feat(discovery): resolve message links into discoverable guilds (#3159)

fluxer_api/src/api/guild/controllers/GuildDiscoveryController.ts

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
-import {createGuildID} from '@app/api/BrandedTypes';
+import {createChannelID, createGuildID} from '@app/api/BrandedTypes';
 import {Config} from '@app/api/Config';
 import type {GuildDiscoveryRow} from '@app/api/database/types/GuildDiscoveryTypes';
 import {DefaultUserOnly, LoginRequired} from '@app/api/middleware/AuthMiddleware';
@@ -15,12 +15,13 @@ import {GuildFeatures, JoinSourceTypes} from '@fluxer/constants/src/GuildConstan
 import {DiscoveryDisabledError} from '@fluxer/errors/src/domains/discovery/DiscoveryDisabledError';
 import {DiscoveryNotDiscoverableError} from '@fluxer/errors/src/domains/discovery/DiscoveryNotDiscoverableError';
 import {InvitesDisabledError} from '@fluxer/errors/src/domains/invite/InvitesDisabledError';
-import {GuildIdParam} from '@fluxer/schema/src/domains/common/CommonParamSchemas';
+import {GuildIdChannelIdParam, GuildIdParam} from '@fluxer/schema/src/domains/common/CommonParamSchemas';
 import {
 	DiscoveryApplicationPatchRequest,
 	DiscoveryApplicationRequest,
 	DiscoveryApplicationResponse,
 	DiscoveryCategoryListResponse,
+	DiscoveryChannelPreviewResponse,
 	DiscoveryGuildListResponse,
 	DiscoverySearchQuery,
 	DiscoveryStatusResponse,
@@ -100,6 +101,31 @@ export function GuildDiscoveryController(app: HonoApp) {
 			return ctx.json(categories);
 		},
 	);
+	app.get(
+		'/discovery/guilds/:guild_id/channels/:channel_id',
+		RateLimitMiddleware(RateLimitConfigs.DISCOVERY_CHANNEL_PREVIEW),
+		LoginRequired,
+		DefaultUserOnly,
+		Validator('param', GuildIdChannelIdParam),
+		OpenAPI({
+			operationId: 'get_discovery_channel_preview',
+			summary: 'Preview a channel in a discoverable guild',
+			description:
+				'Returns the guild and channel behind a channel or message link when the guild is listed in discovery and new members can read the channel.',
+			responseSchema: DiscoveryChannelPreviewResponse,
+			statusCode: 200,
+			security: ['sessionToken', 'bearerToken'],
+			tags: ['Discovery'],
+		}),
+		async (ctx) => {
+			ensureDiscoveryEnabled();
+			const {guild_id, channel_id} = ctx.req.valid('param');
+			const preview = await ctx
+				.get('discoveryService')
+				.getChannelPreview(createGuildID(guild_id), createChannelID(channel_id));
+			return ctx.json(preview);
+		},
+	);
 	app.post(
 		'/discovery/guilds/:guild_id/join',
 		RateLimitMiddleware(RateLimitConfigs.DISCOVERY_JOIN),

fluxer_api/src/api/guild/services/GuildDiscoveryService.ts

@@ -1,7 +1,8 @@
 // SPDX-License-Identifier: AGPL-3.0-or-later
 
-import type {GuildID, UserID} from '@app/api/BrandedTypes';
+import {type ChannelID, type GuildID, guildIdToRoleId, type UserID} from '@app/api/BrandedTypes';
 import {Config} from '@app/api/Config';
+import type {IChannelDataRepository} from '@app/api/channel/repositories/IChannelDataRepository';
 import type {GuildDiscoveryRow} from '@app/api/database/types/GuildDiscoveryTypes';
 import {mapGuildToGuildResponse} from '@app/api/guild/GuildModel';
 import type {IGuildDiscoveryRepository} from '@app/api/guild/repositories/GuildDiscoveryRepository';
@@ -10,6 +11,7 @@ import {contentModerationService} from '@app/api/infrastructure/ContentModeratio
 import type {IGatewayService} from '@app/api/infrastructure/IGatewayService';
 import {Logger} from '@app/api/Logger';
 import type {IGuildSearchService} from '@app/api/search/IGuildSearchService';
+import {Permissions} from '@fluxer/constants/src/ChannelConstants';
 import {
 	DISCOVERY_DEFAULT_LANGUAGE,
 	DISCOVERY_MAX_TAGS,
@@ -83,6 +85,8 @@ export abstract class IGuildDiscoveryService {
 
 	abstract listByStatus(params: {status: string}): Promise<Array<GuildDiscoveryRow>>;
 
