"""适配器接口与中间数据形（ARCH §4.2/§4.4）。

适配器把 `LlmRequest` 翻译成目标厂商请求，并把响应/流/usage 翻译回统一中间形。
"""

from __future__ import annotations

from collections.abc import AsyncIterator
from typing import Protocol, runtime_checkable

from pydantic import BaseModel, ConfigDict

from ..types import LlmRequest


class Capabilities(BaseModel):
    structured_output: bool = False
    prefix_cache: bool = False
    thinking: bool = False


class ProviderUsage(BaseModel):
    input_tokens: int
    output_tokens: int
    cache_read_tokens: int = 0


class ProviderResult(BaseModel):
    model_config = ConfigDict(arbitrary_types_allowed=True)

    text: str
    usage: ProviderUsage
    parsed: BaseModel | None = None  # output_schema 命中时的结构化结果（§4.4）


class StreamChunk(BaseModel):
    """流式块：文本增量（usage=None），或末尾用量块（text=""）。"""

    text: str = ""
    usage: ProviderUsage | None = None


@runtime_checkable
class ProviderAdapter(Protocol):
    provider: str

    def capabilities(self) -> Capabilities: ...

    async def complete(self, req: LlmRequest, model: str) -> ProviderResult: ...

    def stream(self, req: LlmRequest, model: str) -> AsyncIterator[StreamChunk]: ...