feat: add SQLite database and persistent task schema

.gitignore

@@ -17,6 +17,10 @@
 /.next/
 /out/
 
+# local database
+/data/*.sqlite
+/data/*.sqlite-*
+
 # production
 /build
 

db/schema.sql

@@ -0,0 +1,17 @@
+CREATE TABLE IF NOT EXISTS tasks (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  title TEXT NOT NULL CHECK (length(trim(title)) > 0),
+  description TEXT NOT NULL DEFAULT '',
+  due_date TEXT NOT NULL CHECK (due_date GLOB '[0-9][0-9][0-9][0-9]-[0-9][0-9]-[0-9][0-9]'),
+  topic TEXT NOT NULL CHECK (length(trim(topic)) > 0),
+  status TEXT NOT NULL DEFAULT 'Todo' CHECK (status IN ('Todo', 'In-Progress', 'Complete')),
+  archived_at TEXT,
+  created_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX IF NOT EXISTS idx_tasks_active_status
+ON tasks (archived_at, status, due_date);
+
+CREATE INDEX IF NOT EXISTS idx_tasks_topic
+ON tasks (topic COLLATE NOCASE);

lib/db.ts

@@ -0,0 +1,36 @@
+import fs from "node:fs";
+import path from "node:path";
+import { DatabaseSync } from "node:sqlite";
+
+type DatabaseGlobal = typeof globalThis & {
+  plannerDatabase?: DatabaseSync;
+  plannerDatabasePath?: string;
+};
+
+const schemaPath = path.join(process.cwd(), "db", "schema.sql");
+const defaultDatabasePath = path.join(process.cwd(), "data", "planner.sqlite");
+
+export function getDatabase() {
+  const databasePath = process.env.TASKS_DB_PATH ?? defaultDatabasePath;
+  const globalDatabase = globalThis as DatabaseGlobal;
+
+  if (
+    globalDatabase.plannerDatabase &&
+    globalDatabase.plannerDatabasePath === databasePath
+  ) {
+    return globalDatabase.plannerDatabase;
+  }
+
+  fs.mkdirSync(path.dirname(databasePath), { recursive: true });
+
+  const database = new DatabaseSync(databasePath);
+  const schema = fs.readFileSync(schemaPath, "utf8");
+
+  database.exec("PRAGMA foreign_keys = ON;");
+  database.exec(schema);
+
+  globalDatabase.plannerDatabase = database;
+  globalDatabase.plannerDatabasePath = databasePath;
+
+  return database;
+}

types/node-sqlite.d.ts

@@ -0,0 +1,19 @@
+declare module "node:sqlite" {
+  export type RunResult = {
+    changes: number;
+    lastInsertRowid: number | bigint;
+  };
+
+  export class StatementSync {
+    all(...params: unknown[]): unknown[];
+    get(...params: unknown[]): unknown;
+    run(...params: unknown[]): RunResult;
+  }
+
+  export class DatabaseSync {
+    constructor(location?: string | URL, options?: Record<string, unknown>);
+    close(): void;
+    exec(sql: string): void;
+    prepare(sql: string): StatementSync;
+  }
+}