import json
from collections import UserDict
import os
import sys
from . import data

class SettingsLoader(UserDict):
    def __init__(self: object, files: list) -> None:
        self.data = {}
        self.files = files
        self.reload()

    def load_settings_file(self: object, file: str) -> None:
        if not data.exists('conf', file):
            return
        ext = os.path.splitext(file)[1]
        with data.fd_open('conf', file) as fd:
            if ext == '.json':
                self.data.update(json.load(fd))
            else:
                raise ValueError("Cannot open this type of settings file")
    
    def reload(self: object) -> None:
        self.data = {}
        for f in self.files:
            self.load_settings_file(f)

class SettingsReadOnly(SettingsLoader):
    pass

class SettingsMutable(SettingsLoader):
    pass

class SettingsWritable(SettingsMutable):
    def __init__(self: object, files: list, outfile: str):
        super().__init__(files)
        self.outfile = outfile

    def save(self: object):
        defaults = SettingsReadOnly([x for x in self.files if x != self.outfile])
        outdata = {}
        for k in self.data.keys():
            if not k in defaults:
                outdata[k] = self.data[k]
        if outdata or data.exists('conf', self.outfile):
            with data.fd_write('conf', self.outfile) as fd:
                json.dump(outdata, fd, indent=4)
            

init = SettingsWritable(['default.json', 'user.json'], 'user.json')