ruby: use floor for conversion, add integer tests

ruby/lib/plus_codes/open_location_code.rb

@@ -44,14 +44,14 @@ def full?(code)
     # @return [Array<Integer, Integer>] with the latitude and longitude integer
     # values.
     def location_to_integers(latitude, longitude)
-      lat_val = (latitude * PAIR_CODE_PRECISION * LAT_GRID_PRECISION).round
+      lat_val = (latitude * PAIR_CODE_PRECISION * LAT_GRID_PRECISION).floor
       lat_val += 90 * PAIR_CODE_PRECISION * LAT_GRID_PRECISION
       if lat_val.negative?
         lat_val = 0
       elsif lat_val >= 2 * 90 * PAIR_CODE_PRECISION * LAT_GRID_PRECISION
         lat_val = 2 * 90 * PAIR_CODE_PRECISION * LAT_GRID_PRECISION - 1
       end
-      lng_val = (longitude * PAIR_CODE_PRECISION * LNG_GRID_PRECISION).round
+      lng_val = (longitude * PAIR_CODE_PRECISION * LNG_GRID_PRECISION).floor
       lng_val += 180 * PAIR_CODE_PRECISION * LNG_GRID_PRECISION
       if lng_val.negative?
         # Ruby's % operator differs from other languages in that it returns
@@ -72,11 +72,6 @@ def location_to_integers(latitude, longitude)
     # excludes the separator
     # @return [String] a plus+codes
     def encode(latitude, longitude, code_length = PAIR_CODE_LENGTH)
-      if invalid_length?(code_length)
-        raise ArgumentError, 'Invalid Open Location Code(Plus+Codes) length'
-      end
-
-      code_length = MAX_CODE_LENGTH if code_length > MAX_CODE_LENGTH
       lat_val, lng_val = location_to_integers(latitude, longitude)
       encode_integers(lat_val, lng_val, code_length)
     end
@@ -91,6 +86,11 @@ def encode(latitude, longitude, code_length = PAIR_CODE_LENGTH)
     # excludes the separator
     # @return [String] a plus+codes
     def encode_integers(lat_val, lng_val, code_length = PAIR_CODE_LENGTH)
+      if invalid_length?(code_length)
+        raise ArgumentError, 'Invalid Open Location Code(Plus+Codes) length'
+      end
+
+      code_length = MAX_CODE_LENGTH if code_length > MAX_CODE_LENGTH
       # Initialise the code using an Array. Array.join is more efficient that
       # string addition.
       code = Array.new(MAX_CODE_LENGTH + 1, '')

ruby/test/plus_codes_test.rb

@@ -42,12 +42,60 @@ def test_decode
   end
 
   def test_encode
+    # Allow a 5% error rate encoding from degree coordinates (because of
+    # floating point precision).
+    allowed_error_rate = 0.05
+    errors = 0
+    tests = 0
     read_csv_lines('encoding.csv').each do |line|
       next if line.empty?
 
+      tests += 1
       cols = line.split(',')
-      code = @olc.encode(cols[0].to_f, cols[1].to_f, cols[2].to_i)
-      assert_equal(cols[3], code)
+      lat_degrees = cols[0].to_f
+      lng_degrees = cols[1].to_f
+      code_length = cols[4].to_i
+      want = cols[5]
+
+      code = @olc.encode(lat_degrees, lng_degrees, code_length)
+      if want != code
+        errors += 1
+        puts "ENCODING DIFFERENCE: want #{want}, got #{code}"
+      end
+    end
+    assert_compare(errors.to_f / tests, '<=', allowed_error_rate)
+  end
+
+  def test_location_to_integers
+    read_csv_lines('encoding.csv').each do |line|
+      next if line.empty?
+
+      cols = line.split(',')
+      lat_degrees = cols[0].to_f
+      lng_degrees = cols[1].to_f
+      lat_integer = cols[2].to_i
+      lng_integer = cols[3].to_i
+
+      got_lat, got_lng = @olc.location_to_integers(lat_degrees, lng_degrees)
+      # Due to floating point precision limitations, we may get values 1 less
+      # than expected.
+      assert_include([lat_integer - 1, lat_integer], got_lat)
+      assert_include([lng_integer - 1, lng_integer], got_lng)
+    end
+  end
+
+  def test_encode_integers
+    read_csv_lines('encoding.csv').each do |line|
+      next if line.empty?
+
+      cols = line.split(',')
+      lat_integer = cols[2].to_i
+      lng_integer = cols[3].to_i
+      code_length = cols[4].to_i
+      want = cols[5]
+
+      code = @olc.encode_integers(lat_integer, lng_integer, code_length)
+      assert_equal(want, code)
     end
   end