }

    /**
     * 清洗附件，并按上游应用允许的数量截断。
     *
     * Dify 用 file_upload.number_limits 校验单次请求的附件总数，超出即返回
     * 400 invalid_param 拒绝整单。患者纵向资料的附件数量不可控（舌象、报告、
     * 录像可能几十份），因此这里必须主动截断；被截断的附件不会被悄悄丢弃，
     * 而是以清单形式随提示词送达，让模型知道存在哪些它读不到的资料。
     * 保持调用方给定的顺序，由调用方决定哪些附件最值得送上去。
     *
     * @param array<int,mixed> $files
     * @return array{
     *     kept:array<int,array{type:string,transfer_method:string,url:string}>,
     *     dropped:array<int,array{type:string,transfer_method:string,url:string}>
     * }
     */
    private static function normalizeFiles(array $files, int $maxFiles): array
    {
        $maxFiles = max(0, $maxFiles);
        $kept = [];
        $dropped = [];
        $seen = [];
        foreach ($files as $file) {
            if (!is_array($file)) {
                continue;
            }
            $type = strtolower(trim((string) ($file['type'] ?? '')));
            $url = trim((string) ($file['url'] ?? ''));
            if (!in_array($type, ['image', 'document', 'audio', 'video', 'custom'], true)
                || !self::isValidRemoteFileUrl($url)
                || isset($seen[$url])) {
                continue;
            }
            $seen[$url] = true;
            $normalized = [
                'type' => $type,
                'transfer_method' => 'remote_url',
                'url' => $url,
            ];
            if (count($kept) >= $maxFiles) {
                $dropped[] = $normalized;
                continue;
            }
            $kept[] = $normalized;
        }
        return ['kept' => $kept, 'dropped' => $dropped];
    }

    /** @param array<string,mixed> $config */
    private static function maxFiles(array $config): int
    {
        $configured = (int) ($config['max_files'] ?? self::DEFAULT_MAX_FILES);
        return $configured >= 0 ? $configured : self::DEFAULT_MAX_FILES;
    }

    /**
     * 排出两轮尝试：先带附件，附件被上游整体拒绝时再只发文本。
     * 第二轮把全部附件写进清单，保证降级后模型仍知道资料缺口。
     *
     * @param array<int,array<string,string>> $files
     * @param array<int,array<string,string>> $dropped
     * @return array<int,array{files:array<int,array<string,string>>,omitted:array<int,array<string,string>>}>
     */
    private static function buildAttemptPlan(array $files, array $dropped): array
    {
        $attempts = [['files' => $files, 'omitted' => $dropped]];
        if ($files !== []) {
            $attempts[] = ['files' => [], 'omitted' => array_merge($files, $dropped)];
        }
        return $attempts;
    }

    /**
     * @param array<int,array<string,string>> $files
     */
    private static function shouldRetryWithoutFiles(int $httpCode, array $files): bool
    {
        return $files !== [] && in_array($httpCode, self::FILE_REJECTION_CODES, true);
    }

    /**
     * 判断一次上游响应是否属于“这批附件我处理不了”。
     *
     * 除了 4xx 状态码，Dify 拉不到附件时会在 200 的 SSE 流里发 event:error，
     * 这两种形态都必须触发去掉附件的降级重试。
     *
     * @param array<string,mixed> $response
     * @param array<int,array<string,string>> $files
     */
    private static function isFileRejection(array $response, array $files): bool
    {
        if ($files === [] || (int) ($response['errno'] ?? 0) !== 0) {
            return false;
        }
        if (self::shouldRetryWithoutFiles((int) ($response['http_code'] ?? 0), $files)) {
            return true;
        }
        return !empty($response['upstream_error']);
    }

