"""Configuration loader for Airflow DAG Monitor."""

import dataclasses
import pathlib

import yaml


@dataclasses.dataclass
class AirflowConfig:
    """Airflow API connection settings."""

    base_url: str = "http://localhost:8080"
    username: str = "airflow"
    password: str = "airflow"
    api_version: str = "auto"  # "auto", "v1", or "experimental"
    timeout: int = 30
    verify_ssl: bool = True
    request_delay: float = 0.1  # delay between API calls (seconds)


@dataclasses.dataclass
class MonitorConfig:
    """Monitoring behavior settings."""

    cycle_interval: int = 300  # seconds between full cycles
    long_running_threshold: int = 1800  # 30 minutes
    max_failed_age: int = 86400  # ignore failed runs older than 24 hours
    retry_wait: int = 120  # wait after retry before re-check
    max_retries: int = 1
    state_file: str = "/var/lib/airflow-monitor/state.json"
    lock_file: str = "/var/run/airflow-monitor.lock"
    state_max_age: int = 86400  # 24 hours


@dataclasses.dataclass
class ZabbixConfig:
    """Zabbix agent integration settings.

    Monitor writes data to files, Zabbix agent reads via UserParameter.
    """

    enabled: bool = True
    data_dir: str = "/var/lib/airflow-monitor"
    problems_file: str = "problems.json"
    heartbeat_file: str = "heartbeat"
    status_file: str = "status.json"


@dataclasses.dataclass
class LoggingConfig:
    """Logging settings."""

    level: str = "INFO"
    file: str = "/var/log/airflow-monitor/monitor.log"
    max_bytes: int = 10_485_760  # 10 MB
    backup_count: int = 5


@dataclasses.dataclass
class AppConfig:
    """Top-level application configuration."""

    airflow: AirflowConfig
    monitor: MonitorConfig
    zabbix: ZabbixConfig
    logging: LoggingConfig


def _build_dataclass(cls, data: dict):
    """Build a dataclass instance from a dict, ignoring unknown keys."""
    if data is None:
        return cls()
    fields = {f.name for f in dataclasses.fields(cls)}
    filtered = {k: v for k, v in data.items() if k in fields}
    return cls(**filtered)


def load_config(path: str) -> AppConfig:
    """Load configuration from a YAML file.

    Missing sections fall back to defaults.
    Raises FileNotFoundError if the file does not exist.
    Raises ValueError on invalid YAML.
    """
    config_path = pathlib.Path(path)
    if not config_path.exists():
        raise FileNotFoundError(f"Config file not found: {path}")

    with open(config_path, "r", encoding="utf-8") as f:
        raw = yaml.safe_load(f)

    if not isinstance(raw, dict):
        raise ValueError(f"Config file must be a YAML mapping, got {type(raw).__name__}")

    return AppConfig(
        airflow=_build_dataclass(AirflowConfig, raw.get("airflow")),
        monitor=_build_dataclass(MonitorConfig, raw.get("monitor")),
        zabbix=_build_dataclass(ZabbixConfig, raw.get("zabbix")),
        logging=_build_dataclass(LoggingConfig, raw.get("logging")),
    )