//! Milestone 6 Phase 2 Integration Tests: Social Graph Extension + Collaborative Filtering.
//!
//! Exercises the complete M6P2 scenario end-to-end:
//!
//! 1. Reverse relationship index (creator -> follower user IDs).
//! 2. `FilterExpr::SocialGraph` constraining candidates at depth=1 and depth=2.
//! 3. Co-engagement index: pairwise item co-occurrence tracking and scoring.
//! 4. `related` profile boosted by co-engagement edges.
//! 5. Social-graph-scoped trending using `UserSignalIndex`.
//! 6. Co-engagement LRU eviction at capacity.
//! 7. Co-engagement checkpoint/restore across reopen.

#![allow(clippy::unwrap_used, clippy::cast_precision_loss)]

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

use tidaldb::TidalDb;
use tidaldb::entities::RelationshipType;
use tidaldb::query::retrieve::Retrieve;
use tidaldb::schema::{DecaySpec, EntityId, EntityKind, SchemaBuilder, Timestamp, Window};
use tidaldb::storage::indexes::filter::FilterExpr;

// ── Schema ──────────────────────────────────────────────────────────────────

fn m6_social_schema() -> tidaldb::schema::Schema {
    let mut builder = SchemaBuilder::new();

    for &(name, half_life_days) in &[
        ("view", 7),
        ("like", 14),
        ("share", 7),
        ("skip", 1),
        ("completion", 14),
        ("dislike", 1),
        ("hide", 1),
    ] {
        let _ = builder
            .signal(
                name,
                EntityKind::Item,
                DecaySpec::Exponential {
                    half_life: Duration::from_secs(half_life_days * 24 * 3600),
                },
            )
            .windows(&[
                Window::OneHour,
                Window::TwentyFourHours,
                Window::SevenDays,
                Window::AllTime,
            ])
            .velocity(true)
            .add();
    }

    builder.build().expect("m6_social schema must be valid")
}

// ── Helpers ─────────────────────────────────────────────────────────────────

fn item_metadata(category: &str, creator_id: u64) -> HashMap<String, String> {
    let mut meta = HashMap::new();
    meta.insert("category".to_string(), category.to_string());
    meta.insert("format".to_string(), "video".to_string());
    meta.insert("creator_id".to_string(), creator_id.to_string());
    meta.insert(
        "created_at".to_string(),
        Timestamp::now().as_nanos().to_string(),
    );
    meta
}

fn open_ephemeral_db() -> TidalDb {
    TidalDb::builder()
        .ephemeral()
        .with_schema(m6_social_schema())
        .open()
        .expect("db open")
}

// ── Test 1: Reverse relationship index ──────────────────────────────────────

#[test]
fn reverse_index_follows_creator() {
    let db = open_ephemeral_db();
    let ts = Timestamp::now();

    // Users 1, 2, 3 follow creator 100.
    for user_id in 1..=3u64 {
        db.write_relationship(
            EntityId::new(user_id),
            RelationshipType::Follows,
            EntityId::new(100),
            1.0,
            ts,
        )
        .unwrap();
    }

    // Verify reverse index: creator 100 should have followers {1, 2, 3}.
    let followers = db.user_state().follower_ids(100);
    assert_eq!(followers.len(), 3, "creator 100 should have 3 followers");
    for uid in &[1u64, 2, 3] {
        assert!(
            followers.contains(uid),
            "follower {uid} should be in reverse index"
        );
    }

    // Unfollow: user 2 unfollows creator 100.
    db.delete_relationship(
        EntityId::new(2),
        RelationshipType::Follows,
        EntityId::new(100),
    )
    .unwrap();

    let followers = db.user_state().follower_ids(100);
    assert_eq!(
        followers.len(),
        2,
        "creator 100 should have 2 followers after unfollow"
    );
    assert!(!followers.contains(&2), "user 2 should be removed");
    assert!(followers.contains(&1));
    assert!(followers.contains(&3));
}

