feat(appservice): Matrix Application Service core library (M4a) (#530)

packages/appservice/src/registration.ts

@@ -0,0 +1,76 @@
+import type { AppserviceConfig } from './types.js';
+
+export interface RegistrationOptions {
+  /** Unique appservice id in Synapse. Default: "mosaic-as". */
+  id?: string;
+  /** URL where Synapse reaches the appservice, e.g. http://mosaic-as:8008 */
+  url: string;
+  /** Alias namespace regex prefix. Default: "#mosaic-". */
+  aliasPrefix?: string;
+}
+
+const escapeRegex = (value: string): string => value.replace(/[.*+?^${}()|[\]\\]/g, '\\$&');
+
+/**
+ * Build the Synapse appservice registration document (mosaic-as.yaml).
+ * Deployment (infrastructure repo) serializes this to YAML and mounts it via
+ * app_service_config_files.
+ */
+export function buildRegistration(cfg: AppserviceConfig, options: RegistrationOptions) {
+  const prefix = cfg.userPrefix ?? 'agent-';
+  return {
+    id: options.id ?? 'mosaic-as',
+    url: options.url,
+    as_token: cfg.asToken,
+    hs_token: cfg.hsToken,
+    sender_localpart: cfg.senderLocalpart ?? 'mosaic-as',
+    rate_limited: false,
+    namespaces: {
+      users: [
+        {
+          regex: `@${escapeRegex(prefix)}.*:${escapeRegex(cfg.domain)}`,
+          exclusive: true,
+        },
+      ],
+      aliases: [
+        {
+          regex: `${escapeRegex(options.aliasPrefix ?? '#mosaic-')}.*:${escapeRegex(cfg.domain)}`,
+          exclusive: false,
+        },
+      ],
+      rooms: [],
+    },
+  };
+}
+
+const assertYamlSafe = (field: string, value: string): string => {
+  // Tokens/urls/ids are single-line opaque strings; control characters would
+  // let a crafted value terminate the scalar and inject YAML keys.
+  if (/[\r\n\x00-\x08\x0b-\x1f]/.test(value)) {
+    throw new Error(`registration field ${field} contains control characters`);
+  }
+  return value.replace(/'/g, "''");
+};
+
+/** Minimal YAML serialization for the flat registration document. */
+export function registrationToYaml(registration: ReturnType<typeof buildRegistration>): string {
+  const ns = registration.namespaces;
+  const nsBlock = (entries: Array<{ regex: string; exclusive: boolean }>): string =>
+    entries.length === 0
+      ? ' []'
+      : '\n' +
+        entries.map((e) => `    - regex: '${e.regex}'\n      exclusive: ${e.exclusive}`).join('\n');
+  return [
+    `id: '${assertYamlSafe('id', registration.id)}'`,
+    `url: '${assertYamlSafe('url', registration.url)}'`,
+    `as_token: '${assertYamlSafe('as_token', registration.as_token)}'`,
+    `hs_token: '${assertYamlSafe('hs_token', registration.hs_token)}'`,
+    `sender_localpart: '${assertYamlSafe('sender_localpart', registration.sender_localpart)}'`,
+    `rate_limited: ${registration.rate_limited}`,
+    'namespaces:',
+    `  users:${nsBlock(ns.users)}`,
+    `  aliases:${nsBlock(ns.aliases)}`,
+    `  rooms:${nsBlock(ns.rooms)}`,
+    '',
+  ].join('\n');
+}