// Ollama chat provider adapter.
// Calls Ollama's /api/chat endpoint (OpenAI-compatible format) using native fetch().
// No external SDK dependency — zero new dependencies.

const DEFAULT_BASE_URL = "http://localhost:11434";
const DEFAULT_MODEL = "qwen3:latest";
const DEFAULT_TEMPERATURE = 0.2;
const DEFAULT_TIMEOUT_SECONDS = 60;

/**
 * Strip trailing slashes from base URL so path concatenation is always correct.
 */
function normalizeBaseUrl(raw) {
  return (raw || "").replace(/\/+$/, "");
}

/**
 * Derive a safe error category string from a caught error.
 * Does not create new Error classes — just returns a categorising label.
 */
function getErrorKind(error) {
  if (error?.name === "AbortError" || /timed?out/i.test(String(error.message ?? ""))) {
    return "OllamaTimeoutError";
  }

  const status = error?.status ?? error?.response?.status;
  if (typeof status === "number") {
    if (status === 404) return "OllamaModelNotFoundError";
    if (status === 422) return "OllamaValidationError";
    if (status === 501) return "OllamaApiNotAvailableError";
  }

  return "OllamaRequestError";
}

/**
 * Extract a safe error message, never leaking secrets or internals.
 */
function safeErrorMessage(error) {
  const msg = String(error.message ?? "");
  if (!msg) return "unknown Ollama error";
  return msg;
}

/**
 * Chat provider backed by Ollama's /api/chat endpoint.
 * Implements { send(reviewRequest, config) => Promise<{ content: string }> }.
 */
export const ollamaProvider = {
  /**
   * @param {{ prompt?: string }} reviewRequest - ProviderRequest (minimal — only prompt used).
   * @param {object} config - Full config from loadConfig().
   * @returns {Promise<{ content: string }>} Advisory response text.
   */
  async send(reviewRequest, config) {
    const baseUrl = normalizeBaseUrl(config?.ollamaBaseUrl || DEFAULT_BASE_URL);
    const model = config?.ollamaModel || DEFAULT_MODEL;
    const temperature =
      config?.ollamaTemperature != null
        ? Number(config.ollamaTemperature)
        : DEFAULT_TEMPERATURE;
    const timeoutSeconds =
      config?.ollamaTimeout != null
        ? Number(config.ollamaTimeout)
        : DEFAULT_TIMEOUT_SECONDS;

    const prompt = reviewRequest?.prompt || "";

    // Build the request body in OpenAI-compatible chat format.
    const requestBody = JSON.stringify({
      model,
      messages: [{ role: "system", content: prompt }],
      stream: false,
      options: {
        temperature: isNaN(temperature) ? DEFAULT_TEMPERATURE : temperature,
      },
    });

    // Build AbortController for timeout.
    const controller = new AbortController();
    const timeoutId = setTimeout(() => controller.abort(), timeoutSeconds * 1000);

    let response;
    try {
      response = await fetch(`${baseUrl}/api/chat`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: requestBody,
        signal: controller.signal,
      });
    } catch (error) {
      clearTimeout(timeoutId);

      const kind = getErrorKind(error);
      throw new Error(
        `Ollama API error (${kind}): ${safeErrorMessage(error)}`
      );
    } finally {
      clearTimeout(timeoutId);
    }

    // Handle non-2xx status codes.
    if (!response.ok) {
      let bodyText = "";
      try {
        bodyText = await response.text();
      } catch (_) {
        /* ignore unparseable error bodies */
      }

      const errObj = new Error(`HTTP ${response.status}`);
      errObj.status = response.status;
      const kind = getErrorKind(errObj);
      const detail = bodyText ? ` — ${bodyText.slice(0, 200)}` : "";
      throw new Error(
        `Ollama API error (${kind}): HTTP ${response.status}${detail}`
      );
    }

    // Parse JSON response.
    let data;
    try {
      data = await response.json();
    } catch (_) {
      throw new Error(
        "Ollama API error (OllamaRequestError): invalid JSON response."
      );
    }

    // Ollama /api/chat returns: { model, message: { role, content }, done }
    const content = data?.message?.content ?? "";
    return { content };
  },
};