LearnSpace: full-stack educational whiteboard platform

Node.js/Express backend + vanilla JS frontend.
Features: real-time collaborative whiteboard (SSE), multi-page support,
LaTeX formulas, shapes/connectors, coordinate systems, number lines,
compass, zoom/pan, Catmull-Rom pencil smoothing, ruler/protractor with
rotation & resize controls, minimap navigation overlay, auto-measurements,
multi-page thumbnails sidebar, PNG export, page templates.
Student/teacher workflows: classes, assignments, library, dashboard.
Mobile responsive. SQLite (better-sqlite3).

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

backend/src/db/migrations/001_init.sql

@@ -0,0 +1,102 @@
+-- =============================================
+--  LearnSpace — Initial schema
+-- =============================================
+
+-- Расширения
+CREATE EXTENSION IF NOT EXISTS "pgcrypto";
+
+-- ── Пользователи ──────────────────────────────
+CREATE TABLE IF NOT EXISTS users (
+  id            SERIAL PRIMARY KEY,
+  email         VARCHAR(255) UNIQUE NOT NULL,
+  password_hash VARCHAR(255) NOT NULL,
+  name          VARCHAR(255) NOT NULL,
+  role          VARCHAR(20)  NOT NULL DEFAULT 'student'
+                CHECK (role IN ('student', 'teacher', 'admin')),
+  created_at    TIMESTAMPTZ  NOT NULL DEFAULT NOW(),
+  last_login    TIMESTAMPTZ
+);
+
+-- ── Предметы ──────────────────────────────────
+CREATE TABLE IF NOT EXISTS subjects (
+  id   SERIAL PRIMARY KEY,
+  slug VARCHAR(50) UNIQUE NOT NULL,
+  name VARCHAR(100) NOT NULL,
+  icon VARCHAR(10)
+);
+
+INSERT INTO subjects (slug, name, icon) VALUES
+  ('bio',  'Биология',   'dna'),
+  ('chem', 'Химия',      'atom'),
+  ('math', 'Математика', 'compass'),
+  ('phys', 'Физика',     'zap')
+ON CONFLICT DO NOTHING;
+
+-- ── Темы ──────────────────────────────────────
+CREATE TABLE IF NOT EXISTS topics (
+  id          SERIAL PRIMARY KEY,
+  subject_id  INT NOT NULL REFERENCES subjects(id) ON DELETE CASCADE,
+  name        VARCHAR(255) NOT NULL,
+  order_index INT NOT NULL DEFAULT 0
+);
+
+-- ── Банк вопросов ─────────────────────────────
+CREATE TABLE IF NOT EXISTS questions (
+  id          SERIAL PRIMARY KEY,
+  subject_id  INT  NOT NULL REFERENCES subjects(id) ON DELETE CASCADE,
+  topic_id    INT  REFERENCES topics(id) ON DELETE SET NULL,
+  text        TEXT NOT NULL,
+  difficulty  SMALLINT NOT NULL DEFAULT 1 CHECK (difficulty BETWEEN 1 AND 3),
+  year        SMALLINT,
+  explanation TEXT,
+  created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- ── Варианты ответов ──────────────────────────
+CREATE TABLE IF NOT EXISTS options (
+  id          SERIAL PRIMARY KEY,
+  question_id INT  NOT NULL REFERENCES questions(id) ON DELETE CASCADE,
+  text        TEXT NOT NULL,
+  is_correct  BOOLEAN NOT NULL DEFAULT FALSE,
+  order_index SMALLINT NOT NULL DEFAULT 0
+);
+
+-- ── Сессии тестирования ───────────────────────
+CREATE TABLE IF NOT EXISTS test_sessions (
+  id           SERIAL PRIMARY KEY,
+  user_id      INT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+  subject_id   INT REFERENCES subjects(id) ON DELETE SET NULL,
+  mode         VARCHAR(20) NOT NULL DEFAULT 'exam'
+               CHECK (mode IN ('exam', 'practice', 'topic', 'random')),
+  total        INT NOT NULL,
+  score        INT,
+  status       VARCHAR(20) NOT NULL DEFAULT 'in_progress'
+               CHECK (status IN ('in_progress', 'completed', 'abandoned')),
+  started_at   TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  finished_at  TIMESTAMPTZ
+);
+
+-- ── Вопросы сессии ────────────────────────────
+CREATE TABLE IF NOT EXISTS session_questions (
+  id          SERIAL PRIMARY KEY,
+  session_id  INT NOT NULL REFERENCES test_sessions(id) ON DELETE CASCADE,
+  question_id INT NOT NULL REFERENCES questions(id),
+  order_index INT NOT NULL
+);
+
+-- ── Ответы пользователя ───────────────────────
+CREATE TABLE IF NOT EXISTS user_answers (
+  id               SERIAL PRIMARY KEY,
+  session_id       INT NOT NULL REFERENCES test_sessions(id) ON DELETE CASCADE,
+  question_id      INT NOT NULL REFERENCES questions(id),
+  chosen_option_id INT REFERENCES options(id),
+  is_correct       BOOLEAN,
+  time_spent_sec   SMALLINT,
+  answered_at      TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+-- ── Индексы ───────────────────────────────────
+CREATE INDEX IF NOT EXISTS idx_questions_subject ON questions(subject_id);
+CREATE INDEX IF NOT EXISTS idx_questions_topic   ON questions(topic_id);
+CREATE INDEX IF NOT EXISTS idx_sessions_user     ON test_sessions(user_id);
+CREATE INDEX IF NOT EXISTS idx_answers_session   ON user_answers(session_id);

backend/src/db/migrations/002_constraints.sql

@@ -0,0 +1,3 @@
+-- Уникальный индекс для upsert ответов
+CREATE UNIQUE INDEX IF NOT EXISTS idx_answers_session_question
+  ON user_answers (session_id, question_id);