add-budget-report-section

name	add-budget-report-section
description	Add a new section to the Budget Buddy monthly report. Use when asked to add, extend, or include a new metric, breakdown, or summary (for example "top merchants", "weekly spend", or "category trend") in the report produced by main.py.

Skill: Add a Budget Report Section

Follow these steps to add a new section to the Budget Buddy report consistently.

1. Understand the report flow

• The report is assembled in main.py (build_report() and show_transactions()).
• Numeric logic belongs in calculator.py (BudgetCalculator).
• Transaction shaping (grouping, sorting, summaries) belongs in data_processor.py (TransactionProcessor).

2. Implement the logic in the right module

• Add a focused method to BudgetCalculator or TransactionProcessor.
• Keep it small, add type hints, and guard edge cases (empty input, zero income, zero expenses).

3. Wire it into the report

• Call the new method from build_report() in main.py.
• Emit output through logger from logger.py. Do not use print.
• If the section is tabular, reuse DataTable and ColumnDefinition from data_table.py.

4. Add tests

• Add pytest tests under tests/ covering the happy path and at least one edge case.
• Run pytest and confirm the coverage gate in pytest.ini still passes.

5. Update docs

• Note the new section in README.md under "What The App Does".
• Add an entry to CHANGELOG.md.

6. Report back

Summarize the files changed, tests added, test results, and any remaining risks.