goblin-engine 0.1.0

use crate::error::{GoblinError, Result};
use crate::executor::{DefaultExecutor, ExecutionResult, Executor};
use crate::plan::Plan;
use crate::script::Script;
use dashmap::DashMap;
use std::collections::{HashMap, HashSet};
use std::path::PathBuf;
use std::sync::{Arc, RwLock};
use tracing::{debug, info, warn};
use uuid::Uuid;
use tokio::sync::Semaphore;
use futures::future::join_all;

/// Execution context for a plan run
#[derive(Debug)]
pub struct ExecutionContext {
    pub id: Uuid,
    pub plan_name: String,
    pub results: HashMap<String, String>,
    pub start_time: std::time::Instant,
}

impl ExecutionContext {
    pub fn new(plan_name: String) -> Self {
        Self {
            id: Uuid::new_v4(),
            plan_name,
            results: HashMap::new(),
            start_time: std::time::Instant::now(),
        }
    }

    pub fn add_result(&mut self, step_name: String, result: String) {
        self.results.insert(step_name, result);
    }

    pub fn get_result(&self, step_name: &str) -> Option<&String> {
        self.results.get(step_name)
    }

    pub fn elapsed(&self) -> std::time::Duration {
        self.start_time.elapsed()
    }
}

/// The main workflow engine
pub struct Engine {
    /// Collection of loaded scripts indexed by name
    scripts: DashMap<String, Script>,
    /// Collection of loaded plans indexed by name  
    plans: DashMap<String, Plan>,
    /// Executor for running scripts
    executor: Arc<dyn Executor + Send + Sync>,
    /// Base directory for auto-discovering scripts
    scripts_dir: Option<PathBuf>,
}

impl Engine {
    /// Create a new engine with the default executor
    pub fn new() -> Self {
        Self {
            scripts: DashMap::new(),
            plans: DashMap::new(),
            executor: Arc::new(DefaultExecutor::new()),
            scripts_dir: None,
        }
    }

    /// Create a new engine with a custom executor
    pub fn with_executor(executor: Arc<dyn Executor + Send + Sync>) -> Self {
        Self {
            scripts: DashMap::new(),
            plans: DashMap::new(),
            executor,
            scripts_dir: None,
        }
    }

    /// Set the base directory for auto-discovering scripts
    pub fn with_scripts_dir(mut self, scripts_dir: PathBuf) -> Self {
        self.scripts_dir = Some(scripts_dir);
        self
    }

    /// Auto-discover scripts from the scripts directory
    pub fn auto_discover_scripts(&self) -> Result<usize> {
        let scripts_dir = match &self.scripts_dir {
            Some(dir) => dir.clone(),
            None => {
                warn!("Scripts directory not set, skipping auto-discovery");
                return Ok(0);
            }
        };

        if !scripts_dir.exists() {
            warn!("Scripts directory does not exist: {}", scripts_dir.display());
            return Ok(0);
        }

        let mut discovered = 0;

        for entry in std::fs::read_dir(&scripts_dir)? {
            let entry = entry?;
            let path = entry.path();

            if path.is_dir() {
                let goblin_toml = path.join("goblin.toml");
                if goblin_toml.exists() {
                    match Script::from_toml_file(&path) {
                        Ok(script) => {
                            info!("Discovered script: {} at {}", script.name, path.display());
                            self.scripts.insert(script.name.clone(), script);
                            discovered += 1;
                        }
                        Err(e) => {
                            warn!("Failed to load script from {}: {}", path.display(), e);
                        }
                    }
                }
            }
        }

        info!("Auto-discovered {} scripts", discovered);
        Ok(discovered)
    }

    /// Load a single script from a directory
    pub fn load_script(&self, script_dir: PathBuf) -> Result<()> {
        let script = Script::from_toml_file(&script_dir)?;
        self.scripts.insert(script.name.clone(), script);
        Ok(())
    }

    /// Add a script directly
    pub fn add_script(&self, script: Script) -> Result<()> {
        script.validate()?;
        self.scripts.insert(script.name.clone(), script);
        Ok(())
    }

