"""Job to generate replacement dynamo items."""

import boto3
from boto3.dynamodb.conditions import Attr
from boto3.dynamodb.conditions import Key

from reports import config
from reports.report import Report


class ReplacementGenerator:
    """Replacement generator."""

    @staticmethod
    def run(period):
        """Run.

        Get a list of s3 paths relative to the prefix.
        i.e. s3://bucket/prefix/{path}

        Check if each s3 path has a matching dynamodb entry.
        If no item is in dynamo, generate a replacement item.

        """
        reports = ReplacementGenerator.get_s3_listings(period)
        table = ReplacementGenerator.get_dynamo_table()
        print('Found {num} {interval}ly {account_type}s'.format(  # noqa T001
            num=len(reports),
            interval=period.interval,
            account_type=period.account_type))
        for report in reports:
            if ReplacementGenerator.dynamo_record_is_missing(report, table):
                # TODO: stash found items
                print('found missing item', report.ddb_item)  # noqa T001
        # TODO: batch save replacement items to dynamoDB

    @staticmethod
    def get_s3_listings(period):
        """S3 dir parsing."""
        page_iterator = ReplacementGenerator.get_period_reports(period)
        reports = []
        for page in page_iterator:
            for item in page.get('Contents', []):
                reports.append(
                    Report(period, config.S3_REPORT_BUCKET, item.get('Key')))
        return reports

    @staticmethod
    def get_period_reports(period):
        """Get a configured boto3 s3 paginator."""
        paginator = ReplacementGenerator.get_s3_paginator()
        opts = {'Bucket': config.S3_REPORT_BUCKET, 'Prefix': period.prefix}
        return paginator.paginate(**opts)

    @staticmethod
    def get_s3_paginator():
        """Get boto3 s3 paginator."""
        return boto3.client('s3').get_paginator('list_objects')

    @staticmethod
    def get_dynamo_table():
        """Connect to the dynamo table."""
        return boto3.resource('dynamodb', region_name=config.AWS_REGION).Table(
            config.DYNAMO_TABLE)

    @staticmethod
    def dynamo_record_is_missing(report, table):
        """Check if the s3 path has a corresponding dynamo item."""
        key_ex = ReplacementGenerator.get_key_condition_expression(report)
        filter_ex = Attr('file_type').eq(report.file_type)
        result = table.query(
            KeyConditionExpression=key_ex, FilterExpression=filter_ex)
        return len(result.get('Items', [])) == 0

    @staticmethod
    def get_key_condition_expression(report):
        """Get key condition expression."""
        pk_filter = Key('user_id_type').eq(report.user_id_type)
        sk_filter = Key('user_params').eq(report.user_params)
        return pk_filter & sk_filter