fix(app): gate single-source message hover behind an experiment (#2761)

fluxer_api/src/api/instance/InstanceConfigRepository.test.ts

@@ -17,9 +17,14 @@ import {
 	DEFAULT_EXPERIMENT_DELIVERY_CONFIG,
 	type ExperimentDeliveryConfig,
 } from '@fluxer/schema/src/domains/experiment/ExperimentSchemas';
+import {
+	DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG,
+	type MessageHoverTrackingConfig,
+} from '@fluxer/schema/src/domains/experiment/MessageHoverTrackingSchemas';
 import {afterEach, describe, expect, it, vi} from 'vitest';
 
 const VOICE_NOISE_SUPPRESSION_CONFIG_KEY = 'voice_noise_suppression_config';
+const MESSAGE_HOVER_TRACKING_CONFIG_KEY = 'message_hover_tracking_config';
 const EXPERIMENT_DELIVERY_CONFIG_KEY = 'experiment_delivery_config';
 const APP_PUBLIC_CONFIG_KEY = 'app_public_config';
 const INSTANCE_POLICY_CONFIG_KEY = 'instance_policy_config';
@@ -312,6 +317,51 @@ describe('InstanceConfigRepository', () => {
 		await expect(repository.getVoiceNoiseSuppressionConfig()).resolves.toEqual(config);
 	});
 
+	it('returns the default message hover tracking config when the key is absent', async () => {
+		const executor = new CountingInMemoryCassandraQueryExecutor();
+		setCassandraQueryExecutorForTesting(executor);
+		const kvProvider = new MockKVProvider();
+		const repository = createRepository(kvProvider);
+
+		await expect(repository.getMessageHoverTrackingConfig()).resolves.toEqual(DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG);
+	});
+
+	it.each([
+		{name: 'unparseable text', stored: 'not-json'},
+		{name: 'a json array', stored: '[]'},
+		{name: 'out-of-range values', stored: '{"rollout_basis_points":99999}'},
+		{name: 'a target that is not a snowflake', stored: '{"included_user_ids":["nope"]}'},
+	])('falls back to the default message hover tracking config for $name', async ({stored}) => {
+		const executor = new CountingInMemoryCassandraQueryExecutor();
+		setCassandraQueryExecutorForTesting(executor);
+		const kvProvider = new MockKVProvider();
+		const repository = createRepository(kvProvider);
+
+		await repository.setConfig(MESSAGE_HOVER_TRACKING_CONFIG_KEY, stored);
+
+		await expect(repository.getMessageHoverTrackingConfig()).resolves.toEqual(DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG);
+	});
+
+	it('round-trips a stored message hover tracking config', async () => {
+		const executor = new CountingInMemoryCassandraQueryExecutor();
+		setCassandraQueryExecutorForTesting(executor);
+		const kvProvider = new MockKVProvider();
+		const repository = createRepository(kvProvider);
+
+		const config: MessageHoverTrackingConfig = {
+			...DEFAULT_MESSAGE_HOVER_TRACKING_CONFIG,
+			enabled: true,
+			config_version: 5,
+			rollout_basis_points: 2500,
+			rollout_salt: 'message-hover-tracking-v2',
+			included_user_ids: ['1400000000000000001'],
+			excluded_user_ids: ['1400000000000000002'],
+		};
+		await repository.setMessageHoverTrackingConfig(config);
+
+		await expect(repository.getMessageHoverTrackingConfig()).resolves.toEqual(config);
+	});
+
 	it('fills newly added voice noise suppression fields from the schema defaults', async () => {
 		const executor = new CountingInMemoryCassandraQueryExecutor();
 		setCassandraQueryExecutorForTesting(executor);

