// Persistence layer: load, replay, append
//
// capnp logs are the source of truth; redb provides indexed access.

use super::types::*;

use crate::memory_capnp;

use anyhow::{Context, Result};
use capnp::message;
use capnp::serialize;

use std::collections::HashMap;
use std::fs;
use std::io::{BufReader, Seek};
use std::path::Path;

impl Store {
    /// Load store by replaying capnp logs.
    pub fn load() -> Result<Store> {
        let nodes_p = nodes_path();
        let rels_p = relations_path();

        let mut store = Store::default();

        if nodes_p.exists() {
            store.replay_nodes(&nodes_p)?;
        }
        if rels_p.exists() {
            store.replay_relations(&rels_p)?;
        }
        let visits_p = visits_path();
        if visits_p.exists() {
            store.replay_visits(&visits_p)?;
        }
        let tp_p = transcript_progress_path();
        if tp_p.exists() {
            store.replay_transcript_progress(&tp_p)?;
        }

        // Record log sizes after replay
        store.loaded_nodes_size = fs::metadata(&nodes_p).map(|m| m.len()).unwrap_or(0);
        store.loaded_rels_size = fs::metadata(&rels_p).map(|m| m.len()).unwrap_or(0);

        // Drop edges referencing deleted/missing nodes
        store.relations.retain(|r|
            store.nodes.contains_key(&r.source_key) &&
            store.nodes.contains_key(&r.target_key)
        );

        Ok(store)
    }

    /// Replay node log, keeping latest version per UUID.
    /// Tracks all UUIDs seen per key to detect duplicates.
    fn replay_nodes(&mut self, path: &Path) -> Result<()> {
        let file = fs::File::open(path)
            .with_context(|| format!("open {}", path.display()))?;
        let mut reader = BufReader::new(file);

        // Track all non-deleted UUIDs per key to detect duplicates
        let mut key_uuids: HashMap<String, Vec<[u8; 16]>> = HashMap::new();

        while let Ok(msg) = serialize::read_message(&mut reader, message::ReaderOptions::new()) {
            let log = msg.get_root::<memory_capnp::node_log::Reader>()
                .with_context(|| format!("read node log"))?;
            for node_reader in log.get_nodes()
                .with_context(|| format!("get nodes"))? {
                let node = Node::from_capnp_migrate(node_reader)?;
                let existing_version = self.nodes.get(&node.key)
                    .map(|n| n.version)
                    .unwrap_or(0);
                if node.version >= existing_version {
                    if node.deleted {
                        self.nodes.remove(&node.key);
                        self.uuid_to_key.remove(&node.uuid);
                        if let Some(uuids) = key_uuids.get_mut(&node.key) {
                            uuids.retain(|u| *u != node.uuid);
                        }
                    } else {
                        self.uuid_to_key.insert(node.uuid, node.key.clone());
                        self.nodes.insert(node.key.clone(), node.clone());
                        let uuids = key_uuids.entry(node.key).or_default();
                        if !uuids.contains(&node.uuid) {
                            uuids.push(node.uuid);
                        }
                    }
                }
            }
        }

        // Report duplicate keys
        for (key, uuids) in &key_uuids {
            if uuids.len() > 1 {
                dbglog!("WARNING: key '{}' has {} UUIDs (duplicate nodes)", key, uuids.len());
            }
        }

        Ok(())
    }

    /// Replay relation log, keeping latest version per UUID
    fn replay_relations(&mut self, path: &Path) -> Result<()> {
        let file = fs::File::open(path)
            .with_context(|| format!("open {}", path.display()))?;
        let mut reader = BufReader::new(file);

        // Collect all, then deduplicate by UUID keeping latest version
        let mut by_uuid: HashMap<[u8; 16], Relation> = HashMap::new();

        while let Ok(msg) = serialize::read_message(&mut reader, message::ReaderOptions::new()) {
            let log = msg.get_root::<memory_capnp::relation_log::Reader>()
                .with_context(|| format!("read relation log"))?;
            for rel_reader in log.get_relations()
                .with_context(|| format!("get relations"))? {
                let rel = Relation::from_capnp_migrate(rel_reader)?;
                let existing_version = by_uuid.get(&rel.uuid)
                    .map(|r| r.version)
                    .unwrap_or(0);
                if rel.version >= existing_version {
                    by_uuid.insert(rel.uuid, rel);
                }
            }
        }

        self.relations = by_uuid.into_values()
            .filter(|r| !r.deleted)
            .collect();
        Ok(())
    }

