9 files changed, 54 insertions, 16 deletions

diff --git a/service/src/main/java/market/guess/service/LocalGuessMarketContext.java b/service/src/main/java/market/guess/service/LocalGuessMarketContext.java
index 29e3f5c..909a808 100644
--- a/service/src/main/java/market/guess/service/LocalGuessMarketContext.java
+++ b/service/src/main/java/market/guess/service/LocalGuessMarketContext.java
@@ -86,7 +86,7 @@ public final class LocalGuessMarketContext implements GuessMarketContext {
               event.toEventSummary(),
               event.toMarketState(),
               event.getHistory(),
-              event.getWinningOptionKey()));
+              event.getWinningOptionName()));
     }
 
     return Result.error("Couldn't settle event.");
diff --git a/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java b/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java
index 270aadd..ea26107 100644
--- a/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java
+++ b/service/src/main/java/market/guess/service/catalog/LocalCatalogContext.java
@@ -42,7 +42,11 @@ public final class LocalCatalogContext implements CatalogContext {
     var event = optional.get();
 
     return Result.ok(
-        new EventDetailDTO(event.toEventSummary(), event.toMarketState(), event.getHistory(), ""));
+        new EventDetailDTO(
+            event.toEventSummary(),
+            event.toMarketState(),
+            event.getHistory(),
+            event.getWinningOptionName()));
   }
 
   @Override
diff --git a/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java b/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java
index b97114d..bcae787 100644
--- a/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java
+++ b/service/src/main/java/market/guess/service/catalog/infrastructure/provider/v1/XMLLoaderV1.java
@@ -63,7 +63,7 @@ public final class XMLLoaderV1 implements Loader {
         eventRepository.add(mapper.toDomain(event));
       }
 
-      userRepository.add(new User("Tester", 9_999_999));
+      userRepository.add(new User("Tester", 500));
 
       return Result.ok(new LoadResult(path.toString(), eventRepository.getAll().size()));
     } catch (Exception e) {
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 4c78486..e1b366e 100644
--- a/service/src/main/java/market/guess/service/domain/Event.java
+++ b/service/src/main/java/market/guess/service/domain/Event.java
@@ -10,9 +10,11 @@ import market.guess.api.MarketStateDTO;
 import market.guess.api.TradeRowDTO;
 import market.guess.model.event.EventStatus;
 import market.guess.model.event.EventSummaryDTO;
+import market.guess.model.ledger.LedgerType;
 import market.guess.service.helpers.BigDecimalOptions;
 import market.guess.service.helpers.InstantOptions;
 import market.guess.service.ledger.Ledger;
+import market.guess.service.ledger.LedgerEntry;
 import market.guess.service.mechanism.TradingMechanism;
 
 public final class Event {
@@ -54,6 +56,12 @@ public final class Event {
     this.markets = markets;
     this.marketMaker = marketMaker;
     this.ledger = new Ledger(eventKey, BigDecimalOptions.ZERO_MONEY);
+    var seed = mechanism.maxLoss();
+    if (seed.signum() > 0) {
+      ledger.record(
+          new LedgerEntry(
+              0, Instant.now(), LedgerType.SUBSIDY, seed, seed, "Market maker subsidy (max loss)"));
+    }
     this.state = status;
   }
 
@@ -151,6 +159,10 @@ public final class Event {
     return winningOptionKey;
   }
 
+  public String getWinningOptionName() {
+    return winningOptionKey == null ? "" : getOption(winningOptionKey).getName();
+  }
+
   public void setWinningOptionKey(String winningOptionKey) {
     this.winningOptionKey = winningOptionKey;
   }
diff --git a/service/src/main/java/market/guess/service/fulfillment/LocalFulfillmentContext.java b/service/src/main/java/market/guess/service/fulfillment/LocalFulfillmentContext.java
index 64887dc..cbbfafd 100644
--- a/service/src/main/java/market/guess/service/fulfillment/LocalFulfillmentContext.java
+++ b/service/src/main/java/market/guess/service/fulfillment/LocalFulfillmentContext.java
@@ -43,6 +43,11 @@ public final class LocalFulfillmentContext implements FulfillmentContext {
           LedgerType.PURCHASE,
           trade.totalPaid(),
           "Purchase: " + order.market().getName());
+      ledger.credit(
+          event.getLedger(),
+          LedgerType.PURCHASE,
+          trade.totalPaid(),
+          "Purchase: " + order.market().getName());
       order.market().addVolume(trade.quantity());
       recorded.add(trade);
     }
diff --git a/service/src/main/java/market/guess/service/ledger/LedgerContext.java b/service/src/main/java/market/guess/service/ledger/LedgerContext.java
index bb1bf97..fb58107 100644
--- a/service/src/main/java/market/guess/service/ledger/LedgerContext.java
+++ b/service/src/main/java/market/guess/service/ledger/LedgerContext.java
@@ -27,19 +27,23 @@ public final class LedgerContext {
     return true;
   }
 
