Add Domain project and shifted handlers to application.

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

@@ -0,0 +1,54 @@
+namespace FinancialApi.Domain;
+
+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 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 };
+    }
+
+    public Account Credit(decimal amount)
+    {
+        if (amount <= 0)
+        {
+            throw new ArgumentException("Credit amount must be positive.");
+        }
+
+        return this with { Balance = Balance + amount };
+    }
+}

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

@@ -0,0 +1,23 @@
+namespace FinancialApi.Domain;
+
+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.Domain/EntryType.cs

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

wolverine/a-frame-architecture/FinancialApi.Domain/FinancialApi.Domain.csproj

@@ -0,0 +1,9 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+    <PropertyGroup>
+        <TargetFramework>net10.0</TargetFramework>
+        <ImplicitUsings>enable</ImplicitUsings>
+        <Nullable>enable</Nullable>
+    </PropertyGroup>
+
+</Project>

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

@@ -0,0 +1,17 @@
+namespace FinancialApi.Domain;
+
+public record JournalEntry
+{
+    public Guid Id { get; init; }
+    public string Description { get; init; }
+    public DateTimeOffset CreatedAt { get; init; }
+    public List<JournalLine> Lines { get; init; } = [];
+
+    internal JournalEntry(Guid id, string description, DateTimeOffset createdAt, List<JournalLine> lines)
+    {
+        Lines = lines;
+        Id = id;
+        Description = description;
+        CreatedAt = createdAt;
+    }
+}

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

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