import type { ChatMessage, RequestAIParams } from "./types"

/**
 * Generic, reusable OpenAI-compatible chat completion request.
 * Not coupled to any specific business logic.
 */
export async function requestOpenAICompatible(params: RequestAIParams): Promise<string> {
  const {
    baseUrl,
    apiKey,
    model,
    systemPrompt,
    customPrompt,
    messages,
    temperature = 0.3,
    maxTokens = 4000,
    stream = false,
    signal,
  } = params

  const finalMessages: ChatMessage[] = []

  if (systemPrompt) {
    finalMessages.push({ role: "system", content: systemPrompt })
  }

  if (customPrompt) {
    finalMessages.push({ role: "user", content: customPrompt })
  }

  finalMessages.push(...messages)

  const url = `${baseUrl.replace(/\/$/, "")}/chat/completions`

  let response: Response
  try {
    response = await fetch(url, {
      method: "POST",
      signal,
      headers: {
        "Content-Type": "application/json",
        Authorization: `Bearer ${apiKey}`,
      },
      body: JSON.stringify({
        model,
        messages: finalMessages,
        temperature,
        max_tokens: maxTokens,
        stream,
      }),
    })
  } catch (err) {
    if (err instanceof DOMException && err.name === "AbortError") throw err
    throw new Error(`无法连接到 AI 服务：${(err as Error).message}`)
  }

  if (!response.ok) {
    const errorText = await response.text().catch(() => "")
    throw new Error(`AI 请求失败：${response.status} ${errorText}`)
  }

  const data = await response.json()
  const content = data?.choices?.[0]?.message?.content

  if (!content) {
    throw new Error("AI 没有返回有效内容")
  }

  return content as string
}