feat(economy): refactor exam command to use ExamService with status-based flow and full test coverage

shared/modules/economy/exam.service.ts

@@ -0,0 +1,262 @@
+import { users, userTimers, transactions } from "@db/schema";
+import { eq, and, sql } from "drizzle-orm";
+import { TimerType, TransactionType } from "@shared/lib/constants";
+import { config } from "@shared/lib/config";
+import { withTransaction } from "@/lib/db";
+import type { Transaction } from "@shared/lib/types";
+import { UserError } from "@shared/lib/errors";
+
+const EXAM_TIMER_TYPE = TimerType.EXAM_SYSTEM;
+const EXAM_TIMER_KEY = 'default';
+
+export interface ExamMetadata {
+    examDay: number;
+    lastXp: string;
+}
+
+export enum ExamStatus {
+    NOT_REGISTERED = 'NOT_REGISTERED',
+    COOLDOWN = 'COOLDOWN',
+    MISSED = 'MISSED',
+    AVAILABLE = 'AVAILABLE',
+}
+
+export interface ExamActionResult {
+    status: ExamStatus;
+    nextExamAt?: Date;
+    reward?: bigint;
+    xpDiff?: bigint;
+    multiplier?: number;
+    examDay?: number;
+}
+
+export const examService = {
+    /**
+     * Get the current exam status for a user.
+     */
+    async getExamStatus(userId: string, tx?: Transaction) {
+        return await withTransaction(async (txFn) => {
+            const timer = await txFn.query.userTimers.findFirst({
+                where: and(
+                    eq(userTimers.userId, BigInt(userId)),
+                    eq(userTimers.type, EXAM_TIMER_TYPE),
+                    eq(userTimers.key, EXAM_TIMER_KEY)
+                )
+            });
+
+            if (!timer) {
+                return { status: ExamStatus.NOT_REGISTERED };
+            }
+
+            const now = new Date();
+            const expiresAt = new Date(timer.expiresAt);
+            expiresAt.setHours(0, 0, 0, 0);
+
+            if (now < expiresAt) {
+                return { 
+                    status: ExamStatus.COOLDOWN, 
+                    nextExamAt: expiresAt 
+                };
+            }
+
+            const metadata = timer.metadata as unknown as ExamMetadata;
+            const currentDay = now.getDay();
+
+            if (currentDay !== metadata.examDay) {
+                return { 
+                    status: ExamStatus.MISSED, 
+                    nextExamAt: expiresAt,
+                    examDay: metadata.examDay
+                };
+            }
+
+            return { 
+                status: ExamStatus.AVAILABLE,
+                examDay: metadata.examDay,
+                lastXp: BigInt(metadata.lastXp || "0")
+            };
+        }, tx);
+    },
+
+    /**
+     * Register a user for the first time.
+     */
+    async registerForExam(userId: string, username: string, tx?: Transaction): Promise<ExamActionResult> {
+        return await withTransaction(async (txFn) => {
+            // Ensure user exists
+            const { userService } = await import("@shared/modules/user/user.service");
+            const user = await userService.getOrCreateUser(userId, username, txFn);
+            if (!user) throw new Error("Failed to get or create user.");
+
+            const now = new Date();
+            const currentDay = now.getDay();
+
+            // Set next exam to next week
+            const nextExamDate = new Date(now);
+            nextExamDate.setDate(now.getDate() + 7);
+            nextExamDate.setHours(0, 0, 0, 0);
+
+            const metadata: ExamMetadata = {
+                examDay: currentDay,
+                lastXp: (user.xp ?? 0n).toString()
+            };
+
+            await txFn.insert(userTimers).values({
+                userId: BigInt(userId),
+                type: EXAM_TIMER_TYPE,
+                key: EXAM_TIMER_KEY,
+                expiresAt: nextExamDate,
+                metadata: metadata
+            });
+
+            return {
+                status: ExamStatus.NOT_REGISTERED,
+                nextExamAt: nextExamDate,
+                examDay: currentDay
+            };
+        }, tx);
+    },
+
+    /**
+     * Take the exam. Handles missed exams and reward calculations.
