Adding journal entries and database tables. Increased starting balances.

wolverine/a-frame-architecture/FinancialApi.Application/Account.cs

@@ -1,14 +1,40 @@
 namespace FinancialApi.Application;
 
-public record Account(int Id, decimal Balance)
+public record Account(int Id, decimal Balance, string AccountType)
 {
+    public Account ApplyPosting(decimal amount, EntryType entryType)
+    {
+        if (amount <= 0)
+        {
+            throw new ArgumentException("Credit amount must be positive.");
+        }
+
+        var newBalance = Balance;
+        if (AccountType == "Revenue")
+        {
+            newBalance = entryType == EntryType.Credit ? newBalance + amount : newBalance - amount;
+        }
+        else
+        {
+            newBalance = entryType == EntryType.Debit ? newBalance - amount : newBalance + amount;
+        }
+        
+
+        if (newBalance < 0 && AccountType == "Liability")
+        {
+            throw new InvalidOperationException("Insufficient funds.");
+        }
+
+        return this with { Balance = newBalance };
+    }
+
     public Account ApplyFee(decimal amount)
     {
         if (amount <= 0)
         {
             throw new ArgumentException("Fee must be positive.");
         }
-            
+
         if (Balance - amount < 0)
         {
             throw new InvalidOperationException("Insufficient funds.");
@@ -16,18 +42,19 @@ public record Account(int Id, decimal Balance)
 
         return this with { Balance = Balance - amount };
     }
-    
+
     public Account Debit(decimal amount)
     {
         if (amount <= 0)
         {
             throw new ArgumentException("Debit amount must be positive.");
         }
+
         if (Balance - amount < 0)
         {
             throw new InvalidOperationException("Insufficient funds.");
         }
-        
+
         return this with { Balance = Balance - amount };
     }
 
@@ -37,7 +64,7 @@ public record Account(int Id, decimal Balance)
         {
             throw new ArgumentException("Credit amount must be positive.");
         }
-        
+
         return this with { Balance = Balance + amount };
     }
 }

wolverine/a-frame-architecture/FinancialApi.Application/BalancedJournal.cs

@@ -0,0 +1,23 @@
+namespace FinancialApi.Application;
+
+public record BalancedJournal
+{
+    public JournalEntry Entry { get; }
+
+    private BalancedJournal(JournalEntry entry) => Entry = entry;
+
+    public static BalancedJournal Create(Guid id, string description, DateTimeOffset createdAt, List<JournalLine> lines)
+    {
+        var debits = lines.Where(l => l.Type == EntryType.Debit).Sum(l => l.Amount);
+        var credits = lines.Where(l => l.Type == EntryType.Credit).Sum(l => l.Amount);
+
+        if (debits != credits)
+        {
+            throw new InvalidOperationException(
+                $"GAAP Violation: Total Debits ({debits}) must equal Total Credits ({credits})!"
+            );
+        }
+
+        return new(new JournalEntry(id, description, createdAt, lines));
+    }
+}

wolverine/a-frame-architecture/FinancialApi.Application/EntryType.cs

@@ -0,0 +1,7 @@
+namespace FinancialApi.Application;
+
+public enum EntryType
+{
+    Debit,
+    Credit
+}

wolverine/a-frame-architecture/FinancialApi.Application/JournalEntry.cs

@@ -0,0 +1,21 @@
+namespace FinancialApi.Application;
+
+public record JournalEntry
+{
+    public Guid Id { get; init; }
+    public string Description { get; init; }
+    public DateTimeOffset CreatedAt { get; init; }
+    public List<JournalLine> Lines { get; init; } = [];
+
+    private JournalEntry()
+    {
+    }
+
+    internal JournalEntry(Guid id, string description, DateTimeOffset createdAt, List<JournalLine> lines)
+    {
+        Lines = lines;
+        Id = id;
+        Description = description;
+        CreatedAt = createdAt;
+    }
+}

wolverine/a-frame-architecture/FinancialApi.Application/JournalLine.cs

@@ -0,0 +1,3 @@
+namespace FinancialApi.Application;
+
+public record JournalLine(int AccountId, decimal Amount, EntryType Type);