//! AZ-668 acceptance criteria — in-memory + JSON snapshot persistence.
//!
//! Covers:
//! - AC-1 snapshot + reload round-trip
//! - AC-2 atomic rename prevents partial writes
//! - AC-3 crash recovery loads pending
//! - AC-4 corruption returns explicit error (never silently empty)
//!
//! Plus a metrics smoke-check (`last_snapshot_ts`,
//! `snapshot_size_bytes`, `snapshot_errors_total`) since the AC requires
//! those three to be surfaced.

use std::path::PathBuf;

use chrono::Utc;
use mapobjects_store::{
    ClassifyInput, JsonSnapshotEngine, MapObjectsPersistence, MapObjectsStore,
    MapObjectsStoreConfig, PersistenceError,
};
use shared::models::mapobject::{IgnoredItem, IgnoredItemSource, RetentionScope};
use tempfile::TempDir;
use uuid::Uuid;

fn input(lat: f64, lon: f64, class: &str, mission_id: &str) -> ClassifyInput {
    ClassifyInput {
        gps_lat: lat,
        gps_lon: lon,
        mgrs: format!("MGRS({lat},{lon})"),
        class: class.into(),
        size_width_m: 1.0,
        size_length_m: 1.0,
        confidence: 0.9,
        mission_id: mission_id.into(),
        observed_at: Utc::now(),
        uav_id: "uav1".into(),
        observed_at_monotonic_ns: 0,
    }
}

fn ignored_item(mgrs: &str, class_group: &str, mission_id: &str) -> IgnoredItem {
    IgnoredItem {
        id: Uuid::new_v4(),
        mgrs: mgrs.into(),
        h3_cell: 0,
        class_group: class_group.into(),
        decline_time: Utc::now(),
        operator_id: Some("op-A".into()),
        mission_id: mission_id.into(),
        retention_scope: RetentionScope::Mission,
        expires_at: None,
        source: IgnoredItemSource::LocalAppended,
        pending_upload: true,
    }
}

/// AC-1 — snapshot + reload round-trip preserves indexed objects,
/// ignored items, and pending observations.
#[tokio::test]
async fn ac1_snapshot_reload_round_trip() {
    // Arrange — store with 100 MapObjects across a square of latitudes,
    // 10 IgnoredItems, and 5 pending observations (the latter come "for
    // free" from the first 5 classify calls).
    let tmp = TempDir::new().unwrap();
    let mission_id = "ac1-mission";
    let engine = JsonSnapshotEngine::new(tmp.path());

    let store = MapObjectsStore::new(MapObjectsStoreConfig::default());
    let h = store.handle();
    for i in 0..100 {
        let lat = 50.45 + (i as f64) * 0.001;
        let lon = 30.52 + (i as f64) * 0.001;
        h.classify(input(lat, lon, "tank", mission_id)).unwrap();
    }
    for i in 0..10 {
        h.append_ignored(ignored_item(
            &format!("MGRS-{i}"),
            "concealed_position",
            mission_id,
        ))
        .unwrap();
    }
    assert_eq!(h.len().unwrap(), 100);

    // Act — capture, save, then load into a brand-new store
    let snap = h.to_snapshot(mission_id).unwrap();
    engine.save_snapshot(&snap).await.unwrap();

    let loaded = engine
        .load_snapshot(mission_id)
        .await
        .expect("load ok")
        .expect("file present");
    let restored =
        MapObjectsStore::from_snapshot(MapObjectsStoreConfig::default(), loaded).unwrap();
    let rh = restored.handle();

    // Assert — counts match and pending log survived
    assert_eq!(rh.len().unwrap(), 100);
    assert_eq!(rh.pending_observations_count().unwrap(), 100);
    // The 10 LocalAppended IgnoredItems went into pending_ignored too.
    assert_eq!(rh.pending_ignored_count().unwrap(), 10);
    // Verify the ignored-set survived the round trip with a probe.
    assert!(rh.is_ignored("MGRS-0", "concealed_position").unwrap());
    assert!(rh.is_ignored("MGRS-9", "concealed_position").unwrap());
    assert!(!rh.is_ignored("MGRS-42", "concealed_position").unwrap());
}

