feat(core): the e-mail server after Java, measured against Java

SMTP on port 25 stores mails for the domain's accounts as Java reads
them anew and tells a local sender of unknown recipients; POP3 on port
110 hands them out. The mailboxes are in the snapshot and go back into
the project. EmailRun plays four stories over the network; MailCases
feeds Java's workers without one (26 cases, de and en). 18 cases name
Java bugs that the core does not take.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/fls/src/projectSnapshot.ts

@@ -5,15 +5,17 @@
 // Only the cables count: a host's SSID connects nothing at run time, as in
 // Java (Swift joins a wireless host to the switch of its SSID; not taken).
 // A DNS server runs only when it is switched on (Java: DNSServer.aktiv); an
-// echo or web server is there either way, switched on or off (it can be
+// echo, web or e-mail server is there either way, switched on or off (it can be
 // switched at run time). The programs read the nodes' files (a web server its
 // pages).
 //
 // Back the other way: what the simulation changes that Java keeps in the
 // project (its objects are the project's), so a project saved after it holds
-// it. That is a router's or home router's firewall, set on its page konfig.
+// it. That is a router's or home router's firewall, set on its page konfig,
+// and an e-mail server's mailboxes (Java writes them into
+// /mailserver/konten.txt at once).
 
-import { portSnapshot, topologySnapshot, type DnsServerConfiguration, type EchoServerSnapshot, type Id, type WebServerSnapshot, type TopologySnapshot } from '@mdg-filius/core';
+import { portSnapshot, topologySnapshot, type DnsServerConfiguration, type EchoServerSnapshot, type EmailServerSnapshot, type Id, type WebServerSnapshot, type TopologySnapshot } from '@mdg-filius/core';
 import type { ImportedProject } from './importProject.js';
 
 export function projectSnapshot(project: ImportedProject): TopologySnapshot {
@@ -29,6 +31,11 @@ export function projectSnapshot(project: ImportedProject): TopologySnapshot {
   for (const [nodeId, configuration] of project.webServerConfigurations) {
     webServers.set(nodeId, { ...configuration, isActive: project.activePrograms.get(nodeId)?.has('webServer') === true });
   }
+  const emailServers = new Map<Id, EmailServerSnapshot>();
+  for (const [nodeId, configuration] of project.emailServerConfigurations) {
+    if (project.installedPrograms.get(nodeId)?.has('emailServer') !== true) continue;
+    emailServers.set(nodeId, { domain: configuration.domain, accounts: configuration.accounts, isActive: project.activePrograms.get(nodeId)?.has('emailServer') === true });
+  }
   const webBrowsers = new Set([...project.installedPrograms].filter(([, programs]) => programs.has('webBrowser')).map(([nodeId]) => nodeId));
   return topologySnapshot({
     nodes: project.graph.nodes.map((node) => ({
@@ -52,11 +59,22 @@ export function projectSnapshot(project: ImportedProject): TopologySnapshot {
     simpleClientsByNodeId: project.simpleClientConfigurations,
     webServersByNodeId: webServers,
     webBrowserNodeIds: webBrowsers,
+    emailServersByNodeId: emailServers,
     fileSystemsByNodeId: project.virtualFileSystems,
   });
 }
 
-/** The project with what the simulation changed that Java keeps: the firewalls, as the run's snapshot holds them. */
+/**
+ * The project with what the simulation changed that Java keeps, as the run's
+ * snapshot holds it: the firewalls, and the e-mail servers' mailboxes.
+ */
 export function projectWithSimulationChanges(project: ImportedProject, snapshot: TopologySnapshot): ImportedProject {
-  return { ...project, firewallConfigurationsByNodeId: new Map(snapshot.firewallConfigurationsByNodeId) };
+  const emailServers = new Map(project.emailServerConfigurations);
+  for (const [nodeId, server] of snapshot.emailServersByNodeId) {
+    const configuration = emailServers.get(nodeId);
+    if (configuration === undefined) continue;
+    const messages = server.accounts.reduce((count, account) => count + account.mailbox.length, 0);
+    emailServers.set(nodeId, { ...configuration, accounts: server.accounts, nextMessageID: messages + 1 });
+  }
+  return { ...project, firewallConfigurationsByNodeId: new Map(snapshot.firewallConfigurationsByNodeId), emailServerConfigurations: emailServers };
 }

