mod paths;

use std::fmt::Write as _;
use std::path::Path;
use std::sync::Arc;

use anyhow::{Context, bail};
use matrix_sdk::{
    Client, Room, RoomState,
    authentication::matrix::MatrixSession,
    config::SyncSettings,
    ruma::{
        OwnedEventId, OwnedRoomId, OwnedUserId, UserId,
        api::client::{
            filter::FilterDefinition, receipt::create_receipt::v3::ReceiptType as CreateReceiptType,
        },
        events::{
            receipt::ReceiptThread,
            room::{
                member::StrippedRoomMemberEvent,
                message::{MessageType, OriginalSyncRoomMessageEvent, RoomMessageEventContent},
            },
        },
    },
};
use serde::{Deserialize, Serialize};
use tokio::fs;
use tokio::sync::Mutex;
use tracing_subscriber::EnvFilter;

#[derive(Debug, Deserialize)]
struct Config {
    homeserver: String,
    username: String,
    password: String,
    rate_limit_per_min: Option<u32>,
    model: Option<String>,
    max_history: Option<usize>,
}

const DEFAULT_MODEL: &str = "claude-sonnet-4-6";
const DEFAULT_MAX_HISTORY: usize = 20;

#[derive(Debug, Serialize, Deserialize)]
struct PersistedSession {
    homeserver: String,
    db_path: std::path::PathBuf,
    user_session: MatrixSession,
    #[serde(skip_serializing_if = "Option::is_none")]
    sync_token: Option<String>,
}

#[derive(Clone, Debug)]
enum TimelineItem {
    Message {
        event_id: OwnedEventId,
        sender: OwnedUserId,
        body: String,
        is_self: bool,
        /// Unix seconds. 0 if unknown.
        ts: i64,
        in_reply_to: Option<OwnedEventId>,
    },
    Reaction {
        sender: OwnedUserId,
        target_event_id: OwnedEventId,
        key: String,
        is_self: bool,
        ts: i64,
    },
}

impl TimelineItem {
    fn ts(&self) -> i64 {
        match self {
            TimelineItem::Message { ts, .. } | TimelineItem::Reaction { ts, .. } => *ts,
        }
    }

    fn event_id(&self) -> Option<&OwnedEventId> {
        match self {
            TimelineItem::Message { event_id, .. } => Some(event_id),
            TimelineItem::Reaction { .. } => None,
        }
    }

    fn sender(&self) -> &OwnedUserId {
        match self {
            TimelineItem::Message { sender, .. } | TimelineItem::Reaction { sender, .. } => sender,
        }
    }

    fn is_self(&self) -> bool {
        match self {
            TimelineItem::Message { is_self, .. } | TimelineItem::Reaction { is_self, .. } => {
                *is_self
            }
        }
    }
}

struct DaemonState {
    own_user_id: OwnedUserId,
    /// Per-room: the latest event_id that's been "shown" to Claude. Events
    /// after this are "new" on the next invocation. Cleared on daemon restart.
    last_shown: std::collections::HashMap<OwnedRoomId, OwnedEventId>,
    pending_rooms: Vec<OwnedRoomId>,
    rate_budget: u32,
    rate_limit_per_min: u32,
    last_rate_reset: std::time::Instant,
    model: String,
    max_history: usize,
}

const DEFAULT_RATE_LIMIT_PER_MIN: u32 = 1;

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    tracing_subscriber::fmt()
        .with_env_filter(EnvFilter::from_default_env())
        .init();

    tracing::info!("damocles-daemon starting");

    let state_dir = paths::state_dir();
    fs::create_dir_all(&state_dir).await?;
    fs::create_dir_all(paths::identity_dir()).await?;
    fs::create_dir_all(state_dir.join("rooms")).await?;
    fs::create_dir_all(state_dir.join("people")).await?;

    let session_file = paths::session_path();
    let db_path = paths::db_path();

    let config = load_config().await?;
    let rate_limit_per_min = config
        .rate_limit_per_min
        .unwrap_or(DEFAULT_RATE_LIMIT_PER_MIN);
    let model = config
        .model
        .clone()
        .unwrap_or_else(|| DEFAULT_MODEL.to_owned());
    let max_history = config.max_history.unwrap_or(DEFAULT_MAX_HISTORY);

    let (client, sync_token) = if session_file.exists() {
        restore_session(&session_file).await?
    } else {
        (login(&config, &db_path, &session_file).await?, None)
    };

    let own_user_id = client.user_id().context("not logged in")?.to_owned();
    tracing::info!(
        user = %own_user_id,
        rate_limit = rate_limit_per_min,
        model = %model,
        "ready"
    );

