add cohort date columns and use them in student stats

Store start/end/break dates on cohorts table so student stats
uses the cohort date range instead of a hardcoded last-30-days window.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dsshimel

attendabot/backend/src/api/routes/me.ts

@@ -17,6 +17,7 @@ meRouter.get("/", authenticateToken, (req: AuthRequest, res: Response) => {
     discordAccountId?: string;
     studentId?: number;
     studentName?: string;
+    cohortId?: number;
   } = {
     role: user.role,
     name: user.username,
@@ -27,11 +28,12 @@ meRouter.get("/", authenticateToken, (req: AuthRequest, res: Response) => {
   if (user.role === "student" && user.discordAccountId) {
     const db = getDatabase();
     const student = db
-      .prepare(`SELECT id, name FROM students WHERE discord_user_id = ?`)
-      .get(user.discordAccountId) as { id: number; name: string } | undefined;
+      .prepare(`SELECT id, name, cohort_id FROM students WHERE discord_user_id = ?`)
+      .get(user.discordAccountId) as { id: number; name: string; cohort_id: number } | undefined;
     if (student) {
       result.studentId = student.id;
       result.studentName = student.name;
+      result.cohortId = student.cohort_id;
     }
   }
 

attendabot/backend/src/services/db.ts

@@ -178,6 +178,15 @@ function initializeTables(): void {
     db.exec(`ALTER TABLE students ADD COLUMN profile_image TEXT`);
   }
 
+  // Add date columns to cohorts if they don't exist
+  const cohortCols = db.pragma("table_info(cohorts)") as Array<{ name: string }>;
+  if (!cohortCols.some((col) => col.name === "start_date")) {
+    db.exec(`ALTER TABLE cohorts ADD COLUMN start_date TEXT`);
+    db.exec(`ALTER TABLE cohorts ADD COLUMN end_date TEXT`);
+    db.exec(`ALTER TABLE cohorts ADD COLUMN break_start TEXT`);
+    db.exec(`ALTER TABLE cohorts ADD COLUMN break_end TEXT`);
+  }
+
   // Seed default cohorts if they don't exist
   seedDefaultCohorts();
 
@@ -208,6 +217,13 @@ function seedDefaultCohorts(): void {
   const stmt = db.prepare(`INSERT OR IGNORE INTO cohorts (name) VALUES (?)`);
   stmt.run("Fa2025");
   stmt.run("Sp2026");
+
+  // Set Sp2026 dates if not already set
+  db.prepare(`
+    UPDATE cohorts SET start_date='2026-02-02', end_date='2026-05-02',
+      break_start='2026-03-15', break_end='2026-03-22'
+    WHERE name='Sp2026' AND start_date IS NULL
+  `).run();
 }
 
 /** A message record from the database with joined channel and user data. */
@@ -437,13 +453,17 @@ export function closeDatabase(): void {
 export interface CohortRecord {
   id: number;
   name: string;
+  start_date: string | null;
+  end_date: string | null;
+  break_start: string | null;
+  break_end: string | null;
   created_at: string;
 }
 
 /** Retrieves all cohorts from the database, ordered by name. */
 export function getCohorts(): CohortRecord[] {
   const db = getDatabase();
-  const stmt = db.prepare(`SELECT id, name, created_at FROM cohorts ORDER BY name ASC`);
+  const stmt = db.prepare(`SELECT id, name, start_date, end_date, break_start, break_end, created_at FROM cohorts ORDER BY name ASC`);
   return stmt.all() as CohortRecord[];
 }
 
@@ -455,6 +475,10 @@ export function createCohort(name: string): CohortRecord {
   return {
     id: result.lastInsertRowid as number,
     name,
+    start_date: null,
+    end_date: null,
+    break_start: null,
+    break_end: null,
     created_at: new Date().toISOString(),
   };
 }

attendabot/backend/src/test/utils/testUtils.ts

@@ -60,6 +60,10 @@ export function createTestDatabase(): Database.Database {
     CREATE TABLE IF NOT EXISTS cohorts (
       id INTEGER PRIMARY KEY AUTOINCREMENT,
       name TEXT NOT NULL UNIQUE,
+      start_date TEXT,
+      end_date TEXT,
+      break_start TEXT,
+      break_end TEXT,
       created_at TEXT DEFAULT CURRENT_TIMESTAMP
     )
   `);

