//! Integration tests for M7P4 Operational Visibility.
//!
//! Covers all 9 tasks:
//! - Task 01: QueryStats — per-query execution statistics attached to every result
//! - Task 02: Signal + WAL metrics
//! - Task 03: Index health metrics
//! - Task 04: Session + cohort + degradation metrics
//! - Task 05: Prometheus exposition format correctness
//! - Task 06: Structured error context
//! - Task 07: Metrics feature flag (zero-overhead base types)
//! - Task 08: RLHF signal export
//! - Task 09: Cross-session aggregation
#![allow(clippy::unwrap_used)]

use std::collections::HashMap;
use std::time::Duration;

use tidaldb::schema::{DecaySpec, EntityId, EntityKind, Timestamp, Window};
use tidaldb::{ExportFormat, ExportRequest, ExportedSignal, TidalDb};

// ── Prometheus output helpers ────────────────────────────────────────────────

/// Extract the numeric value for a metric from Prometheus text output.
///
/// Looks for a line that starts with `name` (not a comment), then parses
/// the trailing float. Returns `None` if the metric is absent.
#[cfg(feature = "metrics")]
fn prometheus_value(prom: &str, name: &str) -> Option<f64> {
    prom.lines()
        .filter(|l| !l.starts_with('#'))
        .find(|l| l.starts_with(name) && l[name.len()..].starts_with(' '))
        .and_then(|l| l.split_whitespace().last())
        .and_then(|v| v.parse().ok())
}

// ── Shared test schema ───────────────────────────────────────────────────────

fn build_test_schema() -> tidaldb::schema::Schema {
    use tidaldb::AgentPolicy;
    use tidaldb::schema::SchemaBuilder;

    let mut builder = SchemaBuilder::new();
    let _ = builder
        .signal(
            "view",
            EntityKind::Item,
            DecaySpec::Exponential {
                half_life: Duration::from_secs(7 * 24 * 3600),
            },
        )
        .windows(&[Window::OneHour])
        .add();
    let _ = builder
        .signal(
            "like",
            EntityKind::Item,
            DecaySpec::Exponential {
                half_life: Duration::from_secs(30 * 24 * 3600),
            },
        )
        .windows(&[Window::OneHour])
        .add();
    builder.session_policy(
        "default",
        AgentPolicy {
            allowed_signals: vec!["view".to_string(), "like".to_string()],
            denied_signals: vec![],
            max_session_duration: Duration::from_secs(3600),
            max_signals_per_session: 1000,
        },
    );
    builder.build().unwrap()
}

// ── Task 01: QueryStats ──────────────────────────────────────────────────────

/// RETRIEVE results carry QueryStats with the profile name and pipeline counts.
#[test]
fn retrieve_results_include_query_stats() {
    use tidaldb::query::retrieve::{ProfileRef, RetrieveBuilder};

    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    // Write items so the candidate generation stage has something to score.
    for i in 1u64..=5 {
        let mut meta = HashMap::new();
        meta.insert("category".to_string(), "news".to_string());
        db.write_item_with_metadata(EntityId::new(i), &meta)
            .unwrap();
        db.signal("view", EntityId::new(i), 1.0, Timestamp::now())
            .unwrap();
    }

    let query = RetrieveBuilder::new(EntityKind::Item, ProfileRef::new("new"))
        .limit(5)
        .build()
        .unwrap();
    let results = db.retrieve(&query).unwrap();

    // QueryStats is unconditionally populated (not feature-gated).
    assert_eq!(
        results.stats.profile_name, "new",
        "stats must capture the profile name used for scoring"
    );
    // Pipeline stage fields are accessible; exact values depend on item count.
    let _ = results.stats.candidates_considered;
    let _ = results.stats.candidates_after_filter;
    let _ = results.stats.total_time_us;
    let _ = results.stats.scoring_time_us;
    let _ = results.stats.diversity_time_us;
}

/// SEARCH results carry QueryStats with the "search" profile name.
#[test]
fn search_results_include_query_stats() {
    use tidaldb::query::search::Search;

    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    // No text schema, so BM25 returns empty — but stats are still populated.
    let query = Search::builder()
        .query("test article")
        .limit(5)
        .build()
        .unwrap();
    let results = db.search(&query).unwrap();

    assert_eq!(
        results.stats.profile_name, "search",
        "search pipeline must record the 'search' builtin profile in stats"
    );
    let _ = results.stats.candidates_considered;
    let _ = results.stats.total_time_us;
}