    /// Find all duplicate keys: keys with multiple live UUIDs in the log.
    /// Returns a map from key → vec of all live Node versions (one per UUID).
    /// The "winner" in self.nodes is always one of them.
    pub fn find_duplicates(&self) -> Result<HashMap<String, Vec<Node>>> {
        let path = nodes_path();
        if !path.exists() { return Ok(HashMap::new()); }

        let file = fs::File::open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        let mut reader = BufReader::new(file);

        // Track latest version of each UUID
        let mut by_uuid: HashMap<[u8; 16], Node> = HashMap::new();

        while let Ok(msg) = serialize::read_message(&mut reader, message::ReaderOptions::new()) {
            let log = msg.get_root::<memory_capnp::node_log::Reader>()
                .with_context(|| format!("read node log"))?;
            for node_reader in log.get_nodes()
                .with_context(|| format!("get nodes"))? {
                let node = Node::from_capnp_migrate(node_reader)?;
                let dominated = by_uuid.get(&node.uuid)
                    .map(|n| node.version >= n.version)
                    .unwrap_or(true);
                if dominated {
                    by_uuid.insert(node.uuid, node);
                }
            }
        }

        // Group live (non-deleted) nodes by key
        let mut by_key: HashMap<String, Vec<Node>> = HashMap::new();
        for node in by_uuid.into_values() {
            if !node.deleted {
                by_key.entry(node.key.clone()).or_default().push(node);
            }
        }

        // Keep only duplicates
        by_key.retain(|_, nodes| nodes.len() > 1);
        Ok(by_key)
    }

    /// Append nodes to the log file.
    /// Serializes to a Vec first, then does a single write() syscall
    /// so the append is atomic with O_APPEND even without flock.
    pub fn append_nodes(&mut self, nodes: &[Node]) -> Result<()> {
        let _lock = StoreLock::acquire()?;
        self.append_nodes_unlocked(nodes)
    }

    /// Append nodes without acquiring the lock. Caller must hold StoreLock.
    pub(crate) fn append_nodes_unlocked(&mut self, nodes: &[Node]) -> Result<()> {
        let mut msg = message::Builder::new_default();
        {
            let log = msg.init_root::<memory_capnp::node_log::Builder>();
            let mut list = log.init_nodes(nodes.len() as u32);
            for (i, node) in nodes.iter().enumerate() {
                node.to_capnp(list.reborrow().get(i as u32));
            }
        }
        let mut buf = Vec::new();
        serialize::write_message(&mut buf, &msg)
            .with_context(|| format!("serialize nodes"))?;

        let path = nodes_path();
        let file = fs::OpenOptions::new()
            .create(true).append(true).open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        use std::io::Write;
        (&file).write_all(&buf)
            .with_context(|| format!("write nodes"))?;

        self.loaded_nodes_size = file.metadata().map(|m| m.len()).unwrap_or(0);
        Ok(())
    }

    /// Replay only new entries appended to the node log since we last loaded.
    /// Call under StoreLock to catch writes from concurrent processes.
    pub(crate) fn refresh_nodes(&mut self) -> Result<()> {
        let path = nodes_path();
        let current_size = fs::metadata(&path).map(|m| m.len()).unwrap_or(0);
        if current_size <= self.loaded_nodes_size {
            return Ok(()); // no new data
        }

        let file = fs::File::open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        let mut reader = BufReader::new(file);
        reader.seek(std::io::SeekFrom::Start(self.loaded_nodes_size))
            .with_context(|| format!("seek nodes log"))?;

        while let Ok(msg) = serialize::read_message(&mut reader, message::ReaderOptions::new()) {
            let log = msg.get_root::<memory_capnp::node_log::Reader>()
                .with_context(|| format!("read node log delta"))?;
            for node_reader in log.get_nodes()
                .with_context(|| format!("get nodes delta"))? {
                let node = Node::from_capnp_migrate(node_reader)?;
                let dominated = self.nodes.get(&node.key)
                    .map(|n| node.version >= n.version)
                    .unwrap_or(true);
                if dominated {
                    if node.deleted {
                        self.nodes.remove(&node.key);
                        self.uuid_to_key.remove(&node.uuid);
                    } else {
                        self.uuid_to_key.insert(node.uuid, node.key.clone());
                        self.nodes.insert(node.key.clone(), node);
                    }
                }
            }
        }

