ruvector-graph 2.0.6

//! JIT compilation for hot query paths
//!
//! This module provides specialized query operators that are
//! compiled/optimized for common query patterns.

use parking_lot::RwLock;
use std::collections::HashMap;
use std::sync::Arc;

/// JIT compiler for graph queries
pub struct JitCompiler {
    /// Compiled query cache
    compiled_cache: Arc<RwLock<HashMap<String, Arc<JitQuery>>>>,
    /// Query execution statistics
    stats: Arc<RwLock<QueryStats>>,
}

impl JitCompiler {
    pub fn new() -> Self {
        Self {
            compiled_cache: Arc::new(RwLock::new(HashMap::new())),
            stats: Arc::new(RwLock::new(QueryStats::new())),
        }
    }

    /// Compile a query pattern into optimized operators
    pub fn compile(&self, pattern: &str) -> Arc<JitQuery> {
        // Check cache first
        {
            let cache = self.compiled_cache.read();
            if let Some(compiled) = cache.get(pattern) {
                return Arc::clone(compiled);
            }
        }

        // Compile new query
        let query = Arc::new(self.compile_pattern(pattern));

        // Cache it
        self.compiled_cache
            .write()
            .insert(pattern.to_string(), Arc::clone(&query));

        query
    }

    /// Compile pattern into specialized operators
    fn compile_pattern(&self, pattern: &str) -> JitQuery {
        // Parse pattern and generate optimized operator chain
        let operators = self.parse_and_optimize(pattern);

        JitQuery {
            pattern: pattern.to_string(),
            operators,
        }
    }

    /// Parse query and generate optimized operator chain
    fn parse_and_optimize(&self, pattern: &str) -> Vec<QueryOperator> {
        let mut operators = Vec::new();

        // Simple pattern matching for common cases
        if pattern.contains("MATCH") && pattern.contains("WHERE") {
            // Pattern: MATCH (n:Label) WHERE n.prop = value
            operators.push(QueryOperator::LabelScan {
                label: "Label".to_string(),
            });
            operators.push(QueryOperator::Filter {
                predicate: FilterPredicate::Equality {
                    property: "prop".to_string(),
                    value: PropertyValue::String("value".to_string()),
                },
            });
        } else if pattern.contains("MATCH") && pattern.contains("->") {
            // Pattern: MATCH (a)-[r]->(b)
            operators.push(QueryOperator::Expand {
                direction: Direction::Outgoing,
                edge_label: None,
            });
        } else {
            // Generic scan
            operators.push(QueryOperator::FullScan);
        }

        operators
    }

    /// Record query execution
    pub fn record_execution(&self, pattern: &str, duration_ns: u64) {
        self.stats.write().record(pattern, duration_ns);
    }

    /// Get hot queries that should be JIT compiled
    pub fn get_hot_queries(&self, threshold: u64) -> Vec<String> {
        self.stats.read().get_hot_queries(threshold)
    }
}

impl Default for JitCompiler {
    fn default() -> Self {
        Self::new()
    }
}

/// Compiled query with specialized operators
pub struct JitQuery {
    /// Original query pattern
    pub pattern: String,
    /// Optimized operator chain
    pub operators: Vec<QueryOperator>,
}

impl JitQuery {
    /// Execute query with specialized operators
    pub fn execute<F>(&self, mut executor: F) -> QueryResult
    where
        F: FnMut(&QueryOperator) -> IntermediateResult,
    {
        let mut result = IntermediateResult::default();

        for operator in &self.operators {
            result = executor(operator);
        }

        QueryResult {
            nodes: result.nodes,
            edges: result.edges,
        }
    }
}

/// Specialized query operators
#[derive(Debug, Clone)]
pub enum QueryOperator {
    /// Full table scan
    FullScan,

    /// Label index scan
    LabelScan { label: String },

    /// Property index scan
    PropertyScan {
        property: String,
        value: PropertyValue,
    },

    /// Expand edges from nodes
    Expand {
        direction: Direction,
        edge_label: Option<String>,
    },

    /// Filter nodes/edges
    Filter { predicate: FilterPredicate },

    /// Project properties
    Project { properties: Vec<String> },

    /// Aggregate results
    Aggregate { function: AggregateFunction },

    /// Sort results
    Sort { property: String, ascending: bool },

    /// Limit results
    Limit { count: usize },
}

#[derive(Debug, Clone)]
pub enum Direction {
    Incoming,
    Outgoing,
    Both,
}

