Add ledgered credit/debit to Account and trade recording to Event

Drops AccountType (accounts no longer need to self-identify),
gives Account credit()/debit() that append LedgerEntry rows, adds
Event.recordTrade()/tradeVolumeOf()/getCommission(), and implements
LocalGuessMarketContext.listEvents() via the repository.

6 files changed, 67 insertions, 26 deletions

diff --git a/service/src/main/java/market/guess/service/LocalGuessMarketContext.java b/service/src/main/java/market/guess/service/LocalGuessMarketContext.java
index a01d6d7..67e263f 100644
--- a/service/src/main/java/market/guess/service/LocalGuessMarketContext.java
+++ b/service/src/main/java/market/guess/service/LocalGuessMarketContext.java
@@ -9,6 +9,7 @@ import market.guess.api.GuessMarketContext;
 import market.guess.api.LoadResultDTO;
 import market.guess.api.PurchaseReceiptDTO;
 import market.guess.exception.GuessMarketException;
+import market.guess.service.domain.Event;
 import market.guess.service.repository.EventRepository;
 
 public final class LocalGuessMarketContext implements GuessMarketContext {
@@ -26,7 +27,7 @@ public final class LocalGuessMarketContext implements GuessMarketContext {
 
   @Override
   public List<EventSummaryDTO> listEvents() {
-    throw new UnsupportedOperationException("Unimplemented method 'listEvents'");
+    return eventRepository.getAllEvents().stream().map(Event::toEventSummary).toList();
   }
 
   @Override
diff --git a/service/src/main/java/market/guess/service/domain/Account.java b/service/src/main/java/market/guess/service/domain/Account.java
index 274260e..7e24cdb 100644
--- a/service/src/main/java/market/guess/service/domain/Account.java
+++ b/service/src/main/java/market/guess/service/domain/Account.java
@@ -4,28 +4,47 @@ import java.math.BigDecimal;
 import java.time.Clock;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
+import market.guess.api.LedgerType;
 
 public final class Account {
-
-  private final AccountType accountType;
   private final String owner;
   private final Clock clock;
   private final List<LedgerEntry> entries = new ArrayList<>();
   private BigDecimal balance;
+  private AtomicInteger runningId = new AtomicInteger();
 
-  public Account(AccountType accountType, String owner, BigDecimal initialBalance) {
-    this(accountType, owner, initialBalance, Clock.systemUTC());
+  public Account(String owner, BigDecimal initialBalance) {
+    this(owner, initialBalance, Clock.systemUTC());
   }
 
-  public Account(AccountType accountType, String owner, BigDecimal initialBalance, Clock clock) {
+  public Account(String owner, BigDecimal initialBalance, Clock clock) {
     super();
-    this.accountType = accountType;
     this.owner = owner;
     this.balance = BigDecimalOptions.toMoney(initialBalance);
     this.clock = clock;
   }
 
+  public String getOwner() {
+    return owner;
+  }
+
   public BigDecimal getBalance() {
     return balance;
   }
+
+  public boolean credit(LedgerType type, BigDecimal amount, String note) {
+    record(type, amount, note);
+    return true;
+  }
+
+  public boolean debit(LedgerType type, BigDecimal amount, String note) {
+    record(type, amount.negate(), note);
+    return true;
+  }
+
+  private void record(LedgerType type, BigDecimal amount, String note) {
+    entries.add(
+        new LedgerEntry(runningId.incrementAndGet(), clock.instant(), type, amount, balance, note));
+  }
 }
diff --git a/service/src/main/java/market/guess/service/domain/AccountType.java b/service/src/main/java/market/guess/service/domain/AccountType.java
deleted file mode 100644
index 293ff4e..0000000
--- a/service/src/main/java/market/guess/service/domain/AccountType.java
+++ /dev/null
@@ -1,6 +0,0 @@
-package market.guess.service.domain;
-
-public enum AccountType {
-  EVENT,
-  USER
-}
diff --git a/service/src/main/java/market/guess/service/domain/Event.java b/service/src/main/java/market/guess/service/domain/Event.java
index 383126f..2d7ac39 100644
--- a/service/src/main/java/market/guess/service/domain/Event.java
+++ b/service/src/main/java/market/guess/service/domain/Event.java
@@ -1,8 +1,10 @@
 package market.guess.service.domain;
 
 import java.math.BigDecimal;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.concurrent.atomic.AtomicInteger;
 import market.guess.api.CommissionTiming;
 import market.guess.api.EventStatus;
 import market.guess.api.EventSummaryDTO;
@@ -20,10 +22,10 @@ public final class Event {
   private final Account account;
   private final String marketMaker;
 
