import os
import shutil
import sys

import jsonpickle


def capitalize_first_letter(identifier):
    return identifier[0].capitalize() + identifier[1:]


def create_directory(directory, force):
    if os.path.exists(directory):
        if force:
            shutil.rmtree(directory, ignore_errors=True)
        else:
            exit_with_error("output directory {} already exists", directory)

    os.makedirs(directory)


def to_underscore_separated_name(name):
    result = ""
    first_char = True
    for ch in name:
        if ch.islower():
            next_char = ch
        else:
            next_char = ch.lower()
            if not first_char:
                next_char = "_" + next_char
        first_char = False

        result += next_char
    return result


def class_name_to_private_module_name(class_name):
    # The leading underscore indicates that users are not intended to import
    # the class module individually.
    return "_" + to_underscore_separated_name(class_name)


def unpickle_file(path):
    with open(path, mode="rt") as file_obj:
        contents = file_obj.read()
        return jsonpickle.decode(contents)


def exit_with_error(message, *args):
    sys.stderr.write("error : " + message.format(*args) + "\n")
    sys.exit(1)