import { getDb } from '../db/index.js';
import * as schema from '../db/schema.js';
import { and, eq } from 'drizzle-orm';
import { isFederationRelayEnabled } from './federationOutbox.js';
import { buildFederationHeaders, getOurOrigin } from './federationAuth.js';
import type { FederationRelayEvent } from '@backspace/shared';

export type PeerActivationReason =
  | 'initiate_accepted'
  | 'accept_rejected_override'
  | 'accept_awaiting_approval'
  | 'accept_pending'
  | 'accept_new'
  | 'approval_handshake'
  | 'health_check_recovery'
  | 'ensure_peered'
  | 'startup_bootstrap';

// Dedup: concurrent activations for the same peerId share one promise.
const inFlightActivation = new Map<string, Promise<void>>();

/**
 * Called whenever federation_peers.status transitions to 'active' for any reason.
 * Two independent invariants — both run unconditionally:
 *   1. Reset outbox backoff (nextRetryAt = now, attempts = 0) for this peer.
 *   2. Pull-sync mutation log from peer's /api/federation/sync since lastSyncedAt.
 *
 * Call sites (must remain exhaustive — grep `onPeerActivated(` to audit):
 *   - routes/federation.ts /peer/initiate activation
 *   - routes/federation.ts /peer/accept existing-rejected override
 *   - routes/federation.ts /peer/accept existing-awaiting_approval
 *   - routes/federation.ts /peer/accept existing-pending
 *   - routes/federation.ts /peer/accept new-peer
 *   - routes/federation.ts /approval-requests/:id/approve
 *   - utils/federationWorker.ts health check recovery
 *   - utils/federationPeering.ts ensurePeered/performHandshake
 *   - utils/federationWorker.ts startup bootstrap (via startupBootstrapSync)
 *
 * Deduplicated by peerId — concurrent calls share one promise.
 */
export async function onPeerActivated(
  peerId: string,
  reason: PeerActivationReason,
): Promise<void> {
  const existing = inFlightActivation.get(peerId);
  if (existing) return existing;

  const promise = (async () => {
    try {
      resetOutboxBackoff(peerId);
      await syncPeerMutationLog(peerId, reason);
      const { connectionManager } = await import('../ws/handler.js');
      connectionManager.sendToAdmins({ type: 'federation_peers_changed' as const });
    } catch (err) {
      console.error(`[federation] onPeerActivated(${peerId}, ${reason}) failed:`, err);
    }
  })();

  inFlightActivation.set(peerId, promise);
  try {
    await promise;
  } finally {
    inFlightActivation.delete(peerId);
  }
}

/**
 * Reset all outbox backoff state for a peer (nextRetryAt = now, attempts = 0).
 * Unconditional across all entries of the peer — see spec §Invariant 1.
 */
export function resetOutboxBackoff(peerId: string): void {
  const db = getDb();
  const now = Date.now();
  const result = db
    .update(schema.federationOutbox)
    .set({ nextRetryAt: now, attempts: 0 })
    .where(eq(schema.federationOutbox.peerId, peerId))
    .run();
  if (result.changes > 0) {
    console.log(`[federation] Reset backoff on ${result.changes} outbox entries for peer ${peerId}`);
  }
}

/**
 * Pull-sync mutation log from the peer's /api/federation/sync endpoint.
 * Runs three contextType passes (dm, friend, profile), paginating each.
 * Updates peer.lastSyncedAt to Date.now() on success; leaves it untouched
 * on transient failure so the next activation retries.
 */
export async function syncPeerMutationLog(
  peerId: string,
  reason: PeerActivationReason,
): Promise<void> {
  if (!isFederationRelayEnabled()) return;

  const db = getDb();
  const peer = db.select().from(schema.federationPeers)
    .where(eq(schema.federationPeers.id, peerId)).get();
  if (!peer || peer.status !== 'active') return;

  const activePeer = peer;  // narrowed by the guard above

  const ourOrigin = getOurOrigin();
  const signingSecret = (activePeer.pendingHmacSecret && activePeer.secretRotationAt)
    ? activePeer.pendingHmacSecret
    : activePeer.hmacSecret;

  console.log(`[federation] Sync-pull from ${activePeer.origin} (reason=${reason}, since=${activePeer.lastSyncedAt ?? 0})`);

  let totalEvents = 0;
  let skippedEvents = 0;

  type SyncRequestBody = {
    sinceTimestamp: number;
    limit: number;
    contextType?: 'friend' | 'profile';
  };

  async function runPass(contextType?: 'friend' | 'profile'): Promise<boolean> {
    let since = activePeer.lastSyncedAt ?? 0;
    while (true) {
      const bodyObj: SyncRequestBody = { sinceTimestamp: since, limit: 100 };
      if (contextType) bodyObj.contextType = contextType;
      const body = JSON.stringify(bodyObj);
      const headers = buildFederationHeaders(body, signingSecret, ourOrigin);
      const resp = await fetch(`${activePeer.origin}/api/federation/sync`, {
        method: 'POST', headers, body,
        signal: AbortSignal.timeout(30_000),
      });
      if (!resp.ok) {
        console.warn(`[federation] Sync-pull ${contextType ?? 'dm'} pass HTTP ${resp.status} for ${activePeer.origin}`);
        return false;
      }
      const data = await resp.json() as { events: FederationRelayEvent[]; hasMore: boolean; checkpoint: number };
      if (data.events.length === 0) return true;
      const { processRelayEvents } = await import('../routes/federation.js');
      for (const event of data.events) {
        try {
          await processRelayEvents([event], activePeer.origin, activePeer.origin, db);
          totalEvents += 1;
        } catch (err) {
          skippedEvents += 1;
          const errMsg = err instanceof Error ? err.message : String(err);
          console.error(
            `[federation] Skipping poison-pill event during sync-pull from ${activePeer.origin}: ` +
            `eventType=${event.eventType} messageId=${event.messageId} timestamp=${event.timestamp} ` +
            `error=${errMsg}`,
          );
        }
      }
      since = data.checkpoint;
      if (!data.hasMore) return true;
    }
  }

  try {
    if (!(await runPass())) return;
    if (!(await runPass('friend'))) return;
    if (!(await runPass('profile'))) return;

    db.update(schema.federationPeers)
      .set({ lastSyncedAt: Date.now() })
      .where(eq(schema.federationPeers.id, activePeer.id))
      .run();

    if (totalEvents > 0 || skippedEvents > 0) {
      const skipSuffix = skippedEvents > 0 ? ` (${skippedEvents} skipped due to errors)` : '';
      console.log(`[federation] Sync-pull from ${activePeer.origin} replayed ${totalEvents} events${skipSuffix}`);
    }
  } catch (err) {
    console.error(`[federation] Sync-pull from ${activePeer.origin} failed:`, err);
  }
}

/**
 * Startup bootstrap — scan for freshly-peered rows (status='active', lastSyncedAt=0)
 * and run onPeerActivated for each. Replaces runInitialSyncForNewPeers.
 * Invoked from startFederationWorkers.
 */
export async function startupBootstrapSync(): Promise<void> {
  if (!isFederationRelayEnabled()) return;

  const db = getDb();
  const peers = db.select().from(schema.federationPeers)
    .where(and(
      eq(schema.federationPeers.status, 'active'),
      eq(schema.federationPeers.lastSyncedAt, 0),
    )).all();

  for (const peer of peers) {
    await onPeerActivated(peer.id, 'startup_bootstrap');
  }
}