// ── Test 2: Social graph depth=1 filter ─────────────────────────────────────

#[test]
fn social_graph_depth1_filter_constrains_to_followed_creators() {
    let db = open_ephemeral_db();
    let ts = Timestamp::now();

    // Creator 100 has items 10, 11.
    for id in [10u64, 11] {
        db.write_item_with_metadata(EntityId::new(id), &item_metadata("jazz", 100))
            .unwrap();
    }
    // Creator 200 has items 20, 21.
    for id in [20u64, 21] {
        db.write_item_with_metadata(EntityId::new(id), &item_metadata("blues", 200))
            .unwrap();
    }
    // Creator 300 has item 30 (not followed by user 1).
    db.write_item_with_metadata(EntityId::new(30), &item_metadata("rock", 300))
        .unwrap();

    // User 1 follows creator 100 and 200.
    db.write_relationship(
        EntityId::new(1),
        RelationshipType::Follows,
        EntityId::new(100),
        1.0,
        ts,
    )
    .unwrap();
    db.write_relationship(
        EntityId::new(1),
        RelationshipType::Follows,
        EntityId::new(200),
        1.0,
        ts,
    )
    .unwrap();

    // Query with SocialGraph(user_id=1, depth=1) filter.
    let query = Retrieve::builder()
        .profile("new")
        .for_user(1)
        .filter(FilterExpr::social_graph(1, 1))
        .limit(20)
        .build()
        .unwrap();

    let results = db.retrieve(&query).unwrap();
    let ids: Vec<u64> = results.items.iter().map(|r| r.entity_id.as_u64()).collect();

    // Should include items from creator 100 and 200, but NOT creator 300.
    assert!(ids.contains(&10), "item 10 from followed creator 100");
    assert!(ids.contains(&11), "item 11 from followed creator 100");
    assert!(ids.contains(&20), "item 20 from followed creator 200");
    assert!(ids.contains(&21), "item 21 from followed creator 200");
    assert!(
        !ids.contains(&30),
        "item 30 from unfollowed creator 300 should be excluded"
    );
}

// ── Test 3: Social graph depth=2 expands to follower community ──────────────

#[test]
fn social_graph_depth2_expands_to_follower_community() {
    let db = open_ephemeral_db();
    let ts = Timestamp::now();

    // Creator 100 has item 10.
    db.write_item_with_metadata(EntityId::new(10), &item_metadata("jazz", 100))
        .unwrap();

    // Creator 200 has item 20 (not followed by user 1).
    db.write_item_with_metadata(EntityId::new(20), &item_metadata("blues", 200))
        .unwrap();

    // Item 50 exists but belongs to no followed creator.
    db.write_item_with_metadata(EntityId::new(50), &item_metadata("rock", 300))
        .unwrap();

    // User 1 follows creator 100.
    db.write_relationship(
        EntityId::new(1),
        RelationshipType::Follows,
        EntityId::new(100),
        1.0,
        ts,
    )
    .unwrap();

    // User 2 also follows creator 100.
    db.write_relationship(
        EntityId::new(2),
        RelationshipType::Follows,
        EntityId::new(100),
        1.0,
        ts,
    )
    .unwrap();

    // User 2 has seen item 20 (from creator 200, not followed by user 1).
    // This simulates depth-2 expansion: user 2 is a co-follower of creator 100,
    // so items seen by user 2 become visible at depth=2.
    db.signal_with_context("view", EntityId::new(20), 1.0, ts, Some(2), Some(200))
        .unwrap();

    // Query with SocialGraph(user_id=1, depth=2).
    let query = Retrieve::builder()
        .profile("new")
        .for_user(1)
        .filter(FilterExpr::social_graph(1, 2))
        .limit(20)
        .build()
        .unwrap();

    let results = db.retrieve(&query).unwrap();
    let ids: Vec<u64> = results.items.iter().map(|r| r.entity_id.as_u64()).collect();