fluxer_api/src/api/instance/InstanceConfigRepository.ts

@@ -36,6 +36,10 @@ import {
 	type ExperimentDeliveryConfig,
 	ExperimentDeliveryConfigSchema,
 } from '@fluxer/schema/src/domains/experiment/ExperimentSchemas';
+import {
+	type MessageHoverTrackingConfig,
+	MessageHoverTrackingConfigSchema,
+} from '@fluxer/schema/src/domains/experiment/MessageHoverTrackingSchemas';
 import {
 	type InstanceAppPublic,
 	InstanceAppPublicSchema,
@@ -55,6 +59,7 @@ import {z} from 'zod';
 const GATEWAY_ROLLOUT_CONFIG_KEY = 'gateway_rollout_config';
 const VOICE_NOISE_SUPPRESSION_CONFIG_KEY = 'voice_noise_suppression_config';
 const EXPERIMENT_DELIVERY_CONFIG_KEY = 'experiment_delivery_config';
+const MESSAGE_HOVER_TRACKING_CONFIG_KEY = 'message_hover_tracking_config';
 const REGISTRATION_CONFIG_KEY = 'registration_config';
 const REGISTRATION_URLS_KEY = 'registration_urls';
 const REGISTRATION_PENDING_APPROVALS_KEY = 'registration_pending_approvals';
@@ -338,6 +343,7 @@ type StoredConfigSection =
 	| 'gateway rollout'
 	| 'voice noise suppression'
 	| 'experiment delivery'
+	| 'message hover tracking'
 	| 'instance policy'
 	| 'integrations'
 	| 'media'
@@ -479,6 +485,10 @@ function parseStoredExperimentDeliveryConfig(raw: string | null): ExperimentDeli
 	return parseStoredConfigOrDefault(ExperimentDeliveryConfigSchema, raw, 'experiment delivery');
 }
 
+function parseStoredMessageHoverTrackingConfig(raw: string | null): MessageHoverTrackingConfig {
+	return parseStoredConfigOrDefault(MessageHoverTrackingConfigSchema, raw, 'message hover tracking');
+}
+
 function validateStoredCollection<T>(schema: z.ZodType<T>, value: unknown, section: StoredConfigSection): Array<T> {
 	if (!Array.isArray(value)) {
 		throw new Error(`Stored ${section} configuration must be an array`);
@@ -998,6 +1008,7 @@ export class InstanceConfigRepository {
 		);
 		parseStoredVoiceNoiseSuppressionConfig(snapshot.get(VOICE_NOISE_SUPPRESSION_CONFIG_KEY) ?? null);
 		parseStoredExperimentDeliveryConfig(snapshot.get(EXPERIMENT_DELIVERY_CONFIG_KEY) ?? null);
+		parseStoredMessageHoverTrackingConfig(snapshot.get(MESSAGE_HOVER_TRACKING_CONFIG_KEY) ?? null);
 		const policy = parseStoredInstancePolicyConfig(snapshot.get(INSTANCE_POLICY_CONFIG_KEY) ?? null);
 		checkStoredConfig('registration', () =>
 			parseStoredRegistrationConfig(snapshot.get(REGISTRATION_CONFIG_KEY) ?? null),
@@ -1083,6 +1094,16 @@ export class InstanceConfigRepository {
 		return parseStoredExperimentDeliveryConfig(raw);
 	}
 
+	async getMessageHoverTrackingConfig(): Promise<MessageHoverTrackingConfig> {
+		const raw = await this.getConfig(MESSAGE_HOVER_TRACKING_CONFIG_KEY);
+		return parseStoredMessageHoverTrackingConfig(raw);
+	}
+
+	async setMessageHoverTrackingConfig(config: MessageHoverTrackingConfig): Promise<void> {
+		const validated = validateStoredConfig(MessageHoverTrackingConfigSchema, config, 'message hover tracking');
+		await this.setConfig(MESSAGE_HOVER_TRACKING_CONFIG_KEY, JSON.stringify(validated));
+	}
+
 	async setExperimentDeliveryConfig(config: ExperimentDeliveryConfig): Promise<void> {
 		const validated = validateStoredConfig(ExperimentDeliveryConfigSchema, config, 'experiment delivery');
 		await this.setConfig(EXPERIMENT_DELIVERY_CONFIG_KEY, JSON.stringify(validated));