From 141c8489563119abe029859816afb2e654e0b53e Mon Sep 17 00:00:00 2001
From: Tristan Peralta <tristanperalta@protonmail.com>
Date: Thu, 11 Nov 2021 10:42:11 +0800
Subject: [PATCH] Refactor Ledger.is_balanced?/1

Rename from `is_balance?/1` to `is_balanced?/1`
---
 lib/ledger.ex             | 10 +++----
 lib/transaction.ex        |  6 ++++
 test/exledger_test.exs    |  8 +++---
 test/transaction_test.exs | 60 +++++++++++++++++++++++++++------------
 4 files changed, 56 insertions(+), 28 deletions(-)

diff --git a/lib/ledger.ex b/lib/ledger.ex
index c41a3bb..5421297 100644
--- a/lib/ledger.ex
+++ b/lib/ledger.ex
@@ -11,11 +11,9 @@ defmodule ExLedger.Ledger do
     struct!(%__MODULE__{}, attrs)
   end
 
-  @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))
+  @spec is_balanced?(__MODULE__.t()) :: bool()
+  def is_balanced?(%{transactions: transactions} = _ledger) do
+    Enum.map(transactions, &Transaction.is_balanced?/1)
+    |> Enum.all?()
   end
 end
diff --git a/lib/transaction.ex b/lib/transaction.ex
index f92b0fb..e3785f0 100644
--- a/lib/transaction.ex
+++ b/lib/transaction.ex
@@ -32,6 +32,12 @@ defmodule ExLedger.Transaction do
     Map.put(txn, :balances, update_balance(txn.balances, amount))
   end
 
+  @spec is_balanced?(__MODULE__.t()) :: bool()
+  def is_balanced?(txn) do
+    Keyword.values(txn.balances)
+    |> Enum.all?(&(&1 == 0))
+  end
+
   def transactions(entries) do
     entries
     |> Enum.map(& &1.entries)
diff --git a/test/exledger_test.exs b/test/exledger_test.exs
index 79d4214..de41fdf 100644
--- a/test/exledger_test.exs
+++ b/test/exledger_test.exs
@@ -2,7 +2,7 @@ defmodule ExledgerTest do
   use ExUnit.Case
   use ExLedger.LedgerBuilder
 
-  test "Ledger.is_balance?/1" do
+  test "Ledger.is_balanced?/1" do
     transaction =
       Transaction.new("test transaction")
       |> Transaction.add_entry("assets", {1, :USD})
@@ -12,10 +12,10 @@ defmodule ExledgerTest do
 
     ledger = Ledger.new(transactions: [transaction])
 
-    assert Ledger.is_balance?(ledger)
+    assert Ledger.is_balanced?(ledger)
   end
 
-  test "Ledger.is_balance?/1 imbalance" do
+  test "Ledger.is_balanced?/1 imbalance" do
     transaction =
       Transaction.new("test transaction")
       |> Transaction.add_entry("assets", {1, :USD})
@@ -24,6 +24,6 @@ defmodule ExledgerTest do
 
     ledger = Ledger.new(transactions: [transaction])
 
-    assert false == Ledger.is_balance?(ledger)
+    assert false == Ledger.is_balanced?(ledger)
   end
 end
diff --git a/test/transaction_test.exs b/test/transaction_test.exs
index 257a73c..2f94216 100644
--- a/test/transaction_test.exs
+++ b/test/transaction_test.exs
@@ -2,28 +2,52 @@ defmodule Exledger.TransactionTest do
   use ExUnit.Case
   use ExLedger.LedgerBuilder
 
-  test "add_entry/3" do
-    assert %{balances: [usd: 1]} =
-             Transaction.new("test transaction")
-             |> Transaction.add_entry("assets", {1, :usd})
-  end
+  describe "add_entry/3" do
+    setup [:build_transaction]
+
+    test "single currency", %{transaction: txn} do
+      assert %{balances: [usd: 1]} = txn
+    end
 
-  test "add_entry/3 sum 2 common currency" do
-    assert %{balances: [usd: 6]} =
-             Transaction.new("test transaction")
-             |> Transaction.add_entry("assets", {1, :usd})
-             |> Transaction.add_entry("assets", {5, :usd})
+    test "sums 2 common currency", %{transaction: txn} do
+      assert %{balances: [usd: 6]} =
+               txn
+               |> Transaction.add_entry("assets", {5, :usd})
+    end
+
+    test "multiple currency", %{transaction: txn} do
+      assert %{balances: [usd: 0, php: 0]} =
+               txn
+               |> Transaction.add_entry("expenses", {-1, :usd})
+               |> Transaction.add_entry("assets", {1, :php})
+               |> Transaction.add_entry("expenses", {-1, :php})
+    end
   end
 
-  test "compute balances" do
+  describe "is_balanced?/1" do
+    test "returns true when all balances is 0" do
+      txn =
+        Transaction.new("test transaction")
+        |> Transaction.add_entry("assets", {-100, :usd})
+        |> Transaction.add_entry("expenses", {100, :usd})
+
+      assert Transaction.is_balanced?(txn)
+    end
+
+    test "returns false when all imbalances is 0" do
+      txn =
+        Transaction.new("test transaction")
+        |> Transaction.add_entry("assets", {-100, :usd})
+
+      refute Transaction.is_balanced?(txn)
+    end
   end
 
-  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})
+  defp build_transaction(_context) do
+    transaction =
+      Transaction.new("test transaction")
+      |> Transaction.add_entry("assets", {1, :usd})
+
+    [transaction: transaction]
   end
 end