//! Internal CRDT state struct, statics, initialisation, and central write primitive.

#![allow(unused_imports, dead_code)]
use std::collections::HashMap;
use std::path::Path;
use std::sync::{Mutex, OnceLock};

use bft_json_crdt::json_crdt::*;
use bft_json_crdt::keypair::make_keypair;
use fastcrypto::ed25519::Ed25519KeyPair;
use fastcrypto::traits::ToFromBytes;
use serde_json::json;
use sqlx::SqlitePool;
use sqlx::sqlite::SqliteConnectOptions;
use tokio::sync::{broadcast, mpsc};

use super::VectorClock;
use super::hex;
use super::types::{CrdtEvent, PipelineDoc};
use crate::slog;

// ── Sync broadcast channels ──────────────────────────────────────────

pub(super) static CRDT_EVENT_TX: OnceLock<broadcast::Sender<CrdtEvent>> = OnceLock::new();

pub(super) static SYNC_TX: OnceLock<broadcast::Sender<SignedOp>> = OnceLock::new();

/// All persisted ops as JSON strings, in causal (insertion) order.
///
/// Pub(crate) so that `crdt_snapshot` can access it for compaction.
pub(crate) static ALL_OPS: OnceLock<Mutex<Vec<String>>> = OnceLock::new();

/// Live vector clock tracking op counts per author.
///
/// Updated in lockstep with `ALL_OPS` — every time an op is appended to the
/// journal, the corresponding author's count is incremented here.  This avoids
/// re-parsing all ops when a peer requests `our_vector_clock()`.
pub(crate) static VECTOR_CLOCK: OnceLock<Mutex<super::VectorClock>> = OnceLock::new();

/// Append an op's JSON to `ALL_OPS` and bump the author's count in `VECTOR_CLOCK`.
///
/// Centralises the bookkeeping that must stay in sync between the two statics.
pub(super) fn track_op(signed: &SignedOp, json: String) {
    if let Some(all) = ALL_OPS.get()
        && let Ok(mut v) = all.lock()
    {
        v.push(json);
    }
    if let Some(vc) = VECTOR_CLOCK.get()
        && let Ok(mut clock) = vc.lock()
    {
        let author_hex = super::hex::encode(&signed.author());
        *clock.entry(author_hex).or_insert(0) += 1;
    }
}

pub(super) struct CrdtState {
    pub(super) crdt: BaseCrdt<PipelineDoc>,
    pub(super) keypair: Ed25519KeyPair,
    /// Maps story_id → index in the items ListCrdt for O(1) lookup.
    pub(super) index: HashMap<String, usize>,
    /// Maps node_id (hex) → index in the nodes ListCrdt for O(1) lookup.
    pub(super) node_index: HashMap<String, usize>,
    /// Channel sender for fire-and-forget op persistence.
    pub(super) persist_tx: mpsc::UnboundedSender<SignedOp>,
    /// Max sequence number seen across all ops during init() replay.
    ///
    /// Newly-created registers (post-init) must have their Lamport clock
    /// advanced to this floor so they don't re-emit low sequence numbers.
    pub(super) lamport_floor: u64,
}

static CRDT_STATE: OnceLock<Mutex<CrdtState>> = OnceLock::new();

#[cfg(test)]
thread_local! {
    static CRDT_STATE_TL: OnceLock<Mutex<CrdtState>> = const { OnceLock::new() };
}

#[cfg(not(test))]
pub(super) fn get_crdt() -> Option<&'static Mutex<CrdtState>> {
    CRDT_STATE.get()
}

#[cfg(test)]
pub(super) fn get_crdt() -> Option<&'static Mutex<CrdtState>> {
    let tl = CRDT_STATE_TL.with(|lock| {
        if lock.get().is_some() {
            Some(lock as *const OnceLock<Mutex<CrdtState>>)
        } else {
            None
        }
    });
    if let Some(ptr) = tl {
        // SAFETY: The thread-local lives as long as the thread, which outlives
        // any test using it.  We only need 'static for the return type.
        let lock = unsafe { &*ptr };
        lock.get()
    } else {
        CRDT_STATE.get()
    }
}

