feat: add ollama provider

src/providers/ollama.js

@@ -0,0 +1,134 @@
+// 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 };
+  },
+};