Support iframe chatbot. (#3961)

### What problem does this PR solve?

#3909

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

agent/canvas.py

@@ -330,4 +330,7 @@ class Canvas(ABC):
                 q["value"] = v
 
     def get_preset_param(self):
-        return self.components["begin"]["obj"]._param.query
+        return self.components["begin"]["obj"]._param.query
+
+    def get_component_input_elements(self, cpnnm):
+        return self.components["begin"]["obj"].get_input_elements()

agent/component/base.py

@@ -476,7 +476,7 @@ class ComponentBase(ABC):
                     self._param.inputs.append({"component_id": q["component_id"],
                                                "content": "\n".join(
                                                    [str(d["content"]) for d in outs[-1].to_dict('records')])})
-                elif q["value"]:
+                elif q.get("value"):
                     self._param.inputs.append({"component_id": None, "content": q["value"]})
                     outs.append(pd.DataFrame([{"content": q["value"]}]))
             if outs:
@@ -526,6 +526,21 @@ class ComponentBase(ABC):
 
         return df
 
+    def get_input_elements(self):
+        assert self._param.query, "Please identify input parameters firstly."
+        eles = []
+        for q in self._param.query:
+            if q.get("component_id"):
+                if q["component_id"].split("@")[0].lower().find("begin") >= 0:
+                    cpn_id, key = q["component_id"].split("@")
+                    eles.extend(self._canvas.get_component(cpn_id)["obj"]._param.query)
+                    continue
+
+                eles.append({"key": q["key"], "component_id": q["component_id"]})
+            else:
+                eles.append({"key": q["key"]})
+        return eles
+
     def get_stream_input(self):
         reversed_cpnts = []
         if len(self._canvas.path) > 1:

agent/component/generate.py

@@ -17,6 +17,7 @@ import re
 from functools import partial
 import pandas as pd
 from api.db import LLMType
+from api.db.services.conversation_service import structure_answer
 from api.db.services.dialog_service import message_fit_in
 from api.db.services.llm_service import LLMBundle
 from api import settings
@@ -104,9 +105,16 @@ class Generate(ComponentBase):
         if answer.lower().find("invalid key") >= 0 or answer.lower().find("invalid api") >= 0:
             answer += " Please set LLM API-Key in 'User Setting -> Model providers -> API-Key'"
         res = {"content": answer, "reference": reference}
+        res = structure_answer(None, res, "", "")
 
         return res
 
+    def get_input_elements(self):
+        if self._param.parameters:
+            return self._param.parameters
+
+        return [{"key": "input"}]
+
     def _run(self, history, **kwargs):
         chat_mdl = LLMBundle(self._canvas.get_tenant_id(), LLMType.CHAT, self._param.llm_id)
         prompt = self._param.prompt