// ── Task 02: Signal + WAL Metrics ───────────────────────────────────────────

#[cfg(feature = "metrics")]
#[test]
fn signal_write_increments_counter() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let before = prometheus_value(
        &db.metrics().render_prometheus(),
        "tidaldb_signal_writes_total",
    )
    .unwrap_or(0.0);
    db.signal("view", EntityId::new(1), 1.0, Timestamp::now())
        .unwrap();
    db.signal("like", EntityId::new(2), 1.0, Timestamp::now())
        .unwrap();
    db.signal("view", EntityId::new(3), 0.5, Timestamp::now())
        .unwrap();
    let after = prometheus_value(
        &db.metrics().render_prometheus(),
        "tidaldb_signal_writes_total",
    )
    .unwrap();

    assert_eq!(
        (after - before) as u64,
        3,
        "signal_writes_total must increment once per signal write"
    );
}

#[cfg(feature = "metrics")]
#[test]
fn signal_write_latency_appears_in_prometheus() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    for i in 1u64..=3 {
        db.signal("view", EntityId::new(i), 1.0, Timestamp::now())
            .unwrap();
    }

    let prom = db.metrics().render_prometheus();
    assert!(
        prom.contains("tidaldb_signal_write_latency_us"),
        "Prometheus output must include signal write latency histogram"
    );
    assert!(
        prom.contains("tidaldb_signal_writes_total"),
        "Prometheus output must include signal_writes_total counter"
    );
    assert!(
        prom.contains("tidaldb_wal_lag_bytes"),
        "Prometheus output must include wal_lag_bytes gauge"
    );
    assert!(
        prom.contains("tidaldb_checkpoint_age_seconds"),
        "Prometheus output must include checkpoint_age_seconds gauge"
    );
}

// ── Task 03: Index Health Metrics ────────────────────────────────────────────

#[cfg(feature = "metrics")]
#[test]
fn prometheus_output_contains_all_index_gauge_names() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let prom = db.metrics().render_prometheus();

    assert!(
        prom.contains("tidaldb_tantivy_segment_count"),
        "Prometheus output must include tantivy_segment_count gauge"
    );
    assert!(
        prom.contains("tidaldb_tantivy_indexed_docs"),
        "Prometheus output must include tantivy_indexed_docs gauge"
    );
    assert!(
        prom.contains("tidaldb_usearch_vector_count"),
        "Prometheus output must include usearch_vector_count gauge"
    );
    assert!(
        prom.contains("tidaldb_usearch_index_size_bytes"),
        "Prometheus output must include usearch_index_size_bytes gauge"
    );
    assert!(
        prom.contains("tidaldb_bitmap_index_cardinality"),
        "Prometheus output must include bitmap_index_cardinality gauge"
    );
}

// ── Task 04: Session + Cohort + Degradation Metrics ─────────────────────────

#[cfg(feature = "metrics")]
#[test]
fn session_start_increments_active_sessions() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let before = prometheus_value(&db.metrics().render_prometheus(), "tidaldb_active_sessions")
        .unwrap_or(0.0);
    let meta = HashMap::new();
    let _handle = db.start_session(1u64, "agent1", "default", meta).unwrap();
    let after =
        prometheus_value(&db.metrics().render_prometheus(), "tidaldb_active_sessions").unwrap();

    assert_eq!(
        (after - before) as u64,
        1,
        "active_sessions must increment when a session starts"
    );
}

#[cfg(feature = "metrics")]
#[test]
fn session_close_updates_active_and_closed_counters() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let before_active =
        prometheus_value(&db.metrics().render_prometheus(), "tidaldb_active_sessions")
            .unwrap_or(0.0);
    let before_closed = prometheus_value(
        &db.metrics().render_prometheus(),
        "tidaldb_closed_sessions_total",
    )
    .unwrap_or(0.0);

    let meta = HashMap::new();
    let handle = db
        .start_session(42u64, "agent-close-test", "default", meta)
        .unwrap();
    db.close_session(handle).unwrap();

    let after_active =
        prometheus_value(&db.metrics().render_prometheus(), "tidaldb_active_sessions").unwrap();
    let after_closed = prometheus_value(
        &db.metrics().render_prometheus(),
        "tidaldb_closed_sessions_total",
    )
    .unwrap();

    assert_eq!(
        after_active as u64, before_active as u64,
        "active_sessions must return to its previous value after close_session"
    );
    assert_eq!(
        (after_closed - before_closed) as u64,
        1,
        "closed_sessions_total must increment on close_session"
    );
}