    /**
     * 把无法随请求送达的附件写成显式清单。模型必须知道这些资料存在但读不到，
     * 才不会把“没看到”当成“没有”。
     *
     * @param array<int,array<string,string>> $omitted
     */
    private static function withAttachmentManifest(string $query, array $omitted): string
    {
        $lines = [];
        foreach ($omitted as $file) {
            $url = (string) ($file['url'] ?? '');
            if ($url === '') {
                continue;
            }
            $lines[] = strtoupper((string) ($file['type'] ?? 'file')) . ' ' . $url;
        }
        if ($lines === []) {
            return $query;
        }
        return $query . "\n\n<ATTACHMENTS_NOT_INLINE>\n"
            . "以下附件无法随本次请求送达，只提供来源地址；无法读取的附件必须在结论中明确标注为信息缺口。\n"
            . implode("\n", $lines)
            . "\n</ATTACHMENTS_NOT_INLINE>";
    }

    private static function isValidRemoteFileUrl(string $url): bool
    {
        if ($url === '' || preg_match('/[\x00-\x20\x7f]/', $url)) {
            return false;
        }
        $parts = parse_url($url);
        return is_array($parts)
            && in_array(strtolower((string) ($parts['scheme'] ?? '')), ['http', 'https'], true)
            && trim((string) ($parts['host'] ?? '')) !== ''
            && !isset($parts['user'])
            && !isset($parts['pass']);
    }

    private static function buildEndpoint(string $baseUrl, string $endpoint): string
    {
        $baseUrl = rtrim($baseUrl, '/');
        $path = strtolower((string) (parse_url($baseUrl, PHP_URL_PATH) ?? ''));
        if (str_ends_with($path, '/chat-messages') || str_ends_with($path, '/chat/completions')) {
            return $baseUrl;
        }
        if (str_ends_with($path, '/v1')) {
            return $baseUrl . '/' . $endpoint;
        }
        return $baseUrl . '/v1/' . $endpoint;
    }

    /**
     * Decide whether an ambiguous base URL should be tried with the other wire
     * protocol.  A 400/415/422 response cannot have started generation, and a
     * 2xx stream with no delivered delta but no valid terminal frame is also
     * safe to retry.  Authentication, rate-limit and server failures retain
     * their original diagnosis instead of being hidden by a second request.
     *
     * @param array<string,mixed> $response
     */
    private static function shouldTryNextProtocol(array $response, bool $streaming): bool
    {
        if ((int) ($response['errno'] ?? 0) !== 0) {
            return false;
        }
        $httpCode = (int) ($response['http_code'] ?? 0);
        if (in_array($httpCode, [400, 404, 405, 415, 422, 501], true)) {
            return true;
        }
        if (!$streaming || $httpCode < 200 || $httpCode >= 300 || !empty($response['emitted'])) {
            return false;
        }
        return !empty($response['upstream_error']) || empty($response['finished']);
    }

    private static function isValidBaseUrl(string $baseUrl): bool
    {
        if (preg_match('/[\x00-\x20\x7f]/', $baseUrl)) {
            return false;
        }
        $parts = parse_url($baseUrl);
        if (!is_array($parts)) {
            return false;
        }
        $scheme = strtolower((string) ($parts['scheme'] ?? ''));
        return in_array($scheme, ['http', 'https'], true)
            && trim((string) ($parts['host'] ?? '')) !== ''
            && !isset($parts['user'])
            && !isset($parts['pass'])
            && !isset($parts['query'])
            && !isset($parts['fragment']);
    }

    private static function isValidTimeout(int $timeout): bool
    {
        return $timeout >= self::MIN_TIMEOUT && $timeout <= self::MAX_TIMEOUT;
    }

    /**
     * @param array<string,mixed> $payload
     * @return array{body:string,errno:int,http_code:int}
     */
    private static function sendRequest(
        string $url,
        array $payload,
        string $apiKey,
        int $timeout
    ): array {
        $body = json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_INVALID_UTF8_SUBSTITUTE);
        if ($body === false) {
            return ['body' => '', 'errno' => -1, 'http_code' => 0];
        }

        $ch = curl_init();
        if ($ch === false) {
            return ['body' => '', 'errno' => -2, 'http_code' => 0];
        }
        curl_setopt_array($ch, [
            CURLOPT_URL => $url,
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => $body,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_CONNECTTIMEOUT => min(8, max(1, (int) ceil($timeout / 4))),
            CURLOPT_TIMEOUT => $timeout,
            CURLOPT_SSL_VERIFYPEER => true,
            CURLOPT_SSL_VERIFYHOST => 2,
            CURLOPT_HTTPHEADER => [
                'Content-Type: application/json',
                'Accept: application/json',
                'Authorization: Bearer ' . $apiKey,
            ],
        ]);

        $responseBody = curl_exec($ch);
        $errno = curl_errno($ch);
        $httpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        return [
            'body' => is_string($responseBody) ? $responseBody : '',
            'errno' => $errno,
            'http_code' => $httpCode,
        ];
    }

