// Mutation operations on the store
//
// CRUD (upsert, delete), maintenance (decay, cap_degree), and graph metrics.

use super::{index, types::*};

use anyhow::{anyhow, bail, Result};
use std::collections::{HashMap, HashSet};

/// Fallback provenance for non-tool-dispatch paths (CLI, digest, etc.).
/// Tool dispatch passes provenance directly through thought::dispatch.
pub fn current_provenance() -> String {
    std::env::var("POC_PROVENANCE")
        .unwrap_or_else(|_| "manual".to_string())
}

impl Store {
    /// Add or update a node (appends to log + updates index).
    pub fn upsert_node(&mut self, mut node: Node) -> Result<()> {
        if let Some(existing) = self.nodes.get(&node.key) {
            node.uuid = existing.uuid;
            node.version = existing.version + 1;
        }
        let offset = self.append_nodes(&[node.clone()])?;
        if let Some(ref database) = self.db {
            index::index_node(database, &node.key, offset, &node.uuid)?;
        }
        self.uuid_to_key.insert(node.uuid, node.key.clone());
        self.nodes.insert(node.key.clone(), node);
        Ok(())
    }

    /// Add a relation (appends to log + updates cache)
    pub fn add_relation(&mut self, rel: Relation) -> Result<()> {
        self.append_relations(std::slice::from_ref(&rel))?;
        self.relations.push(rel);
        Ok(())
    }

    /// Recent nodes by provenance, sorted newest-first. Returns (key, timestamp).
    pub fn recent_by_provenance(&self, provenance: &str, limit: usize) -> Vec<(String, i64)> {
        let mut nodes: Vec<_> = self.nodes.values()
            .filter(|n| !n.deleted && n.provenance == provenance)
            .map(|n| (n.key.clone(), n.timestamp))
            .collect();
        nodes.sort_by(|a, b| b.1.cmp(&a.1));
        nodes.truncate(limit);
        nodes
    }

    /// Upsert a node: update if exists (and content changed), create if not.
    /// Returns: "created", "updated", or "unchanged".
    ///
    /// Provenance is determined by the POC_PROVENANCE env var if set,
    /// otherwise defaults to Manual.
    pub fn upsert(&mut self, key: &str, content: &str) -> Result<&'static str> {
        let prov = current_provenance();
        self.upsert_provenance(key, content, &prov)
    }

    /// Upsert with explicit provenance (for agent-created nodes).
    pub fn upsert_provenance(&mut self, key: &str, content: &str, provenance: &str) -> Result<&'static str> {
        if let Some(existing) = self.nodes.get(key) {
            if existing.content == content {
                return Ok("unchanged");
            }
            let mut node = existing.clone();
            node.content = content.to_string();
            node.provenance = provenance.to_string();
            node.timestamp = now_epoch();
            node.version += 1;
            let offset = self.append_nodes(std::slice::from_ref(&node))?;
            if let Some(ref database) = self.db {
                index::index_node(database, &node.key, offset, &node.uuid)?;
            }
            self.nodes.insert(key.to_string(), node);
            Ok("updated")
        } else {
            let mut node = new_node(key, content);
            node.provenance = provenance.to_string();
            let offset = self.append_nodes(std::slice::from_ref(&node))?;
            if let Some(ref database) = self.db {
                index::index_node(database, &node.key, offset, &node.uuid)?;
            }
            self.uuid_to_key.insert(node.uuid, node.key.clone());
            self.nodes.insert(key.to_string(), node);
            Ok("created")
        }
    }

    /// Soft-delete a node (appends deleted version, removes from index).
    pub fn delete_node(&mut self, key: &str) -> Result<()> {
        let prov = current_provenance();

        let node = self.nodes.get(key)
            .ok_or_else(|| anyhow!("No node '{}'", key))?;
        let uuid = node.uuid;
        let mut deleted = node.clone();
        deleted.deleted = true;
        deleted.version += 1;
        deleted.provenance = prov;
        deleted.timestamp = now_epoch();
        self.append_nodes(std::slice::from_ref(&deleted))?;
        if let Some(ref database) = self.db {
            index::remove_node(database, key, &uuid)?;
        }
        self.nodes.remove(key);
        Ok(())
    }