#[cfg(feature = "metrics")]
#[test]
fn degradation_level_appears_in_prometheus_output() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let prom = db.metrics().render_prometheus();

    // Default: Full fidelity (level 0).
    let level = prometheus_value(&prom, "tidaldb_degradation_level").unwrap();
    assert_eq!(
        level as u64, 0,
        "initial degradation level must be 0 (Full fidelity)"
    );

    assert!(
        prom.contains("tidaldb_degradation_level"),
        "Prometheus output must include degradation_level gauge"
    );
    assert!(
        prom.contains("tidaldb_rate_limited_total"),
        "Prometheus output must include rate_limited_total counter"
    );
}

// ── Task 05: Prometheus Exposition Format ────────────────────────────────────

/// Every `# HELP` line must be immediately followed by a `# TYPE` line.
#[test]
fn prometheus_format_help_always_followed_by_type() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let prom = db.metrics().render_prometheus();
    let lines: Vec<&str> = prom.lines().collect();

    for (i, line) in lines.iter().enumerate() {
        if line.starts_with("# HELP ") {
            assert!(
                i + 1 < lines.len() && lines[i + 1].starts_with("# TYPE "),
                "# HELP line must be immediately followed by # TYPE at index {i}: {line:?}"
            );
        }
    }
}

/// /healthz JSON contains the required fields.
#[test]
fn healthz_json_contains_required_fields() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let healthz = db.metrics().render_healthz();
    assert!(
        healthz.contains("\"status\":"),
        "healthz must contain status"
    );
    assert!(
        healthz.contains("\"uptime_seconds\":"),
        "healthz must contain uptime_seconds"
    );
    assert!(
        healthz.contains("\"version\":"),
        "healthz must contain version"
    );
    assert!(
        healthz.contains("\"build_hash\":"),
        "healthz must contain build_hash"
    );
}

// ── Task 06: Structured Error Context ────────────────────────────────────────

/// `TidalError::Internal` wraps `ErrorContext` with operation + detail fields.
#[test]
fn tidal_error_internal_wraps_error_context() {
    use tidaldb::TidalError;

    let err = TidalError::internal("test_operation", "something went wrong");

    if let TidalError::Internal(ctx) = &err {
        assert_eq!(ctx.operation, "test_operation");
        assert_eq!(ctx.detail, "something went wrong");
        assert!(ctx.entity_id.is_none(), "entity_id should default to None");
        assert!(
            ctx.entity_kind.is_none(),
            "entity_kind should default to None"
        );
        assert!(
            ctx.signal_type.is_none(),
            "signal_type should default to None"
        );
    } else {
        panic!("expected TidalError::Internal, got {err:?}");
    }

    // Display must include the operation name.
    let display = format!("{err}");
    assert!(
        display.contains("test_operation"),
        "Display must include the operation name: {display}"
    );
}

/// `ErrorContext` builder pattern sets optional fields correctly.
#[test]
fn error_context_builder_sets_optional_fields() {
    use tidaldb::ErrorContext;

    let ctx = ErrorContext::new("write_signal", "WAL append failed")
        .with_entity(42)
        .with_kind(EntityKind::Item)
        .with_signal("view");

    assert_eq!(ctx.operation, "write_signal");
    assert_eq!(ctx.detail, "WAL append failed");
    assert_eq!(ctx.entity_id, Some(42));
    assert_eq!(ctx.entity_kind, Some(EntityKind::Item));
    assert_eq!(ctx.signal_type, Some("view".to_string()));
}

// ── Task 07: Feature Flag ────────────────────────────────────────────────────

/// `QueryStats` is always available regardless of the `metrics` feature flag.
/// This test intentionally has NO `#[cfg(feature = "metrics")]` annotation.
#[test]
fn query_stats_available_without_metrics_feature() {
    use tidaldb::query::stats::QueryStats;

    let stats = QueryStats::new("my_profile".to_owned());
    assert_eq!(stats.profile_name, "my_profile");
    assert_eq!(stats.total_time_us, 0);
    assert_eq!(stats.candidates_considered, 0);
    assert_eq!(stats.filters_applied, 0);
    assert_eq!(stats.degradation_level, 0);
}