    /**
     * @param array<string,mixed> $payload
     * @param callable(string):mixed $onDelta
     * @param callable():bool|null $shouldAbort
     * @return array{
     *     errno:int,http_code:int,content:string,message_id:string,emitted:bool,
     *     upstream_error:bool,client_aborted:bool,callback_error:bool,finished:bool
     * }
     */
    private static function sendStreamRequest(
        string $protocol,
        string $url,
        array $payload,
        string $apiKey,
        int $timeout,
        callable $onDelta,
        ?callable $shouldAbort
    ): array {
        $body = json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_INVALID_UTF8_SUBSTITUTE);
        if ($body === false) {
            return self::emptyStreamResponse(-1);
        }

        $ch = curl_init();
        if ($ch === false) {
            return self::emptyStreamResponse(-2);
        }

        $buffer = '';
        $state = self::newStreamState();
        $responseCode = 0;
        $header = static function ($handle, string $line) use (&$responseCode): int {
            if (preg_match('/^HTTP\/\S+\s+(\d{3})(?:\s|$)/i', trim($line), $matches) === 1) {
                $responseCode = (int) $matches[1];
            }
            return strlen($line);
        };
        $write = static function ($handle, string $chunk) use (
            $protocol,
            &$buffer,
            &$state,
            &$responseCode,
            $onDelta,
            $shouldAbort
        ): int {
            if ($shouldAbort !== null && $shouldAbort()) {
                $state['client_aborted'] = true;
                return 0;
            }
            if ($responseCode < 200 || $responseCode >= 300) {
                // Never decode or forward an error response body. Besides preventing
                // leakage, this keeps 404/405 protocol fallback side-effect free.
                return strlen($chunk);
            }
            self::consumeStreamBytes($protocol, $buffer, $chunk, $state, $onDelta);
            return $state['callback_error'] ? 0 : strlen($chunk);
        };
        $progress = static function () use (&$state, $shouldAbort): int {
            if ($shouldAbort !== null && $shouldAbort()) {
                $state['client_aborted'] = true;
                return 1;
            }
            return 0;
        };

        curl_setopt_array($ch, [
            CURLOPT_URL => $url,
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => $body,
            CURLOPT_RETURNTRANSFER => false,
            CURLOPT_CONNECTTIMEOUT => min(8, max(1, (int) ceil($timeout / 4))),
            CURLOPT_TIMEOUT => $timeout,
            CURLOPT_SSL_VERIFYPEER => true,
            CURLOPT_SSL_VERIFYHOST => 2,
            CURLOPT_HTTPHEADER => [
                'Content-Type: application/json',
                'Accept: text/event-stream',
                'Authorization: Bearer ' . $apiKey,
            ],
            CURLOPT_HEADERFUNCTION => $header,
            CURLOPT_WRITEFUNCTION => $write,
            CURLOPT_NOPROGRESS => false,
            CURLOPT_XFERINFOFUNCTION => $progress,
        ]);

        curl_exec($ch);
        $errno = curl_errno($ch);
        $httpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        if (!$state['client_aborted'] && !$state['callback_error']) {
            self::consumeStreamBytes($protocol, $buffer, '', $state, $onDelta, true);
        }

        return [
            'errno' => $errno,
            'http_code' => $httpCode,
            'content' => $state['content'],
            'message_id' => $state['message_id'],
            'emitted' => $state['emitted'],
            'upstream_error' => $state['upstream_error'],
            'upstream_code' => $state['upstream_code'],
            'client_aborted' => $state['client_aborted'],
            'callback_error' => $state['callback_error'],
            'finished' => $state['finished'],
        ];
    }

    /**
     * @return array{
     *     content:string,message_id:string,emitted:bool,upstream_error:bool,
     *     client_aborted:bool,callback_error:bool,finished:bool
     * }
     */
    private static function newStreamState(): array
    {
        return [
            'content' => '',
            'message_id' => '',
            'emitted' => false,
            'upstream_error' => false,
            'upstream_code' => '',
            'client_aborted' => false,
            'callback_error' => false,
            'finished' => false,
        ];
    }

