import { LangfuseClient } from '@langfuse/client';
import type { PromptFetcher, RawPrompt } from './PromptGateway';

export class LangfusePromptGateway implements PromptFetcher {
  private readonly client: LangfuseClient;

  constructor(opts: { publicKey: string; secretKey: string; baseUrl: string }) {
    this.client = new LangfuseClient({
      publicKey: opts.publicKey,
      secretKey: opts.secretKey,
      baseUrl: opts.baseUrl,
    });
  }

  async fetch(promptName: string): Promise<RawPrompt> {
    const prompt = await this.client.prompt.get(promptName, { type: 'chat' });
    return {
      name: prompt.name,
      version: prompt.version,
      config: (prompt.config ?? {}) as Record<string, unknown>,
      compile: (variables) =>
        prompt.compile(variables as Record<string, string>) as {
          role: 'system' | 'user' | 'assistant';
          content: string;
        }[],
    };
  }
}