        self.loaded_nodes_size = current_size;
        Ok(())
    }

    /// Append relations to the log file.
    /// Single write() syscall for atomic O_APPEND.
    pub fn append_relations(&mut self, relations: &[Relation]) -> Result<()> {
        let _lock = StoreLock::acquire()?;
        self.append_relations_unlocked(relations)
    }

    /// Append relations without acquiring the lock. Caller must hold StoreLock.
    pub(crate) fn append_relations_unlocked(&mut self, relations: &[Relation]) -> Result<()> {
        let mut msg = message::Builder::new_default();
        {
            let log = msg.init_root::<memory_capnp::relation_log::Builder>();
            let mut list = log.init_relations(relations.len() as u32);
            for (i, rel) in relations.iter().enumerate() {
                rel.to_capnp(list.reborrow().get(i as u32));
            }
        }
        let mut buf = Vec::new();
        serialize::write_message(&mut buf, &msg)
            .with_context(|| format!("serialize relations"))?;

        let path = relations_path();
        let file = fs::OpenOptions::new()
            .create(true).append(true).open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        use std::io::Write;
        (&file).write_all(&buf)
            .with_context(|| format!("write relations"))?;

        self.loaded_rels_size = file.metadata().map(|m| m.len()).unwrap_or(0);
        Ok(())
    }

    /// Append agent visit records to the visits log.
    pub fn append_visits(&mut self, visits: &[AgentVisit]) -> Result<()> {
        if visits.is_empty() { return Ok(()); }

        let mut msg = message::Builder::new_default();
        {
            let log = msg.init_root::<memory_capnp::agent_visit_log::Builder>();
            let mut list = log.init_visits(visits.len() as u32);
            for (i, visit) in visits.iter().enumerate() {
                visit.to_capnp(list.reborrow().get(i as u32));
            }
        }
        let mut buf = Vec::new();
        serialize::write_message(&mut buf, &msg)
            .with_context(|| format!("serialize visits"))?;

        let path = visits_path();
        let file = fs::OpenOptions::new()
            .create(true).append(true).open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        use std::io::Write;
        (&file).write_all(&buf)
            .with_context(|| format!("write visits"))?;

        // Update in-memory index
        for v in visits {
            self.visits
                .entry(v.node_key.clone())
                .or_default()
                .insert(v.agent.clone(), v.timestamp);
        }

        Ok(())
    }

    /// Replay visits log to rebuild in-memory index.
    fn replay_visits(&mut self, path: &Path) -> Result<()> {
        let file = fs::File::open(path)
            .with_context(|| format!("open {}", path.display()))?;
        let mut reader = BufReader::new(file);

        while reader.stream_position()?
              < fs::metadata(path)?.len()
        {
            let msg = match serialize::read_message(&mut reader, Default::default()) {
                Ok(m) => m,
                Err(_) => break,
            };
            let log = msg.get_root::<memory_capnp::agent_visit_log::Reader>()
                .with_context(|| format!("read visit log"))?;

            for visit in log.get_visits()? {
                let key = visit.get_node_key().ok()
                    .and_then(|t| t.to_str().ok())
                    .unwrap_or("")
                    .to_string();
                let agent = visit.get_agent().ok()
                    .and_then(|t| t.to_str().ok())
                    .unwrap_or("")
                    .to_string();
                let ts = visit.get_timestamp();

                if !key.is_empty() && !agent.is_empty() {
                    let entry = self.visits.entry(key).or_default();
                    // Keep latest timestamp per agent
                    let existing = entry.entry(agent).or_insert(0);
                    if ts > *existing {
                        *existing = ts;
                    }
                }
            }
        }
        Ok(())
    }

    /// Append transcript segment progress records.
    pub fn append_transcript_progress(&mut self, segments: &[TranscriptSegment]) -> Result<()> {
        if segments.is_empty() { return Ok(()); }

        let mut msg = message::Builder::new_default();
        {
            let log = msg.init_root::<memory_capnp::transcript_progress_log::Builder>();
            let mut list = log.init_segments(segments.len() as u32);
            for (i, seg) in segments.iter().enumerate() {
                seg.to_capnp(list.reborrow().get(i as u32));
            }
        }
        let mut buf = Vec::new();
        serialize::write_message(&mut buf, &msg)
            .with_context(|| format!("serialize transcript progress"))?;

        let path = transcript_progress_path();
        let file = fs::OpenOptions::new()
            .create(true).append(true).open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        use std::io::Write;
        (&file).write_all(&buf)
            .with_context(|| format!("write transcript progress"))?;

        // Update in-memory index
        for seg in segments {
            self.transcript_progress
                .entry((seg.transcript_id.clone(), seg.segment_index))
                .or_default()
                .insert(seg.agent.clone());
        }

        Ok(())
    }

    /// Replay transcript progress log to rebuild in-memory index.
    fn replay_transcript_progress(&mut self, path: &Path) -> Result<()> {
        let file = fs::File::open(path)
            .with_context(|| format!("open {}", path.display()))?;
        let mut reader = BufReader::new(file);

        while reader.stream_position()?
              < fs::metadata(path)?.len()
        {
            let msg = match serialize::read_message(&mut reader, Default::default()) {
                Ok(m) => m,
                Err(_) => break,
            };
            let log = msg.get_root::<memory_capnp::transcript_progress_log::Reader>()
                .with_context(|| format!("read transcript progress"))?;

            for seg in log.get_segments()? {
                let id = seg.get_transcript_id().ok()
                    .and_then(|t| t.to_str().ok())
                    .unwrap_or("")
                    .to_string();
                let agent = seg.get_agent().ok()
                    .and_then(|t| t.to_str().ok())
                    .unwrap_or("")
                    .to_string();
                let idx = seg.get_segment_index();

                if !id.is_empty() && !agent.is_empty() {
                    self.transcript_progress
                        .entry((id, idx))
                        .or_default()
                        .insert(agent);
                }
            }
        }
        Ok(())
    }

    /// Migrate old stub-node transcript markers into the new progress log.
    /// Reads _observed-transcripts-f-*, _mined-transcripts#f-*, and _facts-* keys,
    /// extracts transcript_id and segment_index, writes to transcript-progress.capnp,
    /// then deletes the stub nodes.
    pub fn migrate_transcript_progress(&mut self) -> Result<usize> {
        let mut segments = Vec::new();

        for key in self.nodes.keys() {
            // _observed-transcripts-f-{UUID}.{segment}
            if let Some(rest) = key.strip_prefix("_observed-transcripts-f-") {
                if let Some((uuid, seg_str)) = rest.rsplit_once('.')
                    && let Ok(seg) = seg_str.parse::<u32>() {
                        segments.push(new_transcript_segment(uuid, seg, "observation"));
                    }
            }
            // _mined-transcripts#f-{UUID}.{segment}
            else if let Some(rest) = key.strip_prefix("_mined-transcripts#f-") {
                if let Some((uuid, seg_str)) = rest.rsplit_once('.')
                    && let Ok(seg) = seg_str.parse::<u32>() {
                        segments.push(new_transcript_segment(uuid, seg, "experience"));
                    }
            }
            // _mined-transcripts-f-{UUID}.{segment}
            else if let Some(rest) = key.strip_prefix("_mined-transcripts-f-") {
                if let Some((uuid, seg_str)) = rest.rsplit_once('.')
                    && let Ok(seg) = seg_str.parse::<u32>() {
                        segments.push(new_transcript_segment(uuid, seg, "experience"));
                    }
            }
            // _facts-{UUID}  (whole-file, segment 0)
            else if let Some(uuid) = key.strip_prefix("_facts-") {
                if !uuid.contains('-') || uuid.len() < 30 { continue; } // skip non-UUID
                segments.push(new_transcript_segment(uuid, 0, "fact"));
            }
        }

        let count = segments.len();
        if count > 0 {
            self.append_transcript_progress(&segments)?;
        }

