From 4cdf4f066309d0a0e8a11081aa7bd1b0828a2f91 Mon Sep 17 00:00:00 2001
From: Kostya <mail@sartin.in>
Date: Thu, 13 Aug 2026 22:26:19 +0000
Subject: Add domain model, repositories, and trading mechanism interfaces to
 service module

Introduces Account/Event/Trade/User/Option/LedgerEntry domain types plus
EventRepository/UserRepository and TradingMechanism abstractions.
---
 .../java/market/guess/service/domain/Account.java  | 27 ++++++++++++
 .../market/guess/service/domain/AccountType.java   |  6 +++
 .../guess/service/domain/BigDecimalOptions.java    | 14 ++++++
 .../java/market/guess/service/domain/Event.java    | 51 ++++++++++++++++++++++
 .../market/guess/service/domain/LedgerEntry.java   |  8 ++++
 .../java/market/guess/service/domain/Option.java   | 21 +++++++++
 .../java/market/guess/service/domain/Trade.java    | 19 ++++++++
 .../java/market/guess/service/domain/User.java     | 21 +++++++++
 .../guess/service/mechanism/TradingMechanism.java  | 15 +++++++
 .../service/repositories/EventRepository.java      |  7 +++
 .../guess/service/repositories/UserRepository.java |  8 ++++
 11 files changed, 197 insertions(+)
 create mode 100644 service/src/main/java/market/guess/service/domain/Account.java
 create mode 100644 service/src/main/java/market/guess/service/domain/AccountType.java
 create mode 100644 service/src/main/java/market/guess/service/domain/BigDecimalOptions.java
 create mode 100644 service/src/main/java/market/guess/service/domain/Event.java
 create mode 100644 service/src/main/java/market/guess/service/domain/LedgerEntry.java
 create mode 100644 service/src/main/java/market/guess/service/domain/Option.java
 create mode 100644 service/src/main/java/market/guess/service/domain/Trade.java
 create mode 100644 service/src/main/java/market/guess/service/domain/User.java
 create mode 100644 service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
 create mode 100644 service/src/main/java/market/guess/service/repositories/EventRepository.java
 create mode 100644 service/src/main/java/market/guess/service/repositories/UserRepository.java

diff --git a/service/src/main/java/market/guess/service/domain/Account.java b/service/src/main/java/market/guess/service/domain/Account.java
new file mode 100644
index 0000000..8b510a5
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/Account.java
@@ -0,0 +1,27 @@
+package market.guess.service.domain;
+
+import java.math.BigDecimal;
+import java.time.Clock;
+import java.util.ArrayList;
+import java.util.List;
+
+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;
+
+  public Account(AccountType accountType, String owner, BigDecimal initialBalance) {
+    this(accountType, owner, initialBalance, Clock.systemUTC());
+  }
+
+  public Account(AccountType accountType, String owner, BigDecimal initialBalance, Clock clock) {
+    super();
+    this.accountType = accountType;
+    this.owner = owner;
+    this.balance = initialBalance;
+    this.clock = clock;
+  }
+}
diff --git a/service/src/main/java/market/guess/service/domain/AccountType.java b/service/src/main/java/market/guess/service/domain/AccountType.java
new file mode 100644
index 0000000..293ff4e
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/AccountType.java
@@ -0,0 +1,6 @@
+package market.guess.service.domain;
+
+public enum AccountType {
+  EVENT,
+  USER
+}
diff --git a/service/src/main/java/market/guess/service/domain/BigDecimalOptions.java b/service/src/main/java/market/guess/service/domain/BigDecimalOptions.java
new file mode 100644
index 0000000..159905f
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/BigDecimalOptions.java
@@ -0,0 +1,14 @@
+package market.guess.service.domain;
+
+import java.math.BigDecimal;
+import java.math.RoundingMode;
+
+public record BigDecimalOptions(int scale, RoundingMode roundingMode) {
+  public static final BigDecimalOptions DEFAULT = new BigDecimalOptions(2, RoundingMode.HALF_EVEN);
+  public static final BigDecimal ZERO_MONEY =
+      BigDecimal.ZERO.setScale(DEFAULT.scale(), DEFAULT.roundingMode());
+
+  public static BigDecimal valueOf(double v) {
+    return BigDecimal.valueOf(v).setScale(DEFAULT.scale(), DEFAULT.roundingMode());
+  }
+}
diff --git a/service/src/main/java/market/guess/service/domain/Event.java b/service/src/main/java/market/guess/service/domain/Event.java
new file mode 100644
index 0000000..4c33928
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/Event.java
@@ -0,0 +1,51 @@
+package market.guess.service.domain;
+
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.List;
+import market.guess.api.CommissionTiming;
+import market.guess.api.EventStatus;
+import market.guess.service.mechanism.TradingMechanism;
+
+public final class Event {
+  private final String eventKey;
+  private final int displayId;
+  private final String name;
+  private final String description;
+  private final int commissionPercent;
+  private final CommissionTiming commissionTiming;
+  private final TradingMechanism mechanism;
+  private final List<Option> options;
