🚀 Key Update Summary (v5.0 - Final Logic & Stability Patch)

This submission represents a major engineering upgrade and business logic correction for the book price calculator, aiming for a more stable, aesthetically modern (Modern UI/UX), and functionally accurate pricing tool.

1. Architecture and Engineering Improvements (Stability & Best Practice)

The underlying codebase has been thoroughly refactured to adhere to robust software engineering principles:

• 🛡️ Critical Stability Patching:
  • Introduced the RuntimeFixer module to specifically address the AttributeError crashes in CTkSwitch and CTkOptionMenu that occurred during widget destruction or initialization interruptions. This resolves random application failures under rapid operation or forced exit.
  • Fixed a KeyError: 'TEXT_SUB' in the configuration to ensure the application's stability and correct color rendering across themes.
• 🧩 MVC Architectural Separation:
  • Logic Decoupling: All complex pricing formulas are strictly contained within the PricingEngine static class. This complete separation from the UI layer significantly simplifies future maintenance and unit testing.
  • Configuration Centralization: All variables (e.g., margins, API URLs, colors) are defined in the AppConfig class, enhancing maintainability.
• 🌍 Thread Safety & Performance: The ExchangeRateService utilizes threading.Lock() and asynchronous fetching to ensure data integrity and prevent the GUI from freezing .

2. Modern UI/UX Implementation (Design & Experience)

The application transitions from native Tkinter to CustomTkinter, adopting modern design standards:

• Visual Consistency: Utilizes Dark Mode with rounded, card-style layouts, providing a clean and professional aesthetic.
• Information Hierarchy: The bottom DashboardView highlights the Member Price (large, primary color) while displaying the Standard Price in a muted, smaller font, prioritizing key user information.
• Interaction Refinement: Buttons and input fields feature modern design touches and the status bar provides real-time feedback on synchronization status.

3. Finalized Business Logic (Accurate Pricing Model)

The PricingEngine has been definitively updated to correctly execute the final, complex pricing policy agreed upon:

Pricing Scenario	Member Price Formula (Final AUD)	Standard (Non-Member) Price Formula (Final AUD)
Standard Book	(Price + 15%) $\rightarrow$ AUD	(Price + 15%) $\rightarrow$ CNY $\times$ 0.3 $\rightarrow$ AUD
Manager Recommend	Base Member Price $\times$ 0.9 (Extra 10% off)	Base Member Price (Non-member gets member pricing)
Used Book	Input Price $\rightarrow$ AUD	Input Price $\rightarrow$ AUD

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