    /**
     * 上游错误码只保留可枚举的短标识（如 invalid_param），杜绝把上游文案或
     * 患者资源地址带进日志。
     *
     * @param mixed $code
     */
    private static function cleanUpstreamCode($code): string
    {
        if (!is_string($code)) {
            return '';
        }
        return preg_match('/^[a-z0-9_.-]{1,64}$/i', $code) === 1 ? $code : '';
    }

    /**
     * 按 SSE 空行分帧；仅在完整 data frame 后 json_decode，因此可安全接收任意字节边界。
     *
     * @param array<string,mixed> $state
     * @param callable(string):mixed $onDelta
     */
    private static function consumeStreamBytes(
        string $protocol,
        string &$buffer,
        string $chunk,
        array &$state,
        callable $onDelta,
        bool $final = false
    ): void {
        $buffer .= $chunk;
        while (preg_match('/(?:\r\n|\r|\n){2}/', $buffer, $match, PREG_OFFSET_CAPTURE) === 1) {
            $delimiter = $match[0][0];
            $offset = $match[0][1];
            $frame = substr($buffer, 0, $offset);
            $buffer = (string) substr($buffer, $offset + strlen($delimiter));
            self::consumeStreamFrame($protocol, $frame, $state, $onDelta);
        }
        if ($final && trim($buffer) !== '') {
            self::consumeStreamFrame($protocol, $buffer, $state, $onDelta);
            $buffer = '';
        }
    }

    /**
     * @param array<string,mixed> $state
     * @param callable(string):mixed $onDelta
     */
    private static function consumeStreamFrame(
        string $protocol,
        string $frame,
        array &$state,
        callable $onDelta
    ): void {
        if ($state['finished'] || $state['upstream_error'] || $state['callback_error']) {
            return;
        }

        $dataLines = [];
        foreach (preg_split('/\r\n|\r|\n/', $frame) ?: [] as $line) {
            if ($line === '' || str_starts_with($line, ':')) {
                continue;
            }
            if (str_starts_with($line, 'data:')) {
                $dataLines[] = ltrim(substr($line, 5), ' ');
            }
        }
        if ($dataLines === []) {
            return;
        }

        $data = implode("\n", $dataLines);
        if ($data === '[DONE]') {
            $state['finished'] = true;
            return;
        }
        $decoded = json_decode($data, true);
        if (!is_array($decoded)) {
            return;
        }

        $delta = '';
        if ($protocol === 'dify') {
            $event = strtolower((string) ($decoded['event'] ?? ''));
            if ($event === 'message_end') {
                $state['message_id'] = (string) ($decoded['message_id'] ?? $state['message_id']);
                $state['finished'] = true;
                return;
            }
            if ($event === 'error') {
                $state['upstream_error'] = true;
                // 只留可枚举的错误码用于排障；message 可能含患者资源地址，不落日志。
                $state['upstream_code'] = self::cleanUpstreamCode($decoded['code'] ?? '');
                return;
            }
            if (!in_array($event, ['message', 'agent_message'], true)) {
                return;
            }
            $delta = is_string($decoded['answer'] ?? null) ? $decoded['answer'] : '';
            $state['message_id'] = (string) ($decoded['message_id'] ?? $state['message_id']);
        } else {
            $delta = self::extractStreamDelta($decoded);
            $state['message_id'] = (string) ($decoded['id'] ?? $state['message_id']);
        }

        if ($delta === '') {
            return;
        }
        try {
            $accepted = $onDelta($delta);
            if ($accepted === false) {
                $state['callback_error'] = true;
                return;
            }
        } catch (\Throwable $e) {
            $state['callback_error'] = true;
            return;
        }
        $state['content'] .= $delta;
        $state['emitted'] = true;
    }

    /** @param array<string,mixed> $decoded */
    private static function extractStreamDelta(array $decoded): string
    {
        $content = $decoded['choices'][0]['delta']['content'] ?? '';
        if (is_string($content)) {
            return $content;
        }
        if (!is_array($content)) {
            return '';
        }
        $parts = [];
        foreach ($content as $part) {
            if (is_array($part) && ($part['type'] ?? '') === 'text' && is_string($part['text'] ?? null)) {
                $parts[] = $part['text'];
            }
        }
        return implode('', $parts);
    }

