Facade Exercise 1: Basic Report Facade

Goal

Practice building a basic Facade that coordinates several subsystem components behind one clean entry point.

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Scenario

You are building a reporting tool for a small analytics company.

The tool needs to generate and deliver a weekly sales report. The process involves three steps:

1. Fetch the sales data from a data store.
2. Format the data into a human-readable report string.
3. Email the report to a list of recipients.

The subsystem classes already exist and work correctly. They are defined in exercise1.py. Your job is to build the ReportFacade that hides their coordination from callers.

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What you need to build

Implement the ReportFacade class so that this usage works:

facade = ReportFacade(
    data_fetcher=SalesDataFetcher(),
    formatter=ReportFormatter(),
    emailer=ReportEmailer(),
)

facade.send_weekly_report(recipients=["alice@example.com", "bob@example.com"])

The Facade should:

• Call data_fetcher.fetch_weekly_sales() to get the data.
• Pass the data to formatter.format(data) to produce a report string.
• Pass the report string and recipients to emailer.send(report, recipients).

The caller should not need to know about any of the subsystem classes or the order in which they are called.

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Constraints

• Do not modify any of the existing subsystem classes.
• ReportFacade.__init__ should accept the three subsystem objects as constructor arguments (dependency injection).
• The method on the Facade should be named send_weekly_report.

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File to edit

exercise1.py

Run the tests with:

python -m pytest exercise1.py -v