Add secret class to manage scoped secrets

src/lib/secret.ts

@@ -0,0 +1,51 @@
+export class Secret {
+  // A fauna key, like `fn1234`.
+  key: string;
+  // A database scope, like `["foo", "bar"]`
+  databaseScope: string[];
+
+  constructor(opts: { key: string; databaseScope?: string[] }) {
+    this.key = opts.key;
+    this.databaseScope = opts.databaseScope ?? [];
+  }
+
+  static parse(key: string) {
+    if (key.length === 0) {
+      throw new Error("Secret cannot be empty");
+    }
+    if (key.includes(":")) {
+      throw new Error("Secret cannot be scoped");
+    }
+    return new Secret({ key });
+  }
+
+  buildSecret(opts?: { role?: string }): string {
+    let secret = this.key;
+    if (this.databaseScope.length > 0) {
+      secret += `:${this.databaseScope.join("/")}`;
+    }
+    if (opts?.role !== undefined || this.databaseScope.length > 0) {
+      const role = opts?.role ?? "admin";
+      secret += ["admin", "client", "server", "server-readonly"].includes(role)
+        ? `:${role}`
+        : `:@role/${role}`;
+    }
+    return secret;
+  }
+
+  /**
+   * Parses the given scope, appends it to the `Secret`, and returns the new
+   * secret. This mutates `this`.
+   */
+  appendScope(scope: string) {
+    this.databaseScope.push(...scope.split("/"));
+    return this;
+  }
+
+  clone(): Secret {
+    return new Secret({
+      key: this.key,
+      databaseScope: [...this.databaseScope],
+    });
+  }
+}

test/lib/secret.test.ts

@@ -0,0 +1,68 @@
+import { expect } from "chai";
+import { Secret } from "../../src/lib/secret";
+
+describe("secret", () => {
+  it("appends paths scoped secrets", () => {
+    const secret = Secret.parse("fn1234");
+    expect(secret.databaseScope).to.eql([]);
+
+    secret.appendScope("foo");
+    expect(secret.databaseScope).to.eql(["foo"]);
+
+    secret.appendScope("bar");
+    expect(secret.databaseScope).to.eql(["foo", "bar"]);
+  });
+
+  it("parses database paths from appendScope", () => {
+    const secret = Secret.parse("fn1234");
+    expect(secret.databaseScope).to.eql([]);
+
+    secret.appendScope("foo/bar");
+    expect(secret.databaseScope).to.eql(["foo", "bar"]);
+  });
+
+  it("disallows empty secrets", () => {
+    expect(() => Secret.parse("")).to.throw("Secret cannot be empty");
+  });
+
+  it("disallows scoped secrets", () => {
+    expect(() => Secret.parse("fn1234:foo")).to.throw(
+      "Secret cannot be scoped"
+    );
+  });
+
+  it("builds a secret with a role", () => {
+    const secret = Secret.parse("fn1234");
+    expect(secret.buildSecret()).to.equal("fn1234");
+    expect(secret.buildSecret({ role: "admin" })).to.equal("fn1234:admin");
+    expect(secret.buildSecret({ role: "server" })).to.equal("fn1234:server");
+    expect(secret.buildSecret({ role: "server-readonly" })).to.equal(
+      "fn1234:server-readonly"
+    );
+    expect(secret.buildSecret({ role: "client" })).to.equal("fn1234:client");
+    expect(secret.buildSecret({ role: "foo" })).to.equal("fn1234:@role/foo");
+  });
+
+  it("builds a secret with a scope", () => {
+    const secret = Secret.parse("fn1234");
+    secret.appendScope("foo");
+    expect(secret.buildSecret()).to.equal("fn1234:foo:admin");
+    secret.appendScope("bar");
+    expect(secret.buildSecret()).to.equal("fn1234:foo/bar:admin");
+  });
+
+  it("builds a secret with a scope and role", () => {
+    const secret = Secret.parse("fn1234");
+    secret.appendScope("foo/bar");
+    expect(secret.buildSecret()).to.equal("fn1234:foo/bar:admin");
+    expect(secret.buildSecret({ role: "admin" })).to.equal(
+      "fn1234:foo/bar:admin"
+    );
+    expect(secret.buildSecret({ role: "server" })).to.equal(
+      "fn1234:foo/bar:server"
+    );
+    expect(secret.buildSecret({ role: "foo" })).to.equal(
+      "fn1234:foo/bar:@role/foo"
+    );
+  });
+});