//! SPARQL 1.1 query language support
//!
//! This module implements SPARQL query parsing and execution.
//!
//! # Requirements Coverage
//!
//! - REQ-SPARQL-001: SPARQL 1.1 query language
//! - REQ-SPARQL-002: SPARQL HTTP protocol
//! - REQ-SPARQL-003: Query forms (SELECT, CONSTRUCT, ASK, DESCRIBE)
//! - REQ-SPARQL-004: SPARQL UPDATE operations
//! - REQ-SPARQL-005: Filtering and constraints
//! - REQ-SPARQL-006: Aggregates
//! - REQ-SPARQL-007: Federation (SERVICE keyword)
//! - REQ-SPARQL-008: Query optimization
//!
//! # Example
//!
//! ```rust,ignore
//! use samyama::sparql::{SparqlEngine, SparqlResults};
//! use samyama::rdf::RdfStore;
//!
//! let store = RdfStore::new();
//! let engine = SparqlEngine::new(store);
//!
//! let query = r#"
//!     PREFIX foaf: <http://xmlns.com/foaf/0.1/>
//!     SELECT ?name WHERE {
//!         ?person foaf:name ?name .
//!     }
//! "#;
//!
//! let results = engine.query(query).unwrap();
//! ```

mod parser;
mod executor;
mod algebra;
mod optimizer;
mod results;
mod http;

pub use parser::{SparqlParser, ParseError as SparqlParseError};
pub use executor::{SparqlExecutor, ExecutionError};
pub use results::{SparqlResults, ResultFormat, QuerySolution};
pub use http::{SparqlHttpEndpoint, HttpError};

use crate::rdf::RdfStore;
use thiserror::Error;

/// SPARQL errors
#[derive(Error, Debug)]
pub enum SparqlError {
    /// Parse error
    #[error("Parse error: {0}")]
    Parse(String),

    /// Execution error
    #[error("Execution error: {0}")]
    Execution(String),

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

    /// HTTP error
    #[error("HTTP error: {0}")]
    Http(String),
}

pub type SparqlResult<T> = Result<T, SparqlError>;

/// SPARQL query engine
pub struct SparqlEngine {
    store: RdfStore,
    executor: SparqlExecutor,
}

impl SparqlEngine {
    /// Create a new SPARQL engine
    pub fn new(store: RdfStore) -> Self {
        Self {
            store: store.clone(),
            executor: SparqlExecutor::new(store),
        }
    }

    /// Execute a SPARQL query
    ///
    /// TODO: Full implementation
    pub fn query(&self, _query_str: &str) -> SparqlResult<SparqlResults> {
        // TODO: Implement query execution
        // 1. Parse query using SparqlParser
        // 2. Optimize using optimizer
        // 3. Execute using SparqlExecutor
        // 4. Return results
        Ok(SparqlResults::empty())
    }

    /// Execute a SPARQL UPDATE operation
    ///
    /// TODO: Full implementation
    pub fn update(&mut self, _update_str: &str) -> SparqlResult<()> {
        // TODO: Implement update execution
        Ok(())
    }
}

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

    #[test]
    fn test_engine_creation() {
        let store = RdfStore::new();
        let _engine = SparqlEngine::new(store);
    }

    #[test]
    fn test_query_stub() {
        let store = RdfStore::new();
        let engine = SparqlEngine::new(store);

        let result = engine.query("SELECT * WHERE { ?s ?p ?o }");
        assert!(result.is_ok());
    }
}