    /**
     * 纯解析测试入口：生产流与测试使用同一逐字节解码路径。
     *
     * @param array<int,string> $chunks
     * @return array{content:string,deltas:array<int,string>,message_id:string,finished:bool,upstream_error:bool}
     */
    private static function decodeStreamChunks(string $protocol, array $chunks): array
    {
        $buffer = '';
        $state = self::newStreamState();
        $deltas = [];
        $onDelta = static function (string $delta) use (&$deltas): void {
            $deltas[] = $delta;
        };
        foreach ($chunks as $chunk) {
            self::consumeStreamBytes($protocol, $buffer, $chunk, $state, $onDelta);
        }
        self::consumeStreamBytes($protocol, $buffer, '', $state, $onDelta, true);
        return [
            'content' => $state['content'],
            'deltas' => $deltas,
            'message_id' => $state['message_id'],
            'finished' => $state['finished'],
            'upstream_error' => $state['upstream_error'],
        ];
    }

    /**
     * @return array{
     *     errno:int,http_code:int,content:string,message_id:string,emitted:bool,
     *     upstream_error:bool,client_aborted:bool,callback_error:bool,finished:bool
     * }
     */
    private static function emptyStreamResponse(int $errno): array
    {
        return [
            'errno' => $errno,
            'http_code' => 0,
            'content' => '',
            'message_id' => '',
            'emitted' => false,
            'upstream_error' => false,
            'upstream_code' => '',
            'client_aborted' => false,
            'callback_error' => false,
            'finished' => false,
        ];
    }

    /**
     * @param array<string,mixed> $response
     * @return array{ok:bool,content?:string,message_id?:string,latency_ms:int,error_code?:string,error?:string}
     */
    private static function formatStreamResponse(array $response, float $startedAt): array
    {
        $latencyMs = self::elapsedMilliseconds($startedAt);
        if (!empty($response['client_aborted'])) {
            return self::error('CLIENT_DISCONNECTED', '客户端已断开连接', $latencyMs);
        }
        if (!empty($response['callback_error'])) {
            return self::error('STREAM_DELIVERY_FAILED', '流式响应已中止', $latencyMs);
        }

        $errno = (int) ($response['errno'] ?? 0);
        if ($errno !== 0) {
            if ($errno === CURLE_OPERATION_TIMEDOUT) {
                return self::error('UPSTREAM_TIMEOUT', '模型响应超时，请稍后重试', $latencyMs);
            }
            if ($errno === -1) {
                return self::error('REQUEST_BUILD_FAILED', '病例数据编码失败', $latencyMs);
            }
            if ($errno === -2) {
                return self::error('CURL_INIT_FAILED', '无法初始化 AI 请求', $latencyMs);
            }
            return self::error('UPSTREAM_UNAVAILABLE', '暂时无法连接 AI 服务，请稍后重试', $latencyMs);
        }

        $httpCode = (int) ($response['http_code'] ?? 0);
        if ($httpCode === 401 || $httpCode === 403) {
            return self::error('CONFIG_INVALID', 'AI 服务凭据无效或无权限', $latencyMs);
        }
        if ($httpCode === 429 || $httpCode >= 500) {
            return self::error('UPSTREAM_BUSY', '模型服务繁忙，请稍后重试', $latencyMs);
        }
        if ($httpCode >= 400 || $httpCode < 200 || !empty($response['upstream_error'])) {
            return self::error('UPSTREAM_REJECTED', '模型未能处理本次请求', $latencyMs);
        }
        if (empty($response['finished'])) {
            return self::error('INCOMPLETE_RESPONSE', '模型响应不完整，请重试', $latencyMs);
        }

        $content = (string) ($response['content'] ?? '');
        if (trim($content) === '') {
            return self::error('EMPTY_RESPONSE', '模型未返回报告内容，请重试', $latencyMs);
        }
        return [
            'ok' => true,
            'content' => $content,
            'message_id' => (string) ($response['message_id'] ?? ''),
            'latency_ms' => $latencyMs,
        ];
    }

    /**
     * @param array{body:string,errno:int,http_code:int} $response
     * @return array{ok:bool,content?:string,message_id?:string,latency_ms:int,error_code?:string,error?:string}
     */
    private static function formatResponse(array $response, float $startedAt): array
    {
        $latencyMs = self::elapsedMilliseconds($startedAt);
        $errno = $response['errno'];
        $httpCode = $response['http_code'];

        if ($errno !== 0) {
            if ($errno === CURLE_OPERATION_TIMEDOUT) {
                return self::error('UPSTREAM_TIMEOUT', '模型响应超时，请稍后重试', $latencyMs);
            }
            if ($errno === -1) {
                return self::error('REQUEST_BUILD_FAILED', '病例数据编码失败', $latencyMs);
            }
            if ($errno === -2) {
                return self::error('CURL_INIT_FAILED', '无法初始化 AI 请求', $latencyMs);
            }
            return self::error('UPSTREAM_UNAVAILABLE', '暂时无法连接 AI 服务，请稍后重试', $latencyMs);
        }

