//! Script execution engine for mongosh
//!
//! This module provides JavaScript script execution functionality:
//! - Loading and parsing JavaScript files
//! - Executing JavaScript code in a sandboxed environment
//! - Binding MongoDB client and database context
//! - Error handling and reporting
//! - Result collection and formatting

use std::fs;
use std::path::Path;

use mongodb::Client;

use crate::error::{Result, ScriptError};

/// Script executor for running JavaScript files and code
pub struct ScriptExecutor {
    /// MongoDB client for database operations
    client: Client,

    /// Current database name
    current_database: String,

    /// Script execution timeout in seconds
    timeout_seconds: Option<u64>,
}

/// Script execution context
pub struct ScriptContext {
    /// MongoDB client
    pub client: Client,

    /// Current database name
    pub database: String,

    /// Global variables available in script
    pub globals: ScriptGlobals,
}

/// Global variables and functions available in scripts
pub struct ScriptGlobals {
    /// Print function for output
    pub print_enabled: bool,

    /// Database object (db)
    pub db_available: bool,

    /// Helper functions available
    pub helpers_enabled: bool,
}

/// Result of script execution
#[derive(Debug, Clone)]
pub struct ScriptResult {
    /// Whether execution succeeded
    pub success: bool,

    /// Script output
    pub output: Vec<String>,

    /// Return value (if any)
    pub return_value: Option<String>,

    /// Execution time in milliseconds
    pub execution_time_ms: u64,

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

/// Script loader for reading and validating script files
pub struct ScriptLoader {
    /// Maximum script size in bytes
    max_size_bytes: usize,
}

impl ScriptExecutor {
    /// Create a new script executor
    ///
    /// # Arguments
    /// * `client` - MongoDB client
    /// * `database` - Current database name
    ///
    /// # Returns
    /// * `Self` - New script executor
    pub fn new(client: Client, database: String) -> Self {
        Self {
            client,
            current_database: database,
            timeout_seconds: Some(300), // 5 minutes default
        }
    }

    /// Execute a JavaScript file
    ///
    /// # Arguments
    /// * `path` - Path to the script file
    ///
    /// # Returns
    /// * `Result<ScriptResult>` - Execution result or error
    pub async fn execute_file<P: AsRef<Path>>(&self, path: P) -> Result<ScriptResult> {
        let loader = ScriptLoader::new();
        let script = loader.load_file(path)?;
        self.execute_string(&script).await
    }

    /// Execute JavaScript code from string
    ///
    /// # Arguments
    /// * `script` - JavaScript code to execute
    ///
    /// # Returns
    /// * `Result<ScriptResult>` - Execution result or error
    pub async fn execute_string(&self, script: &str) -> Result<ScriptResult> {
        todo!("Execute JavaScript code with MongoDB context")
    }

    /// Load script from file
    ///
    /// # Arguments
    /// * `path` - Path to script file
    ///
    /// # Returns
    /// * `Result<String>` - Script content or error
    pub fn load_script<P: AsRef<Path>>(&self, path: P) -> Result<String> {
        let loader = ScriptLoader::new();
        loader.load_file(path)
    }

    /// Set execution timeout
    ///
    /// # Arguments
    /// * `seconds` - Timeout in seconds (None for no timeout)
    pub fn set_timeout(&mut self, seconds: Option<u64>) {
        self.timeout_seconds = seconds;
    }

    /// Get current database name
    ///
    /// # Returns
    /// * `&str` - Database name
    pub fn current_database(&self) -> &str {
        &self.current_database
    }

    /// Set current database
    ///
    /// # Arguments
    /// * `database` - New database name
    pub fn set_database(&mut self, database: String) {
        self.current_database = database;
    }

    /// Create script execution context
    ///
    /// # Returns
    /// * `ScriptContext` - Execution context with MongoDB bindings
    fn create_context(&self) -> ScriptContext {
        ScriptContext {
            client: self.client.clone(),
            database: self.current_database.clone(),
            globals: ScriptGlobals::default(),
        }
    }

    /// Validate script syntax before execution
    ///
    /// # Arguments
    /// * `script` - Script code to validate
    ///
    /// # Returns
    /// * `Result<()>` - Ok if valid, error otherwise
    fn validate_syntax(&self, _script: &str) -> Result<()> {
        todo!("Validate JavaScript syntax before execution")
    }

