import os
import configparser

from typing import Optional

class ConfigException(Exception):
    pass

class ConfigSectionException(ConfigException):
    def __init__(self, section: str):
        self.section = section

    def __str__(self):
        return "Missing configuration section '%s'" % (
            self.section
        )

class ConfigOptionException(ConfigException):
    def __init__(self, section: str, value: str):
        self.section = section
        self.value   = value

    def __str__(self):
        return "Missing configuration value '%s' in section '%s'" % (
            self.value, self.section
        )

class ConfigFileException(ConfigException):
    def __init__(self, paths: list):
        self.paths = paths

    def __str__(self):
        return "Unable to locate configuration file in: %s" % (
            ", ".join(self.paths)
        )

class Config(configparser.ConfigParser):
    SEARCH_PATHS = [
        './server.conf',
        '/usr/local/etc/nntp-tiny/server.conf',
        '/etc/nntp-tiny/server.conf'
    ]

    @staticmethod
    def find():
        for path in Config.SEARCH_PATHS:
            if os.path.exists(path):
                return path

        return None

    @staticmethod
    def load(path: Optional[str]=None):
        if path is None:
            path = Config.find()
            
        if path is None:
            raise ConfigFileException(Config.SEARCH_PATHS)

        config = Config()
        config.read(path)

        return config

    def section(self, section: str):
        if not self.has_section(section):
            raise ConfigSectionException(section)

        return self[section]

    def get(self, section: str, option: str, *args, **kwargs):
        if not self.has_section(section):
            raise ConfigSectionException(section)

        if not self.has_option(section, option):
            raise ConfigOptionException(section, option)

        return super().get(section, option, *args, **kwargs)