const DEFAULT_TIMEOUT_MS = 45_000;

function completionEndpoint(apiUrl) {
  const value = String(apiUrl || "").replace(/\/+$/, "");
  return /\/chat\/completions$/i.test(value) ? value : `${value}/chat/completions`;
}

function extractJson(text) {
  const value = String(text || "").trim();
  if (!value) throw new Error("model_response_empty");
  try { return JSON.parse(value); } catch {}
  const fenced = value.match(/```(?:json)?\s*([\s\S]*?)```/i);
  if (fenced) return JSON.parse(fenced[1]);
  const first = value.indexOf("{");
  const last = value.lastIndexOf("}");
  if (first >= 0 && last > first) return JSON.parse(value.slice(first, last + 1));
  throw new Error("model_response_not_json");
}

export class DeepSeekJsonClient {
  constructor({
    apiKey = process.env.DEEPSEEK_API_KEY,
    apiUrl = process.env.DEEPSEEK_API_URL || "https://api.deepseek.com/v1",
    model = process.env.DEEPSEEK_MODEL || "deepseek-chat",
    fetchImpl = globalThis.fetch,
    timeoutMs = DEFAULT_TIMEOUT_MS,
  } = {}) {
    if (!apiKey) throw new Error("deepseek_api_key_missing");
    if (!fetchImpl) throw new Error("fetch_unavailable");
    this.apiKey = apiKey;
    this.apiUrl = apiUrl;
    this.model = model;
    this.fetchImpl = fetchImpl;
    this.timeoutMs = timeoutMs;
  }

  async interpret(input) {
    const controller = new AbortController();
    const timer = setTimeout(() => controller.abort(), this.timeoutMs);
    try {
      const response = await this.fetchImpl(completionEndpoint(this.apiUrl), {
        method: "POST",
        headers: {
          authorization: `Bearer ${this.apiKey}`,
          "content-type": "application/json",
        },
        body: JSON.stringify({
          model: this.model,
          stream: false,
          temperature: 0.2,
          response_format: { type: "json_object" },
          messages: [
            {
              role: "system",
              content: "你是TCS母体大脑的有界语言理解器官。只输出一个JSON对象，不输出隐藏思维过程。不得把候选理解写成事实、不得发明现实权限或冰朔的新意志。",
            },
            {
              role: "user",
              content: JSON.stringify({
                instruction: "理解语言意图与因果关系。精确输出schema,event_id,event_sha256,summary,intent,causal_links,questions,novelty,correction_weight,evidence_weight,next_cognitive_action。causal_links与questions是字符串数组；三个weight是0到100整数；schema必须是guanghu.tcs-mother-interpretation/v1；id和sha必须原样复制。next_cognitive_action只能是COMPARE_WITH_MEMORY、REQUEST_EVIDENCE、REVIEW_CORRECTION、LINK_CROSS_DOMAIN、HOLD_CANDIDATE之一。",
                runtime_input: input,
              }),
            },
          ],
        }),
        signal: controller.signal,
      });
      if (!response.ok) throw new Error(`model_http_${response.status}`);
      const payload = await response.json();
      return extractJson(payload?.choices?.[0]?.message?.content);
    } finally {
      clearTimeout(timer);
    }
  }
}

export { completionEndpoint, extractJson };