"""统一意图分类出口，业务 Agent 不得自行解析模型分类结果。

运行期可选的配置来源是 `agent_intent_config` 中 `status='active'` 的行：装载后只用于
**增强分类提示与置信度阈值**，不改变任何既有契约——仍然是严格 JSON 输出、格式违约与
未声明意图一律失败关闭、意图必须落在 `AgentDefinition.supported_intents` 内、
`needs_clarification = confidence < 阈值`。
"""

import json
from collections.abc import Awaitable, Callable
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 IntentConfigEntry(BaseModel):
    """`agent_intent_config` 生效行在分类链路上的投影（只带分类用得到的字段）。"""

    model_config = ConfigDict(frozen=True)

    intent_code: str = Field(min_length=1, max_length=64)
    intent_name: str = Field(default="", max_length=128)
    description: str | None = Field(default=None, max_length=500)
    examples: tuple[str, ...] = ()
    classifier_instruction: str | None = None
    confidence_threshold: float = Field(default=0.6, ge=0, le=1)


# 装载器按 `agent_type` 读取当前生效的意图配置；无配置时返回空元组。
IntentConfigLoader = Callable[[str], Awaitable[tuple[IntentConfigEntry, ...]]]


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,
        config_loader: IntentConfigLoader | None = None,
    ) -> None:
        if not 0 <= threshold <= 1:
            raise ValueError("intent threshold must be between 0 and 1")
        self.model_service = model_service
        self.threshold = threshold
        self._config_loader = config_loader

    @property
    def config_loader(self) -> IntentConfigLoader | None:
        """暴露装载器便于装配自检（生产装配必须注入，测试可缺省）。"""
        return self._config_loader

    async def classify(
        self,
        *,
        message: str,
        supported_intents: tuple[str, ...],
        endpoints: list[Any],
        agent_type: str | None = None,
    ) -> 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")
        # 只认 AgentDefinition 声明过的意图：配置里多出来的意图既不进提示，也不放宽校验。
        loaded = await self._load(agent_type)
        configured = tuple(
            entry for entry in loaded if entry.intent_code in supported_intents
        )
        prompt = self._build_prompt(message, supported_intents, configured)
        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_for(payload.intent, configured),
        )

    async def _load(self, agent_type: str | None) -> tuple[IntentConfigEntry, ...]:
        if self._config_loader is None or agent_type is None:
            return ()
        return await self._config_loader(agent_type)

    def _threshold_for(self, intent: str, configured: tuple[IntentConfigEntry, ...]) -> float:
        """阈值语义不变（confidence < 阈值 → 需澄清），阈值取值优先生效配置。"""
        for entry in configured:
            if entry.intent_code == intent:
                return entry.confidence_threshold
        return self.threshold

    @staticmethod
    def _build_prompt(
        message: str,
        supported_intents: tuple[str, ...],
        configured: tuple[IntentConfigEntry, ...],
    ) -> str:
        lines = [
            "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。",
        ]
        if configured:
            lines.append("平台配置的意图说明：")
            for entry in configured:
                detail = f"- {entry.intent_code}"
                if entry.intent_name:
                    detail += f"（{entry.intent_name}）"
                if entry.description:
                    detail += f"：{entry.description}"
                if entry.examples:
                    detail += f"；示例：{' / '.join(entry.examples)}"
                lines.append(detail)
                if entry.classifier_instruction:
                    lines.append(f"  分类要求：{entry.classifier_instruction}")
        lines.append(f"用户消息：{message}")
        return "\n".join(lines)

    @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