Add core modules (prompt, template)

src/promptforge/core/template.py

@@ -0,0 +1,59 @@
+from typing import Any, Dict, List, Optional
+from jinja2 import Environment, BaseLoader, TemplateSyntaxError, StrictUndefined, UndefinedError
+from jinja2.exceptions import TemplateError
+
+from .prompt import PromptVariable
+from .exceptions import MissingVariableError, InvalidPromptError
+
+
+class TemplateEngine:
+    def __init__(self):
+        self.env = Environment(
+            loader=BaseLoader(),
+            autoescape=True,
+            trim_blocks=True,
+            lstrip_blocks=True,
+            undefined=StrictUndefined,
+        )
+
+    def get_variables(self, content: str) -> List[str]:
+        from jinja2 import meta
+        ast = self.env.parse(content)
+        return sorted(meta.find_undeclared_variables(ast))
+
+    def render(
+        self,
+        content: str,
+        variables: Optional[Dict[str, Any]] = None,
+        required_variables: Optional[List[PromptVariable]] = None,
+    ) -> str:
+        variables = variables.copy() if variables else {}
+        required_variables = required_variables or []
+
+        for var in required_variables:
+            if var.name not in variables and var.default is not None:
+                variables[var.name] = var.default
+
+        missing = []
+        for var in required_variables:
+            if var.required and var.name not in variables:
+                missing.append(var.name)
+
+        if missing:
+            raise MissingVariableError(
+                f"Missing required variables: {', '.join(missing)}"
+            )
+
+        for var in required_variables:
+            if var.name in variables and var.type.value == "boolean":
+                val = variables[var.name]
+                if isinstance(val, str):
+                    variables[var.name] = val.lower() in ("true", "1", "yes")
+
+        try:
+            template = self.env.from_string(content)
+            return template.render(**variables)
+        except TemplateSyntaxError as e:
+            raise InvalidPromptError(f"Template syntax error: {e.message}")
+        except (UndefinedError, TemplateError) as e:
+            raise InvalidPromptError(f"Template rendering error: {e}")