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"""
This is an example dag for using `S3ToRedshiftOperator` to copy a S3 key into a Redshift table.
"""

from datetime import datetime
from os import getenv

from airflow import DAG
from airflow.decorators import task
from airflow.models.baseoperator import chain
from airflow.providers.amazon.aws.hooks.s3 import S3Hook
from airflow.providers.amazon.aws.operators.redshift import RedshiftSQLOperator
from airflow.providers.amazon.aws.transfers.s3_to_redshift import S3ToRedshiftOperator

# [START howto_operator_s3_to_redshift_env_variables]
S3_BUCKET = getenv("S3_BUCKET", "test-bucket")
S3_KEY = getenv("S3_KEY", "key")
REDSHIFT_TABLE = getenv("REDSHIFT_TABLE", "test_table")
# [END howto_operator_s3_to_redshift_env_variables]


@task(task_id='setup__add_sample_data_to_s3')
def add_sample_data_to_s3():
    s3_hook = S3Hook()
    s3_hook.load_string("0,Airflow", f'{S3_KEY}/{REDSHIFT_TABLE}', S3_BUCKET, replace=True)


@task(task_id='teardown__remove_sample_data_from_s3')
def remove_sample_data_from_s3():
    s3_hook = S3Hook()
    if s3_hook.check_for_key(f'{S3_KEY}/{REDSHIFT_TABLE}', S3_BUCKET):
        s3_hook.delete_objects(S3_BUCKET, f'{S3_KEY}/{REDSHIFT_TABLE}')


with DAG(
    dag_id="example_s3_to_redshift",
    start_date=datetime(2021, 1, 1),
    schedule_interval=None,
    catchup=False,
    tags=['example'],
) as dag:
    add_sample_data_to_s3 = add_sample_data_to_s3()

    setup__task_create_table = RedshiftSQLOperator(
        sql=f'CREATE TABLE IF NOT EXISTS {REDSHIFT_TABLE}(Id int, Name varchar)',
        task_id='setup__create_table',
    )
    # [START howto_operator_s3_to_redshift_task_1]
    task_transfer_s3_to_redshift = S3ToRedshiftOperator(
        s3_bucket=S3_BUCKET,
        s3_key=S3_KEY,
        schema="PUBLIC",
        table=REDSHIFT_TABLE,
        copy_options=['csv'],
        task_id='transfer_s3_to_redshift',
    )
    # [END howto_operator_s3_to_redshift_task_1]
    teardown__task_drop_table = RedshiftSQLOperator(
        sql=f'DROP TABLE IF EXISTS {REDSHIFT_TABLE}',
        task_id='teardown__drop_table',
    )

    remove_sample_data_from_s3 = remove_sample_data_from_s3()

    chain(
        [add_sample_data_to_s3, setup__task_create_table],
        task_transfer_s3_to_redshift,
        [teardown__task_drop_table, remove_sample_data_from_s3],
    )
