Add Math.bigint in SC (#1550)

* Add Math.bigint in SC

* Math.bigint always return an integer or raise

---------

Co-authored-by: bchamagne <[email protected]>

lib/archethic/contracts/interpreter/library/common/math.ex

@@ -4,6 +4,7 @@ defmodule Archethic.Contracts.Interpreter.Library.Common.Math do
 
   alias Archethic.Tag
   alias Archethic.Contracts.Interpreter.ASTHelper, as: AST
+  alias Archethic.Contracts.Interpreter.Library
 
   use Tag
   import Bitwise
@@ -127,6 +128,50 @@ defmodule Archethic.Contracts.Interpreter.Library.Common.Math do
     to_number(res, is_integer(num1) and is_integer(num2))
   end
 
+  @doc """
+
+  ## Example
+
+    iex> Math.bigint(49.85024327, 18)
+    49_850_243_270_000_000_000
+
+    iex> Math.bigint(1.994e-4, 18)
+    199_400_000_000_000
+
+    iex> Math.bigint(0.19941234, 18)
+    199_412_340_000_000_000
+
+    iex> Math.bigint(0.10000006, 18)
+    100_000_060_000_000_000
+
+    iex> Math.bigint(0.002, 18)
+    2_000_000_000_000_000
+
+    iex> Math.bigint(1.2390131, 18)
+    1_239_013_100_000_000_000
+
+    iex> Math.bigint(10, 18)
+    10_000_000_000_000_000_000
+
+    iex> Math.bigint(1, 8)
+    100_000_000
+
+  """
+  @spec bigint(num :: number(), decimals :: number()) :: number()
+  def bigint(num, decimals) do
+    num
+    |> to_string()
+    |> Decimal.new()
+    |> Decimal.mult(Decimal.new(10 ** decimals))
+    |> then(fn dec ->
+      if Decimal.integer?(dec) do
+        Decimal.to_integer(dec)
+      else
+        raise Library.Error, message: "Number exceeds decimals"
+      end
+    end)
+  end
+
   @spec check_types(atom(), list()) :: boolean()
   def check_types(:trunc, [first]) do
     AST.is_number?(first) || AST.is_variable_or_function_call?(first)
@@ -146,6 +191,11 @@ defmodule Archethic.Contracts.Interpreter.Library.Common.Math do
       (AST.is_number?(second) || AST.is_variable_or_function_call?(second))
   end
 
+  def check_types(:bigint, [first, second]) do
+    (AST.is_number?(first) || AST.is_variable_or_function_call?(first)) &&
+      (AST.is_number?(second) || AST.is_variable_or_function_call?(second))
+  end
+
   def check_types(_, _), do: false
 
   defp to_decimal(num) when is_integer(num), do: Decimal.new(num)

test/archethic/contracts/interpreter/library/common/math_test.exs

@@ -1,7 +1,18 @@
 defmodule Archethic.Contracts.Interpreter.Library.Common.MathTest do
   use ArchethicCase
 
+  alias Archethic.Contracts.Interpreter.Library
   alias Archethic.Contracts.Interpreter.Library.Common.Math
 
   doctest Math
+
+  test "exceed decimals raise" do
+    assert_raise Library.Error, "Number exceeds decimals", fn ->
+      Math.bigint(0.1234, 2)
+    end
+
+    assert_raise Library.Error, "Number exceeds decimals", fn ->
+      Math.bigint(0.12345874564, 8)
+    end
+  end
 end