feat: add OCI GenAI streaming agent foundation

tests/test_oci_agent.py

@@ -0,0 +1,79 @@
+import json
+
+import pytest
+
+from voice_assistant.agent.oci import extract_text_delta
+
+
+def test_extract_text_delta():
+    payload = {
+        "index": 0,
+        "message": {
+            "role": "ASSISTANT",
+            "content": [
+                {
+                    "type": "TEXT",
+                    "text": "Olá",
+                }
+            ],
+        },
+    }
+
+    result = extract_text_delta(json.dumps(payload))
+
+    assert result == "Olá"
+
+
+def test_extract_text_delta_preserves_spaces():
+    payload = {
+        "message": {
+            "content": [
+                {
+                    "type": "TEXT",
+                    "text": " mundo",
+                }
+            ],
+        },
+    }
+
+    assert extract_text_delta(json.dumps(payload)) == " mundo"
+
+
+def test_extract_text_delta_ignores_empty_text():
+    payload = {
+        "message": {
+            "content": [
+                {
+                    "type": "TEXT",
+                    "text": "",
+                }
+            ],
+        },
+    }
+
+    assert extract_text_delta(json.dumps(payload)) is None
+
+
+def test_extract_text_delta_done():
+    assert extract_text_delta("[DONE]") is None
+
+
+def test_extract_text_delta_rejects_invalid_json():
+    with pytest.raises(ValueError, match="Invalid JSON"):
+        extract_text_delta("{invalid")
+
+
+def test_extract_text_delta_ignores_non_text_events():
+    payload = {
+        "message": {
+            "content": [
+                {
+                    "type": "OTHER",
+                    "text": "ignored",
+                }
+            ],
+        },
+    }
+
+    assert extract_text_delta(json.dumps(payload)) is None
+