<?php

declare(strict_types=1);

namespace app\common\service;

/**
 * Dify Chat App blocking 客户端。
 *
 * 只接受服务端配置中的模型 profile，避免把上游地址和密钥暴露给前端。
 */
class DifyChatService
{
    /**
     * @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', '处方 AI 解释未启用');
        }

        $modelConfig = $config['models'][$profile] ?? null;
        if (!is_array($modelConfig)) {
            return self::error('INVALID_PROFILE', '不支持的 AI 模型');
        }

        $baseUrl = trim((string) ($config['base_url'] ?? ''));
        $apiKey = trim((string) ($modelConfig['api_key'] ?? ''));
        if ($baseUrl === '' || $apiKey === '') {
            return self::error('CONFIG_MISSING', '该模型尚未配置 Dify 地址或 App Key');
        }
        if (!function_exists('curl_init')) {
            return self::error('CURL_UNAVAILABLE', '服务器尚未启用 cURL 扩展');
        }

        $payload = [
            'inputs' => $inputs,
            'query' => $query,
            'response_mode' => 'blocking',
            'user' => $user,
        ];
        $body = json_encode($payload, JSON_UNESCAPED_UNICODE | JSON_INVALID_UTF8_SUBSTITUTE);
        if ($body === false) {
            return self::error('REQUEST_BUILD_FAILED', '处方数据编码失败');
        }

        $timeout = max(10, min(120, (int) ($config['timeout'] ?? 90)));
        $ch = curl_init();
        if ($ch === false) {
            return self::error('CURL_INIT_FAILED', '无法初始化 AI 请求');
        }
        curl_setopt_array($ch, [
            CURLOPT_URL => self::buildEndpoint($baseUrl),
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => $body,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_CONNECTTIMEOUT => min(8, max(3, (int) ceil($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,
            ],
        ]);

        $startedAt = microtime(true);
        $responseBody = curl_exec($ch);
        $errno = curl_errno($ch);
        $httpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);
        $latencyMs = (int) round((microtime(true) - $startedAt) * 1000);

        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);
            }
            return self::error('UPSTREAM_UNAVAILABLE', '暂时无法连接 AI 服务，请稍后重试', $latencyMs);
        }

        $decoded = json_decode((string) $responseBody, true);
        if ($httpCode === 401 || $httpCode === 403) {
            return self::error('CONFIG_INVALID', '模型 App Key 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) {
            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);
        }

        $answer = trim((string) ($decoded['answer'] ?? ''));
        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'] ?? ''),
            'latency_ms' => $latencyMs,
        ];
    }

    private static function buildEndpoint(string $baseUrl): string
    {
        $baseUrl = rtrim($baseUrl, '/');
        if (str_ends_with($baseUrl, '/chat-messages')) {
            return $baseUrl;
        }
        if (str_ends_with($baseUrl, '/v1')) {
            return $baseUrl . '/chat-messages';
        }
        return $baseUrl . '/v1/chat-messages';
    }

    /**
     * @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,
        ];
    }
}