Modularize readVnNumber function instead of using classes

[hckhanh]

This pull request introduces a major refactor of the Vietnamese number reading module, shifting from an object-oriented approach to a functional, modular design for improved performance, maintainability, and code quality. The public API remains unchanged and fully backward compatible, but the internal structure has been completely rewritten, resulting in significant performance gains, reduced complexity, and better test coverage. Additionally, there is a minor optimization to the formatNumber function.

Major Refactor: Functional Rewrite and Modularization

• Entirely replaced the class-based architecture (NumberReader, Numbers, Thousand, Million, Billion, Zerofill and related files) with a pure functional approach, removing inheritance and dynamic dispatch for better performance and maintainability. The internal logic is now split into five focused modules: digits.ts, utils.ts, three-digits.ts, groups.ts, and index.ts. Public API (readVnNumber) remains unchanged. (.changeset/late-wings-add.md, [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]
• Removed 12 obsolete files (old class implementations and their tests) and added 4 new modular files with clear separation of concerns. (.changeset/late-wings-add.md)

Performance and Code Quality Improvements

• Eliminated class instantiation, property access overhead, and inheritance chain lookups, resulting in faster function calls and more efficient string operations. Benchmarks show maintained or improved performance (2.3-6.8M ops/sec). (.changeset/late-wings-add.md)
• Refactored complex functions (readThreeDigits, readVnNumber) to reduce cognitive complexity below SonarCloud thresholds, improving readability and maintainability. (.changeset/late-wings-add.md)

Testing Enhancements

• Expanded and improved test coverage: increased from 42 to 68 tests (+62%), with comprehensive edge case coverage (leading zeros, tens, hundreds, mixed magnitudes, boundary values, and all Vietnamese reading rules). All 91 tests now pass. (.changeset/late-wings-add.md)

Minor Function Optimization

• Optimized the logic of the formatNumber function in src/format/number.ts for early returns and clearer handling of null, bigint, and number types. (.changeset/wide-things-dig.md, src/format/number.tsL13-R19)

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (239c79a) to head (c603fc2).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #43      +/-   ##
===========================================
+ Coverage   93.02%   100.00%   +6.97%     
===========================================
  Files          12         6       -6     
  Lines         258       245      -13     
  Branches       68        82      +14     
===========================================
+ Hits          240       245       +5     
+ Misses         15         0      -15     
+ Partials        3         0       -3     

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[Copilot]

Pull Request Overview

This PR refactors the formatNumber function to use Number.isNaN() instead of the global isNaN() function for NaN checking. This is a best practice improvement that avoids the type coercion issues associated with the global isNaN() function.

Key Changes:

• Replaced isNaN() with Number.isNaN() for checking NaN values in the number validation logic

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[codspeed-hq]

CodSpeed Performance Report

Merging #43 will degrade performances by 85.15%

_{Comparing optimized (c603fc2) with main (239c79a)}

Summary

⚡ 20 improvements
❌ 1 regression
✅ 43 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	format order count (1,234)	31.7 µs	28.6 µs	+10.65%
⚡	formatVnNumber with different input types	429.2 µs	45.4 µs	×9.5
⚡	bigint input (large transaction)	174 µs	43.3 µs	×4
⚡	mixed input types in data processing (30 values)	659.2 µs	272.4 µs	×2.4
⚡	number input (typical price)	169.5 µs	39.5 µs	×4.3
⚡	string input (from API/form)	172 µs	49.3 µs	×3.5
⚡	display financial dashboard (20 metrics)	468 µs	204 µs	×2.3
⚡	display invoice line items (10 items)	519.1 µs	183.7 µs	×2.8
⚡	display payment receipt (typical transaction)	193 µs	50.9 µs	×3.8
⚡	display product catalog (20 products)	739.1 µs	298.6 µs	×2.5
⚡	display shopping cart (5 items with quantities)	299.9 µs	120 µs	×2.5
⚡	read 50 e-commerce prices (10k-50M VND)	1,409.9 µs	369 µs	×3.8
⚡	read 50 financial amounts (1M-10B VND)	1,182 µs	465.4 µs	×2.5
⚡	read 50 invoice totals (100k-100M VND)	903.6 µs	362.6 µs	×2.5
❌	read 50 product quantities (1-100)	566.3 µs	3,814.3 µs	-85.15%
⚡	annual revenue (2,500,000,000 VND)	183 µs	53.8 µs	×3.4
⚡	invoice total (5,450,000 VND)	171.5 µs	57.8 µs	×3
⚡	large contract value (15,000,000,000 VND)	167.3 µs	49.4 µs	×3.4
⚡	product quantity (5 items)	86 µs	66.7 µs	+28.89%
⚡	transaction amount (19,990,000 VND)	177.9 µs	53 µs	×3.4
...	...	...	...	...

ℹ️ Only the first 20 benchmarks are displayed. Go to the app to view all benchmarks.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud