use std::process::Command;
use std::io::{BufRead, BufReader};
use std::time::{Duration, Instant};
use std::thread;
use std::sync::{Arc, Mutex};
use std::sync::mpsc;

/// Configuration for Python command execution
pub struct PythonExecutorConfig {
    pub timeout_seconds: u64,
    pub working_directory: Option<std::path::PathBuf>,
}

impl Default for PythonExecutorConfig {
    fn default() -> Self {
        Self {
            timeout_seconds: 600, // 10 minutes default
            working_directory: None,
        }
    }
}

/// Execute a Python command with the given arguments
/// 
/// This function handles:
/// - Multiple Python command attempts (python, python3, py)
/// - UTF-8 encoding setup
/// - Concurrent stdout/stderr reading
/// - JSON-RPC message parsing
/// - Timeout handling
/// - Detailed error reporting
pub async fn execute_python_command(
    _app: tauri::AppHandle, 
    args: &[String],
    config: Option<PythonExecutorConfig>
) -> Result<String, String> {
    let config = config.unwrap_or_default();
    
    println!("Executing Python command with args: {:?}", args);

    // Get project root directory
    let current_dir = std::env::current_dir()
        .map_err(|e| format!("Failed to get current directory: {}", e))?;

    let project_root = if let Some(working_dir) = config.working_directory {
        working_dir
    } else if current_dir.ends_with("src-tauri") {
        current_dir.parent().unwrap_or(&current_dir).to_path_buf()
    } else {
        current_dir
    };

    println!("Working directory: {:?}", project_root);

    // Try multiple Python commands in order of preference
    let python_commands = if cfg!(target_os = "windows") {
        vec!["python", "python3", "py"]
    } else {
        vec!["python3", "python"]
    };

    let mut child = None;
    let mut last_error = String::new();

    for python_cmd in python_commands {
        println!("Trying Python command: {}", python_cmd);
        let mut cmd = Command::new(python_cmd);
        cmd.current_dir(&project_root);
        cmd.args(args);
        cmd.stdout(std::process::Stdio::piped());
        cmd.stderr(std::process::Stdio::piped());

        // Set environment variables for consistent encoding
        cmd.env("PYTHONIOENCODING", "utf-8");
        cmd.env("PYTHONUNBUFFERED", "1");

        // On Windows, ensure UTF-8 console output
        if cfg!(target_os = "windows") {
            cmd.env("PYTHONUTF8", "1");
        }

        match cmd.spawn() {
            Ok(process) => {
                println!("Successfully started Python process with: {}", python_cmd);
                child = Some(process);
                break;
            }
            Err(e) => {
                last_error = format!("Failed to start {} process: {}", python_cmd, e);
                println!("{}", last_error);
                continue;
            }
        }
    }

    let mut child = child.ok_or_else(|| {
        format!("Failed to start Python process with any command. Last error: {}", last_error)
    })?;

    let stdout = child.stdout.take().unwrap();
    let stderr = child.stderr.take().unwrap();

    // Use channels for concurrent reading
    let (stdout_tx, _stdout_rx) = mpsc::channel();
    let (stderr_tx, _stderr_rx) = mpsc::channel();
    let (result_tx, result_rx) = mpsc::channel();

    let progress_messages = Arc::new(Mutex::new(Vec::new()));
    let error_messages = Arc::new(Mutex::new(Vec::new()));
    let final_result = Arc::new(Mutex::new(None::<String>));

    // Spawn thread for reading stdout
    let progress_messages_clone = Arc::clone(&progress_messages);
    let final_result_clone = Arc::clone(&final_result);
    thread::spawn(move || {
        let mut reader = BufReader::new(stdout);
        let mut buffer = Vec::new();

        // Read raw bytes and handle encoding issues
        loop {
            buffer.clear();
            match reader.read_until(b'\n', &mut buffer) {
                Ok(0) => break, // EOF
                Ok(_) => {
                    // Convert bytes to string, handling invalid UTF-8
                    let line = String::from_utf8_lossy(&buffer);
                    let line = line.trim_end_matches('\n').trim_end_matches('\r');

                    if line.is_empty() {
                        continue;
                    }
                    println!("Python stdout: {}", line);

                    // Parse JSON-RPC messages
                    if line.starts_with("JSONRPC:") {
                        let json_str = &line[8..]; // Remove "JSONRPC:" prefix
                        if let Ok(json_value) = serde_json::from_str::<serde_json::Value>(json_str) {
                            if let Some(method) = json_value.get("method") {
                                if method == "progress" {
                                    if let Ok(mut messages) = progress_messages_clone.lock() {
                                        messages.push(json_str.to_string());
                                    }
                                    println!("Progress: {}", json_str);
                                }
                            } else if json_value.get("result").is_some() || json_value.get("error").is_some() {
                                // This is a final result or error response
                                if let Ok(mut result) = final_result_clone.lock() {
                                    *result = Some(json_str.to_string());
                                }
                                println!("JSON-RPC result found: {}", json_str);
                            }
                        }
                    } else if line.trim().starts_with('{') && line.trim().ends_with('}') {
                        // Fallback: try to parse as direct JSON result
                        if let Ok(json_value) = serde_json::from_str::<serde_json::Value>(line.trim()) {
                            // Check if this looks like a final result (has status field)
                            if json_value.get("status").is_some() {
                                if let Ok(mut result) = final_result_clone.lock() {
                                    *result = Some(line.trim().to_string());
                                }
                                println!("Direct JSON result: {}", line.trim());
                            }
                        }
                    } else {
                        println!("Python other: {}", line);
                    }