    // Enable persistent event cache (matrix-sdk's sqlite store keeps the timeline)
    client
        .event_cache()
        .subscribe()
        .context("subscribe event cache")?;

    let state = Arc::new(Mutex::new(DaemonState {
        own_user_id,
        last_shown: std::collections::HashMap::new(),
        pending_rooms: Vec::new(),
        rate_budget: rate_limit_per_min,
        rate_limit_per_min,
        last_rate_reset: std::time::Instant::now(),
        model,
        max_history,
    }));

    let processor_state = state.clone();
    let processor_client = client.clone();
    tokio::spawn(async move {
        process_loop(processor_state, processor_client).await;
    });

    sync(client, sync_token, &session_file, state).await
}

async fn load_config() -> anyhow::Result<Config> {
    let data = fs::read_to_string(paths::config_path())
        .await
        .context("failed to read config.json")?;
    serde_json::from_str(&data).context("failed to parse config.json")
}

async fn restore_session(session_file: &Path) -> anyhow::Result<(Client, Option<String>)> {
    let data = fs::read_to_string(session_file).await?;
    let session: PersistedSession = serde_json::from_str(&data)?;

    tracing::info!(user = %session.user_session.meta.user_id, "restoring session");

    let client = Client::builder()
        .homeserver_url(&session.homeserver)
        .sqlite_store(paths::db_path(), None)
        .build()
        .await?;

    client.restore_session(session.user_session).await?;

    Ok((client, session.sync_token))
}

async fn login(config: &Config, db_path: &Path, session_file: &Path) -> anyhow::Result<Client> {
    tracing::info!(homeserver = %config.homeserver, user = %config.username, "logging in");

    let client = Client::builder()
        .homeserver_url(&config.homeserver)
        .sqlite_store(db_path, None)
        .build()
        .await?;

    client
        .matrix_auth()
        .login_username(&config.username, &config.password)
        .initial_device_display_name("damocles-daemon")
        .await?;

    let user_session = client
        .matrix_auth()
        .session()
        .context("no session after login")?;

    let persisted = PersistedSession {
        homeserver: config.homeserver.clone(),
        db_path: db_path.to_owned(),
        user_session,
        sync_token: None,
    };
    fs::write(session_file, serde_json::to_string_pretty(&persisted)?).await?;

    tracing::info!("session persisted");
    Ok(client)
}

async fn sync(
    client: Client,
    initial_sync_token: Option<String>,
    session_file: &Path,
    state: Arc<Mutex<DaemonState>>,
) -> anyhow::Result<()> {
    tracing::info!("initial sync (ignoring past messages)");

    let filter = FilterDefinition::with_lazy_loading();
    let mut sync_settings = SyncSettings::default().filter(filter.into());

    if let Some(token) = initial_sync_token {
        sync_settings = sync_settings.token(token);
    }

    loop {
        match client.sync_once(sync_settings.clone()).await {
            Ok(response) => {
                sync_settings = sync_settings.token(response.next_batch.clone());
                persist_sync_token(session_file, response.next_batch).await?;
                break;
            }
            Err(e) => {
                tracing::warn!("initial sync failed, retrying: {e}");
            }
        }
    }

    tracing::info!("synced, listening for messages");

    client.add_event_handler(move |event: OriginalSyncRoomMessageEvent, room: Room| {
        let state = state.clone();
        async move {
            on_room_message(event, room, state).await;
        }
    });

    client.add_event_handler(on_stripped_state_member);

    client.sync(sync_settings).await?;

