import asyncio
from functools import partial
from typing import Any

from openhands.core.exceptions import UserCancelledError
from openhands.core.logger import openhands_logger as logger
from openhands.llm.async_llm import LLM_RETRY_EXCEPTIONS, AsyncLLM
from openhands.llm.llm import REASONING_EFFORT_SUPPORTED_MODELS


class StreamingLLM(AsyncLLM):
    """Streaming LLM class."""

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self._async_streaming_completion = partial(
            self._call_acompletion,
            model=self.config.model,
            api_key=self.config.api_key.get_secret_value()
            if self.config.api_key
            else None,
            base_url=self.config.base_url,
            api_version=self.config.api_version,
            custom_llm_provider=self.config.custom_llm_provider,
            max_tokens=self.config.max_output_tokens,
            timeout=self.config.timeout,
            temperature=self.config.temperature,
            top_p=self.config.top_p,
            drop_params=self.config.drop_params,
            stream=True,  # Ensure streaming is enabled
        )

        async_streaming_completion_unwrapped = self._async_streaming_completion

        @self.retry_decorator(
            num_retries=self.config.num_retries,
            retry_exceptions=LLM_RETRY_EXCEPTIONS,
            retry_min_wait=self.config.retry_min_wait,
            retry_max_wait=self.config.retry_max_wait,
            retry_multiplier=self.config.retry_multiplier,
        )
        async def async_streaming_completion_wrapper(*args, **kwargs):
            messages: list[dict[str, Any]] | dict[str, Any] = []

            # some callers might send the model and messages directly
            # litellm allows positional args, like completion(model, messages, **kwargs)
            # see llm.py for more details
            if len(args) > 1:
                messages = args[1] if len(args) > 1 else args[0]
                kwargs['messages'] = messages

                # remove the first args, they're sent in kwargs
                args = args[2:]
            elif 'messages' in kwargs:
                messages = kwargs['messages']

            # ensure we work with a list of messages
            messages = messages if isinstance(messages, list) else [messages]

            # if we have no messages, something went very wrong
            if not messages:
                raise ValueError(
                    'The messages list is empty. At least one message is required.'
                )

            # Set reasoning effort for models that support it
            if self.config.model.lower() in REASONING_EFFORT_SUPPORTED_MODELS:
                kwargs['reasoning_effort'] = self.config.reasoning_effort

            self.log_prompt(messages)

            try:
                # Directly call and await litellm_acompletion
                resp = await async_streaming_completion_unwrapped(*args, **kwargs)

                # For streaming we iterate over the chunks
                async for chunk in resp:
                    # Check for cancellation before yielding the chunk
                    if (
                        hasattr(self.config, 'on_cancel_requested_fn')
                        and self.config.on_cancel_requested_fn is not None
                        and await self.config.on_cancel_requested_fn()
                    ):
                        raise UserCancelledError(
                            'LLM request cancelled due to CANCELLED state'
                        )
                    # with streaming, it is "delta", not "message"!
                    message_back = chunk['choices'][0]['delta'].get('content', '')
                    if message_back:
                        self.log_response(message_back)
                    self._post_completion(chunk)

                    yield chunk

            except UserCancelledError:
                logger.debug('LLM request cancelled by user.')
                raise
            except Exception as e:
                logger.error(f'Completion Error occurred:\n{e}')
                raise

            finally:
                # sleep for 0.1 seconds to allow the stream to be flushed
                if kwargs.get('stream', False):
                    await asyncio.sleep(0.1)

        self._async_streaming_completion = async_streaming_completion_wrapper

    @property
    def async_streaming_completion(self):
        """Decorator for the async litellm acompletion function with streaming."""
        return self._async_streaming_completion
