Ensure intuitive behavior when querying across holidays (#71)

lib/day.rb

@@ -3,13 +3,24 @@
 class Day < Sequel::Model
   dataset_module do
     def latest(date = Date.today)
-      where(date: select(:date).where(Sequel.lit("date <= ?", date))
+      where(date: select(:date).where(Sequel[:date] <= date)
                                .order(Sequel.desc(:date))
                                .limit(1))
     end
 
+    # Returns rates for a given date interval
+    #
+    # If the start date falls on a holiday/weekend, rates start from the closest preceding business day.
     def between(interval)
-      where(date: interval)
+      return where(false) if interval.begin > Date.today
+
+      previous_date = select(:date)
+        .where(Sequel[:date] <= interval.begin)
+        .order(Sequel.desc(:date))
+        .limit(1)
+
+      where(Sequel.expr(:date) >= Sequel.function(:coalesce, previous_date, interval.begin))
+        .where(Sequel.expr(:date) <= interval.end)
     end
 
     def currencies

spec/day_spec.rb

@@ -5,29 +5,54 @@ require "day"
 
 describe Day do
   describe ".latest" do
-    it "returns latest rates before given date" do
+    it "returns latest available rates on given date" do
+      date = Date.parse("2010-01-04")
+      data = Day.latest(date)
+      _(data.to_a.sample.date).must_equal(date)
+
       date = Date.parse("2010-01-01")
       data = Day.latest(date)
-      _(data.first.date).must_be(:<=, date)
+      _(data.to_a.sample.date).must_equal(Date.parse("2009-12-31"))
     end
 
-    it "returns nothing if there are no rates before given date" do
-      _(Day.latest(Date.parse("1998-01-01"))).must_be_empty
+    it "returns nothing if date predates dataset" do
+      _(Day.latest(Date.parse("1901-01-01"))).must_be_empty
     end
   end
 
   describe ".between" do
-    it "returns rates between given dates" do
-      start_date = Date.parse("2010-01-01")
-      end_date = Date.parse("2010-01-31")
+    it "returns rates between given working dates" do
+      start_date = Date.parse("2010-01-04")
+      end_date = Date.parse("2010-01-29")
       dates = Day.between((start_date..end_date)).map(:date).sort
-      _(dates.first).must_be(:>=, start_date)
-      _(dates.last).must_be(:<=, end_date)
+      _(dates.first).must_equal(start_date)
+      _(dates.last).must_equal(end_date)
     end
 
-    it "returns nothing if there are no rates between given dates" do
-      interval = (Date.parse("1998-01-01")..Date.parse("1998-01-31"))
+    it "starts on preceding business day if start date is a holiday" do
+      start_date = Date.parse("2024-11-03")
+      end_date = Date.parse("2024-11-04")
+      dates = Day.between((start_date..end_date)).map(:date)
+      _(dates).must_include(Date.parse("2024-11-01"))
+    end
+
+    it "returns nothing if end date predates dataset" do
+      interval = (Date.parse("1901-01-01")..Date.parse("1901-01-31"))
       _(Day.between(interval)).must_be_empty
     end
+
+    it "allows start date to predate dataset" do
+      start_date = Date.parse("1901-01-01")
+      end_date = Date.parse("2024-01-01")
+      dates = Day.between((start_date..end_date)).map(:date)
+      _(dates).wont_be_empty
+    end
+
+    it "returns nothing if queried for the future" do
+      start_date = Date.today + 1
+      end_date = start_date + 1
+      dates = Day.between((start_date..end_date)).map(:date)
+      _(dates).must_be_empty
+    end
   end
 end

spec/quote/interval_spec.rb

@@ -22,8 +22,16 @@ module Quote
     end
 
     it "quotes given date interval" do
-      _(Date.parse(quote.formatted[:start_date])).must_be(:>=, dates.first)
-      _(Date.parse(quote.formatted[:end_date])).must_be(:<=, dates.last)
+      returned_start = Date.parse(quote.formatted[:start_date])
+      returned_end = Date.parse(quote.formatted[:end_date])
+
+      # The returned start date should be the closest working day (before or on) the requested start
+      _(returned_start).must_be(:<=, dates.first)
+      # But it shouldn't be too far back (maybe 10 business days)
+      _(returned_start).must_be(:>, dates.first - 10)
+
+      # End date should still be within the requested range
+      _(returned_end).must_be(:<=, dates.last)
     end
 
     it "quotes against the Euro" do