    bail!("sync loop exited unexpectedly")
}

async fn on_stripped_state_member(event: StrippedRoomMemberEvent, client: Client, room: Room) {
    let Some(my_id) = client.user_id() else {
        return;
    };
    if event.state_key != my_id {
        return;
    }
    let room_id = room.room_id().to_owned();
    tokio::spawn(async move {
        tracing::info!(room = %room_id, "auto-joining invite");
        let mut delay = 2u64;
        loop {
            match room.join().await {
                Ok(()) => {
                    tracing::info!(room = %room_id, "joined");
                    if let Err(e) = ensure_room_notes(&room).await {
                        tracing::warn!(room = %room_id, "failed to write room notes: {e}");
                    }
                    return;
                }
                Err(e) => {
                    tracing::warn!(room = %room_id, "join failed, retry in {delay}s: {e}");
                    tokio::time::sleep(std::time::Duration::from_secs(delay)).await;
                    delay = (delay * 2).min(300);
                    if delay >= 300 {
                        tracing::error!(room = %room_id, "giving up on auto-join");
                        return;
                    }
                }
            }
        }
    });
}

async fn persist_sync_token(session_file: &Path, sync_token: String) -> anyhow::Result<()> {
    let data = fs::read_to_string(session_file).await?;
    let mut session: PersistedSession = serde_json::from_str(&data)?;
    session.sync_token = Some(sync_token);
    fs::write(session_file, serde_json::to_string_pretty(&session)?).await?;
    Ok(())
}

async fn on_room_message(
    event: OriginalSyncRoomMessageEvent,
    room: Room,
    state: Arc<Mutex<DaemonState>>,
) {
    if room.state() != RoomState::Joined {
        return;
    }
    let MessageType::Text(text_content) = &event.content.msgtype else {
        return;
    };

    let room_id = room.room_id().to_owned();
    let is_self = {
        let state = state.lock().await;
        event.sender == state.own_user_id
    };

    tracing::info!(
        room = %room_id,
        sender = %event.sender,
        self_msg = is_self,
        "{}",
        text_content.body
    );

    if let Err(e) = ensure_room_notes(&room).await {
        tracing::warn!(room = %room_id, "failed to ensure room notes: {e}");
    }
    if !is_self {
        if let Err(e) = ensure_person_notes(&room, &event.sender).await {
            tracing::warn!(sender = %event.sender, "failed to ensure person notes: {e}");
        }
    }

    if !is_self {
        let mut state = state.lock().await;
        if !state.pending_rooms.contains(&room_id) {
            state.pending_rooms.push(room_id);
        }
    }
}

/// Create state/rooms/<room_id>/notes.md if it doesn't exist.
async fn ensure_room_notes(room: &Room) -> anyhow::Result<()> {
    let room_id = room.room_id();
    let dir = paths::state_dir().join("rooms").join(room_id.as_str());
    let file = dir.join("notes.md");
    if file.exists() {
        return Ok(());
    }
    fs::create_dir_all(&dir).await?;

    let display_name = room
        .display_name()
        .await
        .map(|n| n.to_string())
        .unwrap_or_else(|_| room_id.to_string());
    let now = chrono_now();

    let body = format!("# {room_id}\n\nDisplay name: {display_name}\n\nFirst joined: {now}\n",);
    fs::write(&file, body).await?;
    tracing::info!(room = %room_id, "created room notes");
    Ok(())
}

/// Create state/people/<user_id>/notes.md if it doesn't exist.
/// Pre-fill with display name (from this room's member info) and the room as
/// "first met in".
async fn ensure_person_notes(room: &Room, user_id: &UserId) -> anyhow::Result<()> {
    let dir = paths::state_dir().join("people").join(user_id.as_str());
    let file = dir.join("notes.md");
    if file.exists() {
        return Ok(());
    }
    fs::create_dir_all(&dir).await?;

    let display_name = room
        .get_member_no_sync(user_id)
        .await
        .ok()
        .flatten()
        .and_then(|m| m.display_name().map(ToOwned::to_owned))
        .unwrap_or_default();
    let display_line = if display_name.is_empty() {
        String::new()
    } else {
        format!("Display name: {display_name}\n")
    };
    let room_id = room.room_id();
    let now = chrono_now();

    let body = format!("# {user_id}\n\n{display_line}First met in: {room_id} on {now}\n",);
    fs::write(&file, body).await?;
    tracing::info!(user = %user_id, "created person notes");
    Ok(())
}

fn chrono_now() -> String {
    use std::time::{SystemTime, UNIX_EPOCH};
    let secs = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs() as i64)
        .unwrap_or(0);
    // Simple ISO-ish without pulling chrono. YYYY-MM-DD only is fine for notes.
    let days = secs / 86400;
    let (y, m, d) = days_to_ymd(days);
    format!("{y:04}-{m:02}-{d:02}")
}