+     */
+    async takeExam(userId: string, tx?: Transaction): Promise<ExamActionResult> {
+        return await withTransaction(async (txFn) => {
+            const user = await txFn.query.users.findFirst({
+                where: eq(users.id, BigInt(userId))
+            });
+
+            if (!user) throw new Error("User not found");
+
+            const timer = await txFn.query.userTimers.findFirst({
+                where: and(
+                    eq(userTimers.userId, BigInt(userId)),
+                    eq(userTimers.type, EXAM_TIMER_TYPE),
+                    eq(userTimers.key, EXAM_TIMER_KEY)
+                )
+            });
+
+            if (!timer) {
+                return { status: ExamStatus.NOT_REGISTERED };
+            }
+
+            const now = new Date();
+            const expiresAt = new Date(timer.expiresAt);
+            expiresAt.setHours(0, 0, 0, 0);
+
+            if (now < expiresAt) {
+                 return { 
+                    status: ExamStatus.COOLDOWN, 
+                    nextExamAt: expiresAt 
+                };
+            }
+
+            const metadata = timer.metadata as unknown as ExamMetadata;
+            const examDay = metadata.examDay;
+            const currentDay = now.getDay();
+
+            if (currentDay !== examDay) {
+                // Missed exam logic
+                let daysUntil = (examDay - currentDay + 7) % 7;
+                if (daysUntil === 0) daysUntil = 7;
+
+                const nextExamDate = new Date(now);
+                nextExamDate.setDate(now.getDate() + daysUntil);
+                nextExamDate.setHours(0, 0, 0, 0);
+
+                const newMetadata: ExamMetadata = {
+                    examDay: examDay,
+                    lastXp: (user.xp ?? 0n).toString()
+                };
+
+                await txFn.update(userTimers)
+                    .set({
+                        expiresAt: nextExamDate,
+                        metadata: newMetadata
+                    })
+                    .where(and(
+                        eq(userTimers.userId, BigInt(userId)),
+                        eq(userTimers.type, EXAM_TIMER_TYPE),
+                        eq(userTimers.key, EXAM_TIMER_KEY)
+                    ));
+
+                return {
+                    status: ExamStatus.MISSED,
+                    nextExamAt: nextExamDate,
+                    examDay: examDay
+                };
+            }
+
+            // Reward Calculation
+            const lastXp = BigInt(metadata.lastXp || "0");
+            const currentXp = user.xp ?? 0n;
+            const diff = currentXp - lastXp;
+
+            const multMin = config.economy.exam.multMin;
+            const multMax = config.economy.exam.multMax;
+            const multiplier = Math.random() * (multMax - multMin) + multMin;
+
+            let reward = 0n;
+            if (diff > 0n) {
+                // Use scaled BigInt arithmetic to avoid precision loss with large XP values
+                const scaledMultiplier = BigInt(Math.round(multiplier * 10000));
+                reward = (diff * scaledMultiplier) / 10000n;
+            }
+
+            const nextExamDate = new Date(now);
+            nextExamDate.setDate(now.getDate() + 7);
+            nextExamDate.setHours(0, 0, 0, 0);
+
+            const newMetadata: ExamMetadata = {
+                examDay: examDay,
+                lastXp: currentXp.toString()
+            };
+
+            // Update Timer
+            await txFn.update(userTimers)
+                .set({
+                    expiresAt: nextExamDate,
+                    metadata: newMetadata
+                })
+                .where(and(
+                    eq(userTimers.userId, BigInt(userId)),
+                    eq(userTimers.type, EXAM_TIMER_TYPE),
+                    eq(userTimers.key, EXAM_TIMER_KEY)
+                ));
+
+            // Add Currency
+            if (reward > 0n) {
+                await txFn.update(users)
+                    .set({
+                        balance: sql`${users.balance} + ${reward}`
+                    })
+                    .where(eq(users.id, BigInt(userId)));
+
+                // Add Transaction Record
+                await txFn.insert(transactions).values({
+                    userId: BigInt(userId),
+                    amount: reward,
+                    type: TransactionType.EXAM_REWARD,
+                    description: `Weekly exam reward (XP Diff: ${diff})`,
+                });
+            }
+
+            // Record dashboard event
+            const { dashboardService } = await import("@shared/modules/dashboard/dashboard.service");
+            await dashboardService.recordEvent({
+                type: 'success',
+                message: `${user.username} passed their exam: ${reward.toLocaleString()} AU`,
+                icon: '🎓'
+            });
+
+            return {
+                status: ExamStatus.AVAILABLE,
+                nextExamAt: nextExamDate,
+                reward,
+                xpDiff: diff,
+                multiplier,
+                examDay
+            };
+        }, tx);
+    }
+};