//! Plugin system for mongosh extensibility
//!
//! This module provides a plugin system that allows third-party extensions:
//! - Plugin trait definition for implementing custom plugins
//! - Plugin manager for loading, managing, and executing plugins
//! - Plugin lifecycle management (load, init, execute, unload)
//! - Plugin discovery and registration
//! - Plugin metadata and versioning
//! - Sandboxed plugin execution for security

use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::sync::Arc;
use tokio::sync::RwLock;

use crate::error::{PluginError, Result};
use mongodb::Client;

/// Plugin trait that must be implemented by all plugins
///
/// Plugins extend mongosh functionality by implementing this trait.
/// They can register custom commands and interact with MongoDB.
pub trait Plugin: Send + Sync {
    /// Get plugin name
    ///
    /// # Returns
    /// * `&str` - Unique plugin name
    fn name(&self) -> &str;

    /// Get plugin version
    ///
    /// # Returns
    /// * `&str` - Version string (semver format)
    fn version(&self) -> &str;

    /// Get plugin metadata
    ///
    /// # Returns
    /// * `PluginMetadata` - Plugin information
    fn metadata(&self) -> PluginMetadata {
        PluginMetadata {
            name: self.name().to_string(),
            version: self.version().to_string(),
            author: "Unknown".to_string(),
            description: "No description".to_string(),
            license: None,
            homepage: None,
        }
    }

    /// Initialize the plugin
    ///
    /// Called once when the plugin is loaded
    ///
    /// # Arguments
    /// * `ctx` - Plugin context with MongoDB client access
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    fn init(&mut self, ctx: &mut PluginContext) -> Result<()>;

    /// Clean up plugin resources
    ///
    /// Called when the plugin is unloaded
    fn cleanup(&mut self) {
        // Default implementation does nothing
    }

    /// Register custom commands
    ///
    /// # Returns
    /// * `Vec<CommandRegistration>` - List of commands to register
    fn register_commands(&self) -> Vec<CommandRegistration> {
        Vec::new()
    }

    /// Execute a plugin command
    ///
    /// # Arguments
    /// * `cmd` - Command name
    /// * `args` - Command arguments
    /// * `ctx` - Execution context
    ///
    /// # Returns
    /// * `Result<PluginResult>` - Command result or error
    fn execute(&self, cmd: &str, args: &[String], ctx: &PluginContext) -> Result<PluginResult>;

    /// Handle plugin-specific configuration
    ///
    /// # Arguments
    /// * `config` - Configuration map
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    fn configure(&mut self, _config: HashMap<String, String>) -> Result<()> {
        // Default implementation ignores configuration
        Ok(())
    }
}

/// Plugin metadata information
#[derive(Debug, Clone)]
pub struct PluginMetadata {
    /// Plugin name
    pub name: String,

    /// Plugin version
    pub version: String,

    /// Plugin author
    pub author: String,

    /// Plugin description
    pub description: String,

    /// License identifier
    pub license: Option<String>,

    /// Homepage URL
    pub homepage: Option<String>,
}

/// Context provided to plugins for execution
pub struct PluginContext {
    /// MongoDB client for database operations
    pub client: Client,

    /// Current database name
    pub database: String,

    /// Plugin-specific data storage
    data: HashMap<String, String>,
}

/// Result of plugin command execution
#[derive(Debug, Clone)]
pub struct PluginResult {
    /// Success status
    pub success: bool,

    /// Output message
    pub output: String,

    /// Additional data
    pub data: Option<HashMap<String, String>>,

    /// Error message if failed
    pub error: Option<String>,
}

/// Command registration information
#[derive(Debug, Clone)]
pub struct CommandRegistration {
    /// Command name
    pub name: String,

    /// Command description
    pub description: String,

    /// Usage string
    pub usage: String,

    /// Command aliases
    pub aliases: Vec<String>,
}

/// Plugin manager for managing all plugins
pub struct PluginManager {
    /// Loaded plugins
    plugins: Arc<RwLock<HashMap<String, Box<dyn Plugin>>>>,

