//! Attach mode — TUI-only client that connects to an existing daemon session
//! over a Unix socket, forwarding key events and rendering state updates.
//!
//! Flow: `run_attach(session_id)` resolves the daemon's socket path from
//! the store → `setup_attach_client()` connects and enters raw mode →
//! enters a render loop: polls for local terminal events (key/resize/paste/
//! scroll) → forwards them as `ClientRequest`s to the daemon via IPC →
//! receives a `DaemonFrame` reply → `handle_daemon_frame()` /
//! `apply_client_update()` applies the state snapshot onto a local
//! `AppStateRest` mirror → `draw()` renders the TUI → on quit,
//! sends `ClientRequest::Close`, cleans up terminal, and saves settings.
//!
//! The client has no agent logic — it is a pure render frontend.

use std::io::{self};

use anyhow::Result;
use crossterm::execute;
use crossterm::terminal::{
    disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen,
};
use ratatui::backend::CrosstermBackend;
use ratatui::layout::{Constraint, Direction, Layout};
use ratatui::widgets::{Block, Borders, Paragraph, Wrap};
use ratatui::Terminal;
use zesdex_domain::SettingsRepository;
use zesdex_infrastructure::ipc::client::IpcClient;
use zesdex_infrastructure::ipc::protocol::{ClientRequest, DaemonFrame, StatePayload};
use zesdex_infrastructure::Toast;
use zesdex_infrastructure::ToastKind;

use crate::key_code::key_code_to_action;
use crate::state::{AppStateRest, ChatMessageDisplay, Overlay, RoleWrapper};

// ---------------------------------------------------------------------------
// apply_client_update — apply a StatePayload onto the local AppStateRest
// ---------------------------------------------------------------------------

/// Apply a `StatePayload` received from the daemon onto the client's
/// local `AppStateRest`, so the attach-mode TUI can render it.
///
/// Flow: copy scalar fields directly → rebuild the transcript cache from
/// `MessageEntry`s (mapping role strings back to role variants) →
/// resolve the overlay name string to an `Overlay` variant → rebuild
/// toasts from `ToastEntry`s.
///
/// Why: unrecognised role/overlay/toast-kind strings fall back to a safe
/// default (`User`, `Overlay::None`, `ToastKind::Info`) rather than
/// panicking, so a protocol/version mismatch degrades gracefully.
fn apply_client_update(state: &mut AppStateRest, payload: StatePayload) {
    tracing::debug!("applying state update from daemon");
    state.session_id = payload.session_id;
    state.dirty = payload.dirty;

    state.transcript_cache.messages = payload
        .messages
        .into_iter()
        .map(|m| ChatMessageDisplay {
            role: match m.role.as_str() {
                "Assistant" => RoleWrapper::Assistant,
                "System" => RoleWrapper::System,
                "Tool" => RoleWrapper::Tool,
                _ => RoleWrapper::User,
            },
            content: m.content,
            timestamp: m.timestamp,
        })
        .collect();
    state.transcript_cache.dirty = true;

    state.misc.overlay = match payload.overlay.as_deref() {
        Some("Help") => Overlay::Help,
        Some("Settings") => Overlay::Settings,
        Some("Bash") => Overlay::Bash,
        Some("QuitConfirm") => Overlay::QuitConfirm,
        Some("KeyInput") => Overlay::KeyInput,
        Some("Editor") => Overlay::Editor,
        Some("Effort") => Overlay::Effort,
        Some("Mcp") => Overlay::Mcp,
        Some("Todo") => Overlay::Todo,
        Some("Rewind") => Overlay::Rewind,
        Some("Learning") => Overlay::Learning,
        Some("Usage") => Overlay::Usage,
        Some("Loading") => Overlay::Loading,
        Some("ModelSelector") => Overlay::ModelSelector,
        Some("ClearConfirm") => Overlay::ClearConfirm,
        _ => Overlay::None,
    };

    state.misc.toasts = payload
        .toasts
        .into_iter()
        .map(|t| Toast {
            kind: match t.kind.as_str() {
                "Success" => ToastKind::Success,
                "Warning" => ToastKind::Warning,
                "Error" => ToastKind::Error,
                "Lesson" => ToastKind::Lesson,
                _ => ToastKind::Info,
            },
            message: t.message,
            created_at: t.created_at,
            lifetime_ms: t.lifetime_ms,
        })
        .collect();

    state.input.buffer = payload.input_buffer;
    state.input.cursor = payload.input_cursor;
}

// ---------------------------------------------------------------------------
// setup_attach_client — connect to daemon and set up terminal
// ---------------------------------------------------------------------------