/// Format a unix-seconds timestamp as `YYYY-MM-DD HH:MM` UTC. Returns "?" for 0.
fn format_ts(secs: i64) -> String {
    if secs == 0 {
        return "?".into();
    }
    let days = secs.div_euclid(86400);
    let day_secs = secs.rem_euclid(86400);
    let (y, m, d) = days_to_ymd(days);
    let h = day_secs / 3600;
    let min = (day_secs % 3600) / 60;
    format!("{y:04}-{m:02}-{d:02} {h:02}:{min:02}")
}

/// Convert days-since-1970-01-01 to (year, month, day). Civil-date algorithm.
fn days_to_ymd(z: i64) -> (i64, u32, u32) {
    let z = z + 719_468;
    let era = z.div_euclid(146_097);
    let doe = z.rem_euclid(146_097) as u32;
    let yoe = (doe - doe / 1460 + doe / 36524 - doe / 146_096) / 365;
    let y = yoe as i64 + era * 400;
    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
    let mp = (5 * doy + 2) / 153;
    let d = doy - (153 * mp + 2) / 5 + 1;
    let m = if mp < 10 { mp + 3 } else { mp - 9 };
    (if m <= 2 { y + 1 } else { y }, m, d)
}

async fn process_loop(state: Arc<Mutex<DaemonState>>, client: Client) {
    loop {
        tokio::time::sleep(std::time::Duration::from_secs(1)).await;

        let room_id = {
            let mut state = state.lock().await;

            if state.last_rate_reset.elapsed() >= std::time::Duration::from_secs(60) {
                state.rate_budget = state.rate_limit_per_min;
                state.last_rate_reset = std::time::Instant::now();
            }

            if state.rate_budget == 0 {
                continue;
            }

            state.pending_rooms.pop()
        };

        let Some(room_id) = room_id else {
            continue;
        };

        let Some(room) = client.get_room(&room_id) else {
            tracing::warn!(room = %room_id, "room not found in client");
            continue;
        };

        // Snapshot last_shown for this room so we can mark seen vs new.
        // If we don't have one in memory (e.g. fresh daemon start), seed from
        // the stored read receipt so we don't reprocess old messages.
        let in_memory = {
            let s = state.lock().await;
            s.last_shown.get(&room_id).cloned()
        };
        let prev_last_shown = if let Some(eid) = in_memory {
            Some(eid)
        } else {
            let from_receipt = match room
                .load_user_receipt(
                    matrix_sdk::ruma::events::receipt::ReceiptType::Read,
                    ReceiptThread::Unthreaded,
                    client.user_id().expect("logged in"),
                )
                .await
            {
                Ok(Some((eid, _))) => Some(eid),
                Ok(None) => None,
                Err(e) => {
                    tracing::warn!(room = %room_id, "failed to load receipt: {e}");
                    None
                }
            };
            if let Some(ref eid) = from_receipt {
                let mut s = state.lock().await;
                s.last_shown.insert(room_id.clone(), eid.clone());
            }
            from_receipt
        };
        let room_name = room
            .display_name()
            .await
            .map_or_else(|_| room_id.to_string(), |n| n.to_string());

        let (own_user, model, max_history) = {
            let state = state.lock().await;
            (
                state.own_user_id.clone(),
                state.model.clone(),
                state.max_history,
            )
        };

        // Load recent timeline (messages + reactions) from matrix-sdk's
        // persistent event cache.
        let mut timeline = match load_timeline(&room, max_history, &own_user).await {
            Ok(t) => t,
            Err(e) => {
                tracing::error!(room = %room_id, "failed to load timeline: {e}");
                continue;
            }
        };

