// tools/bash.rs — Execute shell commands
//
// Runs commands through bash -c with a configurable timeout.
// Uses tokio's async process spawning so timeouts actually work.
//
// Processes are tracked in a shared ProcessTracker so the TUI can
// display running commands and the user can kill them (Ctrl+K).

use anyhow::{Context, Result};
use serde::Deserialize;
use serde_json::json;
use std::process::Stdio;
use std::sync::Arc;
use std::time::Instant;
use tokio::io::AsyncReadExt;
use tokio::sync::Mutex;

use crate::types::ToolDef;

#[derive(Deserialize)]
struct Args {
    command: String,
    #[serde(default = "default_timeout")]
    timeout_secs: u64,
}

fn default_timeout() -> u64 { 120 }

/// Info about a running child process, visible to the TUI.
#[derive(Debug, Clone)]
pub struct ProcessInfo {
    pub pid: u32,
    pub command: String,
    pub started: Instant,
}

/// Shared tracker for running child processes. Allows the TUI to
/// display what's running and kill processes by PID.
#[derive(Debug, Clone, Default)]
pub struct ProcessTracker {
    inner: Arc<Mutex<Vec<ProcessInfo>>>,
}

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

    async fn register(&self, pid: u32, command: &str) {
        self.inner.lock().await.push(ProcessInfo {
            pid,
            command: if command.len() > 120 {
                format!("{}...", &command[..120])
            } else {
                command.to_string()
            },
            started: Instant::now(),
        });
    }

    async fn unregister(&self, pid: u32) {
        self.inner.lock().await.retain(|p| p.pid != pid);
    }

    /// Snapshot of currently running processes.
    pub async fn list(&self) -> Vec<ProcessInfo> {
        self.inner.lock().await.clone()
    }

    /// Kill a process by PID. Returns true if the signal was sent.
    pub async fn kill(&self, pid: u32) -> bool {
        // SIGTERM the process group (negative PID kills the group)
        let ret = unsafe { libc::kill(-(pid as i32), libc::SIGTERM) };
        if ret != 0 {
            // Try just the process
            unsafe { libc::kill(pid as i32, libc::SIGTERM) };
        }
        // Don't unregister — let the normal exit path do that
        // so the tool result says "killed by user"
        true
    }
}

pub fn definition() -> ToolDef {
    ToolDef::new(
        "bash",
        "Execute a bash command and return its output. \
         Use for git operations, building, running tests, and other terminal tasks.",
        json!({
            "type": "object",
            "properties": {
                "command": {
                    "type": "string",
                    "description": "The bash command to execute"
                },
                "timeout_secs": {
                    "type": "integer",
                    "description": "Timeout in seconds (default 120)"
                }
            },
            "required": ["command"]
        }),
    )
}

pub async fn run_bash(args: &serde_json::Value, tracker: &ProcessTracker) -> Result<String> {
    let a: Args = serde_json::from_value(args.clone())
        .context("invalid bash arguments")?;
    let command = &a.command;
    let timeout_secs = a.timeout_secs;

    let mut child = tokio::process::Command::new("bash")
        .arg("-c")
        .arg(command)
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        // Create a process group so we can kill the whole tree
        .process_group(0)
        .spawn()
        .with_context(|| format!("Failed to spawn: {}", command))?;

    let pid = child.id().unwrap_or(0);
    tracker.register(pid, command).await;

    // Take ownership of stdout/stderr handles before waiting,
    // so we can still kill the child on timeout.
    let mut stdout_handle = child.stdout.take().unwrap();
    let mut stderr_handle = child.stderr.take().unwrap();

    let timeout = std::time::Duration::from_secs(timeout_secs);

    let work = async {
        let mut stdout_buf = Vec::new();
        let mut stderr_buf = Vec::new();

        let (_, _, status) = tokio::try_join!(
            async { stdout_handle.read_to_end(&mut stdout_buf).await.map_err(anyhow::Error::from) },
            async { stderr_handle.read_to_end(&mut stderr_buf).await.map_err(anyhow::Error::from) },
            async { child.wait().await.map_err(anyhow::Error::from) },
        )?;

        Ok::<_, anyhow::Error>((stdout_buf, stderr_buf, status))
    };

    let result = match tokio::time::timeout(timeout, work).await {
        Ok(Ok((stdout_buf, stderr_buf, status))) => {
            let stdout = String::from_utf8_lossy(&stdout_buf);
            let stderr = String::from_utf8_lossy(&stderr_buf);

            let mut result = String::new();

            if !stdout.is_empty() {
                result.push_str(&stdout);
            }
            if !stderr.is_empty() {
                if !result.is_empty() {
                    result.push('\n');
                }
                result.push_str("STDERR:\n");
                result.push_str(&stderr);
            }

            // Detect if killed by signal (SIGTERM = 15)
            if let Some(signal) = status.code() {
                if signal == -1 || !status.success() {
                    result.push_str(&format!("\nExit code: {}", signal));
                }
            }
            #[cfg(unix)]
            {
                use std::os::unix::process::ExitStatusExt;
                if let Some(sig) = status.signal() {
                    if sig == libc::SIGTERM {
                        result.push_str("\n(killed by user)");
                    }
                }
            }

            if result.is_empty() {
                result = "(no output)".to_string();
            }

            Ok(super::truncate_output(result, 30000))
        }
        Ok(Err(e)) => {
            Err(anyhow::anyhow!("Command failed: {}", e))
        }
        Err(_) => {
            // Timeout — kill the process group
            tracker.kill(pid).await;
            Err(anyhow::anyhow!("Command timed out after {}s: {}", timeout_secs, command))
        }
    };

    tracker.unregister(pid).await;
    result
}