/// Initialise the CRDT state layer.
///
/// Opens the SQLite database, loads or creates a node keypair, replays any
/// persisted ops to reconstruct state, and spawns a background persistence
/// task.  Safe to call only once; subsequent calls are no-ops.
pub async fn init(db_path: &Path) -> Result<(), sqlx::Error> {
    if CRDT_STATE.get().is_some() {
        return Ok(());
    }

    let options = SqliteConnectOptions::new()
        .filename(db_path)
        .create_if_missing(true);
    let pool = SqlitePool::connect_with(options).await?;
    sqlx::migrate!("./migrations").run(&pool).await?;

    // Load or create the node keypair.
    let keypair = load_or_create_keypair(&pool).await?;
    let mut crdt = BaseCrdt::<PipelineDoc>::new(&keypair);

    // Replay persisted ops to reconstruct state.
    let rows: Vec<(String,)> = sqlx::query_as("SELECT op_json FROM crdt_ops ORDER BY rowid ASC")
        .fetch_all(&pool)
        .await?;

    let mut all_ops_vec = Vec::with_capacity(rows.len());
    let mut vector_clock = VectorClock::new();
    let mut lamport_floor: u64 = 0;
    for (op_json,) in &rows {
        if let Ok(signed_op) = serde_json::from_str::<SignedOp>(op_json) {
            let author_hex = hex::encode(&signed_op.author());
            *vector_clock.entry(author_hex).or_insert(0) += 1;
            lamport_floor = lamport_floor.max(signed_op.inner.seq);
            crdt.apply(signed_op);
            all_ops_vec.push(op_json.clone());
        } else {
            slog!("[crdt] Warning: failed to deserialize stored op");
        }
    }
    let _ = ALL_OPS.set(Mutex::new(all_ops_vec));
    let _ = VECTOR_CLOCK.set(Mutex::new(vector_clock));

    // Build the indices from the reconstructed state.
    let index = rebuild_index(&crdt);
    let node_index = rebuild_node_index(&crdt);

    // Advance the top-level list clocks to the Lamport floor so that
    // list-level inserts (new items / new nodes) don't re-emit low seq numbers.
    crdt.doc.items.advance_seq(lamport_floor);
    crdt.doc.nodes.advance_seq(lamport_floor);

    slog!(
        "[crdt] Initialised: {} ops replayed, {} items indexed, {} nodes indexed, lamport_floor={}",
        rows.len(),
        index.len(),
        node_index.len(),
        lamport_floor,
    );

    // Spawn background persistence task.
    let (persist_tx, mut persist_rx) = mpsc::unbounded_channel::<SignedOp>();

    tokio::spawn(async move {
        while let Some(op) = persist_rx.recv().await {
            let op_json = match serde_json::to_string(&op) {
                Ok(j) => j,
                Err(e) => {
                    slog!("[crdt] Failed to serialize op: {e}");
                    continue;
                }
            };
            let op_id = hex::encode(&op.id());
            let seq = op.inner.seq as i64;
            let now = chrono::Utc::now().to_rfc3339();

            let result = sqlx::query(
                "INSERT INTO crdt_ops (op_id, seq, op_json, created_at) \
                 VALUES (?1, ?2, ?3, ?4) \
                 ON CONFLICT(op_id) DO NOTHING",
            )
            .bind(&op_id)
            .bind(seq)
            .bind(&op_json)
            .bind(&now)
            .execute(&pool)
            .await;

            if let Err(e) = result {
                slog!("[crdt] Failed to persist op {}: {e}", &op_id[..12]);
            }
        }
    });

    let state = CrdtState {
        crdt,
        keypair,
        index,
        node_index,
        persist_tx,
        lamport_floor,
    };

    let _ = CRDT_STATE.set(Mutex::new(state));

    // Initialise the CRDT event broadcast channel.
    let (event_tx, _) = broadcast::channel::<CrdtEvent>(256);
    let _ = CRDT_EVENT_TX.set(event_tx);

    // Initialise the sync broadcast channel for outgoing ops.
    let (sync_tx, _) = broadcast::channel::<SignedOp>(1024);
    let _ = SYNC_TX.set(sync_tx);

