arrow-graph 0.6.2

use datafusion::error::Result as DataFusionResult;

/// Placeholder for window functions - will implement proper DataFusion window functions
/// when we have the core SQL functionality working
pub struct GraphWindowFunctions;

impl GraphWindowFunctions {
    pub fn new() -> Self {
        Self
    }
    
    /// Future implementation of PageRank window function
    /// Will support: SELECT node_id, pagerank() OVER (PARTITION BY component) FROM nodes
    pub fn pagerank_window(&self, _partition_values: &[f64]) -> DataFusionResult<f64> {
        // Placeholder - would implement PageRank calculation over window partition
        Ok(0.25)
    }
    
    /// Future implementation of degree centrality window function
    /// Will support: SELECT node_id, degree_centrality() OVER (PARTITION BY component) FROM nodes
    pub fn degree_centrality_window(&self, _partition_values: &[u64]) -> DataFusionResult<f64> {
        // Placeholder - would implement degree centrality calculation over window partition
        Ok(0.5)
    }
    
    /// Future implementation of betweenness centrality window function
    /// Will support: SELECT node_id, betweenness_centrality() OVER (PARTITION BY component) FROM nodes
    pub fn betweenness_centrality_window(&self, _partition_values: &[f64]) -> DataFusionResult<f64> {
        // Placeholder - would implement betweenness centrality calculation over window partition
        Ok(0.3)
    }
}

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

/// Register window functions with DataFusion (placeholder for now)
pub fn register_window_functions(_ctx: &mut datafusion::execution::context::SessionContext) -> DataFusionResult<()> {
    // TODO: Implement proper DataFusion window function registration
    // This will require implementing the AggregateUDFImpl trait properly
    Ok(())
}

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

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

    #[test]
    fn test_window_functions_basic() {
        let window_funcs = GraphWindowFunctions::new();
        
        // Test basic functionality
        let pagerank_result = window_funcs.pagerank_window(&[]).unwrap();
        assert_eq!(pagerank_result, 0.25);
        
        let degree_result = window_funcs.degree_centrality_window(&[]).unwrap();
        assert_eq!(degree_result, 0.5);
        
        let betweenness_result = window_funcs.betweenness_centrality_window(&[]).unwrap();
        assert_eq!(betweenness_result, 0.3);
    }
}