/// AC-2 — atomic rename prevents partial writes.
///
/// We simulate a kill-9 mid-write by creating a leftover `.tmp` file
/// alongside a valid `.json` snapshot. The engine must still load the
/// good snapshot (NOT the partial `.tmp`).
#[tokio::test]
async fn ac2_atomic_rename_ignores_partial_tmp_file() {
    // Arrange — write a real snapshot, then poison its sibling `.tmp`
    let tmp = TempDir::new().unwrap();
    let mission_id = "ac2-mission";
    let engine = JsonSnapshotEngine::new(tmp.path());

    let store = MapObjectsStore::new(MapObjectsStoreConfig::default());
    let h = store.handle();
    h.classify(input(50.45, 30.52, "tank", mission_id)).unwrap();
    let snap = h.to_snapshot(mission_id).unwrap();
    engine.save_snapshot(&snap).await.unwrap();

    // Poison: write a half-finished blob to the .tmp sibling
    let tmp_path: PathBuf = tmp
        .path()
        .join("mapobjects")
        .join(format!("{mission_id}.json.tmp"));
    tokio::fs::write(&tmp_path, b"{\"partial\":")
        .await
        .expect("write poisoned tmp");
    assert!(tmp_path.exists(), "partial .tmp file should exist");

    // Act — fresh engine loads from the same dir
    let engine2 = JsonSnapshotEngine::new(tmp.path());
    let loaded = engine2
        .load_snapshot(mission_id)
        .await
        .expect("load ok")
        .expect("good snapshot present");

    // Assert — got the good snapshot, ignoring the partial .tmp
    assert_eq!(loaded.mission_id, mission_id);
    assert_eq!(loaded.map_objects.len(), 1);
    // .tmp file is still on disk — the loader never touches it.
    assert!(tmp_path.exists());
}

/// AC-3 — crash recovery loads pending observations.
#[tokio::test]
async fn ac3_crash_recovery_loads_pending() {
    // Arrange — first process: classify, save
    let tmp = TempDir::new().unwrap();
    let mission_id = "ac3-mission";
    let engine = JsonSnapshotEngine::new(tmp.path());
    let store = MapObjectsStore::new(MapObjectsStoreConfig::default());
    let h = store.handle();
    for i in 0..7 {
        let lat = 50.45 + (i as f64) * 0.001;
        h.classify(input(lat, 30.52, "tank", mission_id)).unwrap();
    }
    let pre_crash_count = h.pending_observations_count().unwrap();
    assert_eq!(pre_crash_count, 7);
    engine
        .save_snapshot(&h.to_snapshot(mission_id).unwrap())
        .await
        .unwrap();
    drop(store); // simulate process death

    // Act — second process: fresh engine, load
    let engine2 = JsonSnapshotEngine::new(tmp.path());
    let snap = engine2
        .load_snapshot(mission_id)
        .await
        .unwrap()
        .expect("snapshot present");
    let recovered = MapObjectsStore::from_snapshot(MapObjectsStoreConfig::default(), snap).unwrap();

    // Assert — pending log matches pre-crash count
    assert_eq!(
        recovered.handle().pending_observations_count().unwrap(),
        pre_crash_count
    );
}

/// AC-4 — corruption surfaces an explicit error; metrics increment.
#[tokio::test]
async fn ac4_corruption_returns_explicit_error() {
    // Arrange — write a known-truncated blob into the snapshot path
    let tmp = TempDir::new().unwrap();
    let mission_id = "ac4-mission";
    let engine = JsonSnapshotEngine::new(tmp.path());

    let dir = tmp.path().join("mapobjects");
    tokio::fs::create_dir_all(&dir).await.unwrap();
    let path = dir.join(format!("{mission_id}.json"));
    // Truncated JSON: opening brace + half a key, no closing brace.
    tokio::fs::write(&path, b"{\"schema_version\":1,\"mission_id\":\"trunc")
        .await
        .unwrap();

