<?php

namespace app\service;

use app\model\AiModel;
use think\exception\HttpResponseException;

/**
 * Dify 应用 API 接入服务。
 *
 * Dify 使用的是自己的一套接口协议，跟 OpenAI 的 /chat/completions 完全不同：
 * - 发送消息：POST {api_base_url}/chat-messages
 * - 上传文件：POST {api_base_url}/files/upload
 * - 会话上下文由 Dify 自己维护（通过 conversation_id 串联），不需要像 OpenAI 那样
 *   每次把完整的历史消息数组传过去，只需要传当前这一句 query + 上一次返回的 conversation_id。
 *
 * 参考文档：https://docs.dify.ai/api-reference
 */
class DifyService
{
    public static function chat(AiModel $model, string $query, array $files, ?string $conversationId, string $userId): array
    {
        $url = rtrim($model->api_base_url, '/') . '/chat-messages';
        $conversationReset = false;

        for ($attempt = 0; $attempt < 2; $attempt++) {
            $requestConversationId = $attempt === 0 ? $conversationId : null;
            $payload = self::buildPayload($query, $files, $requestConversationId, $userId, false);

            $ch = curl_init($url);
            curl_setopt_array($ch, [
                CURLOPT_POST           => true,
                CURLOPT_POSTFIELDS     => json_encode($payload),
                CURLOPT_HTTPHEADER     => [
                    'Content-Type: application/json',
                    'Authorization: Bearer ' . $model->api_key,
                ],
                CURLOPT_RETURNTRANSFER => true,
                CURLOPT_TIMEOUT        => 120,
                CURLOPT_CONNECTTIMEOUT => 15,
                CURLOPT_SSL_VERIFYPEER => false,
            ]);

            $response = curl_exec($ch);
            $httpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
            $curlError = curl_error($ch);
            curl_close($ch);

            if ($response === false) {
                throw new HttpResponseException(json([
                    'code'    => 1,
                    'message' => 'Dify 请求失败: ' . ($curlError ?: '网络错误'),
                    'data'    => null,
                ], 502));
            }

            if ($httpCode !== 200) {
                $detail = self::parseErrorBody($response) ?: ('HTTP ' . $httpCode);
                if (
                    $attempt === 0 &&
                    $conversationId &&
                    self::isConversationNotFoundError($response . ' ' . $detail)
                ) {
                    $conversationReset = true;
                    continue;
                }

                throw new HttpResponseException(json([
                    'code'    => 1,
                    'message' => self::humanizeError('Dify 请求失败: ' . $detail . self::urlHint($httpCode)),
                    'data'    => null,
                ], 502));
            }

            $data = json_decode($response, true);
            if (!$data) {
                throw new HttpResponseException(json([
                    'code'    => 1,
                    'message' => 'Dify 响应解析失败',
                    'data'    => null,
                ], 502));
            }

            return [
                'answer'             => $data['answer'] ?? '',
                'conversation_id'    => $data['conversation_id'] ?? null,
                'conversation_reset' => $conversationReset,
                'tokens'             => $data['metadata']['usage']['total_tokens'] ?? 0,
            ];
        }

        throw new \RuntimeException('Dify 会话恢复失败');
    }

    public static function streamChat(
        AiModel $model,
        string $query,
        array $files,
        ?string $conversationId,
        string $userId,
        callable $onChunk,
        callable $onDone,
        ?callable $onError = null,
        ?callable $onConversationReset = null
    ): void {
        $emittedContent = false;
        $attemptError = null;
        $attemptDone = null;