        $decoded = json_decode($response['body'], true);
        if ($httpCode === 401 || $httpCode === 403) {
            return self::error('CONFIG_INVALID', 'AI 服务凭据无效或无权限', $latencyMs);
        }
        if ($httpCode === 429 || $httpCode >= 500) {
            return self::error('UPSTREAM_BUSY', '模型服务繁忙，请稍后重试', $latencyMs);
        }
        if ($httpCode >= 400 || $httpCode < 200) {
            return self::error('UPSTREAM_REJECTED', '模型未能处理本次请求', $latencyMs);
        }
        if (!is_array($decoded)) {
            return self::error('INVALID_RESPONSE', '模型返回格式异常，请重试', $latencyMs);
        }

        $answer = self::extractContent($decoded);
        if ($answer === '') {
            return self::error('EMPTY_RESPONSE', '模型未返回报告内容，请重试', $latencyMs);
        }

        return [
            'ok' => true,
            'content' => $answer,
            'message_id' => (string) ($decoded['message_id'] ?? $decoded['id'] ?? ''),
            'latency_ms' => $latencyMs,
        ];
    }

    /** @param array<string,mixed> $decoded */
    private static function extractContent(array $decoded): string
    {
        $content = $decoded['answer'] ?? $decoded['choices'][0]['message']['content'] ?? '';
        if (is_string($content)) {
            return trim($content);
        }
        if (!is_array($content)) {
            return '';
        }

        $parts = [];
        foreach ($content as $part) {
            if (is_array($part) && ($part['type'] ?? '') === 'text' && is_string($part['text'] ?? null)) {
                $parts[] = $part['text'];
            }
        }
        return trim(implode('', $parts));
    }

    private static function elapsedMilliseconds(float $startedAt): int
    {
        return (int) round((microtime(true) - $startedAt) * 1000);
    }

    /**
     * 记录上游失败的结构化定位信息。按项目约定，绝不写入凭据、上游主机名或
     * 响应正文，只保留可用于排障的协议、路径、状态码和请求规模。
     *
     * @param array<string,mixed> $requestSpec
     * @param array<string,mixed> $response
     * @param array<int,array<string,string>> $files
     * @param array<string,mixed> $formatted
     */
    private static function logUpstreamFailure(
        array $requestSpec,
        array $response,
        string $query,
        array $files,
        array $formatted
    ): void {
        if (!empty($formatted['ok'])) {
            return;
        }
        $url = (string) ($requestSpec['url'] ?? '');
        $upstreamCode = (string) ($response['upstream_code'] ?? '');
        if ($upstreamCode === '' && isset($response['body'])) {
            $decoded = json_decode((string) $response['body'], true);
            $upstreamCode = is_array($decoded)
                ? self::cleanUpstreamCode($decoded['code'] ?? '')
                : '';
        }
        Log::warning('prescription ai upstream request failed', [
            'protocol' => (string) ($requestSpec['protocol'] ?? ''),
            'endpoint_path' => (string) (parse_url($url, PHP_URL_PATH) ?? ''),
            'http_code' => (int) ($response['http_code'] ?? 0),
            'curl_errno' => (int) ($response['errno'] ?? 0),
            // 上游自有错误码（如 invalid_param），用于区分附件超限、鉴权、模型故障。
            'upstream_code' => $upstreamCode,
            'query_bytes' => strlen($query),
            'file_count' => count($files),
            'error_code' => (string) ($formatted['error_code'] ?? 'UNKNOWN'),
            'latency_ms' => (int) ($formatted['latency_ms'] ?? 0),
        ]);
    }

    /**
     * @return array{ok:false,error_code:string,error:string,latency_ms:int}
     */
    private static function error(string $code, string $message, int $latencyMs = 0): array
    {
        return [
            'ok' => false,
            'error_code' => $code,
            'error' => $message,
            'latency_ms' => $latencyMs,
        ];
    }
}