    // depth-1: item 10 (from creator 100)
    assert!(ids.contains(&10), "item 10 from followed creator 100");
    // depth-2: item 20 (seen by user 2, co-follower of creator 100)
    assert!(
        ids.contains(&20),
        "item 20 should appear at depth=2 (seen by co-follower)"
    );
}

// ── Test 4: Co-engagement recording and scoring ─────────────────────────────

#[test]
fn co_engagement_recording_and_scoring() {
    let db = open_ephemeral_db();
    let ts = Timestamp::now();

    // Write items.
    for id in [10u64, 20, 30] {
        db.write_item_with_metadata(EntityId::new(id), &item_metadata("jazz", 100))
            .unwrap();
    }

    // User 1 engages positively with items 10, 20, 30 in sequence.
    // "like" is a positive engagement signal.
    db.signal_with_context("like", EntityId::new(10), 1.0, ts, Some(1), Some(100))
        .unwrap();
    db.signal_with_context("like", EntityId::new(20), 1.0, ts, Some(1), Some(100))
        .unwrap();
    db.signal_with_context("like", EntityId::new(30), 1.0, ts, Some(1), Some(100))
        .unwrap();

    // Co-engagement should record (20, 10), (30, 10), (30, 20) edges.
    let co_eng = db.co_engagement();
    assert!(
        co_eng.score(EntityId::new(20), EntityId::new(10)) > 0.0,
        "co-engagement (20, 10) should be positive"
    );
    assert!(
        co_eng.score(EntityId::new(30), EntityId::new(10)) > 0.0,
        "co-engagement (30, 10) should be positive"
    );
    assert!(
        co_eng.score(EntityId::new(30), EntityId::new(20)) > 0.0,
        "co-engagement (30, 20) should be positive"
    );

    // Asymmetric: reverse direction should be 0.
    assert_eq!(
        co_eng.score(EntityId::new(10), EntityId::new(20)),
        0.0,
        "co-engagement is asymmetric: (10, 20) should be 0"
    );

    // User 2 also likes items 10 and 20 -> (20, 10) weight should increment.
    db.signal_with_context("like", EntityId::new(10), 1.0, ts, Some(2), Some(100))
        .unwrap();
    db.signal_with_context("like", EntityId::new(20), 1.0, ts, Some(2), Some(100))
        .unwrap();

    assert!(
        co_eng.score(EntityId::new(20), EntityId::new(10)) > 1.0,
        "co-engagement (20, 10) should increment from two users"
    );
}

// ── Test 5: Related profile boosts co-engaged items ─────────────────────────

#[test]
fn related_profile_boosts_co_engaged_items() {
    let db = open_ephemeral_db();
    let ts = Timestamp::now();

    // Write 5 items.
    for id in 1..=5u64 {
        db.write_item_with_metadata(EntityId::new(id), &item_metadata("jazz", 100))
            .unwrap();
        // Give all items the same view signal so base scores are equal.
        db.signal("view", EntityId::new(id), 10.0, ts).unwrap();
    }

    // Build co-engagement edges: seed=1 -> items 2 and 3 (strong), item 4 (weak), item 5 (none).
    let co_eng = db.co_engagement();
    co_eng.insert_edge(1, 2, 5.0);
    co_eng.insert_edge(1, 3, 3.0);
    co_eng.insert_edge(1, 4, 0.5);
    // Item 5 has no co-engagement with item 1.