    /// Rename a node: change its key, update debug strings on all edges.
    ///
    /// Graph edges (source/target UUIDs) are unaffected — they're already
    /// UUID-based. We update the human-readable source_key/target_key strings
    /// on relations, and created_at is preserved untouched.
    pub fn rename_node(&mut self, old_key: &str, new_key: &str) -> Result<()> {
        if old_key == new_key {
            return Ok(());
        }
        if self.nodes.contains_key(new_key) {
            bail!("Key '{}' already exists", new_key);
        }
        let node = self.nodes.get(old_key)
            .ok_or_else(|| anyhow!("No node '{}'", old_key))?
            .clone();

        let prov = current_provenance();

        // New version under the new key
        let mut renamed = node.clone();
        renamed.key = new_key.to_string();
        renamed.version += 1;
        renamed.provenance = prov.clone();
        renamed.timestamp = now_epoch();

        // Deletion record for the old key (same UUID, independent version counter)
        let mut tombstone = node.clone();
        tombstone.deleted = true;
        tombstone.version += 1;
        tombstone.provenance = prov;
        tombstone.timestamp = now_epoch();

        // Collect affected relations and update their debug key strings
        let updated_rels: Vec<_> = self.relations.iter()
            .filter(|r| r.source_key == old_key || r.target_key == old_key)
            .map(|r| {
                let mut r = r.clone();
                r.version += 1;
                if r.source_key == old_key { r.source_key = new_key.to_string(); }
                if r.target_key == old_key { r.target_key = new_key.to_string(); }
                r
            })
            .collect();

        // Persist under single lock
        let offset = self.append_nodes(&[renamed.clone(), tombstone.clone()])?;
        if !updated_rels.is_empty() {
            self.append_relations(&updated_rels)?;
        }

        // Update index: remove old key, add renamed
        if let Some(ref database) = self.db {
            index::remove_node(database, old_key, &tombstone.uuid)?;
            index::index_node(database, new_key, offset, &renamed.uuid)?;
        }

        // Update in-memory cache
        self.nodes.remove(old_key);
        self.uuid_to_key.insert(renamed.uuid, new_key.to_string());
        self.nodes.insert(new_key.to_string(), renamed);
        for updated in &updated_rels {
            if let Some(r) = self.relations.iter_mut().find(|r| r.uuid == updated.uuid) {
                r.source_key = updated.source_key.clone();
                r.target_key = updated.target_key.clone();
                r.version = updated.version;
            }
        }

        Ok(())
    }

    /// Cap node degree by soft-deleting edges from mega-hubs.
    pub fn cap_degree(&mut self, max_degree: usize) -> Result<(usize, usize)> {
        let mut node_degree: HashMap<String, usize> = HashMap::new();
        for rel in &self.relations {
            if rel.deleted { continue; }
            *node_degree.entry(rel.source_key.clone()).or_default() += 1;
            *node_degree.entry(rel.target_key.clone()).or_default() += 1;
        }

        let mut node_edges: HashMap<String, Vec<usize>> = HashMap::new();
        for (i, rel) in self.relations.iter().enumerate() {
            if rel.deleted { continue; }
            node_edges.entry(rel.source_key.clone()).or_default().push(i);
            node_edges.entry(rel.target_key.clone()).or_default().push(i);
        }

        let mut to_delete: HashSet<usize> = HashSet::new();
        let mut hubs_capped = 0;

        for (_key, edge_indices) in &node_edges {
            let active: Vec<usize> = edge_indices.iter()
                .filter(|&&i| !to_delete.contains(&i))
                .copied()
                .collect();
            if active.len() <= max_degree { continue; }

            let mut auto_indices: Vec<(usize, f32)> = Vec::new();
            let mut link_indices: Vec<(usize, usize)> = Vec::new();
            for &i in &active {
                let rel = &self.relations[i];
                if rel.rel_type == RelationType::Auto {
                    auto_indices.push((i, rel.strength));
                } else {
                    let other = if &rel.source_key == _key {
                        &rel.target_key
                    } else {
                        &rel.source_key
                    };
                    let other_deg = node_degree.get(other).copied().unwrap_or(0);
                    link_indices.push((i, other_deg));
                }
            }