+  private final AtomicInteger runningId = new AtomicInteger();
   private final List<Trade> trades = new ArrayList<>();
   private EventStatus status;
   private String winningOptionKey;
-  private long nextTradeSeq = 1;
   private BigDecimal settlementCommission = BigDecimalOptions.ZERO_MONEY;
 
   public Event(
@@ -46,7 +48,7 @@ public final class Event {
     this.mechanism = mechanism;
     this.options = List.copyOf(options);
     this.marketMaker = marketMaker;
-    this.account = new Account(AccountType.EVENT, eventKey, BigDecimalOptions.ZERO_MONEY);
+    this.account = new Account(eventKey, BigDecimalOptions.ZERO_MONEY);
     this.status = status;
   }
 
@@ -114,20 +116,40 @@ public final class Event {
     this.winningOptionKey = winningOptionKey;
   }
 
-  public long getNextTradeSeq() {
-    return nextTradeSeq;
-  }
+  public Trade recordTrade(
+      Instant time,
+      String user,
+      Option option,
+      int quantity,
+      BigDecimal cost,
+      BigDecimal commission) {
+    var trade =
+        new Trade(
+            runningId.incrementAndGet(),
+            time,
+            user,
+            option.getKey(),
+            option.getName(),
+            quantity,
+            cost,
+            commission);
+    trades.add(trade);
 
-  public void setNextTradeSeq(long nextTradeSeq) {
-    this.nextTradeSeq = nextTradeSeq;
+    return trade;
   }
 
-  public BigDecimal getSettlementCommission() {
-    return settlementCommission;
+  public BigDecimal tradeVolumeOf(String option) {
+    return trades.stream()
+        .filter(trade -> trade.optionKey().equalsIgnoreCase(option))
+        .map(Trade::sharesCost)
+        .reduce(BigDecimalOptions.ZERO_MONEY, BigDecimal::add);
   }
 
-  public void setSettlementCommission(BigDecimal settlementCommission) {
-    this.settlementCommission = settlementCommission;
+  public BigDecimal getCommission() {
+    return trades.stream()
+        .map(Trade::commission)
+        .reduce(BigDecimalOptions.ZERO_MONEY, BigDecimal::add)
+        .add(settlementCommission);
   }
 
   public EventSummaryDTO toEventSummary() {
diff --git a/service/src/main/java/market/guess/service/domain/LedgerEntry.java b/service/src/main/java/market/guess/service/domain/LedgerEntry.java
index b9173c8..4ca4b92 100644
--- a/service/src/main/java/market/guess/service/domain/LedgerEntry.java
+++ b/service/src/main/java/market/guess/service/domain/LedgerEntry.java
@@ -5,4 +5,9 @@ import java.time.Instant;
 import market.guess.api.LedgerType;
 
 public record LedgerEntry(
-    Instant time, LedgerType type, BigDecimal amount, BigDecimal balanceAfter, String note) {}
+    int id,
+    Instant time,
+    LedgerType type,
+    BigDecimal amount,
+    BigDecimal balanceAfter,
+    String note) {}
diff --git a/service/src/main/java/market/guess/service/domain/User.java b/service/src/main/java/market/guess/service/domain/User.java
index 3ae1d0f..af9ac78 100644
--- a/service/src/main/java/market/guess/service/domain/User.java
+++ b/service/src/main/java/market/guess/service/domain/User.java
@@ -8,7 +8,7 @@ public final class User {
 
   public User(String name, BigDecimal initialBalance) {
     this.name = name;
-    this.account = new Account(AccountType.USER, name, initialBalance);
+    this.account = new Account(name, initialBalance);
   }
 
   public String getName() {