"""Functionality for loading agents."""
import json
from pathlib import Path
from typing import Any, Dict, List, Optional, Type, Union

import yaml

from langchain.agents.agent import BaseSingleActionAgent
from langchain.agents.agent_types import AgentType
from langchain.agents.chat.base import ChatAgent
from langchain.agents.conversational.base import ConversationalAgent
from langchain.agents.conversational_chat.base import ConversationalChatAgent
from langchain.agents.mrkl.base import ZeroShotAgent
from langchain.agents.react.base import ReActDocstoreAgent
from langchain.agents.self_ask_with_search.base import SelfAskWithSearchAgent
from langchain.agents.tools import Tool
from langchain.chains.loading import load_chain, load_chain_from_config
from langchain.llms.base import BaseLLM
from langchain.utilities.loading import try_load_from_hub

AGENT_TO_CLASS: Dict[AgentType, Type[BaseSingleActionAgent]] = {
    AgentType.ZERO_SHOT_REACT_DESCRIPTION: ZeroShotAgent,
    AgentType.REACT_DOCSTORE: ReActDocstoreAgent,
    AgentType.SELF_ASK_WITH_SEARCH: SelfAskWithSearchAgent,
    AgentType.CONVERSATIONAL_REACT_DESCRIPTION: ConversationalAgent,
    AgentType.CHAT_ZERO_SHOT_REACT_DESCRIPTION: ChatAgent,
    AgentType.CHAT_CONVERSATIONAL_REACT_DESCRIPTION: ConversationalChatAgent,
}

URL_BASE = "https://raw.githubusercontent.com/hwchase17/langchain-hub/master/agents/"


def _load_agent_from_tools(
    config: dict, llm: BaseLLM, tools: List[Tool], **kwargs: Any
) -> BaseSingleActionAgent:
    config_type = config.pop("_type")
    if config_type not in AGENT_TO_CLASS:
        raise ValueError(f"Loading {config_type} agent not supported")

    agent_cls = AGENT_TO_CLASS[config_type]
    combined_config = {**config, **kwargs}
    return agent_cls.from_llm_and_tools(llm, tools, **combined_config)


def load_agent_from_config(
    config: dict,
    llm: Optional[BaseLLM] = None,
    tools: Optional[List[Tool]] = None,
    **kwargs: Any,
) -> BaseSingleActionAgent:
    """Load agent from Config Dict."""
    if "_type" not in config:
        raise ValueError("Must specify an agent Type in config")
    load_from_tools = config.pop("load_from_llm_and_tools", False)
    if load_from_tools:
        if llm is None:
            raise ValueError(
                "If `load_from_llm_and_tools` is set to True, "
                "then LLM must be provided"
            )
        if tools is None:
            raise ValueError(
                "If `load_from_llm_and_tools` is set to True, "
                "then tools must be provided"
            )
        return _load_agent_from_tools(config, llm, tools, **kwargs)
    config_type = config.pop("_type")

    if config_type not in AGENT_TO_CLASS:
        raise ValueError(f"Loading {config_type} agent not supported")

    agent_cls = AGENT_TO_CLASS[config_type]
    if "llm_chain" in config:
        config["llm_chain"] = load_chain_from_config(config.pop("llm_chain"))
    elif "llm_chain_path" in config:
        config["llm_chain"] = load_chain(config.pop("llm_chain_path"))
    else:
        raise ValueError("One of `llm_chain` and `llm_chain_path` should be specified.")
    combined_config = {**config, **kwargs}
    return agent_cls(**combined_config)  # type: ignore


def load_agent(path: Union[str, Path], **kwargs: Any) -> BaseSingleActionAgent:
    """Unified method for loading a agent from LangChainHub or local fs."""
    if hub_result := try_load_from_hub(
        path, _load_agent_from_file, "agents", {"json", "yaml"}
    ):
        return hub_result
    else:
        return _load_agent_from_file(path, **kwargs)


def _load_agent_from_file(
    file: Union[str, Path], **kwargs: Any
) -> BaseSingleActionAgent:
    """Load agent from file."""
    # Convert file to Path object.
    if isinstance(file, str):
        file_path = Path(file)
    else:
        file_path = file
    # Load from either json or yaml.
    if file_path.suffix == ".json":
        with open(file_path) as f:
            config = json.load(f)
    elif file_path.suffix == ".yaml":
        with open(file_path, "r") as f:
            config = yaml.safe_load(f)
    else:
        raise ValueError("File type must be json or yaml")
    # Load the agent from the config now.
    return load_agent_from_config(config, **kwargs)