    /// Execute with timeout
    ///
    /// # Arguments
    /// * `script` - Script to execute
    ///
    /// # Returns
    /// * `Result<ScriptResult>` - Execution result or timeout error
    async fn execute_with_timeout(&self, script: &str) -> Result<ScriptResult> {
        todo!("Execute script with timeout handling")
    }
}

impl ScriptContext {
    /// Create a new script context
    ///
    /// # Arguments
    /// * `client` - MongoDB client
    /// * `database` - Database name
    ///
    /// # Returns
    /// * `Self` - New context
    pub fn new(client: Client, database: String) -> Self {
        Self {
            client,
            database,
            globals: ScriptGlobals::default(),
        }
    }

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

    /// Register global functions and variables
    ///
    /// This sets up the JavaScript environment with MongoDB-specific
    /// functions like db, print, etc.
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    pub fn register_globals(&mut self) -> Result<()> {
        todo!("Register global JavaScript functions and variables")
    }

    /// Bind database object to script environment
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    fn bind_database(&self) -> Result<()> {
        todo!("Bind 'db' object to JavaScript environment")
    }

    /// Bind helper functions
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    fn bind_helpers(&self) -> Result<()> {
        todo!("Bind helper functions like print, printjson, etc.")
    }
}

impl ScriptGlobals {
    /// Create script globals with all features enabled
    pub fn new() -> Self {
        Self {
            print_enabled: true,
            db_available: true,
            helpers_enabled: true,
        }
    }

    /// Create minimal globals (restricted mode)
    pub fn minimal() -> Self {
        Self {
            print_enabled: true,
            db_available: false,
            helpers_enabled: false,
        }
    }
}

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

impl ScriptLoader {
    /// Create a new script loader
    ///
    /// # Returns
    /// * `Self` - New loader with default settings
    pub fn new() -> Self {
        Self {
            max_size_bytes: 10 * 1024 * 1024, // 10 MB default
        }
    }

    /// Load script from file
    ///
    /// # Arguments
    /// * `path` - Path to script file
    ///
    /// # Returns
    /// * `Result<String>` - Script content or error
    pub fn load_file<P: AsRef<Path>>(&self, path: P) -> Result<String> {
        let path = path.as_ref();

        // Check if file exists
        if !path.exists() {
            return Err(ScriptError::FileNotFound(path.display().to_string()).into());
        }

        // Check file size
        let metadata = fs::metadata(path)?;
        if metadata.len() > self.max_size_bytes as u64 {
            return Err(ScriptError::ParseError(format!(
                "Script file too large: {} bytes (max: {} bytes)",
                metadata.len(),
                self.max_size_bytes
            ))
            .into());
        }

        // Read file content
        let content = fs::read_to_string(path)
            .map_err(|e| ScriptError::ParseError(format!("Failed to read script file: {}", e)))?;

        // Validate encoding (basic check)
        if !content.is_ascii() && !Self::is_valid_utf8(&content) {
            return Err(ScriptError::ParseError("Invalid file encoding".to_string()).into());
        }

        Ok(content)
    }

    /// Set maximum script size
    ///
    /// # Arguments
    /// * `bytes` - Maximum size in bytes
    pub fn set_max_size(&mut self, bytes: usize) {
        self.max_size_bytes = bytes;
    }

    /// Validate UTF-8 encoding
    ///
    /// # Arguments
    /// * `content` - Content to validate
    ///
    /// # Returns
    /// * `bool` - True if valid UTF-8
    fn is_valid_utf8(content: &str) -> bool {
        content
            .chars()
            .all(|c| !c.is_control() || c.is_whitespace())
    }

    /// Check if file has valid JavaScript extension
    ///
    /// # Arguments
    /// * `path` - File path to check
    ///
    /// # Returns
    /// * `bool` - True if valid extension
    pub fn has_valid_extension(path: &Path) -> bool {
        if let Some(ext) = path.extension() {
            matches!(
                ext.to_str(),
                Some("js") | Some("javascript") | Some("mongodb")
            )
        } else {
            false
        }
    }
}

