from typing import Sequence

from langchain_core.language_models import BaseLanguageModel
from langchain_core.prompts.chat import ChatPromptTemplate
from langchain_core.runnables import Runnable, RunnablePassthrough
from langchain_core.tools import BaseTool

from langchain.agents.format_scratchpad import format_log_to_messages
from langchain.agents.json_chat.prompt import TEMPLATE_TOOL_RESPONSE
from langchain.agents.output_parsers import JSONAgentOutputParser
from langchain.tools.render import render_text_description


def create_json_chat_agent(
    llm: BaseLanguageModel, tools: Sequence[BaseTool], prompt: ChatPromptTemplate
) -> Runnable:
    """Create an agent that uses JSON to format its logic, build for Chat Models.

    Examples:


        .. code-block:: python

            from langchain import hub
            from langchain_community.chat_models import ChatOpenAI
            from langchain.agents import AgentExecutor, create_json_chat_agent

            prompt = hub.pull("hwchase17/react-chat-json")
            model = ChatOpenAI()
            tools = ...

            agent = create_json_chat_agent(model, tools, prompt)
            agent_executor = AgentExecutor(agent=agent, tools=tools)

            agent_executor.invoke({"input": "hi"})

            # Using with chat history
            from langchain_core.messages import AIMessage, HumanMessage
            agent_executor.invoke(
                {
                    "input": "what's my name?",
                    "chat_history": [
                        HumanMessage(content="hi! my name is bob"),
                        AIMessage(content="Hello Bob! How can I assist you today?"),
                    ],
                }
            )

    Args:
        llm: LLM to use as the agent.
        tools: Tools this agent has access to.
        prompt: The prompt to use, must have input keys of
            `tools`, `tool_names`, and `agent_scratchpad`.

    Returns:
        A runnable sequence representing an agent. It takes as input all the same input
        variables as the prompt passed in does. It returns as output either an
        AgentAction or AgentFinish.

    """
    missing_vars = {"tools", "tool_names", "agent_scratchpad"}.difference(
        prompt.input_variables
    )
    if missing_vars:
        raise ValueError(f"Prompt missing required variables: {missing_vars}")

    prompt = prompt.partial(
        tools=render_text_description(list(tools)),
        tool_names=", ".join([t.name for t in tools]),
    )
    llm_with_stop = llm.bind(stop=["\nObservation"])

    agent = (
        RunnablePassthrough.assign(
            agent_scratchpad=lambda x: format_log_to_messages(
                x["intermediate_steps"], template_tool_response=TEMPLATE_TOOL_RESPONSE
            )
        )
        | prompt
        | llm_with_stop
        | JSONAgentOutputParser()
    )
    return agent