/// `MetricsState` base fields (`uptime_seconds`, `health_ok_value`) work
/// unconditionally — they are NOT gated behind the `metrics` feature.
#[test]
fn metrics_state_base_fields_always_available() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    // These methods exist and compile even with --no-default-features.
    assert!(db.metrics().uptime_seconds() >= 0.0);
    assert!((db.metrics().health_ok_value() - 1.0).abs() < f64::EPSILON);
}

// ── Task 08: RLHF Signal Export ──────────────────────────────────────────────

#[test]
#[cfg(feature = "test-utils")]
fn export_signals_ephemeral_returns_empty() {
    use tidaldb::TidalDb;
    use tidaldb::schema::SchemaBuilder;

    let mut builder = SchemaBuilder::new();
    let _ = builder
        .signal(
            "view",
            EntityKind::Item,
            DecaySpec::Exponential {
                half_life: Duration::from_secs(7 * 24 * 3600),
            },
        )
        .windows(&[Window::OneHour])
        .add();
    let schema = builder.build().unwrap();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    // Ephemeral mode: no WAL on disk, always returns empty.
    let req = ExportRequest::time_range(0, u64::MAX);
    let signals = db.export_signals(&req).unwrap();
    assert!(signals.is_empty());
}

#[test]
#[cfg(feature = "test-utils")]
fn export_signals_unknown_type_returns_error() {
    use tidaldb::TidalDb;
    use tidaldb::schema::SchemaBuilder;

    let mut builder = SchemaBuilder::new();
    let _ = builder
        .signal(
            "view",
            EntityKind::Item,
            DecaySpec::Exponential {
                half_life: Duration::from_secs(7 * 24 * 3600),
            },
        )
        .windows(&[Window::OneHour])
        .add();
    let schema = builder.build().unwrap();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let req = ExportRequest::signals_in_range(vec!["nonexistent".into()], 0, u64::MAX);
    let result = db.export_signals(&req);
    assert!(
        result.is_err(),
        "requesting an unknown signal type must return an error"
    );
}

#[test]
fn export_format_json_lines_value() {
    assert_eq!(ExportFormat::JsonLines, ExportFormat::JsonLines);
}

#[test]
fn export_request_time_range_fields() {
    let req = ExportRequest::time_range(1000, 2000);
    assert_eq!(req.since, Some(1000));
    assert_eq!(req.until, Some(2000));
    assert!(req.signal_types.is_empty());
    assert_eq!(req.format, ExportFormat::JsonLines);
    assert!(req.limit.is_none());
    assert!(req.user_id.is_none());
}

#[test]
fn exported_signal_to_json_line_valid() {
    let sig = ExportedSignal {
        entity_id: 42,
        signal_type: "view".to_string(),
        weight: 1.0,
        timestamp_ns: 1_700_000_000_000_000_000,
        user_id: None,
        session_id: None,
        annotation: None,
    };
    let line = sig.to_json_line();
    assert!(line.starts_with('{'));
    assert!(line.ends_with('}'));
    assert!(line.contains("\"entity_id\":42"));
    assert!(line.contains("\"signal_type\":\"view\""));
    // Anonymous signals must not include optional keys.
    assert!(!line.contains("user_id"));
    assert!(!line.contains("session_id"));
    assert!(!line.contains("annotation"));
}

/// `export_signals` reads actual WAL events written to a persistent database.
///
/// Export reads live, uncompacted WAL segments — those fsynced to disk but
/// not yet removed by a clean shutdown. This test exercises the WAL scanning
/// code path (persistent mode) that the ephemeral early-return skips.
///
/// Note: a clean `close()` compacts WAL segments, so export is called on the
/// same open DB instance — not after reopening.
#[test]
#[cfg(feature = "test-utils")]
fn export_signals_reads_wal_events() {
    use tidaldb::TempTidalHome;

    let home = TempTidalHome::new().unwrap();
    let schema = build_test_schema();

    let db = TidalDb::builder()
        .with_data_dir(home.path())
        .with_schema(schema)
        .open()
        .unwrap();

    let since = Timestamp::now().as_nanos();
    db.signal("view", EntityId::new(1), 1.0, Timestamp::now())
        .unwrap();
    db.signal("view", EntityId::new(2), 1.5, Timestamp::now())
        .unwrap();
    db.signal("like", EntityId::new(3), 2.0, Timestamp::now())
        .unwrap();

