dify/api/core/agent/agent/structured_chat.py

import re
from typing import List, Tuple, Any, Union, Sequence, Optional, cast

from langchain import BasePromptTemplate, PromptTemplate
from langchain.agents import StructuredChatAgent, AgentOutputParser, Agent
from langchain.agents.structured_chat.base import HUMAN_MESSAGE_TEMPLATE
from langchain.callbacks.base import BaseCallbackManager
from langchain.callbacks.manager import Callbacks
from langchain.memory.prompt import SUMMARY_PROMPT
from langchain.prompts import SystemMessagePromptTemplate, HumanMessagePromptTemplate, ChatPromptTemplate
from langchain.schema import AgentAction, AgentFinish, AIMessage, HumanMessage, OutputParserException, BaseMessage, \
    get_buffer_string
from langchain.tools import BaseTool
from langchain.agents.structured_chat.prompt import PREFIX, SUFFIX

from core.agent.agent.calc_token_mixin import CalcTokenMixin, ExceededLLMTokensLimitError
from core.chain.llm_chain import LLMChain
from core.model_providers.models.entity.model_params import ModelMode
from core.model_providers.models.llm.base import BaseLLM

FORMAT_INSTRUCTIONS = """Use a json blob to specify a tool by providing an action key (tool name) and an action_input key (tool input).
The nouns in the format of "Thought", "Action", "Action Input", "Final Answer" must be expressed in English.
Valid "action" values: "Final Answer" or {tool_names}

Provide only ONE action per $JSON_BLOB, as shown:

```
{{{{
  "action": $TOOL_NAME,
  "action_input": $INPUT
}}}}
```

Follow this format:

Question: input question to answer
Thought: consider previous and subsequent steps
Action:
```
$JSON_BLOB
```
Observation: action result
... (repeat Thought/Action/Observation N times)
Thought: I know what to respond
Action:
```
{{{{
  "action": "Final Answer",
  "action_input": "Final response to human"
}}}}
```"""


class AutoSummarizingStructuredChatAgent(StructuredChatAgent, CalcTokenMixin):
    moving_summary_buffer: str = ""
    moving_summary_index: int = 0
    summary_model_instance: BaseLLM = None

    class Config:
        """Configuration for this pydantic object."""

        arbitrary_types_allowed = True

    def should_use_agent(self, query: str):
        """
        return should use agent
        Using the ReACT mode to determine whether an agent is needed is costly,
        so it's better to just use an Agent for reasoning, which is cheaper.

        :param query:
        :return:
        """
        return True

    def plan(
        self,
        intermediate_steps: List[Tuple[AgentAction, str]],
        callbacks: Callbacks = None,
        **kwargs: Any,
    ) -> Union[AgentAction, AgentFinish]:
        """Given input, decided what to do.

        Args:
            intermediate_steps: Steps the LLM has taken to date,
                along with observations
            callbacks: Callbacks to run.
            **kwargs: User inputs.

        Returns:
            Action specifying what tool to use.
        """
        full_inputs = self.get_full_inputs(intermediate_steps, **kwargs)
        prompts, _ = self.llm_chain.prep_prompts(input_list=[self.llm_chain.prep_inputs(full_inputs)])

        messages = []
        if prompts:
            messages = prompts[0].to_messages()

        rest_tokens = self.get_message_rest_tokens(self.llm_chain.model_instance, messages)
        if rest_tokens < 0:
            full_inputs = self.summarize_messages(intermediate_steps, **kwargs)

        try:
            full_output = self.llm_chain.predict(callbacks=callbacks, **full_inputs)
        except Exception as e:
            new_exception = self.llm_chain.model_instance.handle_exceptions(e)
            raise new_exception

        try:
            agent_decision = self.output_parser.parse(full_output)
            if isinstance(agent_decision, AgentAction) and agent_decision.tool == 'dataset':
                tool_inputs = agent_decision.tool_input
                if isinstance(tool_inputs, dict) and 'query' in tool_inputs:
                    tool_inputs['query'] = kwargs['input']
                    agent_decision.tool_input = tool_inputs
            return agent_decision
        except OutputParserException:
            return AgentFinish({"output": "I'm sorry, the answer of model is invalid, "
                                          "I don't know how to respond to that."}, "")

    def summarize_messages(self, intermediate_steps: List[Tuple[AgentAction, str]], **kwargs):
        if len(intermediate_steps) >= 2 and self.summary_model_instance:
            should_summary_intermediate_steps = intermediate_steps[self.moving_summary_index:-1]
            should_summary_messages = [AIMessage(content=observation)
                                       for _, observation in should_summary_intermediate_steps]
            if self.moving_summary_index == 0:
                should_summary_messages.insert(0, HumanMessage(content=kwargs.get("input")))

            self.moving_summary_index = len(intermediate_steps)
        else:
            error_msg = "Exceeded LLM tokens limit, stopped."
            raise ExceededLLMTokensLimitError(error_msg)

        if self.moving_summary_buffer and 'chat_history' in kwargs:
            kwargs["chat_history"].pop()

        self.moving_summary_buffer = self.predict_new_summary(
            messages=should_summary_messages,
            existing_summary=self.moving_summary_buffer
        )

        if 'chat_history' in kwargs:
            kwargs["chat_history"].append(AIMessage(content=self.moving_summary_buffer))

        return self.get_full_inputs([intermediate_steps[-1]], **kwargs)

    def predict_new_summary(
        self, messages: List[BaseMessage], existing_summary: str
    ) -> str:
        new_lines = get_buffer_string(
            messages,
            human_prefix="Human",
            ai_prefix="AI",
        )

        chain = LLMChain(model_instance=self.summary_model_instance, prompt=SUMMARY_PROMPT)
        return chain.predict(summary=existing_summary, new_lines=new_lines)