    // RETRIEVE with `related` profile and similar_to=1.
    // Exclude the seed item explicitly (RETRIEVE does not auto-exclude similar_to).
    let query = Retrieve::builder()
        .profile("related")
        .similar_to(EntityId::new(1))
        .exclude(vec![EntityId::new(1)])
        .limit(5)
        .build()
        .unwrap();

    let results = db.retrieve(&query).unwrap();
    let ids: Vec<u64> = results.items.iter().map(|r| r.entity_id.as_u64()).collect();

    // Item 1 should be excluded via the exclude list.
    assert!(
        !ids.contains(&1),
        "seed item 1 should not appear in results"
    );

    // Items 2 and 3 should rank higher than items 4 and 5 due to co-engagement boost.
    // Find rank positions.
    if results.items.len() >= 3 {
        let pos_2 = ids.iter().position(|&id| id == 2);
        let pos_5 = ids.iter().position(|&id| id == 5);

        // Item 2 (co-eng weight 5.0) should rank ahead of item 5 (no co-eng).
        if let (Some(p2), Some(p5)) = (pos_2, pos_5) {
            assert!(
                p2 < p5,
                "item 2 (co-engaged) should rank ahead of item 5 (no co-engagement): pos_2={p2}, pos_5={p5}"
            );
        }
    }
}

// ── Test 6: Social-graph-scoped trending differs from global ────────────────

#[test]
fn social_trending_differs_from_global_trending() {
    let db = open_ephemeral_db();
    let base_ts_ns = 1_708_000_000_000_000_000u64;
    let ts = Timestamp::from_nanos(base_ts_ns);

    // Write items.
    for id in 1..=3u64 {
        db.write_item_with_metadata(EntityId::new(id), &item_metadata("jazz", 100))
            .unwrap();
    }

    // Creator 100 exists.
    let mut creator_meta = HashMap::new();
    creator_meta.insert("name".to_string(), "creator100".to_string());
    db.write_creator(EntityId::new(100), &creator_meta).unwrap();

    // User 1 follows creator 100.
    db.write_relationship(
        EntityId::new(1),
        RelationshipType::Follows,
        EntityId::new(100),
        1.0,
        ts,
    )
    .unwrap();

    // User 2 follows creator 100 (co-follower).
    db.write_relationship(
        EntityId::new(2),
        RelationshipType::Follows,
        EntityId::new(100),
        1.0,
        ts,
    )
    .unwrap();

    // User 2 (in social graph) views item 1 heavily.
    for i in 0..100u64 {
        let t = Timestamp::from_nanos(base_ts_ns + i * 1_000_000_000);
        db.signal_with_context("view", EntityId::new(1), 1.0, t, Some(2), Some(100))
            .unwrap();
    }

    // User 99 (NOT in social graph) views item 2 heavily.
    for i in 0..200u64 {
        let t = Timestamp::from_nanos(base_ts_ns + i * 1_000_000_000);
        db.signal_with_context("view", EntityId::new(2), 1.0, t, Some(99), Some(100))
            .unwrap();
    }

    // Global trending: item 2 should rank higher (200 views vs 100).
    let global_query = Retrieve::builder()
        .profile("trending")
        .limit(10)
        .build()
        .unwrap();

    let global_results = db.retrieve(&global_query).unwrap();
    let global_ids: Vec<u64> = global_results
        .items
        .iter()
        .map(|r| r.entity_id.as_u64())
        .collect();

    // Social-scoped trending for user 1: only signals from user 2 (co-follower)
    // should be counted. Item 1 has 100 views from user 2; item 2 has 0 from user 2.
    let social_query = Retrieve::builder()
        .profile("trending")
        .for_user(1)
        .filter(FilterExpr::social_graph(1, 1))
        .limit(10)
        .build()
        .unwrap();

    let social_results = db.retrieve(&social_query).unwrap();
    let social_ids: Vec<u64> = social_results
        .items
        .iter()
        .map(|r| r.entity_id.as_u64())
        .collect();

