4dcd3a99

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

centjes-chart Tier 1: enforce alignment, select by account type, data-driven render

Address the review's structural gaps:

- Make the days/series alignment a real invariant: ChartReport gets a Validity
  instance asserting every series has one value per day, an aligned-by-
  construction GenValid generator, genValidSpec, and a shouldBeInvalid test
  that proves the check is non-vacuous.
- Select accounts by declared AccountType (produceChartReport takes
  [AccountType]; the assets chart passes [AccountTypeAssets]) instead of a name
  substring, so 'the assets chart' means assets.
- Pick the chart primitive from the data: stacked area only when every value is
  non-negative, overlaid lines otherwise, so a signed series (e.g. an overdraft)
  no longer renders a misleading stack.
- Test the rendering math: stackBands and lineSeries are exported and property-
  tested (bands partition each day's total from zero; one point per day).

Timeline