feat(M3-001): refactor ProviderService into IProviderAdapter pattern (#306)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/adapters/ollama.adapter.ts

@@ -0,0 +1,125 @@
+import { Logger } from '@nestjs/common';
+import type { ModelRegistry } from '@mariozechner/pi-coding-agent';
+import type {
+  CompletionEvent,
+  CompletionParams,
+  IProviderAdapter,
+  ModelInfo,
+  ProviderHealth,
+} from '@mosaic/types';
+
+/**
+ * Ollama provider adapter.
+ *
+ * Registers local Ollama models with the Pi ModelRegistry via the OpenAI-compatible
+ * completions API. Configuration is driven by environment variables:
+ *   OLLAMA_BASE_URL or OLLAMA_HOST — base URL of the Ollama instance
+ *   OLLAMA_MODELS              — comma-separated list of model IDs (default: llama3.2,codellama,mistral)
+ */
+export class OllamaAdapter implements IProviderAdapter {
+  readonly name = 'ollama';
+
+  private readonly logger = new Logger(OllamaAdapter.name);
+  private registeredModels: ModelInfo[] = [];
+
+  constructor(private readonly registry: ModelRegistry) {}
+
+  async register(): Promise<void> {
+    const ollamaUrl = process.env['OLLAMA_BASE_URL'] ?? process.env['OLLAMA_HOST'];
+    if (!ollamaUrl) {
+      this.logger.debug('Skipping Ollama provider registration: OLLAMA_BASE_URL not set');
+      return;
+    }
+
+    const modelsEnv = process.env['OLLAMA_MODELS'] ?? 'llama3.2,codellama,mistral';
+    const modelIds = modelsEnv
+      .split(',')
+      .map((id: string) => id.trim())
+      .filter(Boolean);
+
+    this.registry.registerProvider('ollama', {
+      baseUrl: `${ollamaUrl}/v1`,
+      apiKey: 'ollama',
+      api: 'openai-completions' as never,
+      models: modelIds.map((id) => ({
+        id,
+        name: id,
+        reasoning: false,
+        input: ['text'] as ('text' | 'image')[],
+        cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+        contextWindow: 8192,
+        maxTokens: 4096,
+      })),
+    });
+
+    this.registeredModels = modelIds.map((id) => ({
+      id,
+      provider: 'ollama',
+      name: id,
+      reasoning: false,
+      contextWindow: 8192,
+      maxTokens: 4096,
+      inputTypes: ['text'] as ('text' | 'image')[],
+      cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+    }));
+
+    this.logger.log(
+      `Ollama provider registered at ${ollamaUrl} with models: ${modelIds.join(', ')}`,
+    );
+  }
+
+  listModels(): ModelInfo[] {
+    return this.registeredModels;
+  }
+
+  async healthCheck(): Promise<ProviderHealth> {
+    const ollamaUrl = process.env['OLLAMA_BASE_URL'] ?? process.env['OLLAMA_HOST'];
+    if (!ollamaUrl) {
+      return {
+        status: 'down',
+        lastChecked: new Date().toISOString(),
+        error: 'OLLAMA_BASE_URL not configured',
+      };
+    }
+
+    const checkUrl = `${ollamaUrl}/v1/models`;
+    const start = Date.now();
+
+    try {
+      const res = await fetch(checkUrl, {
+        method: 'GET',
+        headers: { Accept: 'application/json' },
+        signal: AbortSignal.timeout(5000),
+      });
+      const latencyMs = Date.now() - start;
+
+      if (!res.ok) {
+        return {
+          status: 'degraded',
+          latencyMs,
+          lastChecked: new Date().toISOString(),
+          error: `HTTP ${res.status}`,
+        };
+      }
+
+      return { status: 'healthy', latencyMs, lastChecked: new Date().toISOString() };
+    } catch (err) {
+      const latencyMs = Date.now() - start;
+      const error = err instanceof Error ? err.message : String(err);
+      return { status: 'down', latencyMs, lastChecked: new Date().toISOString(), error };
+    }
+  }
+
+  /**
+   * createCompletion is reserved for future direct-completion use.
+   * The current integration routes completions through Pi SDK's ModelRegistry/AgentSession.
+   */
+  async *createCompletion(_params: CompletionParams): AsyncIterable<CompletionEvent> {
+    throw new Error(
+      'OllamaAdapter.createCompletion is not yet implemented. ' +
+        'Use Pi SDK AgentSession for completions.',
+    );
+    // Satisfy the AsyncGenerator return type — unreachable but required for TypeScript.
+    yield undefined as never;
+  }
+}