from __future__ import annotations

from pathlib import Path
from typing import Dict, List, Optional

import yaml


class NavSpec:
    """Parsed representation of docforge.nav.yml."""

    def __init__(
        self,
        home: Optional[str],
        groups: Dict[str, List[str]],
    ) -> None:
        self.home = home
        self.groups = groups

    @classmethod
    def load(cls, path: Path) -> "NavSpec":
        if not path.exists():
            raise FileNotFoundError(path)

        data = yaml.safe_load(path.read_text(encoding="utf-8"))

        if not isinstance(data, dict):
            raise ValueError("Nav spec must be a mapping")

        home = data.get("home")
        groups = data.get("groups", {})

        if home is not None and not isinstance(home, str):
            raise ValueError("home must be a string")

        if not isinstance(groups, dict):
            raise ValueError("groups must be a mapping")

        for key, value in groups.items():
            if not isinstance(key, str):
                raise ValueError("group names must be strings")
            if not isinstance(value, list) or not all(
                isinstance(v, str) for v in value
            ):
                raise ValueError(f"group '{key}' must be a list of strings")

        return cls(home=home, groups=groups)

    def all_patterns(self) -> List[str]:
        patterns: List[str] = []
        if self.home:
            patterns.append(self.home)
        for items in self.groups.values():
            patterns.extend(items)
        return patterns