// observe.rs — Shared observation socket + logfile
//
// Two mechanisms:
//   1. Logfile (~/.consciousness/agent-sessions/observe.log) — append-only
//      plain text of the conversation. `poc-agent read` prints new
//      content since last read using a byte-offset cursor file.
//   2. Unix socket — for live streaming (`poc-agent read -f`) and
//      sending input (`poc-agent write <msg>`).
//
// The logfile is the history. The socket is the live wire.

use std::path::PathBuf;
use std::sync::Arc;
use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
use tokio::net::{UnixListener, UnixStream};
use tokio::sync::{broadcast, Mutex};

use crate::agent::ui_channel::UiMessage;

fn format_message(msg: &UiMessage) -> Option<String> {
    match msg {
        UiMessage::TextDelta(text, _) => {
            let t = text.trim_end();
            if t.is_empty() { None } else { Some(t.to_string()) }
        }
        UiMessage::UserInput(text) => Some(format!("\n> {}", text)),
        UiMessage::ToolCall { name, args_summary } => {
            if args_summary.is_empty() {
                Some(format!("[{}]", name))
            } else {
                Some(format!("[{}: {}]", name, args_summary))
            }
        }
        UiMessage::ToolResult { name, result } => {
            let preview: String = result.lines().take(3).collect::<Vec<_>>().join("\n");
            if name.is_empty() {
                Some(format!("  → {}", preview))
            } else {
                Some(format!("  → {}: {}", name, preview))
            }
        }
        UiMessage::DmnAnnotation(text) => Some(text.clone()),
        UiMessage::Info(text) if !text.is_empty() => Some(text.clone()),
        UiMessage::Reasoning(text) => {
            let t = text.trim();
            if t.is_empty() { None } else { Some(format!("(thinking: {})", t)) }
        }
        _ => None,
    }
}

pub type InputSender = tokio::sync::mpsc::UnboundedSender<String>;
pub type InputReceiver = tokio::sync::mpsc::UnboundedReceiver<String>;

pub fn input_channel() -> (InputSender, InputReceiver) {
    tokio::sync::mpsc::unbounded_channel()
}

fn session_dir() -> PathBuf {
    dirs::home_dir().unwrap_or_default().join(".consciousness/agent-sessions")
}

fn socket_path() -> PathBuf { session_dir().join("agent.sock") }
fn log_path() -> PathBuf {
    let dir = dirs::home_dir().unwrap_or_default().join(".consciousness/logs");
    let _ = std::fs::create_dir_all(&dir);
    dir.join("observe.log")
}
fn cursor_path() -> PathBuf { session_dir().join("read-cursor") }

// --- Client commands ---

/// Print new output since last read. With -f, stream live. With block, wait for one response.
pub async fn cmd_read_inner(follow: bool, block: bool, debug: bool) -> anyhow::Result<()> {
    use std::io::{Read, Seek, SeekFrom, Write};

    let log = log_path();
    let cursor = cursor_path();

    if debug {
        eprintln!("log: {}", log.display());
    }

    let offset: u64 = std::fs::read_to_string(&cursor)
        .ok()
        .and_then(|s| s.trim().parse().ok())
        .unwrap_or(0);

    if let Ok(mut f) = std::fs::File::open(&log) {
        let len = f.metadata()?.len();
        if offset < len {
            f.seek(SeekFrom::Start(offset))?;
            let mut buf = String::new();
            f.read_to_string(&mut buf)?;
            print!("{}", buf);
            let _ = std::io::stdout().flush();
        } else if !follow && !block {
            println!("(nothing new)");
        }
        let _ = std::fs::write(&cursor, len.to_string());
    } else if !follow && !block {
        println!("(no log yet — is poc-agent running?)");
        return Ok(());
    }

    if !follow && !block {
        return Ok(());
    }

    // -f or --block: connect to socket for live output
    let sock = socket_path();
    let stream = UnixStream::connect(&sock).await
        .map_err(|e| anyhow::anyhow!(
            "can't connect for live streaming — is poc-agent running? ({})", e
        ))?;

    let (reader, _) = stream.into_split();
    let mut reader = BufReader::new(reader);
    let mut line = String::new();

    loop {
        line.clear();
        match reader.read_line(&mut line).await {
            Ok(0) => break,
            Ok(_) => {
                print!("{}", line);
                let _ = std::io::stdout().lock().flush();
                
                // In blocking mode, stop when we see a new user input
                // Format: "> X: " where X is a speaker (P, K, etc.)
                if block && line.trim_start().starts_with("> ") {
                    let after_gt = line.trim_start().strip_prefix("> ").unwrap_or("");
                    if after_gt.contains(':') {
                        break;
                    }
                }
            }
            Err(_) => break,
        }
    }
    Ok(())
}

