fix(trading212): normalize GBX/ZAc/ILA fractional currencies

[GeiserX]

Summary

• Trading 212 reports UK stock prices in GBX (pence), not GBP
• The ECB only publishes GBP rates, so getEcbRate("GBX", ...) fails
• Parser now normalizes fractional currencies (GBX→GBP, ZAc→ZAR, ILA→ILS) and divides amounts by 100
• Applies to trade prices, proceeds, dividends, and withholding tax amounts

Closes #86

Test plan

• GBX buy normalized to GBP with price ÷100
• GBX sell proceeds normalized to GBP ÷100
• GBX dividends normalized to GBP ÷100
• GBX withholding tax normalized to GBP ÷100
• Actual GBP prices are NOT divided (guard against false positive)
• All 1015 existing tests pass

Summary by CodeRabbit

• Bug Fixes
  • Trading 212 imports now normalize fractional currencies (GBX, ZAc, ILA) to their standard equivalents (GBP, ZAR, ILS) with appropriate amount conversions for trades, dividends, and withholding tax.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: dbabe86a-365c-45c5-98f7-a1df9a78ba17

📥 Commits

Reviewing files that changed from the base of the PR and between a896b39 and 6a8b29a.

📒 Files selected for processing (2)

• src/parsers/trading212.ts
• tests/parsers/trading212.test.ts

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📝 Walkthrough

Walkthrough

The Trading 212 parser gains support for fractional currencies by normalizing GBX/ZAc/ILA codes to GBP/ZAR/ILS and scaling amounts by 100 during parsing and calculation.

Changes

Fractional Currency Normalization

Layer / File(s)	Summary
Currency Mapping src/parsers/trading212.ts	FRACTIONAL_CURRENCIES map and normalizeCurrency() helper convert GBX/ZAc/ILA to GBP/ZAR/ILS with divisor 100; other currencies return divisor 1.
Currency Resolution src/parsers/trading212.ts	parseTrading212Csv resolves priceDivisor and cashDivisor by normalizing the price and cash currencies from CSV columns.
Cash Transaction Scaling src/parsers/trading212.ts	Withholding tax, dividend, and interest-on-cash amounts are computed by dividing absolute Total by cashDivisor.
Trade Normalization src/parsers/trading212.ts	Buy/sell trade priceDec and totalDec are divided by their respective divisors before gross/cost/proceeds calculations.
Test Coverage tests/parsers/trading212.test.ts	New test suite verifies GBX amounts are divided by 100 for prices, proceeds, dividends, and withholding tax; confirms GBP amounts are not further divided.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• GeiserX/DeclaRenta#146: Main Trading 212 parser addition; this PR extends it with fractional-currency normalization for GBX/ZAc/ILA codes.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/trading212-gbx-normalization

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.64%. Comparing base (8f6bef2) to head (6a8b29a).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #159   +/-   ##
=======================================
  Coverage   97.63%   97.64%           
=======================================
  Files          38       38           
  Lines        7622     7637   +15     
  Branches     1549     1552    +3     
=======================================
+ Hits         7442     7457   +15     
  Misses        179      179           
  Partials        1        1           

Files with missing lines	Coverage Δ
src/parsers/trading212.ts	97.71% <100.00%> (+0.16%)	⬆️

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