# SPDX-License-Identifier: Apache-2.0
from __future__ import annotations

import dataclasses
import functools
import json
from concurrent.futures import Future
from concurrent.futures._base import TimeoutError
from typing import Optional, Union, cast

from vllm.sampling_params import SamplingParams
from vllm.v1.structured_output.backend_types import (StructuredOutputGrammar,
                                                     StructuredOutputKey,
                                                     StructuredOutputOptions)


@dataclasses.dataclass
class StructuredOutputRequest:

    sampling_params: SamplingParams
    _grammar: Optional[Union[Future[StructuredOutputGrammar],
                             StructuredOutputGrammar]] = None

    def _check_grammar_completion(self) -> bool:
        # NOTE: We have to lazy import to gate circular imports
        from vllm.v1.request import RequestStatus

        if isinstance(self._grammar, Future):
            try:
                # We will check whether the future is ready within 100 us
                self._grammar = self._grammar.result(timeout=0.0001)
                self.status = RequestStatus.WAITING
            except TimeoutError:
                return False
        return True

    @property
    def is_grammar_ready(self) -> bool:
        return self._check_grammar_completion()

    @property
    def grammar(self) -> Optional[StructuredOutputGrammar]:
        completed = self._check_grammar_completion()
        return cast(Optional[StructuredOutputGrammar],
                    self._grammar) if completed else None

    @grammar.setter
    def grammar(
        self, grammar: Union[StructuredOutputGrammar,
                             Future[StructuredOutputGrammar]]
    ) -> None:
        self._grammar = grammar

    @functools.cached_property
    def structured_output_key(self) -> StructuredOutputKey:
        return get_structured_output_key(self.sampling_params)


def get_structured_output_key(
        sampling_params: SamplingParams) -> StructuredOutputKey:
    params = sampling_params.guided_decoding
    assert params is not None, "params can't be None."
    if params.json is not None:
        if not isinstance(params.json, str):
            json_str = json.dumps(params.json)
        else:
            json_str = params.json
        return (StructuredOutputOptions.JSON, json_str)
    elif params.json_object:
        return (StructuredOutputOptions.JSON_OBJECT, "")
    elif params.regex is not None:
        return (StructuredOutputOptions.REGEX, params.regex)
    elif params.choice is not None:
        if not isinstance(params.choice, str):
            json_str = json.dumps(params.choice)
        else:
            json_str = params.choice
        return (StructuredOutputOptions.CHOICE, json_str)
    elif params.grammar is not None:
        return (StructuredOutputOptions.GRAMMAR, params.grammar)
    else:
        raise ValueError("No valid structured output parameter found")
