Initial upload: Local LLM Prompt Manager CLI tool

src/templates.py

@@ -0,0 +1,59 @@
+"""Template engine for prompt variable substitution."""
+
+from typing import Any
+
+from jinja2 import BaseLoader, Environment
+from jinja2.exceptions import UndefinedError
+
+from .models import Prompt
+
+
+class TemplateEngine:
+    """Handles Jinja2 template rendering for prompts."""
+
+    def __init__(self):
+        self.env = Environment(
+            loader=BaseLoader(),
+            trim_blocks=True,
+            lstrip_blocks=True,
+        )
+
+    def render(self, template: str, variables: dict[str, Any]) -> str:
+        """Render a template with the provided variables."""
+        try:
+            tmpl = self.env.from_string(template)
+            return tmpl.render(**variables)
+        except UndefinedError as e:
+            raise ValueError(f"Missing template variable: {e}") from None
+
+    def render_prompt(self, prompt: Prompt, variables: dict[str, Any]) -> str:
+        """Render a prompt with the provided variables."""
+        missing = self._check_required_variables(prompt, variables)
+        if missing:
+            raise ValueError(f"Missing required variables: {', '.join(missing)}")
+        return self.render(prompt.template, variables)
+
+    def _check_required_variables(
+        self, prompt: Prompt, variables: dict[str, Any]
+    ) -> list[str]:
+        """Check if all required variables are provided."""
+        required = prompt.get_required_variables()
+        return [v for v in required if v not in variables or variables[v] is None]
+
+    def extract_variables(self, template: str) -> set[str]:
+        """Extract variable names from a template."""
+        try:
+            ast = self.env.parse(template)
+            variables = self.env.find_undeclared_variables(ast)
+            return variables
+        except Exception:
+            return set()
+
+    def validate_variables(
+        self, prompt: Prompt, variables: dict[str, Any]
+    ) -> list[str]:
+        """Validate that provided variables are valid for the prompt."""
+        extracted = self.extract_variables(prompt.template)
+        provided = set(variables.keys())
+        invalid = provided - extracted
+        return list(invalid)