<?php

declare(strict_types=1);

namespace app\common\service;

/**
 * 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;

    /**
     * @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
    {
        $config = config('prescription_ai') ?: [];
        if (empty($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');
        }

        $requestSpecs = self::buildRequestSpecs($baseUrl, $model, $inputs, $query, $user);
        $startedAt = microtime(true);
        $lastResponse = null;

        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;

            // /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 && in_array($response['http_code'], [404, 405], true)) {
                continue;
            }

            return self::formatResponse($response, $startedAt);
        }

        return self::formatResponse($lastResponse ?? [
            'body' => '',
            'errno' => 0,
            'http_code' => 0,
        ], $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 {
        $config = config('prescription_ai') ?: [];
        if (empty($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');
        }

        $requestSpecs = self::buildRequestSpecs(
            $baseUrl,
            $model,
            $inputs,
            $query,
            $user,
            true
        );
        $startedAt = microtime(true);
        $lastResponse = null;

        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;

            // 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 (
                $hasFallback
                && empty($response['emitted'])
                && in_array($response['http_code'], [404, 405], true)
            ) {
                continue;
            }

            return self::formatStreamResponse($response, $startedAt);
        }

        return self::formatStreamResponse($lastResponse ?? [
            'errno' => 0,
            'http_code' => 0,
            'content' => '',
            'message_id' => '',
            'emitted' => false,
            'upstream_error' => false,
            'client_aborted' => false,
            'callback_error' => false,
            'finished' => false,
        ], $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
     * @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 {
        $baseUrl = rtrim($baseUrl, '/');
        $path = strtolower((string) (parse_url($baseUrl, PHP_URL_PATH) ?? ''));

        $difySpec = [
            'protocol' => 'dify',
            'url' => self::buildEndpoint($baseUrl, 'chat-messages'),
            'payload' => [
                'inputs' => $inputs,
                'query' => $query,
                'response_mode' => $streaming ? 'streaming' : 'blocking',
                'user' => $user,
            ],
        ];
        $openAiSpec = [
            'protocol' => 'openai',
            'url' => self::buildEndpoint($baseUrl, 'chat/completions'),
            'payload' => [
                'model' => $model,
                'messages' => [
                    ['role' => 'user', 'content' => $query],
                ],
                '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。
        return [$difySpec, $openAiSpec];
    }

    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;
    }

    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'],
            '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,
            'client_aborted' => false,
            'callback_error' => false,
            'finished' => false,
        ];
    }

    /**
     * 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') {
                $state['upstream_error'] = true;
                return;
            }
            if (!in_array($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,
            '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);
    }

    /**
     * @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,
        ];
    }
}