    // The key assertion: social-scoped results should have different ranking
    // than global results. In social scope, item 1 should rank higher than item 2
    // because user 2 (co-follower) viewed item 1 heavily, while item 2's views
    // came from user 99 (outside the social graph).
    if !social_ids.is_empty() && !global_ids.is_empty() {
        // In the social-scoped query, item 1 should appear and ideally rank first.
        if let Some(pos_1) = social_ids.iter().position(|&id| id == 1) {
            let pos_2 = social_ids.iter().position(|&id| id == 2);
            // If both appear, item 1 should rank above item 2 in social scope.
            if let Some(p2) = pos_2 {
                assert!(
                    pos_1 < p2,
                    "social trending: item 1 (100 views from co-follower) should rank above item 2 (0 views from co-follower): pos_1={pos_1}, pos_2={p2}"
                );
            }
        }
    }
}

// ── Test 7: Co-engagement LRU eviction at capacity ──────────────────────────

#[test]
fn co_engagement_lru_eviction_at_capacity() {
    // Directly test the CoEngagementIndex with a small capacity.
    let index = tidaldb::entities::CoEngagementIndex::with_capacity(10);

    // Build many co-engagement edges: 20 users each liking items 1..5.
    // Each record_positive call adds up to N-1 edges but evicts at most 1.
    for user_id in 1..=20u64 {
        for item_id in 1..=5u64 {
            index.record_positive(user_id, EntityId::new(item_id));
        }
    }

    // The edge count should be bounded -- eviction should have removed
    // some edges rather than allowing unbounded growth.
    let count = index.edge_count();
    // Theoretical max without eviction: many hundreds of edges.
    // With capacity=10 and eviction, the count should be significantly bounded.
    assert!(
        count < 200,
        "co-engagement eviction should bound edge count; got {count}"
    );

    // Verify that the index is still functional: scoring works.
    // Recent edges should still be queryable.
    assert!(index.edge_count() > 0, "index should not be empty");
}

// ── Test 8: Co-engagement checkpoint/restore ────────────────────────────────

#[test]
fn co_engagement_checkpoint_restore() {
    let dir = tempfile::tempdir().unwrap();
    let schema = m6_social_schema();

    // Phase 1: open, record co-engagement, shutdown (triggers checkpoint).
    {
        let db = TidalDb::builder()
            .with_data_dir(dir.path())
            .with_schema(schema.clone())
            .open()
            .unwrap();

        // Write items.
        for id in [10u64, 20, 30] {
            db.write_item_with_metadata(EntityId::new(id), &item_metadata("jazz", 100))
                .unwrap();
        }

        // Build co-engagement edges via direct insert (simulates prior engagement).
        let co_eng = db.co_engagement();
        co_eng.insert_edge(10, 20, 5.0);
        co_eng.insert_edge(10, 30, 2.5);
        co_eng.insert_edge(20, 30, 1.0);

        assert_eq!(co_eng.edge_count(), 3);

        // Shutdown triggers checkpoint.
        db.close().unwrap();
    }

    // Phase 2: reopen and verify co-engagement edges survived.
    {
        let db = TidalDb::builder()
            .with_data_dir(dir.path())
            .with_schema(schema)
            .open()
            .unwrap();

        let co_eng = db.co_engagement();

        // Edges should be restored from checkpoint.
        assert!(
            co_eng.edge_count() >= 3,
            "co-engagement edges should survive restart; got {}",
            co_eng.edge_count()
        );

        // Verify specific edge weights.
        let score_10_20 = co_eng.score(EntityId::new(10), EntityId::new(20));
        assert!(
            (score_10_20 - 5.0).abs() < f32::EPSILON,
            "edge (10, 20) weight should be 5.0 after restore; got {score_10_20}"
        );

        let score_10_30 = co_eng.score(EntityId::new(10), EntityId::new(30));
        assert!(
            (score_10_30 - 2.5).abs() < f32::EPSILON,
            "edge (10, 30) weight should be 2.5 after restore; got {score_10_30}"
        );

        let score_20_30 = co_eng.score(EntityId::new(20), EntityId::new(30));
        assert!(
            (score_20_30 - 1.0).abs() < f32::EPSILON,
            "edge (20, 30) weight should be 1.0 after restore; got {score_20_30}"
        );

        db.close().unwrap();
    }
}