fmt: shared number formatting for HTML and PDF

lib/fmt.rb

@@ -0,0 +1,25 @@
+require 'bigdecimal'
+
+# Number formatting shared by the HTML views and the PDF so they can't drift.
+module Fmt
+  module_function
+
+  # Exchange rate: full captured precision (up to 8 dp), trailing zeros
+  # trimmed, padded to at least min_dp so it reads as a rate. (4 dp matches
+  # the NBG's GEL quoting.)
+  def rate(value, min_dp: 4)
+    int, frac = BigDecimal(value.to_s).round(8).to_s('F').split('.')
+    frac = (frac || '').sub(/0+$/, '').ljust(min_dp, '0')
+    "#{group(int)}.#{frac}"
+  end
+
+  # LTC amount: up to 8 dp, trailing zeros trimmed, no padding.
+  def ltc(value)
+    BigDecimal(value.to_s).round(8).to_s('F').sub(/(\.\d*?)0+$/, '\1').sub(/\.$/, '')
+  end
+
+  # "1234567" -> "1,234,567"
+  def group(int)
+    int.reverse.gsub(/(\d{3})(?=\d)/, '\1,').reverse
+  end
+end