"""统一意图分类出口，业务 Agent 不得自行解析模型分类结果。"""

import json
from typing import Any, Protocol

from pydantic import BaseModel, ConfigDict, Field, ValidationError

from app.core.contracts import IntentResult
from app.core.errors import RecoverableAgentError, ValidationAgentError
from app.service.model_gateway import ModelGenerationService


class IntentEndpointResolver(Protocol):
    async def resolve(self, *, agent_type: str, task_type: str) -> list[Any]: ...


class _IntentPayload(BaseModel):
    model_config = ConfigDict(extra="forbid")

    intent: str = Field(min_length=1, max_length=64)
    confidence: float = Field(ge=0, le=1)


class IntentClassifier:
    """使用已路由模型输出严格 JSON，并绑定 Agent 声明的意图集合。"""

    def __init__(self, model_service: ModelGenerationService, *, threshold: float = 0.65) -> None:
        if not 0 <= threshold <= 1:
            raise ValueError("intent threshold must be between 0 and 1")
        self.model_service = model_service
        self.threshold = threshold

    async def classify(
        self, *, message: str, supported_intents: tuple[str, ...], endpoints: list[Any]
    ) -> IntentResult:
        if not message.strip():
            raise ValidationAgentError("待分类消息不能为空")
        if not supported_intents:
            raise ValidationAgentError("Agent 未声明支持的意图")
        prompt = (
            "请仅输出 JSON，不要 Markdown。字段必须为 intent 和 confidence。"
            f"intent 只能从 {list(supported_intents)!r} 中选择，confidence 为 0 到 1 的数字。"
            f"用户消息：{message}"
        )
        execution = await self.model_service.generate(endpoints, prompt)
        payload = self._parse(execution.text)
        if payload.intent not in supported_intents:
            raise ValidationAgentError("模型返回了未声明的意图")
        return IntentResult(
            intent=payload.intent,
            confidence=payload.confidence,
            needs_clarification=payload.confidence < self.threshold,
        )

    @staticmethod
    def _parse(text: str) -> _IntentPayload:
        candidate = text.strip()
        if candidate.startswith("```"):
            candidate = candidate.removeprefix("```")
            candidate = candidate.removeprefix("json").removesuffix("```").strip()
        try:
            value = json.loads(candidate)
            return _IntentPayload.model_validate(value)
        except (json.JSONDecodeError, ValidationError, TypeError) as exc:
            raise RecoverableAgentError("模型意图输出不是有效 JSON") from exc