    Ok(())
}

/// Initialise a minimal in-memory CRDT state for unit tests.
///
/// This avoids the async SQLite setup from `init()`.  Ops are accepted via a
/// channel whose receiver is immediately dropped, so nothing is persisted.
/// Safe to call multiple times — subsequent calls are no-ops (OnceLock).
#[cfg(test)]
pub fn init_for_test() {
    // Initialise thread-local CRDT for test isolation.
    // Only creates a new CRDT if one isn't set yet on this thread;
    // subsequent calls are no-ops (matching the old OnceLock semantics
    // while keeping each thread isolated).
    CRDT_STATE_TL.with(|lock| {
        if lock.get().is_none() {
            let keypair = make_keypair();
            let crdt = BaseCrdt::<PipelineDoc>::new(&keypair);
            let (persist_tx, _rx) = mpsc::unbounded_channel();
            let state = CrdtState {
                crdt,
                keypair,
                index: HashMap::new(),
                node_index: HashMap::new(),
                persist_tx,
                lamport_floor: 0,
            };
            let _ = lock.set(Mutex::new(state));
        }
    });
    let _ = CRDT_EVENT_TX.get_or_init(|| broadcast::channel::<CrdtEvent>(256).0);
    let _ = SYNC_TX.get_or_init(|| broadcast::channel::<SignedOp>(1024).0);
    let _ = ALL_OPS.get_or_init(|| Mutex::new(Vec::new()));
    let _ = VECTOR_CLOCK.get_or_init(|| Mutex::new(VectorClock::new()));
}

/// Load or create the Ed25519 keypair used by this node.
async fn load_or_create_keypair(pool: &SqlitePool) -> Result<Ed25519KeyPair, sqlx::Error> {
    let row: Option<(Vec<u8>,)> =
        sqlx::query_as("SELECT seed FROM crdt_node_identity WHERE id = 1")
            .fetch_optional(pool)
            .await?;

    if let Some((seed,)) = row {
        // Reconstruct from stored seed.  The seed is the 32-byte private key.
        if let Ok(kp) = Ed25519KeyPair::from_bytes(&seed) {
            return Ok(kp);
        }
        slog!("[crdt] Stored keypair invalid, regenerating");
    }

    let kp = make_keypair();
    let seed = kp.as_bytes().to_vec();
    sqlx::query("INSERT INTO crdt_node_identity (id, seed) VALUES (1, ?1) ON CONFLICT(id) DO UPDATE SET seed = excluded.seed")
        .bind(&seed)
        .execute(pool)
        .await?;

    Ok(kp)
}

/// Rebuild the story_id → list index mapping from the current CRDT state.
pub(super) fn rebuild_index(crdt: &BaseCrdt<PipelineDoc>) -> HashMap<String, usize> {
    let mut map = HashMap::new();
    for (i, item) in crdt.doc.items.iter().enumerate() {
        if let JsonValue::String(ref sid) = item.story_id.view() {
            map.insert(sid.clone(), i);
        }
    }
    map
}

/// Rebuild the node_id → nodes list index mapping from the current CRDT state.
pub(super) fn rebuild_node_index(crdt: &BaseCrdt<PipelineDoc>) -> HashMap<String, usize> {
    let mut map = HashMap::new();
    for (i, node) in crdt.doc.nodes.iter().enumerate() {
        if let JsonValue::String(ref nid) = node.node_id.view() {
            map.insert(nid.clone(), i);
        }
    }
    map
}

// ── Write path ───────────────────────────────────────────────────────

/// Create a CRDT op via `op_fn`, sign it, apply it, and send it to the
/// persistence channel.  The closure receives `&mut CrdtState` so it can
/// mutably access the CRDT document, while `sign` only needs `&keypair`.
pub(super) fn apply_and_persist<F>(state: &mut CrdtState, op_fn: F)
where
    F: FnOnce(&mut CrdtState) -> bft_json_crdt::op::Op<JsonValue>,
{
    let raw_op = op_fn(state);
    let signed = raw_op.sign(&state.keypair);
    state.crdt.apply(signed.clone());
    if let Err(e) = state.persist_tx.send(signed.clone()) {
        crate::slog_error!(
            "[crdt] Failed to send op to persist task: {e}; persist task may be dead. \
             In-memory state is now ahead of persisted state."
        );
    }