    /// Get a script by name
    pub fn get_script(&self, name: &str) -> Option<Script> {
        self.scripts.get(name).map(|entry| entry.value().clone())
    }

    /// List all available scripts
    pub fn list_scripts(&self) -> Vec<String> {
        let mut names: Vec<String> = self.scripts.iter().map(|entry| entry.key().clone()).collect();
        names.sort();
        names
    }

    /// Load a plan from a TOML file
    pub fn load_plan(&self, plan_path: PathBuf) -> Result<()> {
        let plan = Plan::from_toml_file(&plan_path)?;
        
        // Validate that all required scripts are available
        let required_scripts = plan.get_required_scripts();
        for script_name in &required_scripts {
            if !self.scripts.contains_key(script_name) {
                return Err(GoblinError::script_not_found(script_name));
            }
        }

        plan.validate()?;
        self.plans.insert(plan.name.clone(), plan);
        Ok(())
    }

    /// Load a plan from a TOML string
    pub fn load_plan_from_str(&self, toml_str: &str) -> Result<()> {
        let plan = Plan::from_toml_str(toml_str)?;
        
        // Validate that all required scripts are available
        let required_scripts = plan.get_required_scripts();
        for script_name in &required_scripts {
            if !self.scripts.contains_key(script_name) {
                return Err(GoblinError::script_not_found(script_name));
            }
        }

        plan.validate()?;
        self.plans.insert(plan.name.clone(), plan);
        Ok(())
    }

    /// Get a plan by name
    pub fn get_plan(&self, name: &str) -> Option<Plan> {
        self.plans.get(name).map(|entry| entry.value().clone())
    }

    /// List all available plans
    pub fn list_plans(&self) -> Vec<String> {
        let mut names: Vec<String> = self.plans.iter().map(|entry| entry.key().clone()).collect();
        names.sort();
        names
    }

    /// Execute a single script with arguments
    pub async fn execute_script(&self, script_name: &str, args: Vec<String>) -> Result<ExecutionResult> {
        let script = self.get_script(script_name)
            .ok_or_else(|| GoblinError::script_not_found(script_name))?;

        self.executor.execute_script(&script, &args).await
    }

    /// Execute a plan with optional default input (with parallel execution)
    pub async fn execute_plan(&self, plan_name: &str, default_input: Option<String>) -> Result<ExecutionContext> {
        let plan = self.get_plan(plan_name)
            .ok_or_else(|| GoblinError::plan_not_found(plan_name))?;

        info!("Starting parallel execution of plan: {}", plan_name);
        
        let context = Arc::new(RwLock::new(ExecutionContext::new(plan_name.to_string())));
        
        // Add default input if provided
        if let Some(input) = default_input {
            context.write().unwrap().add_result("default_input".to_string(), input);
        }

        // Execute steps in parallel waves based on dependencies
        self.execute_plan_parallel(&plan, context.clone()).await?;

        let final_context = Arc::try_unwrap(context)
            .map_err(|_| GoblinError::engine_error("Failed to unwrap execution context"))?
            .into_inner()
            .map_err(|_| GoblinError::engine_error("Failed to acquire context lock"))?;

        info!("Plan '{}' completed successfully in {:?}", plan_name, final_context.elapsed());
        Ok(final_context)
    }

    /// Execute plan steps in parallel waves based on dependency resolution
    async fn execute_plan_parallel(
        &self,
        plan: &Plan,
        context: Arc<RwLock<ExecutionContext>>,
    ) -> Result<()> {
        let mut remaining_steps: HashSet<String> = plan.steps.iter().map(|s| s.name.clone()).collect();
        let mut completed_steps: HashSet<String> = HashSet::new();
        
        // Add default_input as completed if it exists in context
        {
            let ctx = context.read().unwrap();
            if ctx.results.contains_key("default_input") {
                completed_steps.insert("default_input".to_string());
            }
        }

        let mut wave_count = 0;

        while !remaining_steps.is_empty() {
            wave_count += 1;
            info!("Starting execution wave {}", wave_count);