        // Soft-delete the old stub nodes
        let keys_to_delete: Vec<String> = self.nodes.keys()
            .filter(|k| k.starts_with("_observed-transcripts-")
                || k.starts_with("_mined-transcripts")
                || (k.starts_with("_facts-") && !k.contains("fact_mine")))
            .cloned()
            .collect();

        for key in &keys_to_delete {
            if let Some(node) = self.nodes.get_mut(key) {
                node.deleted = true;
            }
        }

        if !keys_to_delete.is_empty() {
            self.save()?;
        }

        Ok(count)
    }

    /// Record visits for a batch of node keys from a successful agent run.
    pub fn record_agent_visits(&mut self, node_keys: &[String], agent: &str) -> Result<()> {
        let visits: Vec<AgentVisit> = node_keys.iter()
            .filter_map(|key| {
                let node = self.nodes.get(key)?;
                Some(new_visit(node.uuid, key, agent, "processed"))
            })
            .collect();
        self.append_visits(&visits)
    }

    /// Get the last time an agent visited a node. Returns 0 if never visited.
    pub fn last_visited(&self, node_key: &str, agent: &str) -> i64 {
        self.visits.get(node_key)
            .and_then(|agents| agents.get(agent))
            .copied()
            .unwrap_or(0)
    }

    /// Placeholder - indices will be updated on write with redb.
    pub fn save(&self) -> Result<()> {
        Ok(())
    }
}

/// Check and repair corrupt capnp log files.
///
/// Reads each message sequentially, tracking file position. On the first
/// corrupt message, truncates the file to the last good position. Also
/// removes stale caches so the next load replays from the repaired log.
pub fn fsck() -> Result<()> {
    let mut any_corrupt = false;

    for (path, kind) in [
        (nodes_path(), "node"),
        (relations_path(), "relation"),
    ] {
        if !path.exists() { continue; }

        let file = fs::File::open(&path)
            .with_context(|| format!("open {}", path.display()))?;
        let file_len = file.metadata()
            .with_context(|| format!("stat {}", path.display()))?.len();
        let mut reader = BufReader::new(file);

        let mut good_messages = 0u64;
        let mut last_good_pos = 0u64;

        loop {
            let pos = reader.stream_position()
                .with_context(|| format!("tell {}", path.display()))?;

            let msg = match serialize::read_message(&mut reader, message::ReaderOptions::new()) {
                Ok(m) => m,
                Err(_) => {
                    // read_message fails at EOF (normal) or on corrupt framing
                    if pos < file_len {
                        // Not at EOF — corrupt framing
                        eprintln!("{}: corrupt message at offset {}, truncating", kind, pos);
                        any_corrupt = true;
                        drop(reader);
                        let file = fs::OpenOptions::new().write(true).open(&path)
                            .with_context(|| format!("open for truncate"))?;
                        file.set_len(pos)
                            .with_context(|| format!("truncate {}", path.display()))?;
                        eprintln!("{}: truncated from {} to {} bytes ({} good messages)",
                            kind, file_len, pos, good_messages);
                    }
                    break;
                }
            };

            // Validate the message content too
            let valid = if kind == "node" {
                msg.get_root::<memory_capnp::node_log::Reader>()
                    .and_then(|l| l.get_nodes().map(|_| ()))
                    .is_ok()
            } else {
                msg.get_root::<memory_capnp::relation_log::Reader>()
                    .and_then(|l| l.get_relations().map(|_| ()))
                    .is_ok()
            };

            if valid {
                good_messages += 1;
                last_good_pos = reader.stream_position()
                    .with_context(|| format!("tell {}", path.display()))?;
            } else {
                eprintln!("{}: corrupt message content at offset {}, truncating to {}",
                    kind, pos, last_good_pos);
                any_corrupt = true;
                drop(reader);
                let file = fs::OpenOptions::new().write(true).open(&path)
                    .with_context(|| format!("open for truncate"))?;
                file.set_len(last_good_pos)
                    .with_context(|| format!("truncate {}", path.display()))?;
                eprintln!("{}: truncated from {} to {} bytes ({} good messages)",
                    kind, file_len, last_good_pos, good_messages);
                break;
            }
        }

        if !any_corrupt {
            eprintln!("{}: {} messages, all clean", kind, good_messages);
        }
    }

    if any_corrupt {
        eprintln!("repair complete — run `poc-memory status` to verify");
    } else {
        eprintln!("store is clean");
    }

    Ok(())
}