add mbsync config generator

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/services/sync.test.ts

@@ -0,0 +1,29 @@
+import { describe, expect, test } from "bun:test";
+import { generateMbsyncConfig } from "./sync";
+
+describe("generateMbsyncConfig", () => {
+	test("generates valid mbsyncrc for a single IMAP account", () => {
+		const config = generateMbsyncConfig({
+			id: "personal",
+			host: "mail.example.com",
+			user: "user@example.com",
+			passCmd: "cat ~/.mail-pass",
+			sslType: "IMAPS",
+			mailDir: "/home/user/Mail/personal",
+		});
+
+		expect(config).toContain("IMAPAccount personal");
+		expect(config).toContain("Host mail.example.com");
+		expect(config).toContain("User user@example.com");
+		expect(config).toContain('PassCmd "cat ~/.mail-pass"');
+		expect(config).toContain("SSLType IMAPS");
+		expect(config).toContain("Path /home/user/Mail/personal/");
+		expect(config).toContain("Inbox /home/user/Mail/personal/Inbox");
+		expect(config).toContain("Channel personal");
+		expect(config).toContain("Far :personal-remote:");
+		expect(config).toContain("Near :personal-local:");
+		expect(config).toContain("Patterns *");
+		expect(config).toContain("Create Both");
+		expect(config).toContain("SyncState *");
+	});
+});

backend/src/services/sync.ts

@@ -0,0 +1,36 @@
+export interface ImapAccount {
+	id: string;
+	host: string;
+	user: string;
+	passCmd: string;
+	sslType: "IMAPS" | "STARTTLS";
+	mailDir: string;
+}
+
+export function generateMbsyncConfig(account: ImapAccount): string {
+	const { id, host, user, passCmd, sslType, mailDir } = account;
+	const trailingSlashDir = mailDir.endsWith("/") ? mailDir : `${mailDir}/`;
+
+	return `IMAPAccount ${id}
+Host ${host}
+User ${user}
+PassCmd "${passCmd}"
+SSLType ${sslType}
+
+IMAPStore ${id}-remote
+Account ${id}
+
+MaildirStore ${id}-local
+Subfolders Verbatim
+Path ${trailingSlashDir}
+Inbox ${trailingSlashDir}Inbox
+
+Channel ${id}
+Far :${id}-remote:
+Near :${id}-local:
+Patterns *
+Create Both
+Expunge None
+SyncState *
+`;
+}