Change Ledger.balance/1 to Ledger.is_balance?/1

tristanperalta · Nov 10, 2021 · eea8eeb · eea8eeb
1 parent 5c49201
commit eea8eeb
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Showing 3 changed files with 31 additions and 28 deletions.
diff --git a/lib/ledger.ex b/lib/ledger.ex
@@ -11,17 +11,11 @@ defmodule ExLedger.Ledger do
     struct!(%__MODULE__{}, attrs)
   end
 
-  @spec balance(__MODULE__.t()) :: integer()
-  def balance(%{transactions: transactions} = _ledger) do
-    transactions
-    |> Enum.reduce(0, fn totals, acc ->
-      totals =
-        totals
-        |> Transaction.balance()
-        |> Keyword.values()
-        |> Enum.sum()
-
-      acc + totals
+  @spec is_balance?(__MODULE__.t()) :: bool()
+  def is_balance?(%{transactions: transactions} = _ledger) do
+    Enum.flat_map(transactions, fn txn ->
+      Keyword.values(txn.balances)
     end)
+    |> Enum.all?(&(&1 == 0))
   end
 end
diff --git a/test/exledger_test.exs b/test/exledger_test.exs
@@ -2,16 +2,28 @@ defmodule ExledgerTest do
   use ExUnit.Case
   use ExLedger.LedgerBuilder
 
-  test "Ledger.balance/1" do
+  test "Ledger.is_balance?/1" do
     transaction =
-      Transaction.new(%{description: "Test"})
+      Transaction.new("test transaction")
       |> Transaction.add_entry("assets", {1, :USD})
       |> Transaction.add_entry("expensese", {-1, :USD})
       |> Transaction.add_entry("assets", {1, :PHP})
       |> Transaction.add_entry("expenses", {-1, :PHP})
 
     ledger = Ledger.new(transactions: [transaction])
 
-    assert Ledger.balance(ledger) == 0
+    assert Ledger.is_balance?(ledger)
+  end
+
+  test "Ledger.is_balance?/1 imbalance" do
+    transaction =
+      Transaction.new("test transaction")
+      |> Transaction.add_entry("assets", {1, :USD})
+      |> Transaction.add_entry("expensese", {-1, :USD})
+      |> Transaction.add_entry("assets", {1, :PHP})
+
+    ledger = Ledger.new(transactions: [transaction])
+
+    assert false == Ledger.is_balance?(ledger)
   end
 end
diff --git a/test/transaction_test.exs b/test/transaction_test.exs
@@ -2,31 +2,28 @@ defmodule Exledger.TransactionTest do
   use ExUnit.Case
   use ExLedger.LedgerBuilder
 
-  test "add_entry" do
+  test "add_entry/3" do
     assert %{balances: [usd: 1]} =
-             Transaction.new(%{description: "Test"})
+             Transaction.new("test transaction")
              |> Transaction.add_entry("assets", {1, :usd})
   end
 
-  test "add_entry sum 2 common currency" do
+  test "add_entry/3 sum 2 common currency" do
     assert %{balances: [usd: 6]} =
-             Transaction.new(%{description: "Test"})
+             Transaction.new("test transaction")
              |> Transaction.add_entry("assets", {1, :usd})
              |> Transaction.add_entry("assets", {5, :usd})
   end
 
   test "compute balances" do
   end
 
-  test "Transaction.balance/1" do
-    transaction =
-      Transaction.new(%{description: "Test"})
-      |> Transaction.add_entry("assets", {1, :USD})
-      |> Transaction.add_entry("expenses", {-1, :USD})
-      |> Transaction.add_entry("assets", {1, :PHP})
-      |> Transaction.add_entry("expenses", {-1, :PHP})
-      |> Transaction.balance()
-
-    assert [USD: 0, PHP: 0] == transaction
+  test "add_entry/3 with multiple currency" do
+    assert %{balances: [usd: 0, php: 0]} =
+             Transaction.new("test transaction")
+             |> Transaction.add_entry("assets", {1, :usd})
+             |> Transaction.add_entry("expenses", {-1, :usd})
+             |> Transaction.add_entry("assets", {1, :php})
+             |> Transaction.add_entry("expenses", {-1, :php})
   end
 end