arrow-graph 0.6.2

use datafusion::error::Result as DataFusionResult;

/// Basic graph functions for SQL integration
/// These are simplified implementations to establish the foundation
/// Full DataFusion UDF integration will be implemented in a future iteration
pub struct GraphFunctions;

impl GraphFunctions {
    pub fn new() -> Self {
        Self
    }

    /// Calculate graph density: edges / (nodes * (nodes - 1))
    pub fn graph_density(&self, _edges_table: &str) -> DataFusionResult<f64> {
        // Placeholder - would analyze the provided table and compute actual density
        Ok(0.5)
    }

    /// Calculate clustering coefficient for a specific node
    pub fn clustering_coefficient(&self, _node_id: &str, _edges_table: &str) -> DataFusionResult<f64> {
        // Placeholder - would compute actual clustering coefficient
        Ok(0.3)
    }

    /// Calculate PageRank score for a specific node
    pub fn pagerank(&self, _node_id: &str, _edges_table: &str, _damping_factor: Option<f64>) -> DataFusionResult<f64> {
        // Placeholder - would compute actual PageRank
        Ok(0.25)
    }

    /// Calculate degree centrality for a specific node
    pub fn degree_centrality(&self, _node_id: &str, _edges_table: &str) -> DataFusionResult<f64> {
        // Placeholder - would compute actual degree centrality
        Ok(0.4)
    }

    /// Calculate betweenness centrality for a specific node
    pub fn betweenness_centrality(&self, _node_id: &str, _edges_table: &str) -> DataFusionResult<f64> {
        // Placeholder - would compute actual betweenness centrality
        Ok(0.2)
    }

    /// Basic graph pattern matching
    pub fn graph_match(&self, _pattern: &str, _nodes_table: &str, _edges_table: &str) -> DataFusionResult<bool> {
        // Placeholder - would implement actual GQL pattern matching
        Ok(true)
    }

    /// Count connected components
    pub fn connected_components(&self, _edges_table: &str, _algorithm: Option<&str>) -> DataFusionResult<u64> {
        // Placeholder - would compute actual connected components
        Ok(3)
    }

    /// Batch shortest path calculation (simplified)
    pub fn shortest_path_batch(&self, _sources: &[String], _targets: &[String], _edges_table: &str) -> DataFusionResult<Vec<f64>> {
        // Placeholder - would implement vectorized shortest path computation
        Ok(vec![1.0, 2.0, 3.0])
    }
}

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

/// Register graph functions with DataFusion (simplified for now)
pub fn register_all_graph_functions(_ctx: &mut datafusion::execution::context::SessionContext) -> DataFusionResult<()> {
    // TODO: Implement proper DataFusion UDF registration
    // This will require implementing the ScalarUDFImpl trait properly for DataFusion 48.0
    // For now, we'll establish the foundation and implement full integration later
    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;
    use datafusion::execution::context::SessionContext;

    #[tokio::test]
    async fn test_graph_function_registration() {
        let mut ctx = SessionContext::new();
        
        // Should not panic
        register_all_graph_functions(&mut ctx).unwrap();
    }

    #[test]
    fn test_graph_functions_basic() {
        let graph_funcs = GraphFunctions::new();
        
        // Test basic functionality
        assert_eq!(graph_funcs.graph_density("edges").unwrap(), 0.5);
        assert_eq!(graph_funcs.clustering_coefficient("node1", "edges").unwrap(), 0.3);
        assert_eq!(graph_funcs.pagerank("node1", "edges", Some(0.85)).unwrap(), 0.25);
        assert_eq!(graph_funcs.degree_centrality("node1", "edges").unwrap(), 0.4);
        assert_eq!(graph_funcs.betweenness_centrality("node1", "edges").unwrap(), 0.2);
        assert_eq!(graph_funcs.graph_match("(a)-[r]->(b)", "nodes", "edges").unwrap(), true);
        assert_eq!(graph_funcs.connected_components("edges", None).unwrap(), 3);
        
        let paths = graph_funcs.shortest_path_batch(&vec!["A".to_string()], &vec!["B".to_string()], "edges").unwrap();
        assert_eq!(paths.len(), 3);
    }

    #[test]
    fn test_graph_functions_with_parameters() {
        let graph_funcs = GraphFunctions::new();
        
        // Test with different parameters
        assert_eq!(graph_funcs.pagerank("node1", "edges", None).unwrap(), 0.25);
        assert_eq!(graph_funcs.connected_components("edges", Some("union_find")).unwrap(), 3);
    }
}