    /// Plugin directory path
    plugin_dir: PathBuf,

    /// Enabled plugin names
    enabled_plugins: Vec<String>,

    /// Plugin contexts
    contexts: Arc<RwLock<HashMap<String, PluginContext>>>,
}

/// Plugin loader for discovering and loading plugins
pub struct PluginLoader {
    /// Plugin directory
    directory: PathBuf,
}

/// Plugin registry for tracking available plugins
pub struct PluginRegistry {
    /// Registered plugin metadata
    plugins: HashMap<String, PluginMetadata>,
}

impl PluginManager {
    /// Create a new plugin manager
    ///
    /// # Arguments
    /// * `plugin_dir` - Directory containing plugins
    /// * `enabled_plugins` - List of enabled plugin names
    ///
    /// # Returns
    /// * `Self` - New plugin manager
    pub fn new(plugin_dir: PathBuf, enabled_plugins: Vec<String>) -> Self {
        Self {
            plugins: Arc::new(RwLock::new(HashMap::new())),
            plugin_dir,
            enabled_plugins,
            contexts: Arc::new(RwLock::new(HashMap::new())),
        }
    }

    /// Load a plugin from file
    ///
    /// # Arguments
    /// * `path` - Path to plugin file
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    pub async fn load_plugin<P: AsRef<Path>>(&mut self, _path: P) -> Result<()> {
        todo!("Load plugin from dynamic library file")
    }

    /// Unload a plugin
    ///
    /// # Arguments
    /// * `name` - Plugin name
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    pub async fn unload_plugin(&mut self, name: &str) -> Result<()> {
        let mut plugins = self.plugins.write().await;

        if let Some(mut plugin) = plugins.remove(name) {
            plugin.cleanup();
            Ok(())
        } else {
            Err(PluginError::NotFound(name.to_string()).into())
        }
    }

    /// List all loaded plugins
    ///
    /// # Returns
    /// * `Vec<String>` - List of plugin names
    pub async fn list_plugins(&self) -> Vec<String> {
        let plugins = self.plugins.read().await;
        plugins.keys().cloned().collect()
    }

    /// Get plugin metadata
    ///
    /// # Arguments
    /// * `name` - Plugin name
    ///
    /// # Returns
    /// * `Option<PluginMetadata>` - Plugin metadata if found
    pub async fn get_metadata(&self, name: &str) -> Option<PluginMetadata> {
        let plugins = self.plugins.read().await;
        plugins.get(name).map(|p| p.metadata())
    }

    /// Execute a plugin command
    ///
    /// # Arguments
    /// * `plugin_name` - Plugin name
    /// * `command` - Command name
    /// * `args` - Command arguments
    /// * `client` - MongoDB client
    /// * `database` - Current database
    ///
    /// # Returns
    /// * `Result<PluginResult>` - Command result or error
    pub async fn execute_command(
        &self,
        plugin_name: &str,
        command: &str,
        args: &[String],
        client: Client,
        database: String,
    ) -> Result<PluginResult> {
        let plugins = self.plugins.read().await;

        let plugin = plugins
            .get(plugin_name)
            .ok_or_else(|| PluginError::NotFound(plugin_name.to_string()))?;

        let ctx = PluginContext::new(client, database);

        plugin
            .execute(command, args, &ctx)
            .map_err(|e| PluginError::ExecutionFailed(e.to_string()).into())
    }

    /// Load all enabled plugins from plugin directory
    ///
    /// # Arguments
    /// * `client` - MongoDB client for plugin contexts
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    pub async fn load_enabled_plugins(&mut self, _client: Client) -> Result<()> {
        todo!("Discover and load all enabled plugins from directory")
    }

    /// Initialize a plugin with context
    ///
    /// # Arguments
    /// * `name` - Plugin name
    /// * `client` - MongoDB client
    /// * `database` - Database name
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    async fn init_plugin(&mut self, name: &str, client: Client, database: String) -> Result<()> {
        let mut plugins = self.plugins.write().await;

        if let Some(plugin) = plugins.get_mut(name) {
            let mut ctx = PluginContext::new(client, database);
            plugin.init(&mut ctx)?;

            let mut contexts = self.contexts.write().await;
            contexts.insert(name.to_string(), ctx);

