import json
import os

import yaml


def read_config(name):
    if not os.path.isfile(name):
        raise FileNotFoundError(f"File {name} doesn't exist")
    _, ext = os.path.splitext(name)
    ext = ext.lower()
    if ext == '.json':
        return read_json(name)
    elif ext == '.properties':
        return read_prop(name)
    elif ext in ('.yaml', '.yml'):
        return read_yaml(name)
    else:
        raise ValueError(f"Wrong file type: {ext}")


def read_json(name):
    with open(name, 'r', encoding='utf-8') as f:
        return dict(json.load(f))


def read_prop(filepath, sep='=', comment_char='#'):
    """
    Read the file passed as parameter as a properties file.
    """
    conf = {}
    with open(filepath, "rt", encoding='utf-8') as f:
        for line in f:
            l = line.strip()
            if l and not l.startswith(comment_char):
                key, _, value = l.partition(sep)
                conf[key.strip()] = value.strip().strip('"')
    return conf


def read_yaml(name, secrets_file='secrets.yaml'):
    # Load secrets first
    secrets = {}
    secrets_path = os.path.join(os.path.dirname(name), secrets_file)

    if os.path.exists(secrets_path):
        with open(secrets_path, 'r', encoding='utf-8') as f:
            secrets = yaml.safe_load(f) or {}

    def secret_constructor(loader, node):
        secret_key = loader.construct_scalar(node)
        if secret_key not in secrets:
            raise ValueError(f"Secret '{secret_key}' not found in {secrets_file}")
        return secrets[secret_key]

    # Own loader class, so the global yaml.SafeLoader is not modified
    class SecretLoader(yaml.SafeLoader):
        pass

    SecretLoader.add_constructor('!secret', secret_constructor)

    # Load the main configuration
    with open(name, 'r', encoding='utf-8') as f:
        y_conf = yaml.load(f, Loader=SecretLoader)

    if y_conf is None:
        return {}
    if not isinstance(y_conf, dict):
        raise ValueError(f"Wrong config structure in {name}: top level must be a mapping")
    return dict(y_conf)