+	abstract getChannelPreview(guildId: GuildID, channelId: ChannelID): Promise<DiscoveryChannelPreview>;
+
 	abstract searchDiscoverable(params: {
 		query?: string;
 		categoryId?: number;
@@ -118,7 +122,13 @@ interface DiscoveryGuildResult {
 	verification_level: number;
 }
 
+interface DiscoveryChannelPreview {
+	guild: {id: string; name: string; icon: string | null};
+	channel: {id: string; name: string | null; type: number};
+}
+
 const DISCOVERY_CATEGORY_FACET = 'discoveryCategory';
+const PUBLIC_CHANNEL_PERMISSIONS = Permissions.VIEW_CHANNEL | Permissions.READ_MESSAGE_HISTORY;
 
 function toDiscoveryCategoryCounts(
 	counts: Readonly<Record<string, number>> | undefined,
@@ -143,6 +153,7 @@ export class GuildDiscoveryService extends IGuildDiscoveryService {
 		private readonly guildRepository: IGuildRepositoryAggregate,
 		private readonly gatewayService: IGatewayService,
 		private readonly guildSearchService: IGuildSearchService | null,
+		private readonly channelDataRepository: IChannelDataRepository,
 	) {
 		super();
 	}
@@ -382,6 +393,38 @@ export class GuildDiscoveryService extends IGuildDiscoveryService {
 		return this.discoveryRepository.listFullByStatus(params.status);
 	}
 
+	async getChannelPreview(guildId: GuildID, channelId: ChannelID): Promise<DiscoveryChannelPreview> {
+		const [status, guild, channel, everyoneRole] = await Promise.all([
+			this.discoveryRepository.findByGuildId(guildId),
+			this.guildRepository.findUnique(guildId),
+			this.channelDataRepository.findUnique(channelId),
+			this.guildRepository.getRole(guildIdToRoleId(guildId), guildId),
+		]);
+		if (
+			status?.status !== DiscoveryApplicationStatus.APPROVED ||
+			!guild ||
+			guild.features.has(GuildFeatures.INVITES_DISABLED) ||
+			!channel ||
+			channel.guildId !== guildId ||
+			!everyoneRole
+		) {
+			throw new DiscoveryNotDiscoverableError();
+		}
+		if ((everyoneRole.permissions & Permissions.ADMINISTRATOR) === 0n) {
+			const overwrite = channel.permissionOverwrites.get(everyoneRole.id);
+			const permissions = overwrite
+				? (everyoneRole.permissions & ~overwrite.deny) | overwrite.allow
+				: everyoneRole.permissions;
+			if ((permissions & PUBLIC_CHANNEL_PERMISSIONS) !== PUBLIC_CHANNEL_PERMISSIONS) {
+				throw new DiscoveryNotDiscoverableError();
+			}
+		}
+		return {
+			guild: {id: guild.id.toString(), name: guild.name, icon: guild.iconHash},
+			channel: {id: channel.id.toString(), name: channel.name, type: channel.type},
+		};
+	}
+
 	async searchDiscoverable(params: {
 		query?: string;
 		categoryId?: number;