        $chunkProxy = function (string $delta) use (&$emittedContent, $onChunk) {
            $emittedContent = true;
            $onChunk($delta);
        };
        $doneProxy = function (?string $newConversationId, int $tokens) use (&$attemptDone) {
            $attemptDone = [$newConversationId, $tokens];
        };
        $errorProxy = function (string $message) use (&$attemptError) {
            $attemptError = $message;
        };

        self::streamChatAttempt(
            $model,
            $query,
            $files,
            $conversationId,
            $userId,
            $chunkProxy,
            $doneProxy,
            $errorProxy
        );

        if (
            $attemptDone === null &&
            !$emittedContent &&
            $conversationId &&
            self::isConversationNotFoundError((string) $attemptError)
        ) {
            if ($onConversationReset) {
                $onConversationReset();
            }
            $attemptError = null;
            self::streamChatAttempt(
                $model,
                $query,
                $files,
                null,
                $userId,
                $chunkProxy,
                $doneProxy,
                $errorProxy
            );
        }

        if ($attemptDone !== null) {
            $onDone($attemptDone[0], $attemptDone[1]);
            return;
        }

        if ($onError && $attemptError !== null) {
            $onError($attemptError);
        }
    }

    private static function streamChatAttempt(
        AiModel $model,
        string $query,
        array $files,
        ?string $conversationId,
        string $userId,
        callable $onChunk,
        callable $onDone,
        ?callable $onError = null
    ): void {
        $url = rtrim($model->api_base_url, '/') . '/chat-messages';
        $payload = self::buildPayload($query, $files, $conversationId, $userId, true);

        $errorBody = '';
        $httpCode = 0;
        $finalConversationId = $conversationId;
        $finalTokens = 0;
        $eventError = null;
        $streamBuffer = '';

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => json_encode($payload),
            CURLOPT_HTTPHEADER     => [
                'Content-Type: application/json',
                'Authorization: Bearer ' . $model->api_key,
            ],
            CURLOPT_RETURNTRANSFER => false,
            CURLOPT_HEADERFUNCTION => function ($ch, $header) use (&$httpCode) {
                if (preg_match('/^HTTP\/\d+\.\d+\s+(\d+)/', $header, $m)) {
                    $httpCode = (int) $m[1];
                }
                return strlen($header);
            },
            CURLOPT_WRITEFUNCTION => function ($ch, $data) use (
                &$errorBody,
                &$httpCode,
                $onChunk,
                &$finalConversationId,
                &$finalTokens,
                &$eventError,
                &$streamBuffer
            ) {
                if ($httpCode >= 400) {
                    $errorBody .= $data;
                    return strlen($data);
                }

                // cURL may split one SSE data line across arbitrary network chunks.
                $streamBuffer .= $data;
                $lines = preg_split('/\r?\n/', $streamBuffer) ?: [];
                $streamBuffer = (string) (array_pop($lines) ?? '');
                foreach ($lines as $line) {
                    $line = trim($line);
                    if ($line === '' || !str_starts_with($line, 'data:')) {
                        continue;
                    }

                    $json = json_decode(substr($line, 5), true);
                    if (!$json) {
                        continue;
                    }

                    $event = $json['event'] ?? '';

                    if (!empty($json['conversation_id'])) {
                        $finalConversationId = $json['conversation_id'];
                    }

                    if ($event === 'error') {
                        $eventError = $json['message'] ?? 'Dify 返回错误';
                        continue;
                    }

                    if (in_array($event, ['message', 'agent_message'], true)) {
                        $delta = $json['answer'] ?? '';
                        if ($delta !== '') {
                            $onChunk($delta);
                        }
                    }

                    if ($event === 'message_end') {
                        $finalTokens = $json['metadata']['usage']['total_tokens'] ?? $finalTokens;
                    }
                }

                return strlen($data);
            },
            CURLOPT_TIMEOUT        => 120,
            CURLOPT_CONNECTTIMEOUT => 15,
            CURLOPT_SSL_VERIFYPEER => false,
        ]);

        try {
            $result = curl_exec($ch);

            if ($result === false) {
                $message = 'Dify 请求失败: ' . curl_error($ch);
                $onError ? $onError($message) : null;
                return;
            }

            if ($httpCode >= 400) {
                $detail = self::parseErrorBody($errorBody) ?: ('HTTP ' . $httpCode);
                $onError ? $onError(self::humanizeError('Dify 请求失败: ' . $detail . self::urlHint($httpCode))) : null;
                return;
            }

            if ($eventError) {
                $onError ? $onError(self::humanizeError('Dify 请求失败: ' . $eventError)) : null;
                return;
            }
        } finally {
            curl_close($ch);
        }