packages/fls/test/importProject.test.ts

@@ -801,6 +801,41 @@ describe('importProject rules', () => {
     expect(reopened.firewallConfigurationsByNodeId.get(reopenedRouter)).toEqual(expected);
   });
 
+  it("keeps a mail the e-mail server took during the run in the project saved after it (projectWithSimulationChanges)", () => {
+    const project = openProjectArchive(new Uint8Array(readFileSync(join(corpusRoot, 'java-examples/email_komplett.fls'))), counter());
+    const node = (name: string) => project.graph.nodes.find((each) => each.displayName === name)!.id;
+    const server = node('Mail-Server (filius.de)');
+    const sender = node('Rechner 1');
+    const engine = new NetworkRuntimeEngine(14);
+    const snapshot = projectSnapshot(project);
+    expect(snapshot.emailServersByNodeId.get(server)).toEqual({ domain: 'filius.de', accounts: project.emailServerConfigurations.get(server)!.accounts, isActive: true });
+    const switchedOff = { ...project, activePrograms: new Map([...project.activePrograms].map(([id, programs]) => [id, new Set([...programs].filter((each) => each !== 'emailServer'))])) };
+    expect(projectSnapshot(switchedOff).emailServersByNodeId.get(server)?.isActive).toBe(false);
+    engine.handle({
+      type: 'start',
+      snapshot: { ...snapshot, simpleClientsByNodeId: new Map([[sender, { targetAddress: '141.99.50.232', targetPort: 25 }]]) },
+      seed: 14,
+      initialTimeMilliseconds: 0,
+    });
+    const client = engine.simpleClient(sender)!;
+    client.connect('141.99.50.232', 25);
+    const commands = ['HELO 141.99.50.181', 'MAIL FROM:<rechner1@filius.de>', 'RCPT TO:<rechner2@filius.de>', 'DATA', 'From: <rechner1@filius.de>\nTo: <rechner2@filius.de>\nSubject: Hallo\n\nGespeichert?\n.\n', 'QUIT'];
+    for (const [index, command] of commands.entries()) {
+      engine.handle({ type: 'advance', toMilliseconds: 5_000 + index * 2_000 });
+      client.send(command);
+    }
+    engine.handle({ type: 'advance', toMilliseconds: 20_000 });
+    // The project itself is as it was opened, until the run's changes go back into it.
+    expect(project.emailServerConfigurations.get(server)!.accounts[1]!.mailbox).toEqual([]);
+
+    const saved = saveProjectArchive(projectWithSimulationChanges(project, engine.state.topologySnapshot)).archive;
+    const reopened = openProjectArchive(saved, counter());
+    const reopenedServer = reopened.graph.nodes.find((each) => each.displayName === 'Mail-Server (filius.de)')!.id;
+    const [first, second] = reopened.emailServerConfigurations.get(reopenedServer)!.accounts;
+    expect(first!.mailbox).toEqual([]);
+    expect(second!.mailbox).toMatchObject([{ from: { name: null, mailAddress: 'rechner1@filius.de' }, to: [{ name: null, mailAddress: 'rechner2@filius.de' }], subject: 'Hallo', body: 'Gespeichert?\n' }]);
+  });
+
   it("keeps a node's IP forwarding where it differs from its kind's: a host that forwards, a router that does not", () => {
     const system = (ipForwardingEnabled: boolean) => ({ manualRoutes: [], ipForwardingEnabled });
     const project = importProject(