    // Export BEFORE close — WAL segments are live on disk.
    // Clean close compacts (deletes) segments, so export must happen first.
    let req = ExportRequest::time_range(since, u64::MAX);
    let signals = db.export_signals(&req).unwrap();

    assert_eq!(signals.len(), 3, "all 3 WAL events must be exported");

    let views: Vec<_> = signals.iter().filter(|s| s.signal_type == "view").collect();
    assert_eq!(views.len(), 2, "must export 2 view events");

    let likes: Vec<_> = signals.iter().filter(|s| s.signal_type == "like").collect();
    assert_eq!(likes.len(), 1, "must export 1 like event");

    // Entity IDs and weights are preserved end-to-end.
    assert!(
        signals
            .iter()
            .any(|s| s.entity_id == 1 && (s.weight - 1.0).abs() < 0.001),
        "entity 1 view event must be present"
    );
    assert!(
        signals
            .iter()
            .any(|s| s.entity_id == 3 && s.signal_type == "like"),
        "entity 3 like event must be present"
    );

    // Anonymous batch WAL signals must have None for user/session/annotation.
    for sig in &signals {
        assert!(sig.user_id.is_none(), "batch WAL signals have no user_id");
        assert!(
            sig.session_id.is_none(),
            "batch WAL signals have no session_id"
        );
        assert!(
            sig.annotation.is_none(),
            "batch WAL signals have no annotation"
        );
    }

    db.close().unwrap();
}

/// `export_signals` respects the `limit` field.
///
/// Export is called on the same open DB instance (before close) because
/// clean shutdown compacts WAL segments, leaving nothing to scan.
#[test]
#[cfg(feature = "test-utils")]
fn export_signals_respects_limit() {
    use tidaldb::TempTidalHome;

    let home = TempTidalHome::new().unwrap();
    let schema = build_test_schema();

    let db = TidalDb::builder()
        .with_data_dir(home.path())
        .with_schema(schema)
        .open()
        .unwrap();

    for i in 1u64..=10 {
        db.signal("view", EntityId::new(i), 1.0, Timestamp::now())
            .unwrap();
    }

    let mut req = ExportRequest::time_range(0, u64::MAX);
    req.limit = Some(3);
    let signals = db.export_signals(&req).unwrap();
    assert_eq!(signals.len(), 3, "limit must cap the result count");

    db.close().unwrap();
}

/// Anonymous batch WAL signals are excluded when a `user_id` filter is set.
/// In ephemeral mode there is no WAL or session journal on disk, so the
/// result is empty regardless. This test verifies that anonymous signals
/// written via `db.signal()` (no session) do NOT appear in user-filtered
/// exports.
#[test]
fn export_signals_user_id_filter_excludes_anonymous() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    db.signal("view", EntityId::new(1), 1.0, Timestamp::now())
        .unwrap();

    let mut req = ExportRequest::time_range(0, u64::MAX);
    req.user_id = Some(42);
    let signals = db.export_signals(&req).unwrap();
    assert!(
        signals.is_empty(),
        "user_id filter must exclude anonymous batch WAL signals"
    );
}

/// Session signals carry user_id, session_id, and annotation through to export.
///
/// This test exercises the full session-journal export path:
/// 1. Persistent DB with schema and session policy
/// 2. Session signals written with annotations via session_signal()
/// 3. Export with user_id filter returns only that user's session signals
/// 4. Export with a different user_id returns empty
#[test]
#[cfg(feature = "test-utils")]
fn export_signals_with_session_context() {
    use tidaldb::TempTidalHome;

    let home = TempTidalHome::new().unwrap();
    let schema = build_test_schema();

    let db = TidalDb::builder()
        .with_data_dir(home.path())
        .with_schema(schema)
        .open()
        .unwrap();

    let user_id = 42u64;
    let meta = HashMap::new();

    // Start a session for user 42.
    let handle = db
        .start_session(user_id, "test-agent", "default", meta)
        .unwrap();

    let since = Timestamp::now().as_nanos();

