//! SPARQL query executor

use crate::rdf::RdfStore;
use super::results::SparqlResults;
use thiserror::Error;

/// Execution errors
#[derive(Error, Debug)]
pub enum ExecutionError {
    /// Query error
    #[error("Query error: {0}")]
    Query(String),

    /// Type mismatch
    #[error("Type mismatch: {0}")]
    TypeMismatch(String),
}

/// SPARQL query executor
pub struct SparqlExecutor {
    _store: RdfStore,
}

impl SparqlExecutor {
    /// Create a new executor
    pub fn new(store: RdfStore) -> Self {
        Self { _store: store }
    }

    /// Execute a SELECT query
    ///
    /// TODO: Implement SELECT execution
    pub fn execute_select(&self) -> Result<SparqlResults, ExecutionError> {
        Ok(SparqlResults::empty())
    }

    /// Execute a CONSTRUCT query
    ///
    /// TODO: Implement CONSTRUCT execution
    pub fn execute_construct(&self) -> Result<SparqlResults, ExecutionError> {
        Ok(SparqlResults::empty())
    }

    /// Execute an ASK query
    ///
    /// TODO: Implement ASK execution
    pub fn execute_ask(&self) -> Result<bool, ExecutionError> {
        Ok(false)
    }

    /// Execute a DESCRIBE query
    ///
    /// TODO: Implement DESCRIBE execution
    pub fn execute_describe(&self) -> Result<SparqlResults, ExecutionError> {
        Ok(SparqlResults::empty())
    }
}

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

    #[test]
    fn test_executor_creation() {
        let store = RdfStore::new();
        let _exec = SparqlExecutor::new(store);
    }

    #[test]
    fn test_execute_select() {
        let store = RdfStore::new();
        let exec = SparqlExecutor::new(store);
        let result = exec.execute_select();
        assert!(result.is_ok());
    }

    #[test]
    fn test_execute_construct() {
        let store = RdfStore::new();
        let exec = SparqlExecutor::new(store);
        let result = exec.execute_construct();
        assert!(result.is_ok());
    }

    #[test]
    fn test_execute_ask() {
        let store = RdfStore::new();
        let exec = SparqlExecutor::new(store);
        let result = exec.execute_ask();
        assert!(result.is_ok());
        assert!(!result.unwrap()); // Default stub returns false
    }

    #[test]
    fn test_execute_describe() {
        let store = RdfStore::new();
        let exec = SparqlExecutor::new(store);
        let result = exec.execute_describe();
        assert!(result.is_ok());
    }
}