    @classmethod
    def create_prompt(
            cls,
            tools: Sequence[BaseTool],
            prefix: str = PREFIX,
            suffix: str = SUFFIX,
            human_message_template: str = HUMAN_MESSAGE_TEMPLATE,
            format_instructions: str = FORMAT_INSTRUCTIONS,
            input_variables: Optional[List[str]] = None,
            memory_prompts: Optional[List[BasePromptTemplate]] = None,
    ) -> BasePromptTemplate:
        tool_strings = []
        for tool in tools:
            args_schema = re.sub("}", "}}}}", re.sub("{", "{{{{", str(tool.args)))
            tool_strings.append(f"{tool.name}: {tool.description}, args: {args_schema}")
        formatted_tools = "\n".join(tool_strings)
        tool_names = ", ".join([('"' + tool.name + '"') for tool in tools])
        format_instructions = format_instructions.format(tool_names=tool_names)
        template = "\n\n".join([prefix, formatted_tools, format_instructions, suffix])
        if input_variables is None:
            input_variables = ["input", "agent_scratchpad"]
        _memory_prompts = memory_prompts or []
        messages = [
            SystemMessagePromptTemplate.from_template(template),
            *_memory_prompts,
            HumanMessagePromptTemplate.from_template(human_message_template),
        ]
        return ChatPromptTemplate(input_variables=input_variables, messages=messages)

    @classmethod
    def create_completion_prompt(
            cls,
            tools: Sequence[BaseTool],
            prefix: str = PREFIX,
            format_instructions: str = FORMAT_INSTRUCTIONS,
            input_variables: Optional[List[str]] = None,
    ) -> PromptTemplate:
        """Create prompt in the style of the zero shot agent.

        Args:
            tools: List of tools the agent will have access to, used to format the
                prompt.
            prefix: String to put before the list of tools.
            input_variables: List of input variables the final prompt will expect.

        Returns:
            A PromptTemplate with the template assembled from the pieces here.
        """
        suffix = """Begin! Reminder to ALWAYS respond with a valid json blob of a single action. Use tools if necessary. Respond directly if appropriate. Format is Action:```$JSON_BLOB```then Observation:.
Question: {input}
Thought: {agent_scratchpad}
"""

        tool_strings = "\n".join([f"{tool.name}: {tool.description}" for tool in tools])
        tool_names = ", ".join([tool.name for tool in tools])
        format_instructions = format_instructions.format(tool_names=tool_names)
        template = "\n\n".join([prefix, tool_strings, format_instructions, suffix])
        if input_variables is None:
            input_variables = ["input", "agent_scratchpad"]
        return PromptTemplate(template=template, input_variables=input_variables)

    def _construct_scratchpad(
        self, intermediate_steps: List[Tuple[AgentAction, str]]
    ) -> str:
        agent_scratchpad = ""
        for action, observation in intermediate_steps:
            agent_scratchpad += action.log
            agent_scratchpad += f"\n{self.observation_prefix}{observation}\n{self.llm_prefix}"

        if not isinstance(agent_scratchpad, str):
            raise ValueError("agent_scratchpad should be of type string.")
        if agent_scratchpad:
            llm_chain = cast(LLMChain, self.llm_chain)
            if llm_chain.model_instance.model_mode == ModelMode.CHAT:
                return (
                    f"This was your previous work "
                    f"(but I haven't seen any of it! I only see what "
                    f"you return as final answer):\n{agent_scratchpad}"
                )
            else:
                return agent_scratchpad
        else:
            return agent_scratchpad

    @classmethod
    def from_llm_and_tools(
            cls,
            model_instance: BaseLLM,
            tools: Sequence[BaseTool],
            callback_manager: Optional[BaseCallbackManager] = None,
            output_parser: Optional[AgentOutputParser] = None,
            prefix: str = PREFIX,
            suffix: str = SUFFIX,
            human_message_template: str = HUMAN_MESSAGE_TEMPLATE,
            format_instructions: str = FORMAT_INSTRUCTIONS,
            input_variables: Optional[List[str]] = None,
            memory_prompts: Optional[List[BasePromptTemplate]] = None,
            **kwargs: Any,
    ) -> Agent:
        """Construct an agent from an LLM and tools."""
        cls._validate_tools(tools)
        if model_instance.model_mode == ModelMode.CHAT:
            prompt = cls.create_prompt(
                tools,
                prefix=prefix,
                suffix=suffix,
                human_message_template=human_message_template,
                format_instructions=format_instructions,
                input_variables=input_variables,
                memory_prompts=memory_prompts,
            )
        else:
            prompt = cls.create_completion_prompt(
                tools,
                prefix=prefix,
                format_instructions=format_instructions,
                input_variables=input_variables,
            )
        llm_chain = LLMChain(
            model_instance=model_instance,
            prompt=prompt,
            callback_manager=callback_manager,
        )
        tool_names = [tool.name for tool in tools]
        _output_parser = output_parser
        return cls(
            llm_chain=llm_chain,
            allowed_tools=tool_names,
            output_parser=_output_parser,
            **kwargs,
        )