Coverage Summary for Class: SpentByCategory (com.georgeci.moneysurfer.domain.model)

 package com.georgeci.moneysurfer.domain.model
 
 import com.georgeci.moneysurfer.domain.primitives.CurrencyCode
 import com.georgeci.moneysurfer.domain.primitives.Money
 import com.georgeci.moneysurfer.domain.util.TransactionPeriodWindow
 
 /**
  * The cap a single-category budget puts on one category, as the spend breakdown reads it.
  *
  * [limit] is the budget's nominal amount rather than a `BudgetProgress.effectiveLimit`: computing
  * the effective one means folding the whole workspace transaction list per budget, which is the
  * pattern [com.georgeci.moneysurfer.domain.repositories.SpendAnalyticsRepository] exists to
  * replace. A rollover carry is therefore not in [limit] — see [buildSpentByCategory] for
  * what else that costs.
  */
 data class CategoryCap(
     val limit: Money,
     val status: BudgetStatus,
 )
 
 /**
  * One category's spend inside the breakdown's window.
  *
  * [category] is null for the uncategorized bucket — a real slice rather than a missing one, so the
  * entries still add up to what was spent. Naming it is the UI's job: `domain` owns no copy.
  */
 data class CategorySpend(
     val category: Category?,
     val spent: Money,
     /** Share of the window's total spend, `0f..1f`. Zero when nothing was spent at all. */
     val share: Float,
     /** The cap on this category, or null while nothing caps it. */
     val cap: CategoryCap?,
 ) {
 
     /**
      * Spend against [CategoryCap.limit]; can exceed 1, which every meter caps rather than
      * overdrawing. Null when there is no cap — a meter then falls back to [share].
      */
     val capFraction: Float?
         get() = cap?.let { if (it.limit.minor <= 0L) 0f else spent.minor.toFloat() / it.limit.minor.toFloat() }
 }
 
 /**
  * Where a period's money went, category by category — the dashboard's spent-by-category widget.
  *
  * [currency] is non-null by construction: a figure nobody can format is not a figure, and
  * `MoneyFormatter` is backed by `java.util.Currency`, which throws on anything that is not a
  * three-letter ISO code. A workspace whose base currency cannot be read yields no breakdown at
  * all rather than one the UI has to invent a currency for — the same rule [SafeToSpend] follows.
  */
 data class SpentByCategory(
     /** Largest spender first. */
     val entries: List<CategorySpend>,
     val total: Money,
     val currency: CurrencyCode,
     val window: TransactionPeriodWindow,
 )
 
 /**
  * Joins the window's per-category spend to the categories that name it and the budgets that cap it.
  *
  * Pure, so the maths is testable without a repository: [slices] is what
  * [com.georgeci.moneysurfer.domain.repositories.SpendAnalyticsRepository.byCategory] answered for
  * the same window, and [categories] and [budgets] are the workspace's own.
  *
  * **Which budget caps a category.** Only a budget naming *exactly* that one category does —
  * resolved through [resolveCategoryCapCoverage], the same rule the category form's monthly-cap
  * shortcut writes through, so the two can never disagree about which budget speaks for a category.
  * A budget spanning several categories caps the group, not any single member, and overlaying its
  * limit on one member's spend would read as headroom the group does not have. The general
  * (all-categories) budget is the spending envelope above per-category caps, and
  * [resolveCategoryCapCoverage] already excludes both it and archived budgets.
  *
  * **Only caps on [capPeriod]'s cadence count.** [slices] covers [window], so a budget of any other
  * cadence is not a figure for it: measuring a week of spend against a monthly cap reads as
  * comfortable headroom right up to the point the month is blown. Dividing one into a pro-rata limit
  * would invent a cap the user never set, so a category whose only budget runs on another cadence
  * simply shows no overlay — the spend is still drawn, without a state it cannot honestly claim.
  *
  * **The cap's own window is not this one.** Budget windows are anchored on `Budget.startDate`, so a
  * cap created mid-month runs 15th-to-15th while this breakdown runs a calendar span. Every number
  * *here* is measured over [window] — spend, limit and status alike, so the widget is internally
  * consistent — but a status shown here can differ from the same budget's status on the Budgets
  * screen, which reads the budget's own window and includes its rollover carry.
  */
 fun buildSpentByCategory(
     slices: List<CategorySpendSlice>,
     categories: List<Category>,
     budgets: List<Budget>,
     currency: CurrencyCode,
     window: TransactionPeriodWindow,
     capPeriod: BudgetPeriod,
 ): SpentByCategory {
     val total = slices.fold(Money.zero()) { acc, slice -> acc + slice.total }
     val byId = categories.associateBy { it.id }
     // Sorted here rather than trusted from the query: `sortedByDescending` is stable, so the
     // repository's own largest-first order survives for ties, and a caller that forgot to sort
     // cannot leave the widget drawing its rows in an arbitrary order.
     val entries = slices
         .sortedByDescending { it.total.minor }
         .map { slice ->
             CategorySpend(
                 category = slice.categoryId?.let(byId::get),
                 spent = slice.total,
                 share = shareOf(slice.total, total),
                 cap = capFor(slice, budgets, capPeriod),
             )
         }
     return SpentByCategory(entries = entries, total = total, currency = currency, window = window)
 }
 
 /** A zero total reads as no share at all, never as a NaN. */
 private fun shareOf(spent: Money, total: Money): Float =
     if (total.minor <= 0L) 0f else (spent.minor.toFloat() / total.minor.toFloat()).coerceIn(0f, 1f)
 
 private fun capFor(
     slice: CategorySpendSlice,
     budgets: List<Budget>,
     capPeriod: BudgetPeriod,
 ): CategoryCap? {
     val coverage = resolveCategoryCapCoverage(slice.categoryId, budgets)
     val budget = (coverage as? CategoryCapCoverage.Editable)?.budget ?: return null
     if (budget.period != capPeriod) return null
     return CategoryCap(
         limit = budget.amount,
         status = budgetStatusOf(slice.total, budget.amount, budget.alertPercent),
     )
 }