    // Write session signals — one with annotation, one without.
    db.session_signal(
        &handle,
        "view",
        EntityId::new(100),
        1.0,
        Timestamp::now(),
        Some("good content".to_string()),
    )
    .unwrap();
    db.session_signal(
        &handle,
        "like",
        EntityId::new(101),
        2.0,
        Timestamp::now(),
        None,
    )
    .unwrap();

    // Close the session so it is fully flushed to the journal.
    db.close_session(handle).unwrap();

    // Session journal writes are fire-and-forget through the WAL writer thread.
    // Allow time for the writer to drain and fsync the session commands.
    std::thread::sleep(Duration::from_millis(100));

    // Export with user_id filter = Some(42).
    let mut req = ExportRequest::time_range(since, u64::MAX);
    req.user_id = Some(user_id);
    let signals = db.export_signals(&req).unwrap();

    assert!(
        !signals.is_empty(),
        "export with user_id filter must return session signals"
    );
    assert_eq!(signals.len(), 2, "expected 2 session signals for user 42");

    // All results must have user_id == Some(42).
    for sig in &signals {
        assert_eq!(
            sig.user_id,
            Some(user_id),
            "all exported signals must carry the user_id"
        );
        assert!(
            sig.session_id.is_some(),
            "all exported signals must carry a session_id"
        );
    }

    // At least one result has the annotation set.
    assert!(
        signals.iter().any(|s| s.annotation.is_some()),
        "at least one signal must have an annotation"
    );
    let annotated = signals.iter().find(|s| s.annotation.is_some()).unwrap();
    assert_eq!(
        annotated.annotation.as_deref(),
        Some("good content"),
        "annotation text must round-trip through the journal"
    );

    // Export with a different user_id returns empty.
    let mut req2 = ExportRequest::time_range(since, u64::MAX);
    req2.user_id = Some(999);
    let signals2 = db.export_signals(&req2).unwrap();
    assert!(
        signals2.is_empty(),
        "export for non-existent user must return empty"
    );

    db.close().unwrap();
}

// ── Task 09: Cross-Session Aggregation ──────────────────────────────────────

#[test]
fn user_session_summary_aggregates_correctly() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();
    let user_id = 42u64;
    let meta = HashMap::new();

    // Run 3 sessions, each with 2 views + 1 like = 3 signals per session.
    for i in 0u64..3 {
        let handle = db
            .start_session(user_id, "test", "default", meta.clone())
            .unwrap();
        db.session_signal(
            &handle,
            "view",
            EntityId::new(i * 10 + 1),
            1.0,
            Timestamp::now(),
            None,
        )
        .unwrap();
        db.session_signal(
            &handle,
            "view",
            EntityId::new(i * 10 + 2),
            1.0,
            Timestamp::now(),
            None,
        )
        .unwrap();
        db.session_signal(
            &handle,
            "like",
            EntityId::new(i * 10 + 3),
            1.0,
            Timestamp::now(),
            None,
        )
        .unwrap();
        db.close_session(handle).unwrap();
    }

    let summary = db.user_session_summary(user_id, 0).unwrap();
    assert_eq!(summary.sessions_count, 3);
    assert_eq!(summary.total_signals, 9);
    assert_eq!(summary.total_rejections, 0);
    assert_eq!(summary.user_id, user_id);
    assert_eq!(summary.since_ns, 0);
    assert!(summary.earliest_session_ns.is_some());
    assert!(summary.latest_session_ns.is_some());
    assert!(summary.preference_drift.is_none());

    // Top signal types: "view" first (6 total), "like" second (3 total).
    assert_eq!(summary.top_signal_types.len(), 2);
    assert_eq!(summary.top_signal_types[0].0, "view");
    assert_eq!(summary.top_signal_types[0].1, 6);
    assert_eq!(summary.top_signal_types[1].0, "like");
    assert_eq!(summary.top_signal_types[1].1, 3);
}

#[test]
fn user_session_summary_no_sessions_returns_not_found() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();

    let result = db.user_session_summary(999, 0);
    assert!(result.is_err());
    assert!(matches!(result, Err(tidaldb::TidalError::NotFound { .. })));
}

#[test]
fn user_session_summary_different_user_excluded() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();
    let meta = HashMap::new();

