use color_eyre::eyre::{Result, eyre};
use std::collections::HashMap;
use std::process::Stdio;
use std::sync::Arc;
use parking_lot::RwLock;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::process::{Child, Command};
use tokio::sync::Mutex;
use tokio::time::{timeout, Duration};

const MAX_OUTPUT_LINES: usize = 2000;
const DEFAULT_TIMEOUT_MS: u64 = 120000; // 2 minutes
const COMMAND_DELIMITER: &str = "___OWLEN_CMD_END___";

#[derive(Debug, Clone)]
pub struct CommandOutput {
    pub stdout: String,
    pub stderr: String,
    pub exit_code: i32,
    pub success: bool,
}

pub struct BashSession {
    child: Mutex<Child>,
    last_output: Option<String>,
}

impl BashSession {
    /// Create a new persistent bash session
    pub async fn new() -> Result<Self> {
        let child = Command::new("bash")
            .arg("--norc")
            .arg("--noprofile")
            .stdin(Stdio::piped())
            .stdout(Stdio::piped())
            .stderr(Stdio::piped())
            .kill_on_drop(true)
            .spawn()?;

        // Verify the process started
        if child.stdin.is_none() || child.stdout.is_none() || child.stderr.is_none() {
            return Err(eyre!("Failed to capture bash process stdio"));
        }

        Ok(Self {
            child: Mutex::new(child),
            last_output: None,
        })
    }

    /// Execute a command in the persistent bash session
    ///
    /// # Arguments
    /// * `command` - The bash command to execute
    /// * `timeout_ms` - Optional timeout in milliseconds (default: 2 minutes)
    pub async fn execute(&mut self, command: &str, timeout_ms: Option<u64>) -> Result<CommandOutput> {
        let timeout_duration = Duration::from_millis(timeout_ms.unwrap_or(DEFAULT_TIMEOUT_MS));

        let result = timeout(timeout_duration, self.execute_internal(command)).await;

        match result {
            Ok(output) => {
                // Store the output for potential retrieval via BashOutput tool
                let combined = format!("{}{}", output.as_ref().map(|o| o.stdout.as_str()).unwrap_or(""),
                                                output.as_ref().map(|o| o.stderr.as_str()).unwrap_or(""));
                self.last_output = Some(combined);
                output
            },
            Err(_) => Err(eyre!("Command timed out after {}ms", timeout_duration.as_millis())),
        }
    }

    async fn execute_internal(&mut self, command: &str) -> Result<CommandOutput> {
        let mut child = self.child.lock().await;

        // Take ownership of stdio handles
        let mut stdin = child.stdin.take().ok_or_else(|| eyre!("No stdin"))?;
        let stdout = child.stdout.take().ok_or_else(|| eyre!("No stdout"))?;
        let stderr = child.stderr.take().ok_or_else(|| eyre!("No stderr"))?;

        // Write command with delimiter and exit code capture
        let full_command = format!(
            "{}\necho $? > /tmp/owlen_exit_code_$$.tmp\necho '{}'\n",
            command, COMMAND_DELIMITER
        );
        stdin.write_all(full_command.as_bytes()).await?;
        stdin.flush().await?;

        // Read stdout until delimiter
        let mut stdout_reader = BufReader::new(stdout);
        let mut stdout_lines = Vec::new();
        let mut line = String::new();

        loop {
            line.clear();
            let n = stdout_reader.read_line(&mut line).await?;
            if n == 0 {
                return Err(eyre!("Bash process terminated unexpectedly"));
            }

            if line.trim() == COMMAND_DELIMITER {
                break;
            }

            stdout_lines.push(line.clone());

            // Truncate if too many lines
            if stdout_lines.len() > MAX_OUTPUT_LINES {
                stdout_lines.push("<<<...output truncated...>>>\n".to_string());
                break;
            }
        }

        // Read stderr (non-blocking, best effort)
        let mut stderr_reader = BufReader::new(stderr);
        let mut stderr_lines = Vec::new();
        let mut stderr_line = String::new();

        // Try to read stderr without blocking indefinitely
        while let Ok(result) = timeout(Duration::from_millis(100), stderr_reader.read_line(&mut stderr_line)).await {
            match result {
                Ok(n) if n > 0 => {
                    stderr_lines.push(stderr_line.clone());
                    stderr_line.clear();

                    if stderr_lines.len() > MAX_OUTPUT_LINES {
                        stderr_lines.push("<<<...stderr truncated...>>>\n".to_string());
                        break;
                    }
                }
                _ => break,
            }
        }