fluxer_api/src/api/guild/tests/DiscoverySearchAndJoin.test.ts

@@ -3,7 +3,8 @@
 import {createTestAccount, setUserACLs} from '@app/api/auth/tests/AuthTestUtils';
 import type {GuildID} from '@app/api/BrandedTypes';
 import {createTestBotAccount} from '@app/api/bot/tests/BotTestUtils';
-import {createGuild, getUserGuilds} from '@app/api/guild/tests/GuildTestUtils';
+import {createPermissionOverwrite} from '@app/api/channel/tests/ChannelTestUtils';
+import {createChannel, createGuild, getUserGuilds} from '@app/api/guild/tests/GuildTestUtils';
 import {setInjectedGatewayService} from '@app/api/middleware/ServiceRegistry';
 import {getGuildRepository} from '@app/api/middleware/ServiceSingletons';
 import {banUser} from '@app/api/moderation/tests/ModerationTestUtils';
@@ -15,11 +16,13 @@ import {createBuilder, createBuilderWithoutAuth} from '@app/api/test/TestRequest
 import syncDiscoveryIndex from '@app/api/worker/tasks/SyncDiscoveryIndex';
 import {clearWorkerDependencies, setWorkerDependenciesForTest} from '@app/api/worker/WorkerContext';
 import {APIErrorCodes} from '@fluxer/constants/src/ApiErrorCodes';
+import {Permissions} from '@fluxer/constants/src/ChannelConstants';
 import {DiscoveryCategories, DiscoveryCategoryLabels} from '@fluxer/constants/src/DiscoveryConstants';
 import {GuildVerificationLevel} from '@fluxer/constants/src/GuildConstants';
 import type {
 	DiscoveryApplicationResponse,
 	DiscoveryCategoryResponse,
+	DiscoveryChannelPreviewResponse,
 	DiscoveryGuildListResponse,
 } from '@fluxer/schema/src/domains/guild/GuildDiscoverySchemas';
 import type {WorkerTaskHelpers} from '@pkgs/worker/src/contracts/WorkerTask';
@@ -507,4 +510,65 @@ describe('Discovery Search and Join', () => {
 				.execute();
 		});
 	});
+	describe('channel preview', () => {
+		async function createListedGuild(name: string): Promise<{ownerToken: string; guildId: string; channelId: string}> {
+			const owner = await createTestAccount(harness);
+			const guild = await createGuild(harness, owner.token, name);
+			await setGuildMemberCount(harness, guild.id, 10);
+			const admin = await createTestAccount(harness);
+			await setUserACLs(harness, admin, ['admin:authenticate', 'discovery:review']);
+			await applyAndApprove(
+				harness,
+				owner.token,
+				admin.token,
+				guild.id,
+				`${name} welcomes everyone`,
+				DiscoveryCategories.GAMING,
+			);
+			return {ownerToken: owner.token, guildId: guild.id, channelId: guild.system_channel_id!};
+		}
+		test('should preview a channel that new members can read', async () => {
+			const {guildId, channelId} = await createListedGuild('Preview Guild');
+			const viewer = await createTestAccount(harness);
+			const preview = await createBuilder<DiscoveryChannelPreviewResponse>(harness, viewer.token)
+				.get(`/discovery/guilds/${guildId}/channels/${channelId}`)
+				.expect(HTTP_STATUS.OK)
+				.execute();
+			expect(preview.guild.id).toBe(guildId);
+			expect(preview.guild.name).toBe('Preview Guild');
+			expect(preview.channel.id).toBe(channelId);
+		});
+		test('should not preview a channel hidden from everyone', async () => {
+			const {ownerToken, guildId} = await createListedGuild('Hidden Channel Guild');
+			const hidden = await createChannel(harness, ownerToken, guildId, 'staff');
+			await createPermissionOverwrite(harness, ownerToken, hidden.id, guildId, {
+				type: 0,
+				allow: '0',
+				deny: Permissions.VIEW_CHANNEL.toString(),
+			});
+			const viewer = await createTestAccount(harness);
+			await createBuilder(harness, viewer.token)
+				.get(`/discovery/guilds/${guildId}/channels/${hidden.id}`)
+				.expect(HTTP_STATUS.BAD_REQUEST, APIErrorCodes.DISCOVERY_NOT_DISCOVERABLE)
+				.execute();
+		});
+		test('should not preview a channel from another guild', async () => {
+			const {guildId} = await createListedGuild('Listed Guild');
+			const other = await createListedGuild('Other Listed Guild');
+			const viewer = await createTestAccount(harness);
+			await createBuilder(harness, viewer.token)
+				.get(`/discovery/guilds/${guildId}/channels/${other.channelId}`)
+				.expect(HTTP_STATUS.BAD_REQUEST, APIErrorCodes.DISCOVERY_NOT_DISCOVERABLE)
+				.execute();
+		});
+		test('should not preview a guild that is not listed', async () => {
+			const owner = await createTestAccount(harness);
+			const guild = await createGuild(harness, owner.token, 'Unlisted Guild');
+			const viewer = await createTestAccount(harness);
+			await createBuilder(harness, viewer.token)
+				.get(`/discovery/guilds/${guild.id}/channels/${guild.system_channel_id}`)
+				.expect(HTTP_STATUS.BAD_REQUEST, APIErrorCodes.DISCOVERY_NOT_DISCOVERABLE)
+				.execute();
+		});
+	});
 });

fluxer_api/src/api/middleware/ServiceSingletons.ts

@@ -463,6 +463,7 @@ export const getGuildDiscoveryService = singleton(
 			getGuildRepository(),
 			getGatewayService(),
 			getGuildSearchService(),
+			getChannelRepository().channelData,
 		),
 );
 export const getReadStateRequestService = singleton(() => new ReadStateRequestService(getReadStateService()));