            let excess = active.len() - max_degree;

            auto_indices.sort_by(|a, b| a.1.total_cmp(&b.1));
            let auto_prune = excess.min(auto_indices.len());
            for &(i, _) in auto_indices.iter().take(auto_prune) {
                to_delete.insert(i);
            }

            let remaining_excess = excess.saturating_sub(auto_prune);
            if remaining_excess > 0 {
                link_indices.sort_by(|a, b| b.1.cmp(&a.1));
                let link_prune = remaining_excess.min(link_indices.len());
                for &(i, _) in link_indices.iter().take(link_prune) {
                    to_delete.insert(i);
                }
            }

            hubs_capped += 1;
        }

        let mut pruned_rels = Vec::new();
        for &i in &to_delete {
            self.relations[i].deleted = true;
            self.relations[i].version += 1;
            pruned_rels.push(self.relations[i].clone());
        }

        if !pruned_rels.is_empty() {
            self.append_relations(&pruned_rels)?;
        }

        self.relations.retain(|r| !r.deleted);

        Ok((hubs_capped, to_delete.len()))
    }

    /// Set a node's weight directly. Returns (old, new).
    pub fn set_weight(&mut self, key: &str, weight: f32) -> Result<(f32, f32)> {
        let weight = weight.clamp(0.01, 1.0);
        let node = self.nodes.get_mut(key)
            .ok_or_else(|| anyhow!("node not found: {}", key))?;
        let old = node.weight;
        node.weight = weight;
        Ok((old, weight))
    }

    /// Set the strength of a link between two nodes. Deduplicates if
    /// multiple links exist. Returns the old strength, or error if no link.
    pub fn set_link_strength(&mut self, source: &str, target: &str, strength: f32) -> Result<f32> {
        let strength = strength.clamp(0.01, 1.0);
        let mut old = 0.0f32;
        let mut found = false;
        let mut first = true;
        for rel in &mut self.relations {
            if rel.deleted { continue; }
            if (rel.source_key == source && rel.target_key == target)
                || (rel.source_key == target && rel.target_key == source)
            {
                if first {
                    old = rel.strength;
                    rel.strength = strength;
                    first = false;
                } else {
                    rel.deleted = true; // deduplicate
                }
                found = true;
            }
        }
        if !found {
            // Upsert: create the link if it doesn't exist
            self.add_link(source, target, "link_set")?;
            // Set the strength on the newly created link
            for rel in self.relations.iter_mut().rev() {
                if !rel.deleted && rel.source_key == source && rel.target_key == target {
                    rel.strength = strength;
                    break;
                }
            }
            return Ok(0.0);
        }
        Ok(old)
    }

    /// Add a link between two nodes with Jaccard-based initial strength.
    /// Returns the strength, or a message if the link already exists.
    pub fn add_link(&mut self, source: &str, target: &str, provenance: &str) -> Result<f32> {
        // Check for existing
        let exists = self.relations.iter().any(|r|
            !r.deleted &&
            ((r.source_key == source && r.target_key == target) ||
             (r.source_key == target && r.target_key == source)));
        if exists {
            bail!("link already exists: {} ↔ {}", source, target);
        }

        let source_uuid = self.nodes.get(source)
            .map(|n| n.uuid)
            .ok_or_else(|| anyhow!("source not found: {}", source))?;
        let target_uuid = self.nodes.get(target)
            .map(|n| n.uuid)
            .ok_or_else(|| anyhow!("target not found: {}", target))?;

        let graph = self.build_graph();
        let jaccard = graph.jaccard(source, target);
        let strength = (jaccard * 3.0).clamp(0.1, 1.0) as f32;

        let mut rel = new_relation(
            source_uuid, target_uuid,
            RelationType::Link, strength,
            source, target,
        );
        rel.provenance = provenance.to_string();
        self.add_relation(rel)?;
        Ok(strength)
    }
}