            Ok(())
        } else {
            Err(PluginError::NotFound(name.to_string()).into())
        }
    }

    /// Check if a plugin is loaded
    ///
    /// # Arguments
    /// * `name` - Plugin name
    ///
    /// # Returns
    /// * `bool` - True if loaded
    pub async fn is_loaded(&self, name: &str) -> bool {
        let plugins = self.plugins.read().await;
        plugins.contains_key(name)
    }

    /// Get all registered commands from all plugins
    ///
    /// # Returns
    /// * `HashMap<String, Vec<CommandRegistration>>` - Commands by plugin name
    pub async fn get_all_commands(&self) -> HashMap<String, Vec<CommandRegistration>> {
        let plugins = self.plugins.read().await;
        let mut commands = HashMap::new();

        for (name, plugin) in plugins.iter() {
            commands.insert(name.clone(), plugin.register_commands());
        }

        commands
    }
}

impl PluginContext {
    /// Create a new plugin context
    ///
    /// # Arguments
    /// * `client` - MongoDB client
    /// * `database` - Current database name
    ///
    /// # Returns
    /// * `Self` - New context
    pub fn new(client: Client, database: String) -> Self {
        Self {
            client,
            database,
            data: HashMap::new(),
        }
    }

    /// Get database handle
    ///
    /// # Returns
    /// * `mongodb::Database` - Database handle
    pub fn get_database(&self) -> mongodb::Database {
        self.client.database(&self.database)
    }

    /// Store plugin-specific data
    ///
    /// # Arguments
    /// * `key` - Data key
    /// * `value` - Data value
    pub fn set_data(&mut self, key: String, value: String) {
        self.data.insert(key, value);
    }

    /// Retrieve plugin-specific data
    ///
    /// # Arguments
    /// * `key` - Data key
    ///
    /// # Returns
    /// * `Option<&String>` - Data value if exists
    pub fn get_data(&self, key: &str) -> Option<&String> {
        self.data.get(key)
    }

    /// Clear all plugin data
    pub fn clear_data(&mut self) {
        self.data.clear();
    }
}

impl PluginResult {
    /// Create a successful result
    ///
    /// # Arguments
    /// * `output` - Output message
    ///
    /// # Returns
    /// * `Self` - Success result
    pub fn success(output: String) -> Self {
        Self {
            success: true,
            output,
            data: None,
            error: None,
        }
    }

    /// Create a failed result
    ///
    /// # Arguments
    /// * `error` - Error message
    ///
    /// # Returns
    /// * `Self` - Failure result
    pub fn failure(error: String) -> Self {
        Self {
            success: false,
            output: String::new(),
            data: None,
            error: Some(error),
        }
    }

    /// Create result with additional data
    ///
    /// # Arguments
    /// * `output` - Output message
    /// * `data` - Additional data
    ///
    /// # Returns
    /// * `Self` - Result with data
    pub fn with_data(output: String, data: HashMap<String, String>) -> Self {
        Self {
            success: true,
            output,
            data: Some(data),
            error: None,
        }
    }
}

impl CommandRegistration {
    /// Create a new command registration
    ///
    /// # Arguments
    /// * `name` - Command name
    /// * `description` - Command description
    /// * `usage` - Usage string
    ///
    /// # Returns
    /// * `Self` - New registration
    pub fn new(name: String, description: String, usage: String) -> Self {
        Self {
            name,
            description,
            usage,
            aliases: Vec::new(),
        }
    }

    /// Add an alias to the command
    ///
    /// # Arguments
    /// * `alias` - Command alias
    ///
    /// # Returns
    /// * `Self` - Self for chaining
    pub fn with_alias(mut self, alias: String) -> Self {
        self.aliases.push(alias);
        self
    }
}

impl PluginLoader {
    /// Create a new plugin loader
    ///
    /// # Arguments
    /// * `directory` - Plugin directory
    ///
    /// # Returns
    /// * `Self` - New loader
    pub fn new(directory: PathBuf) -> Self {
        Self { directory }
    }

