// GET    /api/offline/status - size, freshness and retention policy, for Settings.
// PUT    /api/offline/status - update the retention policy.
// DELETE /api/offline/status - purge the replica.
//
// The POLICY LIVES IN THE ENCRYPTED STORE, not in renderer localStorage. The
// design review's H1 was that a server-side engine cannot read a renderer-only
// setting; keeping the policy server-side means the retention pass always has the
// value it needs, while the DECISION TO SYNC AT ALL stays with the renderer, so
// nothing is ever materialised for an account that never opted in.
//
// Like every read here, GET makes no network call: an offline user must still be
// able to see what they have and free the space.
import { NextRequest, NextResponse } from 'next/server';
import { clampPolicy, POLICY_LIMITS, type RetentionPolicy } from '@/lib/offline-replica/store';
import { resolveIndexSession, resolveReadAccountId, withReplica } from '@/lib/offline-replica/engine';
import { gateReplicaRoute, NO_STORE, replicaErrorResponse } from '@/lib/offline-replica/route-gate';

export const runtime = 'nodejs';
export const dynamic = 'force-dynamic';

export async function GET(request: NextRequest) {
  const gated = gateReplicaRoute();
  if (gated) return gated;
  try {
    const session = await resolveIndexSession(request);
    const payload = await withReplica(session.accountId, (store) => {
      const jmapAccountId = resolveReadAccountId(store, null);
      const policy = store.getPolicy();
      const flags = store.getFlags(Date.now());
      if (!jmapAccountId) {
        return {
          policy,
          limits: POLICY_LIMITS,
          synced: false,
          stats: null,
          coveragePhase: 'never-run',
          resyncRequired: flags.resyncRequired,
          lastCycleAt: flags.lastCycleAt ?? null,
          lastCycleOk: flags.lastCycleOk ?? null,
        };
      }
      return {
        policy,
        limits: POLICY_LIMITS,
        synced: true,
        stats: store.stats(jmapAccountId),
        coveragePhase: store.getCoverage(jmapAccountId)?.phase ?? 'never-run',
        coveredFrom: store.getCoverage(jmapAccountId)?.coveredFrom ?? null,
        resyncRequired: flags.resyncRequired,
        lastCycleAt: flags.lastCycleAt ?? null,
        lastCycleOk: flags.lastCycleOk ?? null,
        lastCycleError: flags.lastCycleError ?? null,
      };
    });
    return NextResponse.json({ ok: true, ...payload }, { headers: NO_STORE });
  } catch (error) {
    return replicaErrorResponse(error, 'offline status');
  }
}

export async function PUT(request: NextRequest) {
  const gated = gateReplicaRoute();
  if (gated) return gated;

  let body: Record<string, unknown> = {};
  try {
    const text = await request.text();
    if (text.trim()) body = JSON.parse(text) as Record<string, unknown>;
  } catch {
    return NextResponse.json({ error: 'Malformed JSON body' }, { status: 400 });
  }

  const policy = clampPolicy(body as Partial<RetentionPolicy>);
  try {
    const session = await resolveIndexSession(request);
    await withReplica(session.accountId, (store) => {
      store.transaction(() => { store.setPolicy(policy); });
    });
    // The cycle applies it: a widen re-enters coverage scanning, a narrow evicts,
    // and the clock guard is told this was INTENT rather than a glitch by the
    // `lastEnvelopeDays` it compares against.
    return NextResponse.json({ ok: true, policy }, { headers: NO_STORE });
  } catch (error) {
    return replicaErrorResponse(error, 'offline policy update');
  }
}

export async function DELETE(request: NextRequest) {
  const gated = gateReplicaRoute();
  if (gated) return gated;
  try {
    const session = await resolveIndexSession(request);
    await withReplica(session.accountId, (store) => {
      // ALL OF IT, cursors included. A record wipe that leaves cursors behind is
      // the one state no amount of syncing repairs: `/changes` structurally cannot
      // re-deliver mail that already existed when the cursor was captured, so the
      // next cycle would advance a live cursor over an empty store forever.
      store.transaction(() => { store.purgeAll(); });
    });
    return NextResponse.json({ ok: true, purged: true }, { headers: NO_STORE });
  } catch (error) {
    return replicaErrorResponse(error, 'offline purge');
  }
}