//! M9 Retroactive Purge Integration Tests.
//!
//! Exercises the end-to-end retroactive signal purge pipeline:
//! - Contribution log is populated on `signal_with_context` with cohort attribution.
//! - `request_community_purge` retracts contributions from the live cohort ledger.
//! - Purge manifests are persisted to durable storage.
//! - `list_purge_manifests` retrieves persisted manifests.
//! - Second purge on the same user is idempotent (no-op on the ledger).
//! - Scores floor at 0.0 and never go negative.
//! - Purging one user does not affect another user's cohort contributions.

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

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

use tidaldb::TidalDb;
use tidaldb::cohort::{CohortDef, Predicate};
use tidaldb::schema::{DecaySpec, EntityId, EntityKind, SchemaBuilder, Timestamp, Window};

// ── Shared fixtures ──────────────────────────────────────────────────────────

fn purge_schema() -> tidaldb::schema::Schema {
    let mut builder = SchemaBuilder::new();
    let _ = builder
        .signal(
            "view",
            EntityKind::Item,
            DecaySpec::Exponential {
                half_life: Duration::from_secs(7 * 24 * 3600),
            },
        )
        .windows(&[Window::AllTime])
        .velocity(false)
        .add();
    builder.build().expect("purge schema must be valid")
}

fn open_ephemeral() -> TidalDb {
    TidalDb::builder()
        .ephemeral()
        .with_schema(purge_schema())
        .open()
        .expect("ephemeral open")
}

fn setup_cohort(db: &TidalDb, cohort: &str, field: &str, value: &str) {
    db.define_cohort(CohortDef {
        name: cohort.to_string(),
        predicate: Predicate::Eq {
            field: field.into(),
            value: value.into(),
        },
    })
    .unwrap();
}

fn user_meta(locale: &str) -> HashMap<String, String> {
    let mut m = HashMap::new();
    m.insert("locale".to_string(), locale.to_string());
    m
}

// ── Test 1: basic_purge_retracts_score ───────────────────────────────────────

/// Signal from user contributes to cohort; purge reduces the cohort score.
#[test]
fn basic_purge_retracts_score() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let user_id = 1u64;
    let item_id = EntityId::new(100);

    db.write_user(EntityId::new(user_id), &user_meta("en"))
        .unwrap();

    let ts = Timestamp::now();
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_id), None)
        .unwrap();
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_id), None)
        .unwrap();

    // Cohort ledger should have score > 0.
    let score_before = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    assert!(
        score_before > 0.0,
        "cohort score must be positive before purge"
    );

    // Purge user 1's contributions from "en_users".
    let (purge_id, manifest) = db.request_community_purge(user_id, "en_users").unwrap();

    assert_eq!(manifest.user_id, user_id);
    assert_eq!(manifest.cohort, "en_users");
    assert_eq!(manifest.purge_id, purge_id);
    // Manifest must record the contributions that were retracted.
    assert!(
        !manifest.entries.is_empty(),
        "manifest must list retracted entries"
    );

    let score_after = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    assert!(
        score_after < score_before,
        "cohort score must decrease after purge (before={score_before}, after={score_after})"
    );
    assert!(score_after >= 0.0, "score must not go negative");
}

// ── Test 2: second_purge_is_idempotent ────────────────────────────────────────

/// A second purge for the same (user, cohort) finds nothing to retract.
#[test]
fn second_purge_is_idempotent() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let user_id = 2u64;
    let item_id = EntityId::new(200);

    db.write_user(EntityId::new(user_id), &user_meta("en"))
        .unwrap();

    let ts = Timestamp::now();
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_id), None)
        .unwrap();

    let (_, manifest1) = db.request_community_purge(user_id, "en_users").unwrap();
    assert!(
        !manifest1.entries.is_empty(),
        "first purge must drain entries"
    );

    let score_after_first = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);

    let (_, manifest2) = db.request_community_purge(user_id, "en_users").unwrap();
    assert_eq!(
        manifest2.entries.len(),
        0,
        "second purge must find no entries to drain"
    );

    // Score unchanged from first purge.
    let score_after_second = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    let delta = (score_after_second - score_after_first).abs();
    assert!(
        delta < 1e-9,
        "second purge must not change score (delta={delta})"
    );
}

// ── Test 3: purge_does_not_affect_other_users ────────────────────────────────

/// Purging user A's contributions must not retract user B's contributions.
#[test]
fn purge_does_not_affect_other_users() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let user_a = 3u64;
    let user_b = 4u64;
    let item_id = EntityId::new(300);

    db.write_user(EntityId::new(user_a), &user_meta("en"))
        .unwrap();
    db.write_user(EntityId::new(user_b), &user_meta("en"))
        .unwrap();

    let ts = Timestamp::now();
    // Both users signal the same item.
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_a), None)
        .unwrap();
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_b), None)
        .unwrap();

    let score_before = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    assert!(score_before > 0.0);

    // Purge only user A.
    let (_, manifest) = db.request_community_purge(user_a, "en_users").unwrap();
    assert!(
        !manifest.entries.is_empty(),
        "manifest must list user A entries"
    );

    // Score should be lower but still positive (user B's contribution remains).
    let score_after = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    assert!(
        score_after < score_before,
        "score must decrease after purging user A"
    );
    assert!(
        score_after > 0.0,
        "score must remain positive (user B contribution intact)"
    );
}

