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:
    # 仅校验真正影响运行闭环的必填字段；
    # 页面展示字段允许缺失，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:
    """补齐页面和其它模块常用的派生字段，避免模板层重复判断。"""
    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 _read_yaml_file(path: Path) -> dict:
    with path.open("r", encoding="utf-8") as file:
        return yaml.safe_load(file) or {}


def _collect_scenario_load_result() -> tuple[list[dict], list[dict]]:
    """
    统一读取配置目录中的所有场景文件。

    返回值：
    - scenarios: 校验通过的场景列表
    - issues: 非法 YAML / 缺字段等错误摘要，供首页展示
    """
    scenarios = []
    issues = []
    for path in _scenario_files():
        try:
            config = _read_yaml_file(path)
            scenarios.append(validate_scenario(config))
        except (yaml.YAMLError, ScenarioValidationError) as exc:
            issues.append(
                {
                    "file_name": path.name,
                    "message": str(exc),
                }
            )
    return scenarios, issues


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, _issues = _collect_scenario_load_result()
    return scenarios


def list_scenario_issues() -> list[dict]:
    """返回配置异常摘要，便于页面明确提示而不是直接 500。"""
    _scenarios, issues = _collect_scenario_load_result()
    return issues


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}")