        // For any new messages that reply to events outside the window, fetch
        // the replied-to event from cache and prepend it as extra context.
        let in_window: std::collections::HashSet<OwnedEventId> = timeline
            .iter()
            .filter_map(TimelineItem::event_id)
            .cloned()
            .collect();
        let seen_idx_initial = prev_last_shown
            .as_ref()
            .and_then(|id| {
                timeline.iter().position(|t| match t {
                    TimelineItem::Message { event_id, .. } => event_id == id,
                    _ => false,
                })
            })
            .map_or(0, |pos| pos + 1);
        let mut reply_targets: Vec<OwnedEventId> = Vec::new();
        for item in timeline.iter().skip(seen_idx_initial) {
            if let TimelineItem::Message {
                in_reply_to: Some(target),
                ..
            } = item
            {
                if !in_window.contains(target) && !reply_targets.contains(target) {
                    reply_targets.push(target.clone());
                }
            }
        }
        if !reply_targets.is_empty() {
            if let Ok((cache, _h)) = room.event_cache().await {
                for target in &reply_targets {
                    if let Some(found) = fetch_message(&cache, target, &own_user).await {
                        timeline.insert(0, found);
                    }
                }
            }
        }

        // Determine seen split based on the last_shown message event id
        let seen_idx = prev_last_shown
            .as_ref()
            .and_then(|id| {
                timeline.iter().position(|t| match t {
                    TimelineItem::Message { event_id, .. } => event_id == id,
                    _ => false,
                })
            })
            .map_or(0, |pos| pos + 1);

        // The "last shown" pointer should advance to the latest message we've
        // loaded (not a reaction).
        let new_last_event_id = timeline.iter().rev().find_map(|t| match t {
            TimelineItem::Message { event_id, .. } => Some(event_id.clone()),
            _ => None,
        });

        let docs = match invoke_claude(&room_id, &room_name, &timeline, seen_idx, &model).await {
            Ok(d) => d,
            Err(e) => {
                tracing::error!(room = %room_id, "claude invocation failed: {e}");
                continue;
            }
        };

        let mut sent_any = false;
        for doc in docs {
            match doc {
                ClaudeDoc::Skip => {
                    tracing::debug!(room = %room_id, "claude doc: skip");
                }
                ClaudeDoc::Thought(body) => {
                    tracing::info!(room = %room_id, thought = %body.chars().take(120).collect::<String>(), "claude doc: thought");
                    tracing::trace!("full thought: {body}");
                }
                ClaudeDoc::Message { target, body } => {
                    let target_room = match &target {
                        ResponseTarget::Room(rid) => client.get_room(rid),
                        ResponseTarget::Dm(user) => match find_or_create_dm(&client, user).await {
                            Ok(r) => Some(r),
                            Err(e) => {
                                tracing::error!(user = %user, "failed to get/create DM: {e}");
                                None
                            }
                        },
                    };
                    let target_label = match &target {
                        ResponseTarget::Room(rid) => rid.to_string(),
                        ResponseTarget::Dm(user) => format!("dm:{user}"),
                    };
                    if let Some(target_room) = target_room {
                        let content = RoomMessageEventContent::text_plain(&body);
                        match target_room.send(content).await {
                            Ok(_) => {
                                let mut state = state.lock().await;
                                state.rate_budget = state.rate_budget.saturating_sub(1);
                                tracing::info!(
                                    target = %target_label,
                                    "sent response ({} budget remaining)",
                                    state.rate_budget
                                );
                                sent_any = true;
                            }
                            Err(e) => tracing::error!("failed to send: {e}"),
                        }
                    } else {
                        tracing::warn!(target = %target_label, "target not available");
                    }
                }
            }
        }

        // Update last_shown and send read receipt regardless of whether we
        // sent a message - the agent saw the messages either way.
        {
            let mut state = state.lock().await;
            if let Some(eid) = new_last_event_id.clone() {
                state.last_shown.insert(room_id.clone(), eid);
            }
        }
        send_read_receipt(&room, new_last_event_id).await;

        let _ = sent_any;
    }
}

/// Find an existing DM room with the given user, or create one.
async fn find_or_create_dm(client: &Client, user_id: &UserId) -> anyhow::Result<Room> {
    for room in client.joined_rooms() {
        if room.is_direct().await.unwrap_or(false)
            && room
                .direct_targets()
                .iter()
                .any(|t| t.as_str() == user_id.as_str())
        {
            return Ok(room);
        }
    }
    tracing::info!(user = %user_id, "creating new DM room");
    Ok(client.create_dm(user_id).await?)
}

async fn send_read_receipt(room: &Room, event_id: Option<OwnedEventId>) {
    let Some(eid) = event_id else {
        return;
    };
    if let Err(e) = room
        .send_single_receipt(CreateReceiptType::Read, ReceiptThread::Unthreaded, eid)
        .await
    {
        tracing::warn!(room = %room.room_id(), "failed to send read receipt: {e}");
    }
}