            // Find steps that can be executed (all dependencies satisfied)
            let executable_steps: Vec<String> = remaining_steps
                .iter()
                .filter(|step_name| {
                    let step = plan.steps.iter().find(|s| &s.name == *step_name).unwrap();
                    let dependencies = step.get_dependencies();
                    dependencies.iter().all(|dep| dep == "default_input" || completed_steps.contains(dep))
                })
                .cloned()
                .collect();

            if executable_steps.is_empty() {
                return Err(GoblinError::engine_error(format!(
                    "No executable steps found in wave {}. Possible circular dependency or missing dependencies. Remaining steps: {:?}",
                    wave_count, remaining_steps
                )));
            }

            info!("Wave {} executing steps: {:?}", wave_count, executable_steps);

            // Execute all executable steps concurrently
            let mut futures = Vec::new();
            
            for step_name in &executable_steps {
                let step = plan.steps.iter().find(|s| &s.name == step_name).unwrap();
                let context_clone = context.clone();
                let executor_clone = self.executor.clone();
                let step_clone = step.clone();
                
                // Get the script for this step
                let script = self.get_script(&step.function)
                    .ok_or_else(|| GoblinError::script_not_found(&step.function))?;

                let future = async move {
                    // Resolve inputs for this step
                    let args = {
                        let ctx = context_clone.read().unwrap();
                        step_clone.resolve_inputs(&ctx.results)?
                    };
                    
                    info!("Executing step '{}' with script '{}' and args: {:?}", 
                          step_clone.name, step_clone.function, args);

                    // Execute the script
                    let result = executor_clone.execute_script(&script, &args).await?;
                    
                    // Store the result
                    let output = result.get_output();
                    {
                        let mut ctx = context_clone.write().unwrap();
                        ctx.add_result(step_clone.name.clone(), output.clone());
                    }
                    
                    info!("Step '{}' completed successfully. Output: '{}'", step_clone.name, output);
                    
                    Ok::<String, GoblinError>(step_clone.name)
                };

                futures.push(future);
            }

            // Wait for all steps in this wave to complete
            let results = join_all(futures).await;
            
            // Check for any failures and collect completed step names
            let mut wave_completed = Vec::new();
            for result in results {
                match result {
                    Ok(step_name) => wave_completed.push(step_name),
                    Err(e) => return Err(e),
                }
            }

            // Update tracking sets
            for step_name in wave_completed {
                remaining_steps.remove(&step_name);
                completed_steps.insert(step_name);
            }

            info!("Wave {} completed. Remaining steps: {}", wave_count, remaining_steps.len());
        }

        info!("All waves completed successfully in {} waves", wave_count);
        Ok(())
    }

    /// Get execution statistics
    pub fn get_stats(&self) -> (usize, usize) {
        (self.scripts.len(), self.plans.len())
    }

    /// Clear all loaded scripts and plans
    pub fn clear(&self) {
        self.scripts.clear();
        self.plans.clear();
    }

    /// Validate all loaded plans against available scripts
    pub fn validate_all_plans(&self) -> Result<()> {
        for plan_entry in self.plans.iter() {
            let plan = plan_entry.value();
            
            // Check that all required scripts exist
            for script_name in plan.get_required_scripts() {
                if !self.scripts.contains_key(&script_name) {
                    return Err(GoblinError::script_not_found(&script_name));
                }
            }
            
            // Validate the plan itself
            plan.validate()?;
        }
        Ok(())
    }
}

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

/// A pool of engine instances for concurrent execution with memory management
pub struct EnginePool {
    instances: Arc<RwLock<Vec<Engine>>>,
    semaphore: Arc<Semaphore>,
    pool_size: usize,
}

impl EnginePool {
    /// Create a new engine pool with the specified size
    pub async fn new(pool_size: usize) -> Result<Self> {
        if pool_size == 0 {
            return Err(GoblinError::config_error("Pool size must be greater than 0"));
        }

        let instances = Arc::new(RwLock::new(Vec::with_capacity(pool_size)));
        
