import { Injectable, InternalServerErrorException } from '@nestjs/common';
import { request } from 'undici';
import { ProviderStreamResult, StreamChatRequest } from '../types/chat.types';
import { AiProvider } from './provider.interface';

@Injectable()
export class VolcProvider implements AiProvider {
  readonly code = 'volc';

  supports(model?: string): boolean {
    if (!model) return true;
    return (
      model.toLowerCase().includes('volc') ||
      model.toLowerCase().includes('ark')
    );
  }

  async streamChat(req: StreamChatRequest): Promise<ProviderStreamResult> {
    const apiKey = process.env.VOLC_API_KEY;
    const baseUrl =
      process.env.VOLC_BASE_URL || 'https://ark.cn-beijing.volces.com/api/v3';

    if (!apiKey) {
      throw new InternalServerErrorException('VOLC_API_KEY 未配置');
    }

    const model = req.model || 'ep-default';
    const upstreamBody = {
      model,
      stream: false,
      messages: (req.messages || []).map((m) => ({
        role: m.role,
        content: m.content,
      })),
    };

    const { statusCode, body } = await request(`${baseUrl}/chat/completions`, {
      method: 'POST',
      body: JSON.stringify(upstreamBody),
      headers: {
        'Content-Type': 'application/json',
        Authorization: `Bearer ${apiKey}`,
      },
    });

    if (statusCode < 200 || statusCode >= 300) {
      const text = await body.text();
      throw new InternalServerErrorException(
        `火山引擎调用失败: ${statusCode} - ${text}`,
      );
    }

    const json = (await body.json()) as any;
    const content: string =
      json.choices?.[0]?.message?.content ??
      '[Volc] 未返回内容，请检查请求参数或模型配置。';

    const promptTokens: number = json.usage?.prompt_tokens ?? 0;
    const completionTokens: number = json.usage?.completion_tokens ?? 0;
    const totalTokens: number =
      json.usage?.total_tokens ?? Math.max(1, promptTokens + completionTokens);

    const chunks = this.splitText(content, 24).map((c) => ({ content: c }));

    return {
      requestId: json.id || `volc_${Date.now()}`,
      providerCode: this.code,
      model,
      chunks,
      usage: { promptTokens, completionTokens, totalTokens },
    };
  }

  private splitText(text: string, size: number) {
    const result: string[] = [];
    for (let i = 0; i < text.length; i += size) {
      result.push(text.slice(i, i + size));
    }
    return result;
  }
}