/// Load the last N timeline items (messages + reactions) from the room's
/// persistent event cache. Returns oldest-first.
///
/// We walk events newest-first, collect messages until we have `limit`, then
/// also include any reactions whose timestamps fall within the message window.
async fn load_timeline(
    room: &Room,
    limit: usize,
    own_user: &OwnedUserId,
) -> anyhow::Result<Vec<TimelineItem>> {
    use matrix_sdk::ruma::events::AnySyncTimelineEvent;

    let (cache, _handles) = room.event_cache().await?;
    let events = cache.events().await;

    let mut messages: Vec<TimelineItem> = Vec::new();
    let mut reactions: Vec<TimelineItem> = Vec::new();
    let mut earliest_message_ts: Option<i64> = None;

    for ev in events.iter().rev() {
        let raw = ev.raw();
        let Ok(deserialized) = raw.deserialize() else {
            continue;
        };
        let AnySyncTimelineEvent::MessageLike(msg) = deserialized else {
            continue;
        };

        match msg {
            matrix_sdk::ruma::events::AnySyncMessageLikeEvent::RoomMessage(
                matrix_sdk::ruma::events::SyncMessageLikeEvent::Original(orig),
            ) => {
                if messages.len() >= limit {
                    continue;
                }
                let MessageType::Text(text) = &orig.content.msgtype else {
                    continue;
                };
                let ts = ts_secs_from(orig.origin_server_ts.0);
                let in_reply_to = match &orig.content.relates_to {
                    Some(matrix_sdk::ruma::events::room::message::Relation::Reply {
                        in_reply_to,
                    }) => Some(in_reply_to.event_id.clone()),
                    _ => None,
                };
                if earliest_message_ts.is_none_or(|e| ts < e) {
                    earliest_message_ts = Some(ts);
                }
                messages.push(TimelineItem::Message {
                    event_id: orig.event_id.clone(),
                    sender: orig.sender.clone(),
                    body: text.body.clone(),
                    is_self: &orig.sender == own_user,
                    ts,
                    in_reply_to,
                });
            }
            matrix_sdk::ruma::events::AnySyncMessageLikeEvent::Reaction(
                matrix_sdk::ruma::events::SyncMessageLikeEvent::Original(orig),
            ) => {
                let ts = ts_secs_from(orig.origin_server_ts.0);
                reactions.push(TimelineItem::Reaction {
                    sender: orig.sender.clone(),
                    target_event_id: orig.content.relates_to.event_id.clone(),
                    key: orig.content.relates_to.key.clone(),
                    is_self: &orig.sender == own_user,
                    ts,
                });
            }
            _ => {}
        }
    }

    // Drop reactions older than the oldest visible message, to avoid
    // referencing messages we don't have in scope.
    if let Some(min_ts) = earliest_message_ts {
        reactions.retain(|r| r.ts() >= min_ts);
    }

    let mut combined: Vec<TimelineItem> = Vec::with_capacity(messages.len() + reactions.len());
    combined.extend(messages);
    combined.extend(reactions);
    combined.sort_by_key(TimelineItem::ts);
    Ok(combined)
}

/// Render one timeline item into the prompt.
/// Messages: `[ts] $eid... [(you) ]@user: body`
/// Reactions: `[ts] [(you) ]@user reacted to $eid... with KEY`
fn render_timeline_item(prompt: &mut String, item: &TimelineItem) {
    match item {
        TimelineItem::Message {
            event_id,
            sender,
            body,
            is_self,
            ts,
            ..
        } => {
            let ts_str = format_ts(*ts);
            let id = short_event_id(event_id);
            let prefix = if *is_self { "(you) " } else { "" };
            writeln!(prompt, "[{ts_str}] {id} {prefix}{sender}: {body}").unwrap();
        }
        TimelineItem::Reaction {
            sender,
            target_event_id,
            key,
            is_self,
            ts,
        } => {
            let ts_str = format_ts(*ts);
            let id = short_event_id(target_event_id);
            let prefix = if *is_self { "(you) " } else { "" };
            writeln!(
                prompt,
                "[{ts_str}] {prefix}{sender} reacted to {id} with {key}"
            )
            .unwrap();
        }
    }
}

