//! # Ballista Execution Engine
//!
//! This module provides an implementation of the execution engine interface
//! using Apache Arrow Ballista for distributed execution.

#[cfg(feature = "distributed")]
use std::collections::HashMap;
#[cfg(feature = "distributed")]
use std::sync::{Arc, Mutex};

#[cfg(feature = "distributed")]
use crate::distributed::core::config::DistributedConfig;
#[cfg(feature = "distributed")]
use crate::distributed::core::partition::PartitionSet;
#[cfg(feature = "distributed")]
use crate::distributed::execution::{
    AggregateExpr, ExecutionContext, ExecutionEngine, ExecutionMetrics, ExecutionPlan,
    ExecutionResult, JoinType, Operation, SortExpr,
};
#[cfg(feature = "distributed")]
use crate::error::{Error, Result};

/// Ballista execution engine
#[cfg(feature = "distributed")]
pub struct BallistaEngine {
    /// Whether the engine is initialized
    initialized: bool,
    /// Configuration
    config: Option<DistributedConfig>,
}

#[cfg(feature = "distributed")]
impl BallistaEngine {
    /// Creates a new Ballista engine
    pub fn new() -> Self {
        Self {
            initialized: false,
            config: None,
        }
    }
}

#[cfg(feature = "distributed")]
impl ExecutionEngine for BallistaEngine {
    fn initialize(&mut self, config: &DistributedConfig) -> Result<()> {
        self.initialized = true;
        self.config = Some(config.clone());
        Ok(())
    }

    fn is_initialized(&self) -> bool {
        self.initialized
    }

    fn create_context(&self, config: &DistributedConfig) -> Result<Box<dyn ExecutionContext>> {
        if !self.initialized {
            return Err(Error::InvalidValue("Engine not initialized".to_string()));
        }

        let ctx = BallistaContext::new(config);
        Ok(Box::new(ctx))
    }

    fn clone(&self) -> Box<dyn ExecutionEngine> {
        Box::new(Self {
            initialized: self.initialized,
            config: self.config.clone(),
        })
    }
}

/// Ballista execution context
#[cfg(feature = "distributed")]
pub struct BallistaContext {
    /// Configuration
    config: DistributedConfig,
    /// Execution metrics
    metrics: ExecutionMetrics,
}

#[cfg(feature = "distributed")]
impl BallistaContext {
    /// Creates a new Ballista context
    pub fn new(config: &DistributedConfig) -> Self {
        Self {
            config: config.clone(),
            metrics: ExecutionMetrics::new(),
        }
    }
}

#[cfg(feature = "distributed")]
impl ExecutionContext for BallistaContext {
    fn execute_plan(&mut self, plan: ExecutionPlan) -> Result<ExecutionResult> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista execution not yet implemented".to_string(),
        ))
    }

    fn register_in_memory_table(&mut self, name: &str, partitions: PartitionSet) -> Result<()> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista table registration not yet implemented".to_string(),
        ))
    }

    fn register_csv(&mut self, name: &str, path: &str) -> Result<()> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista CSV registration not yet implemented".to_string(),
        ))
    }

    fn register_parquet(&mut self, name: &str, path: &str) -> Result<()> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista Parquet registration not yet implemented".to_string(),
        ))
    }

    fn sql(&mut self, query: &str) -> Result<ExecutionResult> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista SQL execution not yet implemented".to_string(),
        ))
    }

    fn table_schema(&self, name: &str) -> Result<arrow::datatypes::SchemaRef> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista schema retrieval not yet implemented".to_string(),
        ))
    }

    fn explain_plan(&self, plan: &ExecutionPlan, with_statistics: bool) -> Result<String> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista plan explanation not yet implemented".to_string(),
        ))
    }

    fn write_parquet(&mut self, result: &ExecutionResult, path: &str) -> Result<()> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista Parquet writing not yet implemented".to_string(),
        ))
    }

    fn write_csv(&mut self, result: &ExecutionResult, path: &str) -> Result<()> {
        // Implementation will be provided in a future PR
        Err(Error::NotImplemented(
            "Ballista CSV writing not yet implemented".to_string(),
        ))
    }

    fn metrics(&self) -> Result<ExecutionMetrics> {
        Ok(self.metrics.clone())
    }

    fn clone(&self) -> Box<dyn ExecutionContext> {
        // Implementation will be provided in a future PR
        // For now, create a new instance with the same configuration
        Box::new(BallistaContext::new(&DistributedConfig::default()))
    }
}