    // User 1: one view signal.
    let handle = db
        .start_session(1u64, "test", "default", meta.clone())
        .unwrap();
    db.session_signal(
        &handle,
        "view",
        EntityId::new(1),
        1.0,
        Timestamp::now(),
        None,
    )
    .unwrap();
    db.close_session(handle).unwrap();

    // User 2: one like signal.
    let handle = db.start_session(2u64, "test", "default", meta).unwrap();
    db.session_signal(
        &handle,
        "like",
        EntityId::new(2),
        1.0,
        Timestamp::now(),
        None,
    )
    .unwrap();
    db.close_session(handle).unwrap();

    // Query user 1 only — user 2's session must be excluded.
    let summary = db.user_session_summary(1, 0).unwrap();
    assert_eq!(summary.sessions_count, 1);
    assert_eq!(summary.total_signals, 1);
    assert_eq!(summary.top_signal_types.len(), 1);
    assert_eq!(summary.top_signal_types[0].0, "view");
    assert_eq!(summary.top_signal_types[0].1, 1);
}

#[test]
fn user_session_summary_since_ns_filter() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();
    let user_id = 100u64;
    let meta = HashMap::new();

    // Session 1.
    let handle = db
        .start_session(user_id, "test", "default", meta.clone())
        .unwrap();
    db.session_signal(
        &handle,
        "view",
        EntityId::new(1),
        1.0,
        Timestamp::now(),
        None,
    )
    .unwrap();
    db.close_session(handle).unwrap();

    // Record time between sessions.
    let midpoint = Timestamp::now().as_nanos();

    // Session 2 (after midpoint).
    let handle = db.start_session(user_id, "test", "default", meta).unwrap();
    db.session_signal(
        &handle,
        "like",
        EntityId::new(2),
        1.0,
        Timestamp::now(),
        None,
    )
    .unwrap();
    db.close_session(handle).unwrap();

    // since_ns = midpoint must exclude session 1 and include only session 2.
    let summary = db.user_session_summary(user_id, midpoint).unwrap();
    assert_eq!(summary.sessions_count, 1);
    assert_eq!(summary.total_signals, 1);
    assert_eq!(summary.top_signal_types[0].0, "like");
}

#[test]
fn session_snapshot_has_timing_fields() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();
    let user_id = 50u64;
    let meta = HashMap::new();

    let before = Timestamp::now().as_nanos();

    let handle = db.start_session(user_id, "test", "default", meta).unwrap();
    db.session_signal(
        &handle,
        "view",
        EntityId::new(1),
        1.0,
        Timestamp::now(),
        None,
    )
    .unwrap();

    // Active snapshot: started_at_ns populated, closed_at_ns = 0.
    let active_snap = db.session_snapshot(handle.id).unwrap();
    assert!(
        active_snap.started_at_ns >= before,
        "started_at_ns should be after test start"
    );
    assert_eq!(
        active_snap.closed_at_ns, 0,
        "active session should have closed_at_ns = 0"
    );

    db.close_session(handle).unwrap();

    let after = Timestamp::now().as_nanos();

    // Summary timing should bracket the session.
    let summary = db.user_session_summary(user_id, 0).unwrap();
    assert!(summary.earliest_session_ns.unwrap() >= before);
    assert!(summary.latest_session_ns.unwrap() <= after);
}

#[test]
fn signal_snap_entry_has_count() {
    let schema = build_test_schema();
    let db = TidalDb::builder()
        .ephemeral()
        .with_schema(schema)
        .open()
        .unwrap();
    let user_id = 60u64;
    let meta = HashMap::new();

    let handle = db.start_session(user_id, "test", "default", meta).unwrap();
    // Write 3 view signals and 1 like signal.
    for entity in [1u64, 2, 3] {
        db.session_signal(
            &handle,
            "view",
            EntityId::new(entity),
            1.0,
            Timestamp::now(),
            None,
        )
        .unwrap();
    }
    db.session_signal(
        &handle,
        "like",
        EntityId::new(4),
        1.0,
        Timestamp::now(),
        None,
    )
    .unwrap();

    let snap = db.session_snapshot(handle.id).unwrap();
    let view_entry = snap.signals.get("view").unwrap();
    assert_eq!(view_entry.count, 3);
    let like_entry = snap.signals.get("like").unwrap();
    assert_eq!(like_entry.count, 1);

    db.close_session(handle).unwrap();
}