feat: add optional llm extra with OpenRouter client

.github/workflows/test.yml

@@ -19,7 +19,7 @@ jobs:
           python -m pip install --upgrade setuptools wheel
           pip install poetry
           poetry config virtualenvs.create true
-          poetry install --with dev
+          poetry install --with dev --all-extras
       - name: Install Pandoc  # apt version seems too old
         uses: r-lib/actions/setup-pandoc@v2
       - name: Linting Checks

in2lambda/llm/__init__.py

@@ -0,0 +1,10 @@
+"""OpenRouter-backed LLM helpers used by ``in2lambda wizard``.
+
+Everything here is part of the optional ``llm`` extra
+(``pip install in2lambda[llm]``); importing this package without the extra is
+fine, but calling into it raises a clear error.
+"""
+
+from in2lambda.llm.client import DEFAULT_MODEL, get_client, resolve_model
+
+__all__ = ["DEFAULT_MODEL", "get_client", "resolve_model"]

in2lambda/llm/client.py

@@ -0,0 +1,76 @@
+"""Build an OpenAI-compatible client pointed at OpenRouter.
+
+Configuration is read from the environment (a local ``.env`` file is loaded if
+one is present):
+
+* ``OPENROUTER_API_KEY`` - required; create one at https://openrouter.ai/keys.
+* ``IN2LAMBDA_MODEL``    - optional; the model slug to use when none is passed
+  on the command line. Defaults to :data:`DEFAULT_MODEL`.
+"""
+
+import os
+from typing import Optional
+
+try:
+    from dotenv import load_dotenv
+except ImportError:  # pragma: no cover - provided by the `llm` extra
+    load_dotenv = None
+
+try:
+    import openai
+except ImportError:  # pragma: no cover - provided by the `llm` extra
+    openai = None
+
+OPENROUTER_BASE_URL = "https://openrouter.ai/api/v1"
+
+# A cheap, widely-available default. Override per run with --model or the
+# IN2LAMBDA_MODEL environment variable; any OpenRouter model slug works.
+DEFAULT_MODEL = "openai/gpt-4o-mini"
+
+_INSTALL_HINT = (
+    "in2lambda's LLM features need the 'llm' extra: pip install 'in2lambda[llm]'"
+)
+
+
+def resolve_model(cli_value: Optional[str] = None) -> str:
+    """Return the model slug to use.
+
+    Precedence: an explicit CLI value, then ``$IN2LAMBDA_MODEL``, then
+    :data:`DEFAULT_MODEL`.
+
+    Args:
+        cli_value: The value passed via ``--model``, if any.
+
+    Returns:
+        An OpenRouter model slug.
+
+    Examples:
+        >>> from in2lambda.llm.client import resolve_model
+        >>> resolve_model("anthropic/claude-3.5-haiku")
+        'anthropic/claude-3.5-haiku'
+    """
+    return cli_value or os.getenv("IN2LAMBDA_MODEL") or DEFAULT_MODEL
+
+
+def get_client() -> "openai.OpenAI":
+    """Return an OpenAI client configured to talk to OpenRouter.
+
+    Raises:
+        RuntimeError: if the ``llm`` extra is not installed, or
+            ``OPENROUTER_API_KEY`` is not set.
+    """
+    if openai is None:
+        raise RuntimeError(_INSTALL_HINT)
+
+    if load_dotenv is not None:
+        load_dotenv()
+
+    api_key = os.getenv("OPENROUTER_API_KEY")
+    if not api_key:
+        raise RuntimeError(
+            "OPENROUTER_API_KEY is not set. Create a key at "
+            "https://openrouter.ai/keys and put it in your environment or a "
+            ".env file."
+        )
+
+    return openai.OpenAI(base_url=OPENROUTER_BASE_URL, api_key=api_key)