    /// Discover all plugins in directory
    ///
    /// # Returns
    /// * `Result<Vec<PathBuf>>` - List of plugin paths or error
    pub fn discover_plugins(&self) -> Result<Vec<PathBuf>> {
        todo!("Scan directory for plugin files")
    }

    /// Load plugin from file
    ///
    /// # Arguments
    /// * `path` - Path to plugin file
    ///
    /// # Returns
    /// * `Result<Box<dyn Plugin>>` - Loaded plugin or error
    pub fn load_from_file<P: AsRef<Path>>(&self, _path: P) -> Result<Box<dyn Plugin>> {
        todo!("Load plugin from dynamic library")
    }

    /// Validate plugin file
    ///
    /// # Arguments
    /// * `path` - Path to plugin file
    ///
    /// # Returns
    /// * `Result<bool>` - True if valid
    pub fn validate_plugin<P: AsRef<Path>>(&self, _path: P) -> Result<bool> {
        todo!("Validate plugin file format and signature")
    }
}

impl PluginRegistry {
    /// Create a new plugin registry
    ///
    /// # Returns
    /// * `Self` - New registry
    pub fn new() -> Self {
        Self {
            plugins: HashMap::new(),
        }
    }

    /// Register a plugin
    ///
    /// # Arguments
    /// * `metadata` - Plugin metadata
    pub fn register(&mut self, metadata: PluginMetadata) {
        self.plugins.insert(metadata.name.clone(), metadata);
    }

    /// Unregister a plugin
    ///
    /// # Arguments
    /// * `name` - Plugin name
    pub fn unregister(&mut self, name: &str) {
        self.plugins.remove(name);
    }

    /// Get plugin metadata
    ///
    /// # Arguments
    /// * `name` - Plugin name
    ///
    /// # Returns
    /// * `Option<&PluginMetadata>` - Metadata if registered
    pub fn get(&self, name: &str) -> Option<&PluginMetadata> {
        self.plugins.get(name)
    }

    /// List all registered plugins
    ///
    /// # Returns
    /// * `Vec<&PluginMetadata>` - List of plugin metadata
    pub fn list(&self) -> Vec<&PluginMetadata> {
        self.plugins.values().collect()
    }
}

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

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

    #[test]
    fn test_plugin_metadata() {
        let metadata = PluginMetadata {
            name: "test-plugin".to_string(),
            version: "1.0.0".to_string(),
            author: "Test Author".to_string(),
            description: "A test plugin".to_string(),
            license: Some("MIT".to_string()),
            homepage: Some("https://example.com".to_string()),
        };

        assert_eq!(metadata.name, "test-plugin");
        assert_eq!(metadata.version, "1.0.0");
    }

    #[test]
    fn test_plugin_result_success() {
        let result = PluginResult::success("Test output".to_string());
        assert!(result.success);
        assert_eq!(result.output, "Test output");
        assert!(result.error.is_none());
    }

    #[test]
    fn test_plugin_result_failure() {
        let result = PluginResult::failure("Test error".to_string());
        assert!(!result.success);
        assert!(result.error.is_some());
    }

    #[test]
    fn test_command_registration() {
        let cmd = CommandRegistration::new(
            "test".to_string(),
            "Test command".to_string(),
            "test [args]".to_string(),
        )
        .with_alias("t".to_string());

        assert_eq!(cmd.name, "test");
        assert_eq!(cmd.aliases.len(), 1);
        assert_eq!(cmd.aliases[0], "t");
    }

    #[test]
    fn test_plugin_registry() {
        let mut registry = PluginRegistry::new();

        let metadata = PluginMetadata {
            name: "test".to_string(),
            version: "1.0.0".to_string(),
            author: "Test".to_string(),
            description: "Test plugin".to_string(),
            license: None,
            homepage: None,
        };

        registry.register(metadata.clone());
        assert!(registry.get("test").is_some());

        registry.unregister("test");
        assert!(registry.get("test").is_none());
    }
}