+  private final Account account;
+  private final String marketMaker;
+
+  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(
+      String eventKey,
+      int displayId,
+      String name,
+      String description,
+      int commissionPercent,
+      CommissionTiming commissionTiming,
+      TradingMechanism mechanism,
+      EventStatus status,
+      List<Option> options,
+      String marketMaker) {
+    this.eventKey = eventKey;
+    this.displayId = displayId;
+    this.name = name;
+    this.description = description;
+    this.commissionPercent = commissionPercent;
+    this.commissionTiming = commissionTiming;
+    this.mechanism = mechanism;
+    this.options = List.copyOf(options);
+    this.marketMaker = marketMaker;
+    this.account = new Account(AccountType.EVENT, eventKey, BigDecimalOptions.ZERO_MONEY);
+    this.status = status;
+  }
+}
diff --git a/service/src/main/java/market/guess/service/domain/LedgerEntry.java b/service/src/main/java/market/guess/service/domain/LedgerEntry.java
new file mode 100644
index 0000000..b9173c8
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/LedgerEntry.java
@@ -0,0 +1,8 @@
+package market.guess.service.domain;
+
+import java.math.BigDecimal;
+import java.time.Instant;
+import market.guess.api.LedgerType;
+
+public record LedgerEntry(
+    Instant time, LedgerType type, BigDecimal amount, BigDecimal balanceAfter, String note) {}
diff --git a/service/src/main/java/market/guess/service/domain/Option.java b/service/src/main/java/market/guess/service/domain/Option.java
new file mode 100644
index 0000000..c182850
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/Option.java
@@ -0,0 +1,21 @@
+package market.guess.service.domain;
+
+public final class Option {
+
+  private String key;
+  private String name;
+
+  public Option(String key, String name) {
+    super();
+    this.key = key;
+    this.name = name;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public String getKey() {
+    return key;
+  }
+}
diff --git a/service/src/main/java/market/guess/service/domain/Trade.java b/service/src/main/java/market/guess/service/domain/Trade.java
new file mode 100644
index 0000000..cb6ed93
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/Trade.java
@@ -0,0 +1,19 @@
+package market.guess.service.domain;
+
+import java.math.BigDecimal;
+import java.time.Instant;
+
+public record Trade(
+    long seq,
+    Instant at,
+    String userName,
+    String optionKey,
+    String optionName,
+    long quantity,
+    BigDecimal sharesCost,
+    BigDecimal commission) {
+
+  public BigDecimal totalPaid() {
+    return sharesCost.add(commission);
+  }
+}
diff --git a/service/src/main/java/market/guess/service/domain/User.java b/service/src/main/java/market/guess/service/domain/User.java
new file mode 100644
index 0000000..3ae1d0f
--- /dev/null
+++ b/service/src/main/java/market/guess/service/domain/User.java
@@ -0,0 +1,21 @@
+package market.guess.service.domain;
+
+import java.math.BigDecimal;
+
+public final class User {
+  private final String name;
+  private final Account account;
+
+  public User(String name, BigDecimal initialBalance) {
+    this.name = name;
+    this.account = new Account(AccountType.USER, name, initialBalance);
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public Account getAccount() {
+    return account;
+  }
+}
diff --git a/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java b/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
new file mode 100644
index 0000000..d6e38bc
--- /dev/null
+++ b/service/src/main/java/market/guess/service/mechanism/TradingMechanism.java
@@ -0,0 +1,15 @@
+package market.guess.service.mechanism;
+
+import java.math.BigDecimal;
+import market.guess.api.MechanismType;
+
+public interface TradingMechanism {
+
+  MechanismType type();
+
+  BigDecimal openingCost(int optionCount);
+
+  BigDecimal costOfBuying(long[] q, int optionIndex, long quantity);
+
+  double[] prices(long[] q);
+}
diff --git a/service/src/main/java/market/guess/service/repositories/EventRepository.java b/service/src/main/java/market/guess/service/repositories/EventRepository.java
new file mode 100644
index 0000000..7794c99
--- /dev/null
+++ b/service/src/main/java/market/guess/service/repositories/EventRepository.java
@@ -0,0 +1,7 @@
+package market.guess.service.repositories;
+
+import market.guess.service.domain.Event;
+
+public interface EventRepository {
+  Event getEvent(String id);
+}
diff --git a/service/src/main/java/market/guess/service/repositories/UserRepository.java b/service/src/main/java/market/guess/service/repositories/UserRepository.java
new file mode 100644
index 0000000..992a8b3
--- /dev/null
+++ b/service/src/main/java/market/guess/service/repositories/UserRepository.java
@@ -0,0 +1,8 @@
+package market.guess.service.repositories;
+
+import market.guess.service.domain.User;
+
+public interface UserRepository {
+
+  User getUser(String name);
+}
-- 
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