From 568190e32724d60ca456748b08f88c67263257bf Mon Sep 17 00:00:00 2001
From: Marcel Otto <marcelotto@gmx.de>
Date: Mon, 22 Apr 2019 11:17:16 +0200
Subject: [PATCH] Add digit_count and fraction_digit_count to RDF.Decimal

---
 CHANGELOG.md                         |  2 ++
 lib/rdf/datatypes/decimal.ex         | 34 ++++++++++++++++++++++++++++
 lib/rdf/datatypes/integer.ex         | 14 ++++++++++++
 test/unit/datatypes/decimal_test.exs | 27 +++++++++++++++++++++-
 test/unit/datatypes/integer_test.exs |  8 +++++++
 5 files changed, 84 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 65f97d5..64a4f48 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,8 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 ### Added
 
 - `RDF.Literal.matches?/3` for XQuery regex pattern matching
+- `RDF.Decimal.digit_count/1` and `RDF.Decimal.fraction_digit_count/1` for  
+  determining the number of digits of decimal literals
 
 
 [Compare v0.6.0...HEAD](https://github.com/marcelotto/rdf-ex/compare/v0.6.0...HEAD)
diff --git a/lib/rdf/datatypes/decimal.ex b/lib/rdf/datatypes/decimal.ex
index dcab7f9..fc52d4c 100644
--- a/lib/rdf/datatypes/decimal.ex
+++ b/lib/rdf/datatypes/decimal.ex
@@ -8,6 +8,7 @@ defmodule RDF.Decimal do
 
   alias Elixir.Decimal, as: D
 
+  @xsd_integer RDF.Datatype.NS.XSD.integer
 
   @impl RDF.Datatype
   def convert(value, opts)
@@ -113,4 +114,37 @@ defmodule RDF.Decimal do
   @impl RDF.Datatype
   def compare(left, right), do: RDF.Numeric.compare(left, right)
 
+  @doc """
+  The number of digits in the XML Schema canonical form of the literal value.
+  """
+  def digit_count(%RDF.Literal{datatype: @id} = literal) do
+    if valid?(literal) do
+      literal
+      |> canonical()
+      |> lexical()
+      |> String.replace(".", "")
+      |> String.replace("-", "")
+      |> String.length()
+    end
+  end
+
+  def digit_count(%RDF.Literal{datatype: @xsd_integer} = literal),
+    do: RDF.Integer.digit_count(literal)
+
+  @doc """
+  The number of digits to the right of the decimal point in the XML Schema canonical form of the literal value.
+  """
+  def fraction_digit_count(%RDF.Literal{datatype: @id, value: value} = literal) do
+    if valid?(literal) do
+      [_, fraction] =
+        literal
+        |> canonical()
+        |> lexical()
+        |> String.split(".")
+      String.length(fraction)
+    end
+  end
+
+  def fraction_digit_count(%RDF.Literal{datatype: @xsd_integer}), do: 0
+
 end
diff --git a/lib/rdf/datatypes/integer.ex b/lib/rdf/datatypes/integer.ex
index 15ab41c..fbaca0b 100644
--- a/lib/rdf/datatypes/integer.ex
+++ b/lib/rdf/datatypes/integer.ex
@@ -73,4 +73,18 @@ defmodule RDF.Integer do
   @impl RDF.Datatype
   def compare(left, right), do: RDF.Numeric.compare(left, right)
 
+
+  @doc """
+  The number of digits in the XML Schema canonical form of the literal value.
+  """
+  def digit_count(%RDF.Literal{datatype: @id} = literal) do
+    if valid?(literal) do
+      literal
+      |> canonical()
+      |> lexical()
+      |> String.replace("-", "")
+      |> String.length()
+    end
+  end
+
 end
diff --git a/test/unit/datatypes/decimal_test.exs b/test/unit/datatypes/decimal_test.exs
index d346c56..385001c 100644
--- a/test/unit/datatypes/decimal_test.exs
+++ b/test/unit/datatypes/decimal_test.exs
@@ -122,6 +122,32 @@ defmodule RDF.DecimalTest do
     end
   end
 
+  test "digit_count/1" do
+    assert RDF.Decimal.digit_count(RDF.decimal("1.2345")) == 5
+    assert RDF.Decimal.digit_count(RDF.decimal("-1.2345")) == 5
+    assert RDF.Decimal.digit_count(RDF.decimal("+1.2345")) == 5
+    assert RDF.Decimal.digit_count(RDF.decimal("01.23450")) == 5
+    assert RDF.Decimal.digit_count(RDF.decimal("01.23450")) == 5
+    assert RDF.Decimal.digit_count(RDF.decimal("NAN")) == nil
+
+    assert RDF.Decimal.digit_count(RDF.integer("2")) == 1
+    assert RDF.Decimal.digit_count(RDF.integer("23")) == 2
+    assert RDF.Decimal.digit_count(RDF.integer("023")) == 2
+  end
+
+  test "fraction_digit_count/1" do
+    assert RDF.Decimal.fraction_digit_count(RDF.decimal("1.2345")) == 4
+    assert RDF.Decimal.fraction_digit_count(RDF.decimal("-1.2345")) == 4
+    assert RDF.Decimal.fraction_digit_count(RDF.decimal("+1.2345")) == 4
+    assert RDF.Decimal.fraction_digit_count(RDF.decimal("01.23450")) == 4
+    assert RDF.Decimal.fraction_digit_count(RDF.decimal("0.023450")) == 5
+    assert RDF.Decimal.fraction_digit_count(RDF.decimal("NAN")) == nil
+
+    assert RDF.Decimal.fraction_digit_count(RDF.integer("2")) == 0
+    assert RDF.Decimal.fraction_digit_count(RDF.integer("23")) == 0
+    assert RDF.Decimal.fraction_digit_count(RDF.integer("023")) == 0
+  end
+
 
   defmacrop sigil_d(str, _opts) do
     quote do
@@ -151,5 +177,4 @@ defmodule RDF.DecimalTest do
     assert Decimal.canonical_decimal(~d"1.2E3") == ~d"1200.0"
     assert Decimal.canonical_decimal(~d"-42E+3") == ~d"-42000.0"
   end
-
 end
diff --git a/test/unit/datatypes/integer_test.exs b/test/unit/datatypes/integer_test.exs
index c20dde7..4745a82 100644
--- a/test/unit/datatypes/integer_test.exs
+++ b/test/unit/datatypes/integer_test.exs
@@ -76,6 +76,14 @@ defmodule RDF.IntegerTest do
     end
   end
 
+  test "digit_count/1" do
+    assert RDF.Integer.digit_count(RDF.integer("2")) == 1
+    assert RDF.Integer.digit_count(RDF.integer("23")) == 2
+    assert RDF.Integer.digit_count(RDF.integer("023")) == 2
+    assert RDF.Integer.digit_count(RDF.integer("+023")) == 2
+    assert RDF.Integer.digit_count(RDF.integer("-023")) == 2
+    assert RDF.Integer.digit_count(RDF.integer("NaN")) == nil
+  end
 
   describe "equality" do
     test "two literals are equal when they have the same datatype and lexical form" do