fluxer_api/src/api/openapi/openapi.json

@@ -5541,6 +5541,77 @@
 				]
 			}
 		},
+		"/discovery/guilds/{guild_id}/channels/{channel_id}": {
+			"get": {
+				"operationId": "get_discovery_channel_preview",
+				"summary": "Preview a channel in a discoverable guild",
+				"tags": ["Discovery"],
+				"responses": {
+					"200": {
+						"description": "Success",
+						"content": {
+							"application/json": {"schema": {"$ref": "#/components/schemas/DiscoveryChannelPreviewResponse"}}
+						}
+					},
+					"400": {
+						"description": "Bad Request - The request was malformed or contained invalid data",
+						"content": {"application/json": {"schema": {"$ref": "#/components/schemas/Error"}}}
+					},
+					"401": {
+						"description": "Unauthorized - Authentication is required or the token is invalid",
+						"content": {"application/json": {"schema": {"$ref": "#/components/schemas/Error"}}}
+					},
+					"403": {
+						"description": "Forbidden - You do not have permission to perform this action",
+						"content": {"application/json": {"schema": {"$ref": "#/components/schemas/Error"}}}
+					},
+					"429": {
+						"description": "Too Many Requests - You are being rate limited",
+						"content": {"application/json": {"schema": {"$ref": "#/components/schemas/ThrottledError"}}},
+						"headers": {
+							"Retry-After": {
+								"description": "Number of seconds to wait before retrying (only on 429)",
+								"schema": {"type": "integer"}
+							},
+							"X-RateLimit-Limit": {
+								"description": "The number of requests that can be made in the current window",
+								"schema": {"type": "integer"}
+							},
+							"X-RateLimit-Remaining": {
+								"description": "The number of remaining requests that can be made",
+								"schema": {"type": "integer"}
+							},
+							"X-RateLimit-Reset": {
+								"description": "Unix timestamp when the rate limit resets",
+								"schema": {"type": "integer"}
+							}
+						}
+					},
+					"500": {
+						"description": "Internal Server Error - An unexpected error occurred",
+						"content": {"application/json": {"schema": {"$ref": "#/components/schemas/Error"}}}
+					}
+				},
+				"description": "Returns the guild and channel behind a channel or message link when the guild is listed in discovery and new members can read the channel.",
+				"security": [{"sessionToken": []}],
+				"parameters": [
+					{
+						"name": "guild_id",
+						"in": "path",
+						"required": true,
+						"schema": {"description": "The ID of the guild", "$ref": "#/components/schemas/SnowflakeType"},
+						"description": "The ID of the guild"
+					},
+					{
+						"name": "channel_id",
+						"in": "path",
+						"required": true,
+						"schema": {"description": "The ID of the channel", "$ref": "#/components/schemas/SnowflakeType"},
+						"description": "The ID of the channel"
+					}
+				]
+			}
+		},
 		"/discovery/guilds/{guild_id}/join": {
 			"post": {
 				"operationId": "join_discovery_guild",
@@ -28579,6 +28650,35 @@
 				"required": ["url"],
 				"additionalProperties": false
 			},
+			"DiscoveryChannelPreviewResponse": {
+				"type": "object",
+				"properties": {
+					"guild": {
+						"type": "object",
+						"properties": {
+							"id": {"description": "Guild ID", "$ref": "#/components/schemas/SnowflakeStringType"},
+							"name": {"type": "string", "description": "Guild name"},
+							"icon": {"description": "Guild icon hash", "type": ["string", "null"]}
+						},
+						"required": ["id", "name", "icon"],
+						"additionalProperties": false,
+						"description": "The discoverable guild the channel belongs to"
+					},
+					"channel": {
+						"type": "object",
+						"properties": {
+							"id": {"description": "Channel ID", "$ref": "#/components/schemas/SnowflakeStringType"},
+							"name": {"description": "Channel name", "type": ["string", "null"]},
+							"type": {"type": "number", "description": "Channel type"}
+						},
+						"required": ["id", "name", "type"],
+						"additionalProperties": false,
+						"description": "A channel that new members can view"
+					}
+				},
+				"required": ["guild", "channel"],
+				"additionalProperties": false
+			},
 			"DiscoveryGuildListResponse": {
 				"type": "object",
 				"properties": {

fluxer_api/src/api/rate_limit_configs/DiscoveryRateLimitConfig.ts

@@ -16,6 +16,10 @@ export const DiscoveryRateLimitConfigs = {
 		bucket: 'discovery:join',
 		config: {limit: 10, windowMs: ms('1 minute')},
 	} as RouteRateLimitConfig,
+	DISCOVERY_CHANNEL_PREVIEW: {
+		bucket: 'discovery:channel_preview',
+		config: {limit: 60, windowMs: ms('10 seconds')},
+	} as RouteRateLimitConfig,
 	DISCOVERY_APPLY: {
 		bucket: 'discovery:apply::guild_id',
 		config: {limit: 5, windowMs: ms('1 minute')},