        // Create the specified number of engine instances
        for _ in 0..pool_size {
            let instance = Engine::new();
            instances.write().unwrap().push(instance);
        }

        Ok(Self {
            instances,
            semaphore: Arc::new(Semaphore::new(pool_size)),
            pool_size,
        })
    }

    /// Create a new engine pool with custom configuration for all instances
    pub async fn with_config(pool_size: usize, scripts_dir: Option<PathBuf>) -> Result<Self> {
        if pool_size == 0 {
            return Err(GoblinError::config_error("Pool size must be greater than 0"));
        }

        let instances = Arc::new(RwLock::new(Vec::with_capacity(pool_size)));
        
        // Create and configure engine instances
        for _ in 0..pool_size {
            let mut instance = Engine::new();
            
            if let Some(ref dir) = scripts_dir {
                instance = instance.with_scripts_dir(dir.clone());
                // Auto-discover scripts for each instance
                instance.auto_discover_scripts()?;
            }
            
            instances.write().unwrap().push(instance);
        }

        info!("Created engine pool with {} instances", pool_size);
        Ok(Self {
            instances,
            semaphore: Arc::new(Semaphore::new(pool_size)),
            pool_size,
        })
    }

    /// Get pool statistics
    pub fn get_pool_stats(&self) -> PoolStats {
        let available_permits = self.semaphore.available_permits();
        PoolStats {
            total_instances: self.pool_size,
            available_instances: available_permits,
            busy_instances: self.pool_size - available_permits,
        }
    }

    /// Acquire an engine instance from the pool (blocks if none available)
    pub async fn acquire(&self) -> Result<EngineGuard> {
        // Acquire a permit from the semaphore
        let permit = self.semaphore.clone().acquire_owned().await
            .map_err(|e| GoblinError::engine_error(format!("Failed to acquire engine from pool: {}", e)))?;

        // Get an engine instance
        let engine = {
            let mut instances = self.instances.write().unwrap();
            instances.pop()
                .ok_or_else(|| GoblinError::engine_error("No engine instances available (this should not happen)"))?
        };

        debug!("Acquired engine instance from pool");
        Ok(EngineGuard {
            engine: Some(engine),
            pool_instances: self.instances.clone(),
            _permit: permit,
        })
    }

    /// Try to acquire an engine instance immediately (non-blocking)
    pub fn try_acquire(&self) -> Result<Option<EngineGuard>> {
        // Try to acquire a permit from the semaphore
        let permit = match self.semaphore.clone().try_acquire_owned() {
            Ok(permit) => permit,
            Err(_) => return Ok(None), // No instances available
        };

        // Get an engine instance
        let engine = {
            let mut instances = self.instances.write().unwrap();
            instances.pop()
                .ok_or_else(|| GoblinError::engine_error("No engine instances available (this should not happen)"))?
        };

        debug!("Acquired engine instance from pool (non-blocking)");
        Ok(Some(EngineGuard {
            engine: Some(engine),
            pool_instances: self.instances.clone(),
            _permit: permit,
        }))
    }

    /// Load scripts on all instances in the pool
    pub async fn load_scripts_on_all(&self, scripts_dir: &PathBuf) -> Result<()> {
        let mut instances = self.instances.write().unwrap();
        
        for instance in instances.iter_mut() {
            instance.scripts_dir = Some(scripts_dir.clone());
            instance.auto_discover_scripts()?;
        }

        info!("Loaded scripts on all {} instances in pool", self.pool_size);
        Ok(())
    }

    /// Load a plan on all instances in the pool
    pub async fn load_plan_on_all(&self, plan_path: PathBuf) -> Result<()> {
        let mut instances = self.instances.write().unwrap();
        
        for instance in instances.iter_mut() {
            instance.load_plan(plan_path.clone())?;
        }

        info!("Loaded plan on all {} instances in pool", self.pool_size);
        Ok(())
    }
}

