HealthLog/src/lib/ai/openai-client.ts

import type { AIProvider, CompletionParams, CompletionResult } from "./types";

interface OpenAIClientConfig {
  apiKey: string;
  model: string;
  baseUrl: string;
}

export class OpenAIClient implements AIProvider {
  readonly type = "admin-key" as const;
  private config: OpenAIClientConfig;

  constructor(config: OpenAIClientConfig) {
    this.config = config;
  }

  async generateCompletion(
    params: CompletionParams,
  ): Promise<CompletionResult> {
    const url = `${this.config.baseUrl.replace(/\/$/, "")}/chat/completions`;

    const res = await fetch(url, {
      method: "POST",
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${this.config.apiKey}`,
      },
      body: JSON.stringify({
        model: this.config.model,
        messages: [
          { role: "system", content: params.systemPrompt },
          { role: "user", content: params.userPrompt },
        ],
        temperature: params.temperature ?? 0.3,
        max_tokens: params.maxTokens ?? 1000,
        response_format: { type: "json_object" },
      }),
    });

    if (!res.ok) {
      // Pull as much of the body as we can so upstream incidents (OpenAI 5xx,
      // model-not-found, quota exceeded) are diagnosable from logs instead of
      // surfacing as an opaque "OpenAI request failed (500)". Strip anything
      // that looks like an API key from the excerpt before logging.
      const rawBody = await res.text().catch(() => "");
      const bodyExcerpt = rawBody
        .slice(0, 500)
        .replace(/sk-[A-Za-z0-9_-]{8,}/g, "sk-***redacted***")
        .replace(/Bearer\s+[A-Za-z0-9_.-]+/gi, "Bearer ***redacted***");
      const err = new Error(`OpenAI request failed (${res.status})`);
      // Keep the body in a structured field rather than the message so
      // Error.message stays short and the excerpt lands in dedicated log
      // fields (bodyExcerpt) that can be filtered/truncated centrally.
      Object.assign(err, {
        httpStatus: res.status,
        upstream: "openai",
        model: this.config.model,
        bodyExcerpt,
      });
      throw err;
    }

    const json = await res.json();
    const content = json.choices?.[0]?.message?.content;

    if (!content) {
      throw new Error("OpenAI returned empty content");
    }

    return {
      content,
      tokensUsed: json.usage?.total_tokens ?? null,
      model: this.config.model,
      providerType: "admin-key",
    };
  }
}