+  public boolean credit(Ledger ledger, LedgerType type, BigDecimal amount, String note) {
+    record(ledger, type, amount, note);
+    return true;
+  }
+
+  public boolean debit(Ledger ledger, LedgerType type, BigDecimal amount, String note) {
+    record(ledger, type, amount.negate(), note);
+    return true;
+  }
+
   private void record(String name, LedgerType type, BigDecimal amount, String note) {
-    users
-        .get(name)
-        .ifPresent(
-            u ->
-                u.getLedger()
-                    .record(
-                        new LedgerEntry(
-                            runningId++,
-                            clock.instant(),
-                            type,
-                            amount,
-                            u.getLedger().getBalance().add(amount),
-                            note)));
+    users.get(name).ifPresent(u -> record(u.getLedger(), type, amount, note));
+  }
+
+  private void record(Ledger ledger, LedgerType type, BigDecimal amount, String note) {
+    ledger.record(
+        new LedgerEntry(
+            runningId++, clock.instant(), type, amount, ledger.getBalance().add(amount), note));
   }
 }
diff --git a/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java b/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java
index 062a095..981e733 100644
--- a/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java
+++ b/service/src/main/java/market/guess/service/mechanism/LmsrTradingMechanism.java
@@ -63,6 +63,11 @@ public final class LmsrTradingMechanism implements TradingMechanism {
   }
 
   @Override
+  public BigDecimal maxLoss() {
+    return BigDecimalOptions.toMoney(cost(new int[q.length]));
+  }
+
+  @Override
   public BigDecimal[] prices() {
     var max = Arrays.stream(q).mapToDouble(qi -> (double) qi / liquidity).max().orElse(0);
 
diff --git a/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java b/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
index 6fc5a9a..30d076d 100644
--- a/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
+++ b/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
@@ -7,6 +7,7 @@ import market.guess.api.MechanismType;
 import market.guess.service.domain.Event;
 import market.guess.service.domain.Market;
 import market.guess.service.domain.Trade;
+import market.guess.service.helpers.BigDecimalOptions;
 
 public sealed interface TradingMechanism permits LmsrTradingMechanism, OrderBookTradingMechanism {
 
@@ -15,4 +16,9 @@ public sealed interface TradingMechanism permits LmsrTradingMechanism, OrderBook
   List<Trade> buy(Event event, Market market, Instant at, long quantity);
 
   BigDecimal[] prices();
+
+  /** The subsidy needed to cover the market maker's worst-case loss, if any. */
+  default BigDecimal maxLoss() {
+    return BigDecimalOptions.ZERO_MONEY;
+  }
 }
diff --git a/service/src/main/java/market/guess/service/settlement/LocalSettlementContext.java b/service/src/main/java/market/guess/service/settlement/LocalSettlementContext.java
index 118e349..f6e9b67 100644
--- a/service/src/main/java/market/guess/service/settlement/LocalSettlementContext.java
+++ b/service/src/main/java/market/guess/service/settlement/LocalSettlementContext.java
@@ -40,6 +40,8 @@ public final class LocalSettlementContext implements SettlementContext {
       var net = gross.subtract(commission);
 
       ledger.credit(entry.getKey(), LedgerType.PAYOUT, net, "Payout: " + winningOption.getName());
+      ledger.debit(
+          event.getLedger(), LedgerType.PAYOUT, net, "Payout: " + winningOption.getName());
       event.addSettlementCommission(commission);
       totalPayout = totalPayout.add(net);
     }