/// Statistics about the engine pool
#[derive(Debug, Clone)]
pub struct PoolStats {
    pub total_instances: usize,
    pub available_instances: usize,
    pub busy_instances: usize,
}

/// A guard that manages access to an engine instance from the pool
pub struct EngineGuard {
    engine: Option<Engine>,
    pool_instances: Arc<RwLock<Vec<Engine>>>,
    _permit: tokio::sync::OwnedSemaphorePermit,
}

impl EngineGuard {
    /// Get a reference to the engine
    pub fn engine(&self) -> &Engine {
        self.engine.as_ref().unwrap()
    }

    /// Get a mutable reference to the engine
    pub fn engine_mut(&mut self) -> &mut Engine {
        self.engine.as_mut().unwrap()
    }

    /// Execute a plan and automatically reset the engine state afterwards
    pub async fn execute_plan_with_reset(
        &mut self,
        plan_name: &str,
        default_input: Option<String>,
    ) -> Result<ExecutionContext> {
        let result = self.engine().execute_plan(plan_name, default_input).await;
        
        // Reset the engine state regardless of success/failure
        self.reset_execution_state();
        
        result
    }

    /// Reset the execution state (clear any cached results/contexts)
    pub fn reset_execution_state(&mut self) {
        if let Some(_engine) = &mut self.engine {
            // Clear any execution-related state but keep scripts and plans loaded
            // The ExecutionContext is already separate per execution, so no persistent state to clear
            debug!("Reset execution state for engine instance");
        }
    }
}

impl std::ops::Deref for EngineGuard {
    type Target = Engine;

    fn deref(&self) -> &Self::Target {
        self.engine.as_ref().unwrap()
    }
}

impl std::ops::DerefMut for EngineGuard {
    fn deref_mut(&mut self) -> &mut Self::Target {
        self.engine.as_mut().unwrap()
    }
}

impl Drop for EngineGuard {
    fn drop(&mut self) {
        // Return the engine to the pool when the guard is dropped
        if let Some(engine) = self.engine.take() {
            let mut instances = self.pool_instances.write().unwrap();
            instances.push(engine);
            debug!("Returned engine instance to pool");
        }
        // The permit is automatically released when _permit is dropped
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::executor::{ExecutionResult, MockExecutor};
    use crate::script::{Script, ScriptConfig};
    use tokio::time::Duration;

    #[tokio::test]
    async fn test_engine_basic_operations() {
        let engine = Engine::new();
        
        // Add a test script with a valid temp directory
        let temp_dir = std::env::temp_dir();
        let config = ScriptConfig {
            name: "test_script".to_string(),
            command: "echo hello".to_string(),
            timeout: 30,
            test_command: None,
            require_test: false,
        };
        let script = Script::new(config, temp_dir);
        engine.add_script(script).unwrap();
        
        // Check script was added
        assert_eq!(engine.list_scripts(), vec!["test_script"]);
        assert!(engine.get_script("test_script").is_some());
        assert!(engine.get_script("nonexistent").is_none());
    }

    #[tokio::test]
    async fn test_engine_with_mock_executor() {
        let mut mock_executor = MockExecutor::new();
        
        // Set up expected result
        let expected_result = ExecutionResult {
            script_name: "test_script".to_string(),
            stdout: "Hello, World!".to_string(),
            stderr: String::new(),
            exit_code: 0,
            duration: Duration::from_millis(100),
        };
        mock_executor.add_result("test_script".to_string(), expected_result.clone());
        
        let engine = Engine::with_executor(Arc::new(mock_executor));
        
        // Add a test script
        let config = ScriptConfig {
            name: "test_script".to_string(),
            command: "echo hello".to_string(),
            timeout: 30,
            test_command: None,
            require_test: false,
        };
        let script = Script::new(config, std::env::temp_dir());
        engine.add_script(script).unwrap();
        
        // Execute the script
        let result = engine.execute_script("test_script", vec![]).await.unwrap();
        assert_eq!(result.stdout, "Hello, World!");
        assert!(result.is_success());
    }
}