backspace/packages/server/src/routes/federation/dmChannels.ts

import { getDb, schema } from '../../db/index.js';
import { getOurOrigin } from '../../utils/federationAuth.js';
import { sanitizeUser } from '../../utils/sanitize.js';
import { generateSnowflake } from '../../utils/snowflake.js';
import { connectionManager } from '../../ws/handler.js';
import { getDmMessageWithUser } from '../dm.js';
import { and, desc, eq, inArray, isNull, or } from 'drizzle-orm';
import type { FederatedCallEntry } from '../../ws/handler.js';
import type { DmChannel, DmMessageWithUser } from '@backspace/shared';

/**
 * Build the full DM channel payload used by `dm_channel_created` events.
 * Hydrates members, fetches the last message, and returns a `DmChannel`-shaped
 * object — or `null` when the channel row doesn't exist / is deleted.
 *
 * An optional `lastMessageOverride` lets callers supply the message object
 * directly (e.g. the just-relayed message) instead of querying the DB.
 */
export function buildDmChannelPayload(
  channelId: string,
  db: ReturnType<typeof getDb>,
  lastMessageOverride?: DmMessageWithUser | null,
): DmChannel | null {
  const dmChannel = db.select()
    .from(schema.dmChannels)
    .where(and(eq(schema.dmChannels.id, channelId), isNull(schema.dmChannels.deletedAt)))
    .get();
  if (!dmChannel) return null;

  const allMemberRows = db.select()
    .from(schema.dmMembers)
    .where(eq(schema.dmMembers.dmChannelId, channelId))
    .all();
  const memberUserIds = allMemberRows.map(m => m.userId);
  const users = memberUserIds.length > 0
    ? db.select().from(schema.users).where(inArray(schema.users.id, memberUserIds)).all()
    : [];

  let lastMessage: DmMessageWithUser | null = lastMessageOverride ?? null;
  if (!lastMessageOverride) {
    const lastMsgRow = db.select({ id: schema.dmMessages.id })
      .from(schema.dmMessages)
      .where(eq(schema.dmMessages.dmChannelId, channelId))
      .orderBy(desc(schema.dmMessages.createdAt))
      .limit(1)
      .get();
    if (lastMsgRow) {
      lastMessage = getDmMessageWithUser(lastMsgRow.id);
    }
  }

  return {
    id: dmChannel.id,
    ownerId: dmChannel.ownerId ?? null,
    federatedId: dmChannel.federatedId ?? null,
    createdAt: dmChannel.createdAt,
    members: users.map(u => sanitizeUser(u)),
    lastMessage,
  };
}

// ─── Relay Event Processors ──────────────────────────────────────────────────


/**
 * Find or create a local DM channel for a federated DM.
 * Uses federated_id for deterministic cross-instance lookup.
 */
export function findOrCreateDmChannel(
  federatedId: string,
  localUserIds: string[],
  db: ReturnType<typeof getDb>,
): string {
  // Try to find existing channel by federated ID
  const existing = db
    .select()
    .from(schema.dmChannels)
    .where(eq(schema.dmChannels.federatedId, federatedId))
    .get();

  if (existing) {
    // Ensure all users are members (they might have been removed)
    for (const userId of localUserIds) {
      const member = db
        .select()
        .from(schema.dmMembers)
        .where(
          and(
            eq(schema.dmMembers.dmChannelId, existing.id),
            eq(schema.dmMembers.userId, userId),
          ),
        )
        .get();

      if (!member) {
        db.insert(schema.dmMembers)
          .values({
            dmChannelId: existing.id,
            userId,
            closed: 0,
          })
          .run();
      }
    }
    // Late-bind: if a FederatedCallEntry exists for this federatedId with null dmChannelId,
    // update it now that we have a local channel
    connectionManager.lateBindFederatedCall(federatedId, existing.id);
    return existing.id;
  }

  // Create new DM channel with federated ID
  const channelId = generateSnowflake();
  const now = Date.now();

  db.insert(schema.dmChannels)
    .values({
      id: channelId,
      federatedId,
      createdAt: now,
    })
    .run();

  for (const userId of localUserIds) {
    db.insert(schema.dmMembers)
      .values({
        dmChannelId: channelId,
        userId,
        closed: 0,
      })
      .run();
  }

  // Late-bind: if a FederatedCallEntry exists for this federatedId with null dmChannelId,
  // update it now that we have a local channel
  connectionManager.lateBindFederatedCall(federatedId, channelId);

  return channelId;
}


/**
 * Build a DmMessageWithUser payload for WebSocket broadcasting.
 */
export function buildDmMessagePayload(
  messageRow: {
    id: string;
    dmChannelId: string;
    userId: string;
    content: string | null;
    replyToId: string | null;
    editedAt: number | null;
    createdAt: number;
  },
  userRow: typeof schema.users.$inferSelect,
): DmMessageWithUser {
  return {
    id: messageRow.id,
    dmChannelId: messageRow.dmChannelId,
    channelId: messageRow.dmChannelId,
    userId: messageRow.userId,
    content: messageRow.content,
    replyToId: messageRow.replyToId,
    editedAt: messageRow.editedAt,
    createdAt: messageRow.createdAt,
    user: sanitizeUser(userRow),
    attachments: [],
    embeds: [],
    reactions: [],
  };
}


/**
 * Validate that a URL's hostname matches the peer origin's hostname (SSRF protection).
 */
export function isUrlFromPeer(sourceUrl: string, peerOrigin: string): boolean {
  try {
    const sourceHost = new URL(sourceUrl).hostname;
    const peerHost = new URL(peerOrigin).hostname;
    return sourceHost === peerHost;
  } catch {
    return false;
  }
}


/**
 * Resolve a local DM message from a federation relay event's canonical identity.
 * Uses messageHomeInstance to branch the lookup:
 * - If the message originated on THIS instance → find by local ID
 * - Otherwise → find by sourceInstance + sourceMessageId tracking
 * Falls back to relay sender origin when messageHomeInstance is absent (backward compat).
 */
export function resolveLocalDmMessage(
  canonicalMessageId: string,
  messageHomeInstance: string | undefined,
  sourceInstance: string,
  db: ReturnType<typeof getDb>,
): typeof schema.dmMessages.$inferSelect | undefined {
  if (messageHomeInstance && messageHomeInstance === getOurOrigin()) {
    return db
      .select()
      .from(schema.dmMessages)
      .where(
        and(
          eq(schema.dmMessages.id, canonicalMessageId),
          isNull(schema.dmMessages.sourceInstance),
        ),
      )
      .get();
  }
  const originInstance = messageHomeInstance || sourceInstance;
  return db
    .select()
    .from(schema.dmMessages)
    .where(
      and(
        eq(schema.dmMessages.sourceInstance, originInstance),
        eq(schema.dmMessages.sourceMessageId, canonicalMessageId),
      ),
    )
    .get();
}