// ── Test 4: manifest_persisted_and_listable ──────────────────────────────────

/// After purge, manifest appears in `list_purge_manifests`.
/// Ephemeral mode uses an in-memory backend so the manifest is persisted.
#[test]
fn manifest_persisted_and_listable() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let user_id = 5u64;
    let item_id = EntityId::new(500);

    db.write_user(EntityId::new(user_id), &user_meta("en"))
        .unwrap();

    let ts = Timestamp::now();
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_id), None)
        .unwrap();

    let (purge_id, _) = db.request_community_purge(user_id, "en_users").unwrap();

    // Manifest must appear in the list.
    let manifests = db.list_purge_manifests(user_id).unwrap();
    assert_eq!(manifests.len(), 1, "one manifest must be persisted");
    assert_eq!(
        manifests[0].purge_id, purge_id,
        "manifest purge_id must match"
    );
    assert_eq!(manifests[0].user_id, user_id);
    assert_eq!(manifests[0].cohort, "en_users");

    // A second purge creates a second manifest.
    db.request_community_purge(user_id, "en_users").unwrap();
    let manifests2 = db.list_purge_manifests(user_id).unwrap();
    assert_eq!(manifests2.len(), 2, "two manifests must be persisted");
}

// ── Test 5: purge_unknown_cohort_is_noop ─────────────────────────────────────

/// Purging a user from a cohort they never belonged to returns an empty manifest.
#[test]
fn purge_unknown_cohort_is_noop() {
    let db = open_ephemeral();

    let user_id = 6u64;
    db.write_user(EntityId::new(user_id), &user_meta("en"))
        .unwrap();

    // No signals were recorded, no cohort was defined.
    let (_, manifest) = db
        .request_community_purge(user_id, "nonexistent_cohort")
        .unwrap();
    assert_eq!(
        manifest.entries.len(),
        0,
        "purge of unknown cohort must return empty manifest"
    );
}

// ── Test 6: score_never_goes_negative ────────────────────────────────────────

/// Even if the contribution log is replayed twice (bug scenario), the ledger
/// score must be floored at 0.0.
#[test]
fn score_never_goes_negative() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let user_id = 7u64;
    let item_id = EntityId::new(700);

    db.write_user(EntityId::new(user_id), &user_meta("en"))
        .unwrap();

    let ts = Timestamp::now();
    db.signal_with_context("view", item_id, 1.0, ts, Some(user_id), None)
        .unwrap();

    // Normal purge.
    db.request_community_purge(user_id, "en_users").unwrap();

    let score = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    assert!(
        score >= 0.0,
        "cohort score must be non-negative after purge (score={score})"
    );
}

// ── Test 7: multiple_items_purged_together ────────────────────────────────────

/// Signals to multiple items by the same user are all retracted in one purge.
#[test]
fn multiple_items_purged_together() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let user_id = 8u64;
    let item_a = EntityId::new(801);
    let item_b = EntityId::new(802);

    db.write_user(EntityId::new(user_id), &user_meta("en"))
        .unwrap();

    let ts = Timestamp::now();
    db.signal_with_context("view", item_a, 1.0, ts, Some(user_id), None)
        .unwrap();
    db.signal_with_context("view", item_b, 1.0, ts, Some(user_id), None)
        .unwrap();

    let score_a_before = db
        .cohort_ledger()
        .read_decay_score("en_users", item_a, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    let score_b_before = db
        .cohort_ledger()
        .read_decay_score("en_users", item_b, "view", 0)
        .unwrap()
        .unwrap_or(0.0);

    assert!(score_a_before > 0.0);
    assert!(score_b_before > 0.0);

    let (_, manifest) = db.request_community_purge(user_id, "en_users").unwrap();
    // Both items should appear in the manifest.
    assert_eq!(
        manifest.entries.len(),
        2,
        "manifest must cover all items signalled by the user"
    );

    let score_a_after = db
        .cohort_ledger()
        .read_decay_score("en_users", item_a, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    let score_b_after = db
        .cohort_ledger()
        .read_decay_score("en_users", item_b, "view", 0)
        .unwrap()
        .unwrap_or(0.0);

    assert!(
        score_a_after < score_a_before,
        "item A score must decrease after purge"
    );
    assert!(
        score_b_after < score_b_before,
        "item B score must decrease after purge"
    );
}

// ── Test 8: only_signaling_cohort_member_contributes ─────────────────────────

/// A user who is not in a cohort does not appear in the contribution log for
/// that cohort, so purging them is a no-op on the ledger.
#[test]
fn non_cohort_member_purge_is_noop() {
    let db = open_ephemeral();
    setup_cohort(&db, "en_users", "locale", "en");

    let en_user = 9u64;
    let fr_user = 10u64;
    let item_id = EntityId::new(900);

    db.write_user(EntityId::new(en_user), &user_meta("en"))
        .unwrap();
    db.write_user(EntityId::new(fr_user), &user_meta("fr"))
        .unwrap();

    let ts = Timestamp::now();
    // Both users signal; only en_user lands in the cohort.
    db.signal_with_context("view", item_id, 1.0, ts, Some(en_user), None)
        .unwrap();
    db.signal_with_context("view", item_id, 1.0, ts, Some(fr_user), None)
        .unwrap();

    let score_before = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    assert!(score_before > 0.0, "en_users must have score from en_user");

    // Purge fr_user from en_users (they were never in the log for this cohort).
    let (_, manifest) = db.request_community_purge(fr_user, "en_users").unwrap();
    assert_eq!(
        manifest.entries.len(),
        0,
        "fr_user has no contributions to en_users"
    );

    let score_after = db
        .cohort_ledger()
        .read_decay_score("en_users", item_id, "view", 0)
        .unwrap()
        .unwrap_or(0.0);
    let delta = (score_after - score_before).abs();
    assert!(
        delta < 1e-9,
        "score must be unchanged when purging non-member (delta={delta})"
    );
}