import tomllib
from dataclasses import dataclass
from pathlib import Path
from typing import Iterable

from ..util import merge_dicts
from .model import Preset


@dataclass
class PresetLoaderConfig:
    default: bool = True
    user: bool = True
    project: bool = True


class PresetLoader:
    _source_cache: dict[Path, dict] = {}

    def __init__(self, basepath: Path, config: PresetLoaderConfig | None = None):
        self._basepath = basepath
        self._config = config or PresetLoaderConfig()

    def _iter_sources(self) -> Iterable[Path]:
        if self._config.default:
            yield from (Path(__file__).parent / "default").iterdir()
        if self._config.user:
            user_preset = Path.home() / ".pm.toml"
            if user_preset.exists():
                yield user_preset
        if self._config.project:
            projectpath = self._basepath
            while projectpath.exists():
                project_preset = projectpath / ".pm.toml"
                if project_preset.exists():
                    yield project_preset
                if projectpath.parent == projectpath:
                    break
                projectpath = projectpath.parent

    def load(self) -> Preset:
        result_preset_data = {}
        for filepath in self._iter_sources():
            if filepath not in self._source_cache:
                with open(filepath, "rb") as fd:
                    self._source_cache[filepath] = tomllib.load(fd)
            merge_dicts(result_preset_data, self._source_cache[filepath])
        return Preset(**result_preset_data)