"""Lambda shared module."""

import os
from contextlib import contextmanager
from dateutil.parser import parse
import json
from tempfile import NamedTemporaryFile
import urllib

import boto3
from botocore.exceptions import ClientError
from xlsx2csv import Xlsx2csv

from common_config import logger
from common_config import SLACK_WEBHOOK_URL
from constants import errors
from connectors import sentry


def say_hello():
    """Generate high SLA Orchard greeting and logs it."""
    logger.info('Hello, world!')


def convert_xsl_to_csv(bucket_name, xls_key, csv_key):
    """Download an xsl from S3, convert it to csv and upload it to S3.

    Args:
        bucket_name (str): s3 bucket name
        xls_key (str): the name of the xls file key to convert
        csv_key (str): the name of the destination csv file key

    Returns:
        bool: True if file was converted and uploaded successfully
            False if xls file does not exist
    """
    s3_bucket = boto3.resource('s3').Bucket(bucket_name)
    with tmp_file_path() as xls_path, tmp_file_path() as csv_path:
        if download_file(s3_bucket, xls_key, xls_path):
            Xlsx2csv(xls_path, outputencoding='utf8').convert(csv_path)
            s3_bucket.upload_file(csv_path, csv_key)
            return True
        else:
            return False


@contextmanager
def tmp_file_path():
    """Temporary file context manager.

    Returns:
         str: temp file path
    """
    f = NamedTemporaryFile(delete=False)
    f.close()
    path = f.name
    try:
        yield path
    finally:
        os.unlink(path)


def download_file(s3_bucket, s3_key, destination_path):
    """Download an S3 object to a file.

    Args:
        s3_bucket: boto3.resource('s3').Bucket
        s3_key (str): the name of the xls file key to download from
        destination_path (str): the path to the file to download to

    Returns:
        bool: True if file was downloaded successfully
            False if file does not exist
    """
    try:
        s3_bucket.download_file(s3_key, destination_path)
    except ClientError as e:
        try:
            err_code = e.response['Error']['Code']
            if err_code == '404':
                # file does not exist
                return False
            else:
                raise e
        except (KeyError, AttributeError):
            raise e
    return True


def notify_slack(message):
    """Send message to Slack.

    Args:
        message (str): message to send
    """
    data = json.dumps({'text': message}).encode('ascii')
    try:
        urllib.request.urlopen(SLACK_WEBHOOK_URL, data)
    except Exception:
        logger.error(errors.NOTIFY_SLACK_ERROR.format(message))
        sentry.capture_exception()


def get_date_from_report_key(xls_key):
    """Extract date from the xls report S3 key.

    Args:
        xls_key (str): the name of the xls file key

    Returns:
        date: date extracted from the S3 key
    """
    try:
        return parse(xls_key.split('/')[-2]).date()
    except (IndexError, ValueError):
        raise ValueError(errors.INVALID_XLS_KEY.format(xls_key))