    // Track in ALL_OPS + VECTOR_CLOCK, then broadcast to sync peers.
    if let Ok(json) = serde_json::to_string(&signed) {
        track_op(&signed, json);
    }
    if let Some(tx) = SYNC_TX.get() {
        let _ = tx.send(signed);
    }
}

/// Broadcast a CRDT event to all subscribers.
pub(super) fn emit_event(event: CrdtEvent) {
    if let Some(tx) = CRDT_EVENT_TX.get() {
        let _ = tx.send(event);
    }
}

#[cfg(test)]
mod tests {
    use super::super::hex;
    use super::super::read::{extract_item_view, read_item};
    use super::super::types::PipelineItemCrdt;
    use super::super::write::write_item;
    use super::*;
    use bft_json_crdt::json_crdt::OpState;
    use bft_json_crdt::keypair::make_keypair;
    use bft_json_crdt::op::ROOT_ID;
    use serde_json::json;

    #[test]
    fn crdt_ops_replay_reconstructs_state() {
        let kp = make_keypair();
        let mut crdt1 = BaseCrdt::<PipelineDoc>::new(&kp);

        // Build state with a series of ops.
        let item_json: JsonValue = json!({
            "story_id": "30_story_replay",
            "stage": "1_backlog",
            "name": "Replay Test",
            "agent": "",
            "retry_count": 0.0,
            "blocked": false,
            "depends_on": "",
            "claimed_by": "",
            "claimed_at": 0.0,
        })
        .into();

        let op1 = crdt1.doc.items.insert(ROOT_ID, item_json).sign(&kp);
        crdt1.apply(op1.clone());

        let op2 = crdt1.doc.items[0]
            .stage
            .set("2_current".to_string())
            .sign(&kp);
        crdt1.apply(op2.clone());

        let op3 = crdt1.doc.items[0]
            .name
            .set("Updated Name".to_string())
            .sign(&kp);
        crdt1.apply(op3.clone());

        // Replay ops on a fresh CRDT.
        let mut crdt2 = BaseCrdt::<PipelineDoc>::new(&kp);
        crdt2.apply(op1);
        crdt2.apply(op2);
        crdt2.apply(op3);

        assert_eq!(
            crdt1.doc.items[0].stage.view(),
            crdt2.doc.items[0].stage.view()
        );
        assert_eq!(
            crdt1.doc.items[0].name.view(),
            crdt2.doc.items[0].name.view()
        );
    }

    #[test]
    fn rebuild_index_maps_story_ids() {
        let kp = make_keypair();
        let mut crdt = BaseCrdt::<PipelineDoc>::new(&kp);

        for (sid, stage) in &[("10_story_a", "1_backlog"), ("20_story_b", "2_current")] {
            let item: JsonValue = json!({
                "story_id": sid,
                "stage": stage,
                "name": "",
                "agent": "",
                "retry_count": 0.0,
                "blocked": false,
                "depends_on": "",
            "claimed_by": "",
            "claimed_at": 0.0,
            })
            .into();
            let op = crdt.doc.items.insert(ROOT_ID, item).sign(&kp);
            crdt.apply(op);
        }

        let index = rebuild_index(&crdt);
        assert_eq!(index.len(), 2);
        assert!(index.contains_key("10_story_a"));
        assert!(index.contains_key("20_story_b"));
    }

    #[tokio::test]
    async fn init_and_write_read_roundtrip() {
        let tmp = tempfile::tempdir().unwrap();
        let db_path = tmp.path().join("crdt_test.db");

        // Init directly (not via the global singleton, for test isolation).
        let options = SqliteConnectOptions::new()
            .filename(&db_path)
            .create_if_missing(true);
        let pool = SqlitePool::connect_with(options).await.unwrap();
        sqlx::migrate!("./migrations").run(&pool).await.unwrap();

        let keypair = make_keypair();
        let mut crdt = BaseCrdt::<PipelineDoc>::new(&keypair);

