//! m8p5 integration tests: Control Plane, Multi-Tenancy, and Routing.
//! All tests are sync (`#[test]`). No `tokio::test`.

#![allow(clippy::unwrap_used)]

use std::sync::{Arc, RwLock};

use tidaldb::replication::state::ReplicationState;
use tidaldb::replication::{
    ClusterTopology, ControlPlane, MigrationState, RegionId, ReplicationLagGauge, ShardAssignment,
    ShardId, TenantConfig, TenantId, TenantMigration, TenantRouter, UpgradePhase,
};
use tidaldb::schema::EntityId;

fn make_router_and_cp() -> (Arc<TenantRouter>, Arc<ControlPlane>) {
    let topo = Arc::new(RwLock::new(ClusterTopology::single()));
    let router = Arc::new(TenantRouter::new(Arc::clone(&topo)));
    let state = Arc::new(ReplicationState::single());
    let lag = Arc::new(ReplicationLagGauge::new(ShardId::SINGLE, state));
    let cp = Arc::new(ControlPlane::new(topo, Arc::clone(&router), lag));
    (router, cp)
}

fn make_two_shard_router_and_cp() -> (Arc<TenantRouter>, Arc<ControlPlane>) {
    let topo = Arc::new(RwLock::new(ClusterTopology {
        shards: vec![
            ShardAssignment {
                shard_id: ShardId(0),
                region_id: RegionId(0),
            },
            ShardAssignment {
                shard_id: ShardId(1),
                region_id: RegionId(1),
            },
        ],
    }));
    let router = Arc::new(TenantRouter::new(Arc::clone(&topo)));
    let state = Arc::new(ReplicationState::single());
    let lag = Arc::new(ReplicationLagGauge::new(ShardId::SINGLE, state));
    let cp = Arc::new(ControlPlane::new(topo, Arc::clone(&router), lag));
    (router, cp)
}

// ─── Rate Limiting ──────────────────────────────────────────────────────────

#[test]
fn test_tenant_rate_limiting() {
    use tidaldb::TidalError;

    let (router, _cp) = make_router_and_cp();
    let mut cfg = TenantConfig::default_tenant();
    cfg.max_signals_per_sec = Some(100);
    router.register_tenant(cfg);

    let limiter = router.rate_limiter_for(TenantId::DEFAULT).expect("limiter");
    // Burst capacity = 2× rate = 200 tokens. All 200 should succeed.
    for i in 0..200 {
        assert!(
            limiter.try_acquire().is_ok(),
            "acquisition #{i} should succeed (burst capacity = 200)"
        );
    }
    let err = limiter.try_acquire().expect_err("should be quota exceeded");
    assert!(matches!(err, TidalError::QuotaExceeded(_)));
}

// ─── Noisy Neighbor ──────────────────────────────────────────────────────────

#[test]
fn test_noisy_neighbor_isolation() {
    let (router, _cp) = make_router_and_cp();

    let mut cfg_a = TenantConfig::default_tenant();
    cfg_a.max_signals_per_sec = Some(50);
    router.register_tenant(cfg_a);

    let mut cfg_b = TenantConfig::unlimited(TenantId(1), "tenant-b");
    cfg_b.max_signals_per_sec = Some(50);
    router.register_tenant(cfg_b);

    let limiter_a = router
        .rate_limiter_for(TenantId::DEFAULT)
        .expect("limiter A");
    let limiter_b = router.rate_limiter_for(TenantId(1)).expect("limiter B");

    // Exhaust tenant A's bucket (2× burst = 100 tokens).
    for _ in 0..100 {
        let _ = limiter_a.try_acquire();
    }
    assert!(
        limiter_a.try_acquire().is_err(),
        "tenant A should be rate limited"
    );
    assert!(
        limiter_b.try_acquire().is_ok(),
        "tenant B should not be affected by tenant A's exhaustion"
    );
}