                    if stdout_tx.send(line.to_string()).is_err() {
                        break;
                    }
                }
                Err(e) => {
                    println!("Error reading stdout: {}", e);
                    break;
                }
            }
        }
    });

    // Spawn thread for reading stderr
    let error_messages_clone = Arc::clone(&error_messages);
    thread::spawn(move || {
        let mut reader = BufReader::new(stderr);
        let mut buffer = Vec::new();

        // Read raw bytes and handle encoding issues
        loop {
            buffer.clear();
            match reader.read_until(b'\n', &mut buffer) {
                Ok(0) => break, // EOF
                Ok(_) => {
                    // Convert bytes to string, handling invalid UTF-8
                    let line = String::from_utf8_lossy(&buffer);
                    let line = line.trim_end_matches('\n').trim_end_matches('\r');

                    if line.is_empty() {
                        continue;
                    }

                    println!("Python stderr: {}", line);
                    if let Ok(mut messages) = error_messages_clone.lock() {
                        messages.push(line.to_string());
                    }
                    if stderr_tx.send(line.to_string()).is_err() {
                        break;
                    }
                }
                Err(e) => {
                    println!("Error reading stderr: {}", e);
                    break;
                }
            }
        }
    });

    // Spawn thread to wait for process completion
    thread::spawn(move || {
        match child.wait() {
            Ok(status) => {
                let _ = result_tx.send(Ok(status));
            }
            Err(e) => {
                let _ = result_tx.send(Err(format!("Failed to wait for process: {}", e)));
            }
        }
    });

    // Wait for process to complete with timeout
    println!("Waiting for Python process to complete...");
    let timeout_duration = Duration::from_secs(config.timeout_seconds);
    let start_time = Instant::now();

    let exit_status = loop {
        match result_rx.try_recv() {
            Ok(Ok(status)) => break status,
            Ok(Err(e)) => return Err(e),
            Err(mpsc::TryRecvError::Empty) => {
                if start_time.elapsed() > timeout_duration {
                    return Err(format!("Python process timed out after {} seconds", config.timeout_seconds));
                }
                thread::sleep(Duration::from_millis(100));
                continue;
            }
            Err(mpsc::TryRecvError::Disconnected) => {
                return Err("Process monitoring thread disconnected".to_string());
            }
        }
    };

    println!("Python process terminated with code: {:?}", exit_status.code());

    // Extract final results from shared state
    let final_result_value = {
        final_result.lock().unwrap().clone()
    };
    let progress_messages_value = {
        progress_messages.lock().unwrap().clone()
    };
    let error_messages_value = {
        error_messages.lock().unwrap().clone()
    };

    // Return the final result if we found one
    if let Some(result) = final_result_value {
        println!("Extracted JSON-RPC result: {}", result);
        return Ok(result);
    }

    // If no JSON-RPC result found, provide detailed error information
    if exit_status.success() {
        // Process succeeded but no output - this is unusual
        let error_msg = if progress_messages_value.is_empty() {
            "Python script completed successfully but produced no output"
        } else {
            "Python script completed but did not return a valid JSON result"
        };
        Err(error_msg.to_string())
    } else {
        // Process failed - provide detailed error based on exit code
        let error_msg = if let Some(code) = exit_status.code() {
            let unsigned_code = code as u32;
            match code {
                1 => "Python script failed with general error. Check if all dependencies are installed.".to_string(),
                120 => "Python module import failed or function not supported. This may be due to missing dependencies or incompatible Python environment. Please run the environment test first.".to_string(),
                -1073741510 => "Python process was terminated by antivirus or system security. Please add the application to your antivirus whitelist.".to_string(),
                _ if unsigned_code == 3221225786 => "Python process was terminated by antivirus or system security. Please add the application to your antivirus whitelist.".to_string(),
                _ => format!("Python script failed with exit code: {}. This may indicate a system or environment issue.", code)
            }
        } else {
            "Python process was killed by external signal. This may be caused by antivirus software or system security policies.".to_string()
        };

        // Include any error output we captured
        let mut full_error = error_msg;

        if !progress_messages_value.is_empty() {
            full_error.push_str(&format!("\n\nLast stdout: {}", progress_messages_value.join("\n")));
        }

        if !error_messages_value.is_empty() {
            full_error.push_str(&format!("\n\nStderr: {}", error_messages_value.join("\n")));
        }

        Err(full_error)
    }
}