// execution.rs — Rust execution engine

use serde::{Deserialize, Serialize};

/// Execution result.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct ExecutionResult {
    pub success: bool,
    pub output: Option<String>,
    pub error: Option<String>,
    pub gas_used: u64,
}

/// Execution engine for Fontana declarations.
pub struct ExecutionEngine {
    gas_limit: u64,
}

impl ExecutionEngine {
    pub fn new(gas_limit: u64) -> Self {
        Self { gas_limit }
    }

    /// Execute a declaration.
    pub fn execute(&self, declaration: &str) -> ExecutionResult {
        // Minimal execution: just validate input
        if declaration.is_empty() {
            return ExecutionResult {
                success: false,
                output: None,
                error: Some("Empty declaration".to_string()),
                gas_used: 0,
            };
        }

        ExecutionResult {
            success: true,
            output: Some(format!("Executed: {}", declaration)),
            error: None,
            gas_used: 100,
        }
    }
}