feat: refactor template_engine to only consume prompt_var role fields [AC-MRS-14]

ai-service/app/services/flow/template_engine.py

@@ -1,6 +1,7 @@
 """
 Template Engine for Intent-Driven Script Flow.
 [AC-IDS-06] Template mode script generation with variable filling.
+[AC-MRS-14] 只消费 field_roles 包含 prompt_var 的字段
 """
 
 import asyncio
@@ -8,40 +9,53 @@ import logging
 import re
 from typing import Any
 
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.models.entities import FieldRole
+from app.services.mid.role_based_field_provider import RoleBasedFieldProvider
+
 logger = logging.getLogger(__name__)
 
 
 class TemplateEngine:
     """
     [AC-IDS-06] Template script engine.
+    [AC-MRS-14] 只消费 field_roles 包含 prompt_var 的字段
+    
     Fills template variables using context or LLM generation.
     """
 
     VARIABLE_PATTERN = re.compile(r'\{(\w+)\}')
     DEFAULT_TIMEOUT = 5.0
 
-    def __init__(self, llm_client: Any = None):
+    def __init__(self, llm_client: Any = None, session: AsyncSession | None = None):
         """
         Initialize TemplateEngine.
 
         Args:
             llm_client: LLM client for variable generation (optional)
+            session: Database session for role-based field provider (optional)
         """
         self._llm_client = llm_client
+        self._session = session
+        self._role_provider = RoleBasedFieldProvider(session) if session else None
 
     async def fill_template(
         self,
         template: str,
         context: dict[str, Any] | None,
         history: list[dict[str, str]] | None,
+        tenant_id: str | None = None,
     ) -> str:
         """
         [AC-IDS-06] Fill template variables with context or LLM-generated values.
+        [AC-MRS-14] 只消费 prompt_var 角色的字段
 
         Args:
             template: Script template with {variable} placeholders
             context: Session context with collected inputs
             history: Conversation history for context
+            tenant_id: Tenant ID for role-based field filtering
 
         Returns:
             Filled template string
@@ -52,11 +66,28 @@ class TemplateEngine:
             if not variables:
                 return template
 
+            prompt_var_fields = []
+            if tenant_id and self._role_provider:
+                prompt_var_fields = await self._role_provider.get_prompt_var_field_keys(tenant_id)
+                logger.info(
+                    f"[AC-MRS-14] Retrieved {len(prompt_var_fields)} prompt_var fields for tenant={tenant_id}: {prompt_var_fields}"
+                )
+
+            filtered_context = {}
+            if context:
+                if prompt_var_fields:
+                    filtered_context = {k: v for k, v in context.items() if k in prompt_var_fields}
+                    logger.info(
+                        f"[AC-MRS-14] Applied prompt_var context: {list(filtered_context.keys())}"
+                    )
+                else:
+                    filtered_context = context
+
             variable_values = {}
             for var in variables:
                 value = await self._generate_variable_value(
                     variable_name=var,
-                    context=context,
+                    context=filtered_context,
                     history=history,
                 )
                 variable_values[var] = value