/// Set up the IPC client connection, terminal, and initial state for attach mode.
///
/// Flow: resolve socket path → connect → enable raw/alt mode → create state.
///
/// Return: (client, terminal, `client_state`) on success.
fn setup_attach_client(
    session_id: &str,
) -> Result<(
    IpcClient,
    Terminal<CrosstermBackend<io::Stdout>>,
    AppStateRest,
)> {
    tracing::debug!("setting up attach client for session {session_id}");
    let store = zesdex_infrastructure::Store::new();
    let socket_path = store
        .base_dir
        .join("run")
        .join(format!("{session_id}.sock"));
    let addr = socket_path.to_string_lossy().to_string();
    let client = IpcClient::connect_unix(&addr)?;

    enable_raw_mode()?;
    let mut stdout = io::stdout();
    execute!(stdout, EnterAlternateScreen)?;
    execute!(stdout, crossterm::event::EnableBracketedPaste)?;
    execute!(stdout, crossterm::event::EnableMouseCapture)?;
    let backend = CrosstermBackend::new(stdout);
    let mut terminal = Terminal::new(backend)?;
    terminal.clear()?;

    let workspace_roots = vec![std::env::current_dir()?];
    let session_dir = store.base_dir.join("sessions").join(session_id);
    std::fs::create_dir_all(&session_dir)?;
    let mut client_state = AppStateRest::new(workspace_roots, &session_dir, store.memory_dir);
    client_state.session_id = session_id.to_string();

    Ok((client, terminal, client_state))
}

// ---------------------------------------------------------------------------
// handle_daemon_frame — process a single DaemonFrame from the daemon
// ---------------------------------------------------------------------------

/// Process a single daemon frame from the IPC channel, updating state accordingly.
fn handle_daemon_frame(client_state: &mut AppStateRest, frame: Option<DaemonFrame>) {
    tracing::debug!("received daemon frame");
    match frame {
        Some(DaemonFrame::StateUpdate(payload)) => {
            apply_client_update(client_state, *payload);
        }
        Some(DaemonFrame::StreamToken(_token)) => {}
        Some(DaemonFrame::SystemNote { kind: _, message }) => {
            client_state.push_toast(Toast::new(ToastKind::Info, message));
        }
        Some(DaemonFrame::ClipboardCopy(text)) => {
            let _ = zesdex_infrastructure::utils::write_osc52(&mut io::stdout(), &text);
            client_state.push_toast(Toast::new(
                ToastKind::Success,
                "Copied to clipboard".to_string(),
            ));
        }
        Some(DaemonFrame::Closed) | None => {
            client_state.quit = true;
        }
    }
}

// ---------------------------------------------------------------------------
// draw — minimal TUI render function
// ---------------------------------------------------------------------------

/// Render the current application state onto the terminal.
///
/// Layout:
/// - Top: title bar with session ID and overlay status
/// - Middle: transcript message list (scrollable)
/// - Bottom: input line with cursor
/// - Overlay name shown when an overlay is active
fn draw(frame: &mut ratatui::Frame, state: &AppStateRest) {
    let area = frame.area();

    // Vertical layout: main content + input line
    let chunks = Layout::default()
        .direction(Direction::Vertical)
        .constraints([
            Constraint::Min(1),    // main content (transcript + toasts)
            Constraint::Length(3), // input line
        ])
        .split(area);

    // ── Main content area ───────────────────────────────────────────────
    let title = format!(
        " Zesdex — {} {}",
        &state.session_id[..state.session_id.len().min(8)],
        if state.misc.overlay.is_active() {
            format!("[{}]", state.misc.overlay)
        } else {
            String::new()
        }
    );

    let mut content_lines: Vec<String> = Vec::new();

    // Show toasts at the top if present.
    for toast in &state.misc.toasts {
        content_lines.push(format!("[{:?}] {}", toast.kind, toast.message));
    }

    // Show active overlay name.
    if state.misc.overlay.is_active() {
        content_lines.push(String::new());
        content_lines.push(format!("=== {} ===", state.misc.overlay));
        content_lines.push(String::new());
    }

    // Transcript messages.
    for msg in &state.transcript_cache.messages {
        let prefix = match msg.role {
            RoleWrapper::User => "You",
            RoleWrapper::Assistant => "AI",
            RoleWrapper::System => "System",
            RoleWrapper::Tool => "Tool",
        };
        content_lines.push(format!("{}: {}", prefix, msg.content));
    }