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

impl ScriptResult {
    /// Create a successful script result
    ///
    /// # Arguments
    /// * `output` - Script output lines
    /// * `execution_time_ms` - Execution time
    ///
    /// # Returns
    /// * `Self` - Success result
    pub fn success(output: Vec<String>, execution_time_ms: u64) -> Self {
        Self {
            success: true,
            output,
            return_value: None,
            execution_time_ms,
            error: None,
        }
    }

    /// Create a failed script result
    ///
    /// # Arguments
    /// * `error` - Error message
    ///
    /// # Returns
    /// * `Self` - Failure result
    pub fn failure(error: String) -> Self {
        Self {
            success: false,
            output: Vec::new(),
            return_value: None,
            execution_time_ms: 0,
            error: Some(error),
        }
    }

    /// Add output line
    ///
    /// # Arguments
    /// * `line` - Output line to add
    pub fn add_output(&mut self, line: String) {
        self.output.push(line);
    }

    /// Set return value
    ///
    /// # Arguments
    /// * `value` - Return value
    pub fn set_return_value(&mut self, value: String) {
        self.return_value = Some(value);
    }

    /// Get all output as single string
    ///
    /// # Returns
    /// * `String` - Combined output
    pub fn get_output(&self) -> String {
        self.output.join("\n")
    }
}

/// Script runtime for executing JavaScript
///
/// This is a placeholder for the actual JavaScript runtime integration.
/// In a full implementation, this would use a JS engine like QuickJS or Deno.
pub struct ScriptRuntime {
    /// Execution context
    context: ScriptContext,
}

impl ScriptRuntime {
    /// Create a new script runtime
    ///
    /// # Arguments
    /// * `context` - Script execution context
    ///
    /// # Returns
    /// * `Self` - New runtime
    pub fn new(context: ScriptContext) -> Self {
        Self { context }
    }

    /// Initialize the runtime
    ///
    /// # Returns
    /// * `Result<()>` - Success or error
    pub fn initialize(&mut self) -> Result<()> {
        todo!("Initialize JavaScript runtime engine")
    }

    /// Execute JavaScript code
    ///
    /// # Arguments
    /// * `code` - JavaScript code to execute
    ///
    /// # Returns
    /// * `Result<ScriptResult>` - Execution result or error
    pub async fn execute(&mut self, code: &str) -> Result<ScriptResult> {
        todo!("Execute JavaScript code in runtime")
    }

    /// Evaluate expression
    ///
    /// # Arguments
    /// * `expr` - Expression to evaluate
    ///
    /// # Returns
    /// * `Result<String>` - Evaluation result or error
    pub fn evaluate(&mut self, _expr: &str) -> Result<String> {
        todo!("Evaluate JavaScript expression")
    }

    /// Clean up runtime resources
    pub fn cleanup(&mut self) {
        todo!("Clean up JavaScript runtime resources")
    }
}

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

    #[test]
    fn test_script_loader_creation() {
        let loader = ScriptLoader::new();
        assert_eq!(loader.max_size_bytes, 10 * 1024 * 1024);
    }

    #[test]
    fn test_script_loader_valid_extension() {
        use std::path::PathBuf;

        let path = PathBuf::from("test.js");
        assert!(ScriptLoader::has_valid_extension(&path));

        let path = PathBuf::from("test.javascript");
        assert!(ScriptLoader::has_valid_extension(&path));

        let path = PathBuf::from("test.txt");
        assert!(!ScriptLoader::has_valid_extension(&path));
    }

    #[test]
    fn test_script_result_success() {
        let result = ScriptResult::success(vec!["line1".to_string()], 100);
        assert!(result.success);
        assert_eq!(result.execution_time_ms, 100);
        assert!(result.error.is_none());
    }

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

    #[test]
    fn test_script_result_output() {
        let mut result = ScriptResult::success(Vec::new(), 0);
        result.add_output("line1".to_string());
        result.add_output("line2".to_string());
        assert_eq!(result.get_output(), "line1\nline2");
    }

    #[test]
    fn test_script_globals() {
        let globals = ScriptGlobals::new();
        assert!(globals.print_enabled);
        assert!(globals.db_available);
        assert!(globals.helpers_enabled);

        let minimal = ScriptGlobals::minimal();
        assert!(minimal.print_enabled);
        assert!(!minimal.db_available);
        assert!(!minimal.helpers_enabled);
    }
}
