from google import genai
from google.genai import types

from backend.app.core.config import settings

_client: genai.Client | None = None


def get_client() -> genai.Client:
    global _client
    if _client is None:
        _client = genai.Client(api_key=settings.GEMINI_API_KEY)
    return _client


def chat_sync(
    messages: list[dict[str, str]],
    system_instruction: str | None = None,
    temperature: float = 0.7,
    max_tokens: int = 8192,
) -> str:
    """
    Synchronous chat with Gemini.

    messages: list of {"role": "user"|"model", "text": "..."}
    Returns the model's text response.
    """
    client = get_client()

    contents = [
        types.Content(
            role=m["role"],
            parts=[types.Part.from_text(text=m["text"])],
        )
        for m in messages
    ]

    config = types.GenerateContentConfig(
        temperature=temperature,
        max_output_tokens=max_tokens,
    )
    if system_instruction:
        config.system_instruction = system_instruction

    response = client.models.generate_content(
        model=settings.GEMINI_MODEL,
        contents=contents,
        config=config,
    )

    return response.text or ""


async def chat_async(
    messages: list[dict[str, str]],
    system_instruction: str | None = None,
    temperature: float = 0.7,
    max_tokens: int = 8192,
) -> str:
    """
    Async chat with Gemini.

    messages: list of {"role": "user"|"model", "text": "..."}
    Returns the model's text response.
    """
    client = get_client()

    contents = [
        types.Content(
            role=m["role"],
            parts=[types.Part.from_text(text=m["text"])],
        )
        for m in messages
    ]

    config = types.GenerateContentConfig(
        temperature=temperature,
        max_output_tokens=max_tokens,
    )
    if system_instruction:
        config.system_instruction = system_instruction

    response = await client.aio.models.generate_content(
        model=settings.GEMINI_MODEL,
        contents=contents,
        config=config,
    )

    return response.text or ""


async def chat_stream(
    messages: list[dict[str, str]],
    system_instruction: str | None = None,
    temperature: float = 0.7,
    max_tokens: int = 8192,
):
    """
    Async streaming chat with Gemini. Yields text chunks.

    messages: list of {"role": "user"|"model", "text": "..."}
    """
    client = get_client()

    contents = [
        types.Content(
            role=m["role"],
            parts=[types.Part.from_text(text=m["text"])],
        )
        for m in messages
    ]

    config = types.GenerateContentConfig(
        temperature=temperature,
        max_output_tokens=max_tokens,
    )
    if system_instruction:
        config.system_instruction = system_instruction

    async for chunk in client.aio.models.generate_content_stream(
        model=settings.GEMINI_MODEL,
        contents=contents,
        config=config,
    ):
        if chunk.text:
            yield chunk.text