#[derive(Debug, Clone)]
pub enum FilterPredicate {
    Equality {
        property: String,
        value: PropertyValue,
    },
    Range {
        property: String,
        min: PropertyValue,
        max: PropertyValue,
    },
    Regex {
        property: String,
        pattern: String,
    },
}

#[derive(Debug, Clone)]
pub enum PropertyValue {
    String(String),
    Integer(i64),
    Float(f64),
    Boolean(bool),
}

#[derive(Debug, Clone)]
pub enum AggregateFunction {
    Count,
    Sum { property: String },
    Avg { property: String },
    Min { property: String },
    Max { property: String },
}

/// Intermediate result during query execution
#[derive(Default)]
pub struct IntermediateResult {
    pub nodes: Vec<u64>,
    pub edges: Vec<(u64, u64)>,
}

/// Final query result
pub struct QueryResult {
    pub nodes: Vec<u64>,
    pub edges: Vec<(u64, u64)>,
}

/// Query execution statistics
struct QueryStats {
    /// Execution count per pattern
    execution_counts: HashMap<String, u64>,
    /// Total execution time per pattern
    total_time_ns: HashMap<String, u64>,
}

impl QueryStats {
    fn new() -> Self {
        Self {
            execution_counts: HashMap::new(),
            total_time_ns: HashMap::new(),
        }
    }

    fn record(&mut self, pattern: &str, duration_ns: u64) {
        *self
            .execution_counts
            .entry(pattern.to_string())
            .or_insert(0) += 1;
        *self.total_time_ns.entry(pattern.to_string()).or_insert(0) += duration_ns;
    }

    fn get_hot_queries(&self, threshold: u64) -> Vec<String> {
        self.execution_counts
            .iter()
            .filter(|(_, &count)| count >= threshold)
            .map(|(pattern, _)| pattern.clone())
            .collect()
    }

    fn avg_time_ns(&self, pattern: &str) -> Option<u64> {
        let count = self.execution_counts.get(pattern)?;
        let total = self.total_time_ns.get(pattern)?;

        if *count > 0 {
            Some(total / count)
        } else {
            None
        }
    }
}

/// Specialized operator implementations
pub mod specialized_ops {
    use super::*;

    /// Vectorized label scan
    pub fn vectorized_label_scan(label: &str, nodes: &[u64]) -> Vec<u64> {
        // In a real implementation, this would use SIMD to check labels in parallel
        nodes.iter().copied().collect()
    }

    /// Vectorized property filter
    pub fn vectorized_property_filter(
        property: &str,
        predicate: &FilterPredicate,
        nodes: &[u64],
    ) -> Vec<u64> {
        // In a real implementation, this would use SIMD for comparisons
        nodes.iter().copied().collect()
    }

    /// Cache-friendly edge expansion
    pub fn cache_friendly_expand(nodes: &[u64], direction: Direction) -> Vec<(u64, u64)> {
        // In a real implementation, this would use prefetching and cache-optimized layout
        Vec::new()
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_jit_compiler() {
        let compiler = JitCompiler::new();

        let query = compiler.compile("MATCH (n:Person) WHERE n.age > 18");
        assert!(!query.operators.is_empty());
    }

    #[test]
    fn test_query_stats() {
        let compiler = JitCompiler::new();

        compiler.record_execution("MATCH (n)", 1000);
        compiler.record_execution("MATCH (n)", 2000);
        compiler.record_execution("MATCH (n)", 3000);

        let hot = compiler.get_hot_queries(2);
        assert_eq!(hot.len(), 1);
        assert_eq!(hot[0], "MATCH (n)");
    }

    #[test]
    fn test_operator_chain() {
        let operators = vec![
            QueryOperator::LabelScan {
                label: "Person".to_string(),
            },
            QueryOperator::Filter {
                predicate: FilterPredicate::Range {
                    property: "age".to_string(),
                    min: PropertyValue::Integer(18),
                    max: PropertyValue::Integer(65),
                },
            },
            QueryOperator::Limit { count: 10 },
        ];

        assert_eq!(operators.len(), 3);
    }
}