        // Insert and update like write_item does.
        let item_json: JsonValue = json!({
            "story_id": "50_story_roundtrip",
            "stage": "1_backlog",
            "name": "Roundtrip",
            "agent": "",
            "retry_count": 0.0,
            "blocked": false,
            "depends_on": "",
            "claimed_by": "",
            "claimed_at": 0.0,
        })
        .into();

        let insert_op = crdt.doc.items.insert(ROOT_ID, item_json).sign(&keypair);
        crdt.apply(insert_op.clone());

        // Persist the op.
        let op_json = serde_json::to_string(&insert_op).unwrap();
        let op_id = hex::encode(&insert_op.id());
        let now = chrono::Utc::now().to_rfc3339();
        sqlx::query(
            "INSERT INTO crdt_ops (op_id, seq, op_json, created_at) VALUES (?1, ?2, ?3, ?4)",
        )
        .bind(&op_id)
        .bind(insert_op.inner.seq as i64)
        .bind(&op_json)
        .bind(&now)
        .execute(&pool)
        .await
        .unwrap();

        // Reconstruct from DB.
        let rows: Vec<(String,)> =
            sqlx::query_as("SELECT op_json FROM crdt_ops ORDER BY rowid ASC")
                .fetch_all(&pool)
                .await
                .unwrap();

        let mut crdt2 = BaseCrdt::<PipelineDoc>::new(&keypair);
        for (json_str,) in &rows {
            let op: SignedOp = serde_json::from_str(json_str).unwrap();
            crdt2.apply(op);
        }

        let view = extract_item_view(&crdt2.doc.items[0]).unwrap();
        assert_eq!(view.story_id, "50_story_roundtrip");
        assert_eq!(view.stage, "1_backlog");
        assert_eq!(view.name.as_deref(), Some("Roundtrip"));
    }

    #[test]
    fn persist_tx_send_failure_logs_error() {
        let kp = make_keypair();
        let crdt = BaseCrdt::<PipelineDoc>::new(&kp);
        let (persist_tx, persist_rx) = mpsc::unbounded_channel::<SignedOp>();

        let mut state = CrdtState {
            crdt,
            keypair: kp,
            index: HashMap::new(),
            node_index: HashMap::new(),
            persist_tx,
            lamport_floor: 0,
        };

        // Drop the receiver so that the next send fails immediately.
        drop(persist_rx);

        let item_json: JsonValue = json!({
            "story_id": "518_story_persist_fail",
            "stage": "1_backlog",
            "name": "Persist Fail Test",
            "agent": "",
            "retry_count": 0.0,
            "blocked": false,
            "depends_on": "",
            "claimed_by": "",
            "claimed_at": 0.0,
        })
        .into();

        let before_errors = crate::log_buffer::global()
            .get_recent_entries(1000, None, Some(&crate::log_buffer::LogLevel::Error))
            .len();

        apply_and_persist(&mut state, |s| s.crdt.doc.items.insert(ROOT_ID, item_json));

        let error_entries = crate::log_buffer::global().get_recent_entries(
            1000,
            None,
            Some(&crate::log_buffer::LogLevel::Error),
        );

        assert!(
            error_entries.len() > before_errors,
            "expected an ERROR log entry when persist_tx send fails, but none was added"
        );

        let last_error = &error_entries[error_entries.len() - 1];
        assert!(
            last_error.message.contains("persist"),
            "error message should mention persist: {}",
            last_error.message
        );
        assert!(
            last_error.message.contains("ahead") || last_error.message.contains("diverged"),
            "error message should note in-memory/persisted divergence: {}",
            last_error.message
        );
    }

    /// After replaying ops from a journal, a brand-new register created
    /// post-init must emit its first local op with seq = lamport_floor + 1,
    /// not seq = 1.  This is the Phase C integration test.
    #[tokio::test]
    async fn restart_new_register_resumes_from_lamport_floor() {
        let tmp = tempfile::tempdir().unwrap();
        let db_path = tmp.path().join("lamport_floor.db");

        let options = SqliteConnectOptions::new()
            .filename(&db_path)
            .create_if_missing(true);
        let pool = SqlitePool::connect_with(options).await.unwrap();
        sqlx::migrate!("./migrations").run(&pool).await.unwrap();

        let kp = make_keypair();
        let mut crdt = BaseCrdt::<PipelineDoc>::new(&kp);