        $onDone($finalConversationId, $finalTokens);
    }

    /**
     * 把本地已上传的文件转发上传到 Dify（Dify 需要自己的 upload_file_id 才能在
     * chat-messages 里引用文件），失败时返回 null，调用方应做优雅降级处理。
     */
    public static function uploadFile(AiModel $model, string $path, string $mime, string $originalName, string $userId): ?string
    {
        [$fileId] = self::uploadFileWithDetail($model, $path, $mime, $originalName, $userId);
        return $fileId;
    }

    /**
     * 上传文件到 Dify，失败时返回 [null, errorMessage]
     */
    public static function uploadFileWithDetail(AiModel $model, string $path, string $mime, string $originalName, string $userId): array
    {
        if (!is_file($path)) {
            return [null, '本地文件不存在'];
        }

        $url = rtrim($model->api_base_url, '/') . '/files/upload';
        $safeName = self::safeUploadFilename($originalName, $path, $mime);

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => [
                'file' => curl_file_create($path, $mime, $safeName),
                'user' => $userId,
            ],
            CURLOPT_HTTPHEADER     => [
                'Authorization: Bearer ' . $model->api_key,
            ],
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 60,
            CURLOPT_CONNECTTIMEOUT => 15,
            CURLOPT_SSL_VERIFYPEER => false,
        ]);

        $response = curl_exec($ch);
        $httpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $curlError = curl_error($ch);
        curl_close($ch);

        if ($response === false) {
            return [null, '网络错误: ' . ($curlError ?: '无法连接 Dify')];
        }

        if ($httpCode !== 200 && $httpCode !== 201) {
            $detail = self::parseErrorBody($response) ?: ('HTTP ' . $httpCode);
            return [null, $detail];
        }

        $data = json_decode($response, true);
        $fileId = $data['id'] ?? ($data['data']['id'] ?? null);

        return $fileId ? [$fileId, null] : [null, 'Dify 未返回 file_id'];
    }

    private static function safeUploadFilename(string $originalName, string $path, string $mime): string
    {
        $ext = strtolower(pathinfo($originalName, PATHINFO_EXTENSION) ?: pathinfo($path, PATHINFO_EXTENSION));
        if ($ext === '') {
            $ext = match (true) {
                str_starts_with($mime, 'image/png') => 'png',
                str_starts_with($mime, 'image/gif') => 'gif',
                str_starts_with($mime, 'image/webp') => 'webp',
                default => 'jpg',
            };
        }

        return 'upload_' . uniqid('', true) . '.' . $ext;
    }

    /**
     * 测试 Dify 应用连接是否正常
     */
    public static function testConnection(array $config): array
    {
        $apiBaseUrl = rtrim($config['api_base_url'] ?? '', '/');
        $apiKey = $config['api_key'] ?? '';

        if (!$apiBaseUrl) {
            throw new \InvalidArgumentException('请填写 API 地址（Dify 应用的 API Base URL，如 https://api.dify.ai/v1）');
        }
        if (!$apiKey) {
            throw new \InvalidArgumentException('请填写 API Key（在 Dify 应用的"访问 API"页面获取）');
        }

        $url = $apiBaseUrl . '/chat-messages';
        $payload = [
            'inputs'          => new \stdClass(),
            'query'           => '请只回复：测试成功',
            'response_mode'   => 'blocking',
            'conversation_id' => '',
            'user'            => 'connection-test',
        ];

        $start = microtime(true);
        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_POSTFIELDS     => json_encode($payload),
            CURLOPT_HTTPHEADER     => [
                'Content-Type: application/json',
                'Authorization: Bearer ' . $apiKey,
            ],
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT        => 30,
            CURLOPT_CONNECTTIMEOUT => 10,
            CURLOPT_SSL_VERIFYPEER => false,
        ]);