    // Scroll offset indicator.
    if state.scroll.offset > 0 {
        content_lines.push(format!("--- scrolled up {} lines ---", state.scroll.offset));
    }

    let content = content_lines.join("\n");

    let main_block = Block::default().title(title).borders(Borders::TOP);
    let paragraph = Paragraph::new(content)
        .block(main_block)
        .wrap(Wrap { trim: false })
        .scroll((state.scroll.offset as u16, 0));
    frame.render_widget(paragraph, chunks[0]);

    // ── Input line ──────────────────────────────────────────────────────
    let input_block = Block::default().borders(Borders::TOP);
    let input_display = if state.input.buffer.is_empty() {
        "Type a message...".to_string()
    } else {
        state.input.buffer.clone()
    };
    let input_paragraph = Paragraph::new(input_display).block(input_block);
    frame.render_widget(input_paragraph, chunks[1]);

    // Set cursor position for the input line.
    use ratatui::layout::Position;
    frame.set_cursor_position(Position::new(
        chunks[1].x + state.input.cursor as u16 + 1,
        chunks[1].y + 1,
    ));
}

// ---------------------------------------------------------------------------
// run_attach — main attach-mode entry point
// ---------------------------------------------------------------------------

/// Run zesdex as a TUI-only client attached to an existing daemon session.
///
/// Flow: connect to the daemon's Unix socket → enter raw mode/alternate
/// screen → build a local `AppStateRest` mirror (only used for rendering
/// and toast/overlay bookkeeping, not agent logic) → loop: poll for a
/// terminal event (key/resize) and forward it as a `ClientRequest`, or
/// send a `Tick` if idle → read the daemon's `DaemonFrame` reply and
/// apply it via `apply_client_update` → redraw → exit when the daemon
/// closes or the user quits (sending `ClientRequest::Close` first).
///
/// Why: Ctrl+C is intercepted locally to quit the client without going
/// through the daemon, since the daemon has no notion of "this client
/// wants to leave" beyond the explicit `Close` request.
pub fn run_attach(session_id: &str) -> Result<()> {
    use crossterm::event::{Event, KeyCode, KeyEventKind, KeyModifiers, MouseEventKind};

    let (client, mut terminal, mut client_state) = setup_attach_client(session_id)?;
    let _rt = tokio::runtime::Runtime::new()?;

    loop {
        if client_state.quit {
            let _ = client.send(&ClientRequest::Close);
            break;
        }

        let now_ms = chrono::Utc::now().timestamp_millis();
        client_state.misc.drain_expired_toasts(now_ms);

        if crossterm::event::poll(std::time::Duration::from_millis(50))? {
            match crossterm::event::read()? {
                Event::Key(key) => {
                    if key.kind == KeyEventKind::Press || key.kind == KeyEventKind::Repeat {
                        let ctrl = key.modifiers.contains(KeyModifiers::CONTROL);
                        let alt = key.modifiers.contains(KeyModifiers::ALT);
                        let shift = key.modifiers.contains(KeyModifiers::SHIFT);

                        if key.code == KeyCode::Char('c') && ctrl {
                            client_state.quit = true;
                            continue;
                        }

                        if let Some(key_action) = key_code_to_action(key.code) {
                            client.send(&ClientRequest::KeyPress {
                                key: key_action,
                                ctrl,
                                alt,
                                shift,
                            })?;
                        }
                    }
                }
                Event::Paste(text) => {
                    client.send(&ClientRequest::Paste(text))?;
                }
                Event::Resize(w, h) => {
                    client.send(&ClientRequest::Resize(w, h))?;
                }
                Event::Mouse(mouse_event) => {
                    if mouse_event.kind == MouseEventKind::ScrollUp {
                        client.send(&ClientRequest::ScrollUp)?;
                    } else if mouse_event.kind == MouseEventKind::ScrollDown {
                        client.send(&ClientRequest::ScrollDown)?;
                    }
                }
                _ => {}
            }
        } else {
            client.send(&ClientRequest::Tick)?;
        }

        handle_daemon_frame(&mut client_state, client.receive::<DaemonFrame>()?);

        terminal.draw(|f| {
            draw(f, &client_state);
        })?;
    }

    let _ = execute!(io::stdout(), crossterm::event::DisableBracketedPaste);
    let _ = execute!(io::stdout(), crossterm::event::DisableMouseCapture);
    let _ = execute!(io::stdout(), LeaveAlternateScreen);
    let _ = disable_raw_mode();

    let _ = zesdex_infrastructure::persistence::JsonSettingsRepository::new()
        .save(&client_state.store_base_dir(), &client_state.settings);

    Ok(())
}