        // Insert an item and update its stage a few times to push seq up.
        let item: JsonValue = json!({
            "story_id": "664_story_original",
            "stage": "1_backlog",
            "name": "Original",
            "agent": "",
            "retry_count": 0.0,
            "blocked": false,
            "depends_on": "",
            "claimed_by": "",
            "claimed_at": 0.0,
            "merged_at": 0.0,
        })
        .into();

        let mut ops = Vec::new();

        let op1 = crdt.doc.items.insert(ROOT_ID, item).sign(&kp);
        crdt.apply(op1.clone());
        ops.push(op1);

        let idx = rebuild_index(&crdt)["664_story_original"];
        let op2 = crdt.doc.items[idx]
            .stage
            .set("2_current".to_string())
            .sign(&kp);
        crdt.apply(op2.clone());
        ops.push(op2);

        let op3 = crdt.doc.items[idx]
            .stage
            .set("3_review".to_string())
            .sign(&kp);
        crdt.apply(op3.clone());
        ops.push(op3);

        // Record the max seq across all persisted ops — this is the floor.
        let max_seq = ops.iter().map(|o| o.inner.seq).max().unwrap();

        // Persist all ops.
        let now = chrono::Utc::now().to_rfc3339();
        for op in &ops {
            let op_json = serde_json::to_string(op).unwrap();
            let op_id = hex::encode(&op.id());
            sqlx::query(
                "INSERT INTO crdt_ops (op_id, seq, op_json, created_at) VALUES (?1, ?2, ?3, ?4)",
            )
            .bind(&op_id)
            .bind(op.inner.seq as i64)
            .bind(&op_json)
            .bind(&now)
            .execute(&pool)
            .await
            .unwrap();
        }

        // --- Simulate restart: replay from journal into a fresh CRDT ---
        let rows: Vec<(String,)> =
            sqlx::query_as("SELECT op_json FROM crdt_ops ORDER BY rowid ASC")
                .fetch_all(&pool)
                .await
                .unwrap();

        let mut crdt2 = BaseCrdt::<PipelineDoc>::new(&kp);
        let mut lamport_floor: u64 = 0;
        for (json_str,) in &rows {
            let signed: SignedOp = serde_json::from_str(json_str).unwrap();
            lamport_floor = lamport_floor.max(signed.inner.seq);
            crdt2.apply(signed);
        }

        // Advance top-level lists (mirrors what init() does).
        crdt2.doc.items.advance_seq(lamport_floor);
        crdt2.doc.nodes.advance_seq(lamport_floor);

        assert_eq!(lamport_floor, max_seq);

        // Insert a brand-new item — simulating a new story arriving after restart.
        let new_item: JsonValue = json!({
            "story_id": "664_story_new_after_restart",
            "stage": "1_backlog",
            "name": "New After Restart",
            "agent": "",
            "retry_count": 0.0,
            "blocked": false,
            "depends_on": "",
            "claimed_by": "",
            "claimed_at": 0.0,
            "merged_at": 0.0,
        })
        .into();

        let insert_op = crdt2.doc.items.insert(ROOT_ID, new_item);
        // The list-level insert must have seq > lamport_floor.
        assert!(
            insert_op.seq > max_seq,
            "list insert seq ({}) must be > lamport_floor ({})",
            insert_op.seq,
            max_seq,
        );
        let insert_signed = insert_op.sign(&kp);
        crdt2.apply(insert_signed);

        // Advance the new item's inner registers to the floor (mirrors write_item).
        let idx2 = rebuild_index(&crdt2)["664_story_new_after_restart"];
        let new_crdt_item = &mut crdt2.doc.items[idx2];
        new_crdt_item.stage.advance_seq(lamport_floor);

        // Now update the stage — the first field-level op must also be > floor.
        let stage_op = crdt2.doc.items[idx2].stage.set("2_current".to_string());
        assert!(
            stage_op.seq > max_seq,
            "first field op seq ({}) on new register must be > lamport_floor ({}); \
             got seq = 1 means the register reset its clock on restart",
            stage_op.seq,
            max_seq,
        );
    }
}