attendabot/frontend/src/App.tsx

@@ -5,7 +5,7 @@
 
 import { useState, useEffect } from "react";
 import { setUsername as storeUsername, clearSession, onAuthFailure, getMe, getCohorts, getStudentsByCohort } from "./api/client";
-import type { Student } from "./api/client";
+import type { Student, Cohort } from "./api/client";
 import { authClient } from "./lib/auth-client";
 import { Login } from "./components/Login";
 import { MessageFeed } from "./components/MessageFeed";
@@ -27,14 +27,21 @@ function App() {
   const [username, setUsername] = useState<string | null>(null);
   const [role, setRole] = useState<"instructor" | "student" | null>(null);
   const [sessionInvalid, setSessionInvalid] = useState(false);
-  const [impersonating, setImpersonating] = useState<{ discordId: string; name: string } | null>(null);
-  const [impersonateStudents, setImpersonateStudents] = useState<{ discordId: string; name: string }[]>([]);
+  const [impersonating, setImpersonating] = useState<{ discordId: string; name: string; cohortId: number } | null>(null);
+  const [impersonateStudents, setImpersonateStudents] = useState<{ discordId: string; name: string; cohortId: number }[]>([]);
+  const [cohorts, setCohorts] = useState<Cohort[]>([]);
+  const [studentCohortId, setStudentCohortId] = useState<number | null>(null);
 
   /** Fetches the user's role and identity after login. */
   const fetchRole = async () => {
     const me = await getMe();
     if (me) {
       setRole(me.role);
+      if (me.role === "student" && me.cohortId) {
+        setStudentCohortId(me.cohortId);
+        const allCohorts = await getCohorts();
+        setCohorts(allCohorts);
+      }
     }
   };
 
@@ -62,15 +69,16 @@ function App() {
   useEffect(() => {
     if (role !== "instructor") return;
     (async () => {
-      const cohorts = await getCohorts();
+      const allCohorts = await getCohorts();
+      setCohorts(allCohorts);
       const allStudents: Student[] = [];
-      for (const cohort of cohorts) {
+      for (const cohort of allCohorts) {
         const students = await getStudentsByCohort(cohort.id);
         allStudents.push(...students);
       }
       const withDiscord = allStudents
         .filter((s) => s.discordUserId)
-        .map((s) => ({ discordId: s.discordUserId!, name: s.name }))
+        .map((s) => ({ discordId: s.discordUserId!, name: s.name, cohortId: s.cohortId }))
         .sort((a, b) => a.name.localeCompare(b.name));
       setImpersonateStudents(withDiscord);
     })();
@@ -106,11 +114,14 @@ function App() {
 
   // Student portal
   if (role === "student") {
+    const cohort = cohorts.find((c) => c.id === studentCohortId);
     return (
       <StudentPortal
         username={username}
         sessionInvalid={sessionInvalid}
         onLogout={handleLogout}
+        cohortStartDate={cohort?.startDate ?? undefined}
+        cohortEndDate={cohort?.endDate ?? undefined}
       />
     );
   }
@@ -179,6 +190,8 @@ function App() {
           sessionInvalid={sessionInvalid}
           onLogout={handleLogout}
           studentDiscordId={impersonating.discordId}
+          cohortStartDate={cohorts.find((c) => c.id === impersonating.cohortId)?.startDate ?? undefined}
+          cohortEndDate={cohorts.find((c) => c.id === impersonating.cohortId)?.endDate ?? undefined}
         />
       ) : (
         <>

attendabot/frontend/src/api/client.ts

@@ -227,6 +227,10 @@ export async function syncDisplayNames(): Promise<{
 export interface Cohort {
   id: number;
   name: string;
+  startDate: string | null;
+  endDate: string | null;
+  breakStart: string | null;
+  breakEnd: string | null;
 }
 
