from pathlib import Path

import yaml
from django.conf import settings


REQUIRED_FIELDS = [
    ("id",),
    ("name",),
    ("description",),
    ("agent", "role"),
    ("agent", "goal"),
    ("agent", "instructions"),
    ("rag", "enabled"),
    ("tools",),
    ("output", "type"),
    ("audit", "enabled"),
]


class ScenarioNotFound(KeyError):
    pass


class ScenarioValidationError(ValueError):
    pass


def _get_nested(config: dict, path: tuple[str, ...]):
    value = config
    for key in path:
        if not isinstance(value, dict) or key not in value:
            raise ScenarioValidationError("缺失必填字段: " + ".".join(path))
        value = value[key]
    return value


def validate_scenario(config: dict) -> dict:
    # 只校验真正影响运行闭环的必填字段；
    # 页面展示类字段如 applicable_questions 允许缺失，并在归一化阶段补默认值。
    for field_path in REQUIRED_FIELDS:
        _get_nested(config, field_path)
    return normalize_scenario(config)


def normalize_scenario(config: dict) -> dict:
    """补齐页面和其他模块常用的派生字段，减少模板中的条件判断。"""
    normalized = dict(config)
    normalized["applicable_questions"] = list(config.get("applicable_questions") or [])
    normalized["rag"] = dict(config.get("rag", {}))
    normalized["rag"]["enabled"] = bool(normalized["rag"].get("enabled"))
    normalized["tools"] = list(config.get("tools") or [])
    normalized["tool_count"] = len(normalized["tools"])
    normalized["is_enabled"] = True
    return normalized


def _scenario_files() -> list[Path]:
    config_dir = Path(settings.SCENARIO_CONFIG_DIR)
    if not config_dir.exists():
        return []
    return sorted([*config_dir.glob("*.yaml"), *config_dir.glob("*.yml")])


def list_scenarios() -> list[dict]:
    # 首页每次读取最新 YAML，便于复试现场快速改题。
    scenarios = []
    for path in _scenario_files():
        with path.open("r", encoding="utf-8") as file:
            config = yaml.safe_load(file) or {}
        scenarios.append(validate_scenario(config))
    return scenarios


def get_scenario(scenario_id: str) -> dict:
    for scenario in list_scenarios():
        if scenario["id"] == scenario_id:
            return scenario
    raise ScenarioNotFound(f"场景不存在: {scenario_id}")