/// Send a message to the running agent.
pub async fn cmd_write(message: &str, debug: bool) -> anyhow::Result<()> {
    let sock = socket_path();
    if debug {
        eprintln!("connecting to {}", sock.display());
    }
    let stream = UnixStream::connect(&sock).await
        .map_err(|e| anyhow::anyhow!(
            "can't connect — is poc-agent running? ({})", e
        ))?;

    let (_, mut writer) = stream.into_split();
    writer.write_all(message.as_bytes()).await?;
    writer.write_all(b"\n").await?;
    writer.shutdown().await?;
    Ok(())
}

// --- Server ---

/// Start the observation socket + logfile writer.
pub fn start(
    socket_path_override: PathBuf,
    mut ui_rx: broadcast::Receiver<UiMessage>,
    input_tx: InputSender,
) {
    let _ = std::fs::remove_file(&socket_path_override);

    let listener = UnixListener::bind(&socket_path_override)
        .expect("failed to bind observation socket");

    // Open logfile
    let logfile = Arc::new(Mutex::new(
        std::fs::OpenOptions::new()
            .create(true)
            .append(true)
            .open(log_path())
            .expect("failed to open observe log"),
    ));

    let (line_tx, _) = broadcast::channel::<String>(256);
    let line_tx2 = line_tx.clone();

    // Receive UiMessages → write to logfile + broadcast to socket clients.
    // TextDelta and Reasoning tokens are buffered and flushed on turn
    // boundaries so the log reads as complete messages, not token fragments.
    tokio::spawn(async move {
        let mut text_buf = String::new();
        let mut reasoning_buf = String::new();

        loop {
            match ui_rx.recv().await {
                Ok(msg) => {
                    // Buffer streaming tokens
                    match &msg {
                        UiMessage::TextDelta(text, _) => {
                            text_buf.push_str(text);
                            continue;
                        }
                        UiMessage::Reasoning(text) => {
                            reasoning_buf.push_str(text);
                            continue;
                        }
                        _ => {}
                    }

                    // Flush reasoning buffer as one line
                    if !reasoning_buf.is_empty() {
                        let thinking = format!("(thinking: {})", reasoning_buf.trim());
                        use std::io::Write;
                        let mut f = logfile.lock().await;
                        let _ = writeln!(f, "{}", thinking);
                        let _ = f.flush();
                        let _ = line_tx2.send(thinking);
                        reasoning_buf.clear();
                    }

                    // Flush text buffer
                    if !text_buf.is_empty() {
                        use std::io::Write;
                        let mut f = logfile.lock().await;
                        let _ = writeln!(f, "{}", text_buf);
                        let _ = f.flush();
                        let _ = line_tx2.send(std::mem::take(&mut text_buf));
                    }

                    // Write the non-streaming message
                    if let Some(line) = format_message(&msg) {
                        use std::io::Write;
                        let mut f = logfile.lock().await;
                        let _ = writeln!(f, "{}", line);
                        let _ = f.flush();
                        let _ = line_tx2.send(line);
                    }
                }
                Err(broadcast::error::RecvError::Lagged(_)) => {}
                Err(broadcast::error::RecvError::Closed) => {
                    use std::io::Write;
                    if !reasoning_buf.is_empty() {
                        let thinking = format!("(thinking: {})", reasoning_buf.trim());
                        let mut f = logfile.lock().await;
                        let _ = writeln!(f, "{}", thinking);
                        let _ = f.flush();
                        let _ = line_tx2.send(thinking);
                    }
                    if !text_buf.is_empty() {
                        let mut f = logfile.lock().await;
                        let _ = writeln!(f, "{}", text_buf);
                        let _ = f.flush();
                        let _ = line_tx2.send(text_buf);
                    }
                    break;
                }
            }
        }
    });

    // Accept socket connections (live streaming + input)
    tokio::spawn(async move {
        loop {
            match listener.accept().await {
                Ok((stream, _)) => {
                    let mut line_rx = line_tx.subscribe();
                    let input_tx = input_tx.clone();

                    tokio::spawn(async move {
                        let (reader, mut writer) = stream.into_split();
                        let mut reader = BufReader::new(reader);
                        let mut input_buf = String::new();

                        loop {
                            tokio::select! {
                                biased;

                                result = reader.read_line(&mut input_buf) => {
                                    match result {
                                        Ok(0) | Err(_) => break,
                                        Ok(_) => {
                                            let line = input_buf.trim().to_string();
                                            if !line.is_empty() {
                                                let _ = input_tx.send(line);
                                            }
                                            input_buf.clear();
                                        }
                                    }
                                }

                                result = line_rx.recv() => {
                                    match result {
                                        Ok(line) => {
                                            let data = format!("{}\n", line);
                                            if writer.write_all(data.as_bytes()).await.is_err() {
                                                break;
                                            }
                                            let _ = writer.flush().await;
                                        }
                                        Err(broadcast::error::RecvError::Lagged(_)) => {
                                            let _ = writer.write_all(
                                                b"[some output was dropped]\n"
                                            ).await;
                                        }
                                        Err(broadcast::error::RecvError::Closed) => break,
                                    }
                                }
                            }
                        }
                    });
                }
                Err(_) => break,
            }
        }
    });
}