// ─── Residency Policy ────────────────────────────────────────────────────────

#[test]
fn test_tenant_residency_policy() {
    let topo = Arc::new(RwLock::new(ClusterTopology {
        shards: vec![
            ShardAssignment {
                shard_id: ShardId(0),
                region_id: RegionId(0),
            },
            ShardAssignment {
                shard_id: ShardId(1),
                region_id: RegionId(1),
            },
        ],
    }));
    let router = Arc::new(TenantRouter::new(Arc::clone(&topo)));

    let cfg = TenantConfig {
        tenant_id: TenantId(42),
        max_signals_per_sec: None,
        max_entities: None,
        max_storage_bytes: None,
        required_regions: vec![RegionId(1)],
        label: "region-1-only".to_string(),
    };
    router.register_tenant(cfg);

    for i in 0u64..100 {
        let assignment = router.route(TenantId(42), EntityId::new(i)).expect("route");
        assert_eq!(
            assignment.shard_id,
            ShardId(1),
            "entity {i} routed to wrong shard"
        );
        assert_eq!(assignment.region_id, RegionId(1));
    }
}

// ─── Migration State Machine ─────────────────────────────────────────────────

#[test]
fn test_migration_state_machine() {
    use tidaldb::TidalError;

    let (router, cp) = make_router_and_cp();
    let migration = TenantMigration::new(
        TenantId(10),
        ShardId::SINGLE,
        ShardId(1),
        Arc::clone(&cp),
        Arc::clone(&router),
    );

    assert_eq!(migration.current_state(), MigrationState::Idle);

    // Invalid: enter_dual_write before prepare_target.
    let err = migration.enter_dual_write(0).expect_err("should fail");
    assert!(matches!(err, TidalError::InvalidState(_)));

    // Idle -> PreparingTarget
    let seqno = migration.prepare_target(50).expect("prepare_target");
    assert_eq!(seqno, 50);
    assert!(matches!(
        migration.current_state(),
        MigrationState::PreparingTarget {
            last_shipped_seqno: 50
        }
    ));

    // Invalid: prepare_target again.
    let err = migration.prepare_target(99).expect_err("should fail");
    assert!(matches!(err, TidalError::InvalidState(_)));

    // PreparingTarget -> DualWrite
    let cutover = migration.enter_dual_write(100).expect("enter_dual_write");
    assert_eq!(cutover, 100);
    assert!(matches!(
        migration.current_state(),
        MigrationState::DualWrite { cutover_seqno: 100 }
    ));

    // Invalid: finalize when target behind cutover — NotReady (not InvalidState).
    let err = migration.finalize(50).expect_err("should fail");
    assert!(
        matches!(err, TidalError::NotReady(_)),
        "expected NotReady, got: {err}"
    );

    // DualWrite -> Finalizing
    migration.finalize(150).expect("finalize");
    assert!(matches!(
        migration.current_state(),
        MigrationState::Finalizing { .. }
    ));

    // Invalid: finalize again.
    let err = migration.finalize(200).expect_err("should fail");
    assert!(matches!(err, TidalError::InvalidState(_)));

    // Finalizing -> Complete (GC window = 0)
    migration.gc_source(0).expect("gc_source");
    assert_eq!(migration.current_state(), MigrationState::Complete);

    // Invalid: transition from Complete.
    let err = migration.prepare_target(1).expect_err("should fail");
    assert!(matches!(err, TidalError::InvalidState(_)));
}

/// GC window enforcement: `gc_source` must reject calls before the window elapses.
#[test]
fn test_gc_source_rejects_before_window_elapses() {
    use tidaldb::TidalError;

    let (router, cp) = make_router_and_cp();
    let migration = TenantMigration::new(
        TenantId(11),
        ShardId::SINGLE,
        ShardId(1),
        Arc::clone(&cp),
        Arc::clone(&router),
    );
    migration.prepare_target(10).unwrap();
    migration.enter_dual_write(20).unwrap();
    migration.finalize(25).unwrap();

    // A 10-minute GC window has definitely not elapsed since finalize() just ran.
    let err = migration
        .gc_source(600_000_000_000)
        .expect_err("should be rejected");
    assert!(
        matches!(err, TidalError::InvalidState(_)),
        "expected InvalidState for GC window not elapsed, got: {err}"
    );
}

