velesdb-core 1.7.1

//! Property index for fast graph node lookups.
//!
//! Provides O(1) lookups on (label, property_name, value) instead of O(n) scans.
//! Also includes composite indexes for (label, property1, property2, ...) lookups.

// SAFETY: Numeric casts in property indexing are intentional:
// - u128->u64 for millisecond timestamps: values fit within u64 range
// - u64/usize->f64 for statistics: precision loss acceptable for query planning
// - All values are bounded by collection sizes and query counts
// - Used for index selection heuristics, not financial calculations
#![allow(clippy::cast_precision_loss)]
#![allow(clippy::cast_possible_truncation)]

mod advisor;
mod composite;
mod range;

// Reason: EPIC-047 types are dead_code (not yet used externally), suppress unused import warnings
#[allow(unused_imports)]
pub use advisor::{
    IndexAdvisor, IndexSuggestion, PatternStats, PredicateType, QueryPattern, QueryPatternTracker,
};
#[allow(unused_imports)]
pub use composite::{CompositeGraphIndex, CompositeIndexManager, CompositeIndexType};
#[allow(unused_imports)]
pub use range::{CompositeRangeIndex, EdgePropertyIndex, IndexIntersection, OrderedValue};

use super::helpers::{make_label_prop_key, safe_bitmap_id, PostcardPersistence};
use roaring::RoaringBitmap;
use serde::{Deserialize, Serialize};
use serde_json::Value;
use std::collections::HashMap;

/// Current schema version for PropertyIndex serialization.
/// Increment this when making breaking changes to the index format.
pub const PROPERTY_INDEX_VERSION: u32 = 1;

/// Index for fast property-based node lookups.
///
/// Maps (label, property_name) -> (value -> node_ids) for O(1) lookups.
///
/// # Example
///
/// ```rust,ignore
/// let mut index = PropertyIndex::new();
/// index.create_index("Person", "email");
/// index.insert("Person", "email", &json!("alice@example.com"), 1);
///
/// let nodes = index.lookup("Person", "email", &json!("alice@example.com"));
/// assert!(nodes.map_or(false, |b| b.contains(1)));
/// ```
#[derive(Debug, Default, Serialize, Deserialize)]
pub struct PropertyIndex {
    /// Schema version for forward compatibility.
    #[serde(default = "default_version")]
    version: u32,
    /// (label, property_name) -> (value_json -> node_ids)
    indexes: HashMap<(String, String), HashMap<String, RoaringBitmap>>,
}

fn default_version() -> u32 {
    PROPERTY_INDEX_VERSION
}

impl PropertyIndex {
    /// Create a new empty property index.
    #[must_use]
    pub fn new() -> Self {
        Self::default()
    }

    /// Create an index for a (label, property) pair.
    ///
    /// This must be called before inserting values for this pair.
    pub fn create_index(&mut self, label: &str, property: &str) {
        self.indexes
            .entry(make_label_prop_key(label, property))
            .or_default();
    }

    /// Check if an index exists for this (label, property) pair.
    #[must_use]
    pub fn has_index(&self, label: &str, property: &str) -> bool {
        self.indexes
            .contains_key(&make_label_prop_key(label, property))
    }

    /// Insert a node into the index.
    ///
    /// Returns `true` if the index exists and the node was added.
    ///
    /// # Note
    ///
    /// Uses `RoaringBitmap` internally which only supports u32 IDs.
    /// Returns `false` if `node_id > u32::MAX` to prevent data corruption.
    pub fn insert(&mut self, label: &str, property: &str, value: &Value, node_id: u64) -> bool {
        let Some(safe_id) = safe_bitmap_id(node_id) else {
            tracing::warn!(
                node_id = node_id,
                label = label,
                property = property,
                "PropertyIndex: node_id exceeds u32::MAX ({}), cannot index. \
                 RoaringBitmap only supports u32 IDs.",
                u32::MAX
            );
            return false;
        };

        let key = make_label_prop_key(label, property);
        if let Some(value_map) = self.indexes.get_mut(&key) {
            let value_key = value.to_string();
            value_map.entry(value_key).or_default().insert(safe_id);
            true
        } else {
            false
        }
    }

    /// Remove a node from the index.
    ///
    /// Returns `true` if the node was removed.
    /// Returns `false` if `node_id > u32::MAX` (cannot exist in index).
    pub fn remove(&mut self, label: &str, property: &str, value: &Value, node_id: u64) -> bool {
        let Some(safe_id) = safe_bitmap_id(node_id) else {
            return false;
        };

        let key = make_label_prop_key(label, property);
        if let Some(value_map) = self.indexes.get_mut(&key) {
            let value_key = value.to_string();
            if let Some(bitmap) = value_map.get_mut(&value_key) {
                let removed = bitmap.remove(safe_id);
                if bitmap.is_empty() {
                    value_map.remove(&value_key);
                }
                return removed;
            }
        }
        false
    }

