"""Sources."""
from __future__ import annotations

from abc import ABC, abstractmethod
from pathlib import Path
from typing import Any, Iterator, List

from tox.config.loader.api import Loader, OverrideMap

from ..loader.section import Section
from ..sets import ConfigSet, CoreConfigSet


class Source(ABC):
    """
    Source is able to return a configuration value (for either the core or per environment source).
    """

    FILENAME = ""

    def __init__(self, path: Path) -> None:
        self.path: Path = path  #: the path to the configuration source
        self._section_to_loaders: dict[str, list[Loader[Any]]] = {}

    def get_loaders(
        self,
        section: Section,
        base: list[str] | None,
        override_map: OverrideMap,
        conf: ConfigSet,
    ) -> Iterator[Loader[Any]]:
        """
        Return a loader that loads settings from a given section name.

        :param section: the section to load
        :param base: base sections to fallback to
        :param override_map: a list of overrides to apply
        :param conf: the config set to use
        :returns: the loaders to use
        """
        section = self.transform_section(section)
        key = section.key
        if key in self._section_to_loaders:
            yield from self._section_to_loaders[key]
            return
        loaders: list[Loader[Any]] = []
        self._section_to_loaders[key] = loaders
        loader: Loader[Any] | None = self.get_loader(section, override_map)
        if loader is not None:
            loaders.append(loader)
            yield loader

        if base is not None:
            conf.add_config(
                keys="base",
                of_type=List[str],
                desc="inherit missing keys from these sections",
                default=base,
            )
            for base_section in self.get_base_sections(conf["base"], section):
                child = loader
                loader = self.get_loader(base_section, override_map)
                if loader is None:
                    loader = child
                    continue
                if child is not None and loader is not None:
                    child.parent = loader
                yield loader
                loaders.append(loader)

    @abstractmethod
    def transform_section(self, section: Section) -> Section:
        raise NotImplementedError

    @abstractmethod
    def get_loader(self, section: Section, override_map: OverrideMap) -> Loader[Any] | None:
        raise NotImplementedError

    @abstractmethod
    def get_base_sections(self, base: list[str], in_section: Section) -> Iterator[Section]:
        raise NotImplementedError

    @abstractmethod
    def sections(self) -> Iterator[Section]:
        """
        Return a loader that loads the core configuration values.

        :returns: the core loader from this source
        """
        raise NotImplementedError

    @abstractmethod
    def envs(self, core_conf: CoreConfigSet) -> Iterator[str]:
        """
        :param core_conf: the core configuration set
        :returns: a list of environments defined within this source
        """
        raise NotImplementedError

    @abstractmethod
    def get_tox_env_section(self, item: str) -> tuple[Section, list[str], list[str]]:
        """:returns: the section for a tox environment"""
        raise NotImplementedError

    @abstractmethod
    def get_core_section(self) -> Section:
        """:returns: the core section"""
        raise NotImplementedError


__all__ = [
    "Section",
    "Source",
]