Add an SQL DB abstraction layer

Because what self-respecting Enterprise(R) project doesn't have
one of those?

src/sql/api.ts

@@ -0,0 +1,19 @@
+import * as sql from "sql-bricks-postgres";
+
+export type Id<T> = bigint & { __id: T };
+
+export interface Row {
+  [key: string]: any;
+}
+
+export interface Transaction {
+  modify(stmt: sql.Statement): Promise<void>;
+
+  fetchRow(stmt: sql.SelectStatement): Promise<Row | undefined>;
+
+  fetchRows(stmt: sql.SelectStatement): Promise<Row[]>;
+}
+
+export interface DataSource {
+  transaction<T>(callback: (txn: Transaction) => Promise<T>): Promise<T>;
+}

src/sql/index.ts

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+export * from "./api";
+export * from "./pg";
+export * from "./util";

src/sql/pg.ts

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+import { Pool, PoolClient } from "pg";
+import * as sql from "sql-bricks-postgres";
+
+import { DataSource, Row, Transaction } from "./api";
+
+class PgTransaction implements Transaction {
+  constructor(private readonly _conn: PoolClient) {}
+
+  async modify(stmt: sql.Statement): Promise<void> {
+    await this._conn.query(stmt.toParams());
+  }
+
+  async fetchRow(stmt: sql.SelectStatement): Promise<Row | undefined> {
+    const { rows } = await this._conn.query(stmt.toParams());
+
+    return rows[0];
+  }
+
+  async fetchRows(stmt: sql.SelectStatement): Promise<Row[]> {
+    const { rows } = await this._conn.query(stmt.toParams());
+
+    return rows;
+  }
+}
+
+class PgDataSource implements DataSource {
+  private readonly _pool: Pool;
+
+  constructor() {
+    this._pool = new Pool();
+  }
+
+  async transaction<T>(
+    callback: (txn: Transaction) => Promise<T>
+  ): Promise<T> {
+    const conn = await this._pool.connect();
+
+    await conn.query("begin");
+
+    try {
+      const txn = new PgTransaction(conn);
+      const result = await callback(txn);
+
+      await conn.query("commit");
+
+      return result;
+    } catch (e) {
+      await conn.query("rollback");
+
+      return Promise.reject(e);
+    }
+  }
+}
+
+export function openDataSource(): DataSource {
+  return new PgDataSource();
+}

src/sql/util.ts

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+import { randomBytes } from "crypto";
+
+export function generateId(): bigint {
+  const buf = randomBytes(8);
+
+  buf[0] &= 0x7f; // Force number to be non-negative
+
+  // Let's not depend on Node v12 for the sake of 3 LoC just yet.
+
+  const hi = buf.readUInt32BE(0);
+  const lo = buf.readUInt32BE(4);
+
+  return (BigInt(hi) << 32n) | BigInt(lo);
+}