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

 package com.georgeci.moneysurfer.domain.model
 
 import com.georgeci.moneysurfer.domain.primitives.TransactionId
 
 private const val REFERENCE_PREFIX = "TX-"
 private const val REFERENCE_DIGITS = 4
 
 /**
  * Short human-facing label for a transaction (`TX-8A13`), shown on the details screen.
  *
  * Derived, never stored: it is a pure function of [TransactionId], so there is no column to
  * migrate, no wire field for the rules to validate, and nothing that can drift from the id it
  * labels. [TransactionId] is UUID-backed, so its trailing hex digits are already uniformly
  * distributed and no hashing is needed.
  *
  * This is a display label, not a key: four hex digits collide, and nothing looks a transaction
  * up by it. If a bank-supplied reference ever has to survive a statement import, that is a
  * *stored* field with different semantics — add it then, next to this one, not instead of it.
  */
 val TransactionId.reference: String
     get() {
         val digits = value.filter(Char::isReferenceDigit)
             .takeLast(REFERENCE_DIGITS)
             .padStart(REFERENCE_DIGITS, '0')
         return REFERENCE_PREFIX + digits.uppercase()
     }
 
 // Ids reaching us from an import may not be UUIDs; keeping only hex digits guarantees a
 // stable, printable label for any id shape rather than echoing stray punctuation.
 private fun Char.isReferenceDigit(): Boolean =
     this in '0'..'9' || this in 'a'..'f' || this in 'A'..'F'