// ─── Dual-Write Routing ───────────────────────────────────────────────────────

/// During dual-write mode, `write_assignments` returns both source and target shards.
#[test]
fn test_dual_write_routing_returns_both_shards() {
    let (router, _cp) = make_two_shard_router_and_cp();

    router.set_dual_write(TenantId(5), ShardId(0), ShardId(1));
    assert!(router.is_dual_write(TenantId(5)));

    let assignments = router
        .write_assignments(TenantId(5), EntityId::new(42))
        .expect("write_assignments");
    assert_eq!(assignments.len(), 2, "dual-write must return 2 assignments");

    let shard_ids: Vec<_> = assignments.iter().map(|a| a.shard_id).collect();
    assert!(
        shard_ids.contains(&ShardId(0)),
        "source shard must be in assignments"
    );
    assert!(
        shard_ids.contains(&ShardId(1)),
        "target shard must be in assignments"
    );
}

/// After `finalize_migration`, routing pins to the target shard.
#[test]
fn test_finalize_migration_pins_to_target() {
    let (router, _cp) = make_two_shard_router_and_cp();

    router.set_dual_write(TenantId(7), ShardId(0), ShardId(1));
    router.finalize_migration(TenantId(7), ShardId(1));

    // No longer in dual-write mode.
    assert!(!router.is_dual_write(TenantId(7)));

    // Pinned to target shard.
    assert_eq!(router.pinned_shard(TenantId(7)), Some(ShardId(1)));

    // All routing goes to the target shard.
    for i in 0u64..20 {
        let assignment = router.route(TenantId(7), EntityId::new(i)).unwrap();
        assert_eq!(
            assignment.shard_id,
            ShardId(1),
            "post-migration routing must pin to target shard"
        );
    }

    // write_assignments returns only the target after finalization.
    let writes = router
        .write_assignments(TenantId(7), EntityId::new(99))
        .unwrap();
    assert_eq!(writes.len(), 1);
    assert_eq!(writes[0].shard_id, ShardId(1));
}

// ─── Rolling Upgrade ─────────────────────────────────────────────────────────

#[test]
fn test_rolling_upgrade_drain_rejoin() {
    use tidaldb::TidalError;

    // Use a 2-shard topology so that draining 1 shard still leaves 1 serving.
    let (_router, cp) = make_two_shard_router_and_cp();
    let coordinator = tidaldb::replication::RollingUpgradeCoordinator::new(Arc::clone(&cp));

    assert_eq!(coordinator.current_phase(), UpgradePhase::Ready);
    assert!(!coordinator.is_drained(ShardId(0)));

    coordinator.drain(ShardId(0)).expect("drain shard 0");
    assert!(coordinator.is_drained(ShardId(0)));
    assert!(matches!(
        coordinator.current_phase(),
        UpgradePhase::Draining {
            shard_id: ShardId(0)
        }
    ));

    // Cannot start a second concurrent drain.
    let err = coordinator.drain(ShardId(1)).expect_err("should fail");
    assert!(matches!(err, TidalError::InvalidState(_)));

    coordinator.rejoin(ShardId(0)).expect("rejoin");
    assert!(!coordinator.is_drained(ShardId(0)));
    assert_eq!(coordinator.current_phase(), UpgradePhase::Ready);

    // Can drain the other shard after rejoin.
    coordinator.drain(ShardId(1)).expect("drain shard 1");
    assert!(coordinator.is_drained(ShardId(1)));
}

/// Draining the sole shard in a single-node cluster must be refused.
#[test]
fn test_drain_single_node_cluster_is_refused() {
    use tidaldb::TidalError;

    let (_router, cp) = make_router_and_cp(); // single-shard
    let coordinator = tidaldb::replication::RollingUpgradeCoordinator::new(Arc::clone(&cp));

    let err = coordinator
        .drain(ShardId::SINGLE)
        .expect_err("must refuse to drain the only node");
    assert!(
        matches!(err, TidalError::InvalidState(_)),
        "expected InvalidState, got: {err}"
    );
}