refactor: answer_type single TEXT + new 'question' type

- Convert TEXT[] back to TEXT (take first element of existing arrays)
- Valid values: yes_no, text, question, word
- API validation updated for single string

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

src/db-migrate.js

@@ -319,11 +319,18 @@ async function migrate() {
     )
   `);
 
-  // pairs.answer_type → TEXT[] (multi-select)
+  // pairs.answer_type → single TEXT (was TEXT[], now back to single value + new 'question' type)
   await query(`ALTER TABLE pairs DROP CONSTRAINT IF EXISTS pairs_answer_type_check`).catch(() => {});
   await query(`
-    ALTER TABLE pairs ALTER COLUMN answer_type TYPE TEXT[]
-    USING ARRAY[answer_type]::TEXT[]
+    ALTER TABLE pairs ALTER COLUMN answer_type TYPE TEXT
+    USING (CASE
+      WHEN answer_type IS NULL OR array_length(answer_type::TEXT[], 1) IS NULL THEN 'text'
+      ELSE (answer_type::TEXT[])[1]
+    END)
+  `).catch(() => {});
+  await query(`
+    ALTER TABLE pairs ADD CONSTRAINT pairs_answer_type_check
+    CHECK (answer_type IN ('yes_no', 'text', 'question', 'word'))
   `).catch(() => {});
 
   // statements.answer — boolean nullable (for yes/no correct answer)

src/routes/pairs.js

@@ -2,12 +2,11 @@ const router = require('express').Router();
 const { query } = require('../db');
 
 const STATUSES = ['draft', 'blocked', 'published'];
-const ANSWER_TYPES = new Set(['yes_no', 'text', 'word']);
+const ANSWER_TYPES = new Set(['yes_no', 'text', 'question', 'word']);
 
 function validateAnswerType(val) {
-  const arr = Array.isArray(val) ? val : (val ? [val] : []);
-  if (!arr.length) return 'answer_type must be a non-empty array of: yes_no, text, word';
-  if (!arr.every(t => ANSWER_TYPES.has(t))) return `answer_type values must be: ${[...ANSWER_TYPES].join(', ')}`;
+  if (!val || typeof val !== 'string') return `answer_type must be one of: ${[...ANSWER_TYPES].join(', ')}`;
+  if (!ANSWER_TYPES.has(val)) return `answer_type must be one of: ${[...ANSWER_TYPES].join(', ')}`;
   return null;
 }
 
@@ -50,13 +49,12 @@ router.post('/', async (req, res, next) => {
 
     const atErr = validateAnswerType(answer_type);
     if (atErr) return res.status(400).json({ error: atErr });
-    const atArr = Array.isArray(answer_type) ? answer_type : [answer_type];
 
     const result = await query(
       `INSERT INTO pairs
          (answer_type, difficulty_level, question_id, positive_statement_id, negative_statement_id, blocked_topic)
        VALUES ($1, $2, $3, $4, $5, $6) RETURNING *`,
-      [atArr, difficulty_level || null, question_id || null,
+      [answer_type, difficulty_level || null, question_id || null,
        positive_statement_id || null, negative_statement_id || null, blocked_topic || null]
     );
     res.status(201).json(result.rows[0]);
@@ -74,8 +72,10 @@ router.patch('/:id', async (req, res, next) => {
 
     if (req.body.status && !STATUSES.includes(req.body.status))
       return res.status(400).json({ error: `status must be one of: ${STATUSES.join(', ')}` });
-    if (req.body.answer_type && !ANSWER_TYPES.includes(req.body.answer_type))
-      return res.status(400).json({ error: `answer_type must be one of: ${ANSWER_TYPES.join(', ')}` });
+    if (req.body.answer_type) {
+      const atErr = validateAnswerType(req.body.answer_type);
+      if (atErr) return res.status(400).json({ error: atErr });
+    }
 
     const tsField = STATUS_TIMESTAMP[req.body.status];
     if (tsField && !req.body[tsField]) {