import logging
from calendar import monthrange
from datetime import date, datetime, timedelta

import boto3

from billing_report.config import Config


def assumed_role_session(role_arn: str, base_session: boto3.session.Session = None) -> boto3.session.Session:
    base_session = base_session or boto3.Session()
    sts_client = base_session.client("sts")

    # Call the assume_role method of the STSConnection object and pass the role
    # ARN and a role session name.
    assumed_role_object = sts_client.assume_role(RoleArn=role_arn, RoleSessionName=Config.ROLE_SESSION_NAME)

    # From the response that contains the assumed role, get the temporary
    # credentials that can be used to make subsequent API calls
    credentials = assumed_role_object["Credentials"]
    return boto3.Session(
        aws_access_key_id=credentials["AccessKeyId"],
        aws_secret_access_key=credentials["SecretAccessKey"],
        aws_session_token=credentials["SessionToken"],
        region_name=Config.AWS_REGION,
    )


def month_year_iter(start_month: int, start_year: int, end_month: int, end_year: int) -> tuple:
    ym_start = 12 * start_year + start_month - 1
    ym_end = 12 * end_year + end_month  # (- 1) removed to include the last month
    for ym in range(ym_start, ym_end):
        y, m = divmod(ym, 12)
        yield y, m + 1


def date_range_split_montly(logger: logging.Logger, start_date: str, end_date: str) -> tuple:
    """Generate start date,start date for the next month, and year-month
    for each month between given dates. End date is adjusted to today
    in case it is current month.
    """
    start_date_obj = datetime.strptime(start_date, "%Y-%m-%d").date()
    if end_date != "":
        end_date_obj = datetime.strptime(end_date, "%Y-%m-%d").date()
    else:
        end_date_obj = date.today()

    if start_date_obj >= end_date_obj:
        raise "Start date can not be earlier than end date"

    for year, month in month_year_iter(
        start_year=start_date_obj.year,
        start_month=start_date_obj.month,
        end_year=end_date_obj.year,
        end_month=end_date_obj.month,
    ):

        current_month_start = date(year, month, 1).strftime("%Y-%m-%d")
        current_month = date(year, month, 1).strftime("%Y-%m")
        if year != end_date_obj.year or month != end_date_obj.month:
            # The end date is excluded, so we set the first day of the next month
            next_month = date(year, month, 1) + timedelta(monthrange(year, month)[1])
            current_month_end = next_month.strftime("%Y-%m-%d")
            logger.info("{} {} {} {}".format(year, month, end_date_obj.year, end_date_obj.month))
            logger.info("{} {} {}".format(current_month, current_month_start, current_month_end))
            yield current_month, current_month_start, current_month_end
        elif end_date_obj.day > Config.MIN_MONTHLY_REPORT_DAYS:
            logger.info("{}".format(str(end_date_obj)))
            current_month_end = end_date_obj.strftime("%Y-%m-%d")
            logger.info(current_month_end)
            yield current_month, current_month_start, current_month_end
        else:
            logger.info(
                "Month {0} skipped because MIN_MONTHLY_REPORT_DAYS has not been reached.".format(
                    end_date_obj.strftime("%Y-%m-%d")
                )
            )