/// Shorten an event id for prompt display: `$abc123def456...` → `$abc123de`.
fn short_event_id(id: &OwnedEventId) -> String {
    let s = id.as_str();
    let prefix: String = s.chars().take(9).collect();
    if s.len() > 9 {
        format!("{prefix}…")
    } else {
        prefix
    }
}

fn ts_secs_from(ts: matrix_sdk::ruma::UInt) -> i64 {
    let ms: u64 = ts.into();
    i64::try_from(ms).unwrap_or(0) / 1000
}

/// Fetch a single text message by event_id from the room's event cache.
async fn fetch_message(
    cache: &matrix_sdk::event_cache::RoomEventCache,
    event_id: &matrix_sdk::ruma::EventId,
    own_user: &OwnedUserId,
) -> Option<TimelineItem> {
    use matrix_sdk::ruma::events::AnySyncTimelineEvent;

    let ev = cache.find_event(event_id).await?;
    let deserialized = ev.raw().deserialize().ok()?;
    let AnySyncTimelineEvent::MessageLike(msg) = deserialized else {
        return None;
    };
    let matrix_sdk::ruma::events::AnySyncMessageLikeEvent::RoomMessage(
        matrix_sdk::ruma::events::SyncMessageLikeEvent::Original(orig),
    ) = msg
    else {
        return None;
    };
    let MessageType::Text(text) = &orig.content.msgtype else {
        return None;
    };
    let ts = ts_secs_from(orig.origin_server_ts.0);
    Some(TimelineItem::Message {
        event_id: orig.event_id.clone(),
        sender: orig.sender.clone(),
        body: text.body.clone(),
        is_self: &orig.sender == own_user,
        ts,
        in_reply_to: None,
    })
}

enum ResponseTarget {
    Room(OwnedRoomId),
    Dm(OwnedUserId),
}

/// One document within Claude's multi-doc output. Each doc has its own
/// frontmatter; the daemon routes based on which fields are present.
enum ClaudeDoc {
    /// A chat message to send.
    Message {
        target: ResponseTarget,
        body: String,
    },
    /// Agent's internal monologue. Not sent to chat. Logged to tracing.
    Thought(String),
    /// Explicit "do nothing for this slot". Useful as a placeholder.
    Skip,
}

async fn invoke_claude(
    source_room: &OwnedRoomId,
    room_name: &str,
    timeline: &[TimelineItem],
    seen_idx: usize,
    model: &str,
) -> anyhow::Result<Vec<ClaudeDoc>> {
    let identity_dir = paths::identity_dir();
    let identity_str = identity_dir.to_string_lossy();

    let mut prompt = String::new();
    writeln!(prompt, "[room_id: {source_room}]").unwrap();
    writeln!(prompt, "[room_name: {room_name}]").unwrap();
    writeln!(
        prompt,
        "[room notes path: ../rooms/{source_room}/notes.md (create dir if needed)]"
    )
    .unwrap();

    // Collect unique non-self participants (message senders + reactors)
    let mut senders: Vec<&OwnedUserId> = timeline
        .iter()
        .filter(|t| !t.is_self())
        .map(TimelineItem::sender)
        .collect();
    senders.sort();
    senders.dedup();
    if !senders.is_empty() {
        writeln!(
            prompt,
            "\n[people in this room — check ../people/<user_id>/notes.md for each]"
        )
        .unwrap();
        for s in &senders {
            writeln!(prompt, "  {s}").unwrap();
        }
    }

    let seen = seen_idx.min(timeline.len());
    let (old, new) = timeline.split_at(seen);

    if !old.is_empty() {
        writeln!(prompt, "\n[previously seen events — for context]").unwrap();
        for item in old {
            render_timeline_item(&mut prompt, item);
        }
    }

