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name: app-logic description: Logic for financial calculations, period management, and complex application flows.

App Logic Skill

This skill handles the "brain" of the application, focusing on financial math and state transitions.

🔢 Financial Calculations

• Estimates: Calculate future liabilities by summing fixed payments and linked installment plans for a given period.
• Progress: Calculate "percentage paid" based on transaction status in the current month.
• Installment Chains: When a parent payment is marked paid, automatically update linked InstallmentPlans.

📅 Period Management

• Key Format: Always use YYYY-MM for period_key.
• Date Picking: Use date-fns for robust date manipulations (adding months, comparing days).

🚀 Navigation Flows

• Deep Linking: Handle navigation between Dashboard, Payment Detail, and Add scenes.
• Modals: Use Bottom Sheets for quick actions (Quick Pay, Add Note).

⚡ Error Handling

• Prevent negative amounts in inputs.
• Validate due_day is between 1-31.
• Handle "Leap Year" date edge cases gracefully.