Use SQLite for shared program state

vite.config.js

@@ -1,13 +1,18 @@
 import fs from 'node:fs/promises';
 import path from 'node:path';
+import { DatabaseSync } from 'node:sqlite';
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
 
-const databasePath = path.resolve(process.cwd(), 'data', 'flow-db.json');
+const dataDirectory = path.resolve(process.cwd(), 'data');
+const sqlitePath = path.join(dataDirectory, 'flow.db');
+const seedJsonPath = path.join(dataDirectory, 'flow-db.json');
 
-async function readDatabase() {
+let database;
+
+async function readSeedJson() {
   try {
-    const raw = await fs.readFile(databasePath, 'utf8');
+    const raw = await fs.readFile(seedJsonPath, 'utf8');
     return JSON.parse(raw);
   } catch (error) {
     if (error.code === 'ENOENT') return null;
@@ -15,12 +20,74 @@ async function readDatabase() {
   }
 }
 
+async function getDatabase() {
+  if (database) return database;
+
+  await fs.mkdir(dataDirectory, { recursive: true });
+  database = new DatabaseSync(sqlitePath);
+  database.exec(`
+    CREATE TABLE IF NOT EXISTS app_state (
+      id INTEGER PRIMARY KEY CHECK (id = 1),
+      content TEXT NOT NULL,
+      program_states TEXT NOT NULL,
+      updated_at TEXT NOT NULL
+    )
+  `);
+
+  const existing = database.prepare('SELECT id FROM app_state WHERE id = 1').get();
+  if (!existing) {
+    const seed = await readSeedJson();
+    if (seed) writeDatabase(seed);
+  } else {
+    const seed = await readSeedJson();
+    const row = database.prepare('SELECT content FROM app_state WHERE id = 1').get();
+    const existingContent = row ? JSON.parse(row.content) : null;
+    const existingExtraCount = existingContent?.extraPrograms?.length ?? 0;
+    const seedExtraCount = seed?.content?.extraPrograms?.length ?? 0;
+
+    if (existingExtraCount === 0 && seedExtraCount > 0) {
+      writeDatabase(seed);
+    }
+  }
+
+  return database;
+}
+
+async function readDatabase() {
+  const db = await getDatabase();
+  const row = db
+    .prepare('SELECT content, program_states AS programStates, updated_at AS updatedAt FROM app_state WHERE id = 1')
+    .get();
+
+  if (!row) return null;
+
+  return {
+    content: JSON.parse(row.content),
+    programStates: JSON.parse(row.programStates),
+    updatedAt: row.updatedAt
+  };
+}
+
 async function writeDatabase(data) {
-  await fs.mkdir(path.dirname(databasePath), { recursive: true });
-  await fs.writeFile(databasePath, JSON.stringify({
-    ...data,
-    updatedAt: new Date().toISOString()
-  }, null, 2));
+  const db = await getDatabase();
+  const updatedAt = new Date().toISOString();
+  const content = data.content ?? {};
+  const programStates = data.programStates ?? {};
+
+  db.prepare(`
+    INSERT INTO app_state (id, content, program_states, updated_at)
+    VALUES (1, ?, ?, ?)
+    ON CONFLICT(id) DO UPDATE SET
+      content = excluded.content,
+      program_states = excluded.program_states,
+      updated_at = excluded.updated_at
+  `).run(JSON.stringify(content), JSON.stringify(programStates), updatedAt);
+
+  return {
+    content,
+    programStates,
+    updatedAt
+  };
 }
 
 function readRequestBody(request) {
@@ -48,7 +115,7 @@ function sendJson(response, statusCode, payload) {
 
 function serverDatabasePlugin() {
   return {
-    name: 'flow-server-database',
+    name: 'flow-server-sqlite-database',
     configureServer(server) {
       server.middlewares.use('/api/state', async (request, response) => {
         try {
@@ -66,11 +133,10 @@ function serverDatabasePlugin() {
             const current = request.method === 'PATCH' ? (await readDatabase()) ?? {} : {};
             const body = await readRequestBody(request);
             const payload = body ? JSON.parse(body) : {};
-            const nextData = {
+            const nextData = await writeDatabase({
               ...current,
               ...payload
-            };
-            await writeDatabase(nextData);
+            });
             sendJson(response, 200, nextData);
             return;
           }