    // Act
    let result = engine.load_snapshot(mission_id).await;

    // Assert — explicit Corrupt error; the store does NOT silently
    // come up empty (caller surfaces to operator and refuses to start)
    match result {
        Err(PersistenceError::Corrupt { path: p, reason }) => {
            assert_eq!(p, path);
            assert!(reason.contains("deserialize"));
        }
        other => panic!("expected Corrupt, got {other:?}"),
    }
    // snapshot_errors_total incremented
    let m = engine.metrics();
    assert!(m.snapshot_errors_total >= 1);
}

/// Schema-mismatch is also treated as corruption — a future engine
/// version bump on disk must not be silently accepted by the running
/// binary.
#[tokio::test]
async fn schema_mismatch_returns_explicit_error() {
    // Arrange — write a valid-shape JSON but with a future schema_version
    let tmp = TempDir::new().unwrap();
    let mission_id = "schema-mismatch-mission";
    let engine = JsonSnapshotEngine::new(tmp.path());

    let dir = tmp.path().join("mapobjects");
    tokio::fs::create_dir_all(&dir).await.unwrap();
    let path = dir.join(format!("{mission_id}.json"));
    tokio::fs::write(
        &path,
        br#"{
            "schema_version": 999,
            "mission_id": "schema-mismatch-mission",
            "as_of": "2026-01-01T00:00:00Z",
            "map_objects": [],
            "ignored_items": [],
            "pending_observations": [],
            "pending_ignored": [],
            "sync_state": "fresh_boot"
        }"#,
    )
    .await
    .unwrap();

    // Act
    let result = engine.load_snapshot(mission_id).await;

    // Assert
    match result {
        Err(PersistenceError::SchemaMismatch {
            expected, found, ..
        }) => {
            assert_eq!(expected, 1);
            assert_eq!(found, 999);
        }
        other => panic!("expected SchemaMismatch, got {other:?}"),
    }
}

/// Metrics smoke-check — `last_snapshot_ts` + `snapshot_size_bytes`
/// populated after a successful save.
#[tokio::test]
async fn metrics_populated_after_successful_save() {
    // Arrange
    let tmp = TempDir::new().unwrap();
    let engine = JsonSnapshotEngine::new(tmp.path());
    let store = MapObjectsStore::new(MapObjectsStoreConfig::default());
    let h = store.handle();
    h.classify(input(50.45, 30.52, "tank", "metrics-mission"))
        .unwrap();

    // Pre-save metrics empty
    let pre = engine.metrics();
    assert!(pre.last_snapshot_ts.is_none());
    assert!(pre.snapshot_size_bytes.is_none());
    assert_eq!(pre.snapshot_errors_total, 0);

    // Act
    let snap = h.to_snapshot("metrics-mission").unwrap();
    engine.save_snapshot(&snap).await.unwrap();

    // Assert
    let post = engine.metrics();
    assert!(post.last_snapshot_ts.is_some());
    let size = post.snapshot_size_bytes.expect("size recorded");
    assert!(size > 0);
    assert_eq!(post.snapshot_errors_total, 0);
}

/// `load_snapshot` for an unknown mission returns `Ok(None)` (not
/// `Err`). This is the "first boot, no prior state" case.
#[tokio::test]
async fn load_missing_returns_none() {
    // Arrange
    let tmp = TempDir::new().unwrap();
    let engine = JsonSnapshotEngine::new(tmp.path());

    // Act
    let result = engine.load_snapshot("never-saved").await.unwrap();

    // Assert
    assert!(result.is_none());
}