    /// Lookup nodes by property value.
    ///
    /// Returns `None` if no index exists for this (label, property) pair.
    /// Returns `Some(&RoaringBitmap)` with matching node IDs (empty if no matches).
    #[must_use]
    pub fn lookup(&self, label: &str, property: &str, value: &Value) -> Option<&RoaringBitmap> {
        let key = make_label_prop_key(label, property);
        self.indexes
            .get(&key)
            .and_then(|value_map| value_map.get(&value.to_string()))
    }

    /// Get all indexed (label, property) pairs.
    #[must_use]
    pub fn indexed_properties(&self) -> Vec<(String, String)> {
        self.indexes.keys().cloned().collect()
    }

    /// Get the number of unique values for a (label, property) pair.
    #[must_use]
    pub fn cardinality(&self, label: &str, property: &str) -> Option<usize> {
        let key = make_label_prop_key(label, property);
        self.indexes.get(&key).map(HashMap::len)
    }

    /// Drop an index for a (label, property) pair.
    pub fn drop_index(&mut self, label: &str, property: &str) -> bool {
        self.indexes
            .remove(&make_label_prop_key(label, property))
            .is_some()
    }

    /// Clear all indexes.
    pub fn clear(&mut self) {
        self.indexes.clear();
    }

    /// Get total memory estimate in bytes.
    #[must_use]
    pub fn memory_usage(&self) -> usize {
        let mut total = std::mem::size_of::<Self>();
        for ((label, prop), value_map) in &self.indexes {
            total += label.len() + prop.len();
            for (value_key, bitmap) in value_map {
                total += value_key.len();
                total += bitmap.serialized_size();
            }
        }
        total
    }

    // =========================================================================
    // Maintenance hooks - called automatically on graph mutations
    // =========================================================================

    /// Hook called when a node is added to the graph.
    ///
    /// Indexes all properties that have an active index.
    pub fn on_add_node(&mut self, label: &str, node_id: u64, properties: &HashMap<String, Value>) {
        for (prop_name, value) in properties {
            if self.has_index(label, prop_name) {
                self.insert(label, prop_name, value, node_id);
            }
        }
    }

    /// Hook called when a node is removed from the graph.
    ///
    /// Removes all indexed properties for this node.
    pub fn on_remove_node(
        &mut self,
        label: &str,
        node_id: u64,
        properties: &HashMap<String, Value>,
    ) {
        for (prop_name, value) in properties {
            if self.has_index(label, prop_name) {
                self.remove(label, prop_name, value, node_id);
            }
        }
    }

    /// Hook called when a property is updated on a node.
    ///
    /// Removes old value and inserts new value if property is indexed.
    pub fn on_update_property(
        &mut self,
        label: &str,
        node_id: u64,
        property: &str,
        old_value: &Value,
        new_value: &Value,
    ) {
        if self.has_index(label, property) {
            self.remove(label, property, old_value, node_id);
            self.insert(label, property, new_value, node_id);
        }
    }

    /// Hook to index all properties of a node after creating an index.
    ///
    /// Use this to backfill an index after creation.
    pub fn index_node(&mut self, label: &str, node_id: u64, properties: &HashMap<String, Value>) {
        self.on_add_node(label, node_id, properties);
    }
}

impl PostcardPersistence for PropertyIndex {}

// Inherent persistence methods that delegate to `PostcardPersistence`.
// Required so callers can use `PropertyIndex::load_from_file` without
// importing the trait.
impl PropertyIndex {
    /// Serialize the index to bytes using postcard.
    ///
    /// # Errors
    /// Returns an error if serialization fails.
    pub fn to_bytes(&self) -> Result<Vec<u8>, postcard::Error> {
        <Self as PostcardPersistence>::to_bytes(self)
    }

    /// Deserialize an index from bytes.
    ///
    /// # Errors
    /// Returns an error if deserialization fails (corrupted data).
    pub fn from_bytes(bytes: &[u8]) -> Result<Self, postcard::Error> {
        <Self as PostcardPersistence>::from_bytes(bytes)
    }

    /// Save the index to a file.
    ///
    /// # Errors
    /// Returns an error if serialization or file I/O fails.
    pub fn save_to_file(&self, path: &std::path::Path) -> std::io::Result<()> {
        <Self as PostcardPersistence>::save_to_file(self, path)
    }

    /// Load an index from a file.
    ///
    /// # Errors
    /// Returns an error if file I/O or deserialization fails.
    pub fn load_from_file(path: &std::path::Path) -> std::io::Result<Self> {
        <Self as PostcardPersistence>::load_from_file(path)
    }
}