fix: resolve CI linting and type errors

src/promptforge/core/template.py

@@ -1,3 +1,5 @@
+"""Jinja2-based template engine for prompt rendering."""
+
 from typing import Any, Dict, List, Optional
 from jinja2 import Environment, BaseLoader, TemplateSyntaxError, StrictUndefined, UndefinedError
 from jinja2.exceptions import TemplateError
@@ -7,6 +9,8 @@ from .exceptions import MissingVariableError, InvalidPromptError
 
 
 class TemplateEngine:
+    """Jinja2 template engine for prompt rendering with variable substitution."""
+
     def __init__(self):
         self.env = Environment(
             loader=BaseLoader(),
@@ -17,6 +21,14 @@ class TemplateEngine:
         )
 
     def get_variables(self, content: str) -> List[str]:
+        """Extract variable names from template content.
+
+        Args:
+            content: Template content with {{variable}} syntax.
+
+        Returns:
+            List of variable names found.
+        """
         from jinja2 import meta
         ast = self.env.parse(content)
         return sorted(meta.find_undeclared_variables(ast))
@@ -27,6 +39,20 @@ class TemplateEngine:
         variables: Optional[Dict[str, Any]] = None,
         required_variables: Optional[List[PromptVariable]] = None,
     ) -> str:
+        """Render template with variable substitution.
+
+        Args:
+            content: Template content.
+            variables: Dictionary of variable values.
+            required_variables: List of variable definitions for validation.
+
+        Returns:
+            Rendered content.
+
+        Raises:
+            MissingVariableError: If a required variable is missing.
+            InvalidPromptError: If template has syntax errors.
+        """
         variables = variables.copy() if variables else {}
         required_variables = required_variables or []
 
@@ -57,3 +83,75 @@ class TemplateEngine:
             raise InvalidPromptError(f"Template syntax error: {e.message}")
         except (UndefinedError, TemplateError) as e:
             raise InvalidPromptError(f"Template rendering error: {e}")
+
+    def validate_variables(
+        self,
+        variables: Dict[str, Any],
+        required_variables: List[PromptVariable],
+    ) -> List[str]:
+        """Validate variable values against definitions.
+
+        Args:
+            variables: Provided variable values.
+            required_variables: Variable definitions.
+
+        Returns:
+            List of validation error messages (empty if valid).
+        """
+        errors = []
+
+        for var in required_variables:
+            if var.name not in variables:
+                if var.required and var.default is None:
+                    errors.append(f"Missing required variable: {var.name}")
+                continue
+
+            value = variables[var.name]
+            var_type = var.type.value
+
+            if var_type == "string":
+                if not isinstance(value, str):
+                    errors.append(f"{var.name}: must be a string")
+            elif var_type == "integer":
+                try:
+                    int(value)
+                except (ValueError, TypeError):
+                    errors.append(f"{var.name}: must be an integer")
+            elif var_type == "float":
+                try:
+                    float(value)
+                except (ValueError, TypeError):
+                    errors.append(f"{var.name}: must be a number")
+            elif var_type == "boolean":
+                if isinstance(value, str):
+                    if value.lower() not in ("true", "false", "0", "1"):
+                        errors.append(f"{var.name}: must be a boolean")
+            elif var_type == "choice":
+                if var.choices and value not in var.choices:
+                    errors.append(
+                        f"{var.name}: must be one of {', '.join(var.choices)}"
+                    )
+
+        return errors
+
+    def render_prompt(
+        self,
+        prompt_content: str,
+        variables: Dict[str, Any],
+        variable_definitions: List[PromptVariable],
+    ) -> str:
+        """Render a complete prompt with validation.
+
+        Args:
+            prompt_content: Raw prompt template content.
+            variables: Variable values.
+            variable_definitions: Variable definitions from prompt.
+
+        Returns:
+            Rendered prompt string.
+        """
+        errors = self.validate_variables(variables, variable_definitions)
+        if errors:
+            raise MissingVariableError(f"Variable validation failed: {', '.join(errors)}")
+
+        return self.render(prompt_content, variables, variable_definitions)