        // Read exit code
        let exit_code_cmd = "cat /tmp/owlen_exit_code_$$.tmp 2>/dev/null; rm -f /tmp/owlen_exit_code_$$.tmp\n";
        stdin.write_all(exit_code_cmd.as_bytes()).await?;
        stdin.flush().await?;

        let mut exit_line = String::new();
        stdout_reader.read_line(&mut exit_line).await?;

        let exit_code: i32 = exit_line.trim().parse().unwrap_or(0);

        // Restore stdio handles
        child.stdin = Some(stdin);
        child.stdout = Some(stdout_reader.into_inner());
        child.stderr = Some(stderr_reader.into_inner());

        Ok(CommandOutput {
            stdout: stdout_lines.join(""),
            stderr: stderr_lines.join(""),
            exit_code,
            success: exit_code == 0,
        })
    }

    /// Close the bash session
    pub async fn close(self) -> Result<()> {
        let mut child = self.child.into_inner();

        if let Some(mut stdin) = child.stdin.take() {
            let _ = stdin.write_all(b"exit\n").await;
            let _ = stdin.flush().await;
        }

        let _ = child.wait().await?;
        Ok(())
    }
}

/// Manages background bash shells by ID
#[derive(Clone, Default)]
pub struct ShellManager {
    shells: Arc<RwLock<HashMap<String, BashSession>>>,
}

impl ShellManager {
    pub fn new() -> Self {
        Self::default()
    }

    /// Start a new background shell, returns shell ID
    pub async fn start_shell(&self) -> Result<String> {
        let id = uuid::Uuid::new_v4().to_string();
        let session = BashSession::new().await?;
        self.shells.write().insert(id.clone(), session);
        Ok(id)
    }

    /// Execute command in background shell
    pub async fn execute(&self, shell_id: &str, command: &str, timeout: Option<Duration>) -> Result<CommandOutput> {
        // We need to handle this carefully to avoid holding the lock across await
        // First check if the shell exists and clone what we need
        let exists = self.shells.read().contains_key(shell_id);
        if !exists {
            return Err(eyre!("Shell not found: {}", shell_id));
        }

        // For now, we need to use a more complex approach since BashSession contains async operations
        // We'll execute and then update in a separate critical section
        let timeout_ms = timeout.map(|d| d.as_millis() as u64);

        // Take temporary ownership for execution
        let mut session = {
            let mut shells = self.shells.write();
            shells.remove(shell_id)
                .ok_or_else(|| eyre!("Shell not found: {}", shell_id))?
        };

        // Execute without holding the lock
        let result = session.execute(command, timeout_ms).await;

        // Put the session back
        self.shells.write().insert(shell_id.to_string(), session);

        result
    }

    /// Get output from a shell (BashOutput tool)
    pub fn get_output(&self, shell_id: &str) -> Result<Option<String>> {
        let shells = self.shells.read();
        let session = shells.get(shell_id)
            .ok_or_else(|| eyre!("Shell not found: {}", shell_id))?;
        // Return any buffered output
        Ok(session.last_output.clone())
    }

    /// Kill a shell (KillShell tool)
    pub fn kill_shell(&self, shell_id: &str) -> Result<()> {
        let mut shells = self.shells.write();
        if shells.remove(shell_id).is_some() {
            Ok(())
        } else {
            Err(eyre!("Shell not found: {}", shell_id))
        }
    }

    /// List active shells
    pub fn list_shells(&self) -> Vec<String> {
        self.shells.read().keys().cloned().collect()
    }
}

/// Start a background bash command, returns shell ID
pub async fn run_background(manager: &ShellManager, command: &str) -> Result<String> {
    let shell_id = manager.start_shell().await?;
    // Execute in background (non-blocking)
    tokio::spawn({
        let manager = manager.clone();
        let command = command.to_string();
        let shell_id = shell_id.clone();
        async move {
            let _ = manager.execute(&shell_id, &command, None).await;
        }
    });
    Ok(shell_id)
}

/// Get output from background shell (BashOutput tool)
pub fn bash_output(manager: &ShellManager, shell_id: &str) -> Result<String> {
    manager.get_output(shell_id)?
        .ok_or_else(|| eyre!("No output available"))
}

/// Kill a background shell (KillShell tool)
pub fn kill_shell(manager: &ShellManager, shell_id: &str) -> Result<String> {
    manager.kill_shell(shell_id)?;
    Ok(format!("Shell {} terminated", shell_id))
}

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

    #[tokio::test]
    async fn can_create_session() {
        let session = BashSession::new().await;
        assert!(session.is_ok());
    }
}