import json

from pydantic_ai import Agent
from pydantic_ai_skills import SkillsToolset
from openai import AsyncOpenAI
from pydantic_ai.models.openai import OpenAIModel
from pydantic_ai.providers.openai import OpenAIProvider

from schemas import LoadPlanRequest, LoadPlanResult
from .load_plan_tools import (
    get_transport_vehicle_by_license_plate,
    list_unshipped_shipments,
)


class LoadPlanConfigurationError(RuntimeError):
    pass


class LoadPlanGuardrailError(RuntimeError):
    pass


def _required_env(name: str) -> str:
    import os

    value = os.getenv(name, "").strip()
    if not value:
        raise LoadPlanConfigurationError(f"Missing required environment variable: {name}")
    return value


def _env_positive_float(name: str, default: float) -> float:
    import os

    raw_value = os.getenv(name, str(default)).strip()
    try:
        parsed = float(raw_value)
    except ValueError as exc:
        raise LoadPlanConfigurationError(f"Environment variable {name} must be a number") from exc

    if parsed <= 0:
        raise LoadPlanConfigurationError(f"Environment variable {name} must be greater than 0")
    return parsed


def _build_model() -> OpenAIModel:
    openai_client = AsyncOpenAI(
        base_url=_required_env("LOAD_PLAN_BASE_URL"),
        api_key=_required_env("LOAD_PLAN_API_KEY"),
        timeout=_env_positive_float("LOAD_PLAN_REQUEST_TIMEOUT_SECONDS", 120.0),
    )
    provider = OpenAIProvider(
        openai_client=openai_client,
    )
    return OpenAIModel(
        _required_env("LOAD_PLAN_MODEL"),
        provider=provider,
    )


INSTRUCTIONS = (
    "你是一个装载规划 Agent。"
    "你的任务是根据请求中的 merchant_id、area 和 license_plate，"
    "调用工具获取待出货出货单与车辆容量，并严格遵守已加载的 skill 来选择出货单。"
    "你必须先获取出货单，再获取车辆容量。"
    "车辆容量按销售品条数计算，不按 quantity 米数计算。"
    "目标是在不超过车辆容量的前提下尽量多装；若无法满载，允许欠载，但必须给出 warning。"
    "不要臆造 sales_items、printing_job_width、面料类型、数量或容量。"
    "如果无法依据真实返回判断装载结果，就返回空的 selected_shipment_ids，并在 summary/warnings 中说明。"
)


def _build_user_prompt(request: LoadPlanRequest) -> str:
    request_json = json.dumps(request.model_dump(mode="json"), ensure_ascii=False, indent=2)
    return (
        "请根据下面的 LoadPlanRequest JSON 执行装载规划。\n"
        "你必须调用工具获取真实数据，并根据 skill 中的规则完成判断。\n\n"
        "LoadPlanRequest JSON:\n"
        f"{request_json}"
    )


def create_load_plan_agent() -> Agent[None, LoadPlanResult]:
    return Agent(
        model=_build_model(),
        instructions=INSTRUCTIONS,
        output_type=LoadPlanResult,
        tools=[
            get_transport_vehicle_by_license_plate,
            list_unshipped_shipments,
        ],
        toolsets=[
            SkillsToolset(
                directories=["./skills"],
                auto_reload=True,
                exclude_tools={"run_skill_script"},
            )
        ],
    )


async def run_load_plan(request: LoadPlanRequest) -> LoadPlanResult:
    agent = create_load_plan_agent()
    async with agent:
        result = await agent.run(_build_user_prompt(request))
    return result.output