 /** A student in a cohort. */
@@ -257,9 +261,13 @@ export async function getCohorts(): Promise<Cohort[]> {
     const res = await fetchWithAuth(`${API_BASE}/cohorts`);
     if (!res.ok) return [];
     const data = await res.json();
-    return data.cohorts.map((c: { id: number; name: string }) => ({
+    return data.cohorts.map((c: { id: number; name: string; start_date: string | null; end_date: string | null; break_start: string | null; break_end: string | null }) => ({
       id: c.id,
       name: c.name,
+      startDate: c.start_date,
+      endDate: c.end_date,
+      breakStart: c.break_start,
+      breakEnd: c.break_end,
     }));
   } catch (error) {
     console.error(error);
@@ -957,6 +965,7 @@ export interface MeResponse {
   discordAccountId?: string;
   studentId?: number;
   studentName?: string;
+  cohortId?: number;
 }
 
 /** Fetches the current user's role and identity. */

attendabot/frontend/src/components/StudentPortal.tsx

@@ -15,10 +15,12 @@ interface StudentPortalProps {
   sessionInvalid: boolean;
   onLogout: () => void;
   studentDiscordId?: string;
+  cohortStartDate?: string;
+  cohortEndDate?: string;
 }
 
 /** Student portal with tabs for Stats, My EODs, and Simulations. */
-export function StudentPortal({ username, sessionInvalid, onLogout, studentDiscordId }: StudentPortalProps) {
+export function StudentPortal({ username, sessionInvalid, onLogout, studentDiscordId, cohortStartDate, cohortEndDate }: StudentPortalProps) {
   const [activeTab, setActiveTab] = useState<StudentTab>("stats");
   const embedded = !!studentDiscordId;
 
@@ -47,7 +49,7 @@ export function StudentPortal({ username, sessionInvalid, onLogout, studentDisco
 
       <main>
         {activeTab === "stats" ? (
-          <StudentStats studentDiscordId={studentDiscordId} />
+          <StudentStats studentDiscordId={studentDiscordId} cohortStartDate={cohortStartDate} cohortEndDate={cohortEndDate} />
         ) : activeTab === "eods" ? (
           <MyEods studentDiscordId={studentDiscordId} />
         ) : (

attendabot/frontend/src/components/StudentStats.tsx

@@ -9,33 +9,36 @@ import type { DailyStats } from "../api/client";
 
 interface StudentStatsProps {
   studentDiscordId?: string;
+  cohortStartDate?: string;
+  cohortEndDate?: string;
 }
 
 /** A row in the stats table — either a single day or a weekly summary. */
 type StatsRow =
   | { type: "day"; day: DailyStats }
   | { type: "week"; sundayDate: string; weekDays: DailyStats[] };
 
-/** Renders a table of daily stats for the student over the last 30 days. */
-export function StudentStats({ studentDiscordId }: StudentStatsProps) {
+/** Renders a table of daily stats for the student over the cohort date range (or last 30 days as fallback). */
+export function StudentStats({ studentDiscordId, cohortStartDate, cohortEndDate }: StudentStatsProps) {
   const [days, setDays] = useState<DailyStats[]>([]);
   const [loading, setLoading] = useState(true);
 
   useEffect(() => {
     setLoading(true);
-    const end = new Date();
-    const start = new Date();
-    start.setDate(start.getDate() - 30);
-    const startStr = start.toISOString().split("T")[0];
-    const endStr = end.toISOString().split("T")[0];
+    const today = new Date().toISOString().split("T")[0];
+    const fallbackStart = new Date();
+    fallbackStart.setDate(fallbackStart.getDate() - 30);
+
+    const startStr = cohortStartDate ?? fallbackStart.toISOString().split("T")[0];
+    const endStr = cohortEndDate && cohortEndDate < today ? cohortEndDate : today;
 
     getMyStats(startStr, endStr, studentDiscordId).then((result) => {
       if (result) {
         setDays(result.days);
       }
       setLoading(false);
     });
-  }, [studentDiscordId]);
+  }, [studentDiscordId, cohortStartDate, cohortEndDate]);
 
   /** Build rows: normal days for Mon-Sat, weekly summary rows replacing Sundays. */
   const rows: StatsRow[] = useMemo(() => {
@@ -77,7 +80,7 @@ export function StudentStats({ studentDiscordId }: StudentStatsProps) {
 
   return (
     <div className="panel" style={{ gridColumn: "span 2" }}>
-      <h2>Daily Stats (Last 30 Days)</h2>
+      <h2>Daily Stats{cohortStartDate ? "" : " (Last 30 Days)"}</h2>
       {days.length === 0 ? (
         <p className="no-messages">No stats available.</p>
       ) : (