        $response = curl_exec($ch);
        $httpCode = (int) curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $curlError = curl_error($ch);
        curl_close($ch);

        $latencyMs = (int) round((microtime(true) - $start) * 1000);

        if ($response === false) {
            throw new \RuntimeException('连接失败: ' . ($curlError ?: '网络不可达'));
        }

        if ($httpCode !== 200) {
            $detail = self::parseErrorBody($response) ?: ('HTTP ' . $httpCode);
            throw new \RuntimeException('API 返回错误: ' . $detail . self::urlHint($httpCode));
        }

        $data = json_decode($response, true);
        if (!$data) {
            throw new \RuntimeException('响应解析失败，请确认接口地址正确');
        }

        $reply = $data['answer'] ?? '';
        if ($reply === '') {
            throw new \RuntimeException('接口连接成功，但未返回有效内容');
        }

        return [
            'success'    => true,
            'latency_ms' => $latencyMs,
            'reply'      => $reply,
            'model'      => 'dify',
            'tokens'     => $data['metadata']['usage']['total_tokens'] ?? null,
        ];
    }

    private static function buildPayload(string $query, array $files, ?string $conversationId, string $userId, bool $streaming): array
    {
        $payload = [
            // 注意：必须用 stdClass 而不是 []，PHP 的空数组 json_encode 后是 "[]"，
            // 但 Dify（Pydantic）要求 inputs 必须是字典 "{}"，否则会报
            // "Input should be a valid dictionary" 的校验错误
            'inputs'          => new \stdClass(),
            'query'           => $query,
            'response_mode'   => $streaming ? 'streaming' : 'blocking',
            'conversation_id' => $conversationId ?: '',
            'user'            => $userId,
        ];

        if ($files) {
            $payload['files'] = $files;
        }

        return $payload;
    }

    private static function urlHint(int $httpCode): string
    {
        if ($httpCode === 404) {
            return '（请确认 API 地址填写的是 Dify 的 API 根路径，如 https://api.dify.ai/v1 或自部署的 http://your-host/v1，Dify 使用 /chat-messages 接口，不是 OpenAI 的 /chat/completions）';
        }
        if ($httpCode === 401) {
            return '（请确认 API Key 是在 Dify 应用"访问 API"页面获取的密钥，而不是账号登录密码或 OpenAI Key）';
        }
        return '';
    }

    public static function isConversationNotFoundError(string $message): bool
    {
        $message = mb_strtolower($message);
        foreach ([
            'conversation not exists',
            'conversation does not exist',
            'conversation not found',
            'conversation_not_exists',
            'conversation_not_found',
            'dify 会话已失效',
        ] as $needle) {
            if (str_contains($message, $needle)) {
                return true;
            }
        }

        return false;
    }

    private static function parseErrorBody(?string $body): ?string
    {
        if (!$body) {
            return null;
        }
        $json = json_decode($body, true);
        if (json_last_error() === JSON_ERROR_NONE) {
            return $json['message'] ?? null;
        }
        return trim($body) ?: null;
    }

    /**
     * 将 Dify 插件/模型层的英文错误转为可操作的中文提示
     */
    public static function humanizeError(string $message): string
    {
        if (self::isConversationNotFoundError($message)) {
            return 'Dify 会话已失效，系统创建新会话后仍未恢复，请稍后重新发送。';
        }

        if (str_contains($message, "Unsupported chat content part type: 'file'")
            || str_contains($message, 'Unsupported chat content part type')) {
            return 'Dify 模型层仍不接受 file 类型。请确认 Dify 应用已开启文档上传，且 files.type 使用 document（不是 file）。'
                . ' 原始错误：' . mb_substr($message, 0, 180);
        }

        if (str_contains($message, 'PluginInvokeError')) {
            return 'Dify 插件调用失败，请检查 Dify 应用内模型供应商配置是否与图片输入兼容。'
                . ' 详情：' . mb_substr($message, 0, 300);
        }

        return $message;
    }
}