feat: add local chat provider and CLI

src/javis/providers/ollama.py

@@ -0,0 +1,82 @@
+"""Ollama implementation of the local model provider contract."""
+
+from __future__ import annotations
+
+import json
+import socket
+from urllib.error import HTTPError, URLError
+from urllib.request import Request, urlopen
+
+from javis.providers.base import (
+    ChatMessage,
+    InvalidProviderResponseError,
+    ModelNotInstalledError,
+    ProviderTimeoutError,
+    ProviderUnavailableError,
+    ResponseAbortedError,
+)
+
+
+class OllamaProvider:
+    name = "ollama"
+
+    def __init__(self, model: str, base_url: str, timeout_seconds: float) -> None:
+        self.model = model
+        self._endpoint = f"{base_url.rstrip('/')}/api/chat"
+        self._timeout_seconds = timeout_seconds
+
+    def chat(self, messages: list[ChatMessage]) -> str:
+        payload = {
+            "model": self.model,
+            "messages": [
+                {"role": message.role, "content": message.content} for message in messages
+            ],
+            "stream": False,
+            "think": False,
+        }
+        request = Request(
+            self._endpoint,
+            data=json.dumps(payload).encode("utf-8"),
+            headers={"Content-Type": "application/json"},
+            method="POST",
+        )
+
+        try:
+            with urlopen(request, timeout=self._timeout_seconds) as response:
+                raw_response = response.read()
+        except HTTPError as exc:
+            details = exc.read().decode("utf-8", errors="replace")
+            if exc.code == 404 or "not found" in details.lower():
+                raise ModelNotInstalledError(
+                    f"Das lokale Modell '{self.model}' ist nicht installiert."
+                ) from exc
+            raise ProviderUnavailableError(f"Ollama meldet HTTP-Fehler {exc.code}.") from exc
+        except TimeoutError as exc:
+            raise ProviderTimeoutError(
+                "Die Modellantwort hat das Zeitlimit überschritten."
+            ) from exc
+        except URLError as exc:
+            if isinstance(exc.reason, (TimeoutError, socket.timeout)):
+                raise ProviderTimeoutError(
+                    "Die Modellantwort hat das Zeitlimit überschritten."
+                ) from exc
+            raise ProviderUnavailableError(
+                "Ollama ist unter der konfigurierten lokalen Adresse nicht erreichbar."
+            ) from exc
+
+        try:
+            result = json.loads(raw_response)
+        except (json.JSONDecodeError, UnicodeDecodeError) as exc:
+            raise InvalidProviderResponseError(
+                "Ollama hat keine gültige JSON-Antwort geliefert."
+            ) from exc
+
+        if result.get("done") is False:
+            raise ResponseAbortedError("Die Modellantwort wurde vorzeitig abgebrochen.")
+
+        content = result.get("message", {}).get("content")
+        if not isinstance(content, str) or not content.strip():
+            raise InvalidProviderResponseError(
+                "Ollama hat keine verwendbare Textantwort geliefert."
+            )
+        return content.strip()