    writeln!(prompt, "\n[new events — respond to these]").unwrap();
    if new.is_empty() {
        writeln!(prompt, "(none)").unwrap();
    } else {
        for item in new {
            render_timeline_item(&mut prompt, item);
        }
    }

    let new_msg_count = new
        .iter()
        .filter(|t| matches!(t, TimelineItem::Message { .. }))
        .count();
    let new_react_count = new.len() - new_msg_count;
    tracing::info!(
        "invoking claude: {} new ({} msg + {} react), {} seen",
        new.len(),
        new_msg_count,
        new_react_count,
        old.len()
    );
    tracing::trace!("full prompt:\n{prompt}");

    use tokio::process::Command;
    let mut cmd = Command::new("claude");
    cmd.args([
        "--print",
        "--model",
        model,
        "--add-dir",
        &identity_str,
        "--allowedTools",
        "Read Edit Write Glob Grep",
        "-p",
        &prompt,
    ]);
    cmd.current_dir(&identity_dir);
    cmd.stdin(std::process::Stdio::null());
    let output = cmd.output().await.context("failed to run claude")?;

    let stderr = String::from_utf8_lossy(&output.stderr);
    let stdout = String::from_utf8_lossy(&output.stdout);

    if !output.status.success() {
        bail!(
            "claude exited with {}:\nstdout: {}\nstderr: {}",
            output.status,
            stdout,
            stderr
        );
    }

    if !stderr.is_empty() {
        tracing::warn!("claude stderr: {stderr}");
    }

    let raw = String::from_utf8_lossy(&output.stdout).to_string();
    Ok(parse_response(&raw, source_room))
}

/// Parse Claude's stdout into a list of documents.
///
/// Format: each doc starts with a line `=== <type> [arg]`. Body is everything
/// until the next `===` line or EOF. Types:
///   - `=== thought` → ClaudeDoc::Thought (logged, not sent)
///   - `=== room [<room_id>]` → ClaudeDoc::Message to that room (or source room if no arg)
///   - `=== dm <user_id>` → ClaudeDoc::Message as DM
///   - `=== skip` → ClaudeDoc::Skip (no-op)
///
/// Anything before the first `===` line is treated as a preamble thought.
/// Bare text with no `===` is treated as a single message to default_room.
fn parse_response(raw: &str, default_room: &OwnedRoomId) -> Vec<ClaudeDoc> {
    let trimmed = raw.trim();
    if trimmed.is_empty() {
        return Vec::new();
    }

    // Walk lines, splitting on lines that start with "=== "
    let mut docs = Vec::new();
    let mut current_header: Option<String> = None;
    let mut current_body = String::new();
    let mut preamble = String::new();

    for line in trimmed.lines() {
        if let Some(header) = line.strip_prefix("===") {
            // Flush previous doc
            if let Some(h) = current_header.take() {
                if let Some(doc) = build_doc(&h, current_body.trim(), default_room) {
                    docs.push(doc);
                }
                current_body.clear();
            } else {
                // We were collecting preamble
                let p = preamble.trim();
                if !p.is_empty() {
                    docs.push(ClaudeDoc::Thought(p.to_owned()));
                }
                preamble.clear();
            }
            current_header = Some(header.trim().to_owned());
        } else if current_header.is_some() {
            current_body.push_str(line);
            current_body.push('\n');
        } else {
            preamble.push_str(line);
            preamble.push('\n');
        }
    }

    // Flush the last doc or preamble
    if let Some(h) = current_header {
        if let Some(doc) = build_doc(&h, current_body.trim(), default_room) {
            docs.push(doc);
        }
    } else {
        // No `===` headers at all - treat whole output as a single message
        let p = preamble.trim();
        if !p.is_empty() {
            docs.push(ClaudeDoc::Message {
                target: ResponseTarget::Room(default_room.clone()),
                body: p.to_owned(),
            });
        }
    }

    docs
}

fn build_doc(header: &str, body: &str, default_room: &OwnedRoomId) -> Option<ClaudeDoc> {
    let mut parts = header.splitn(2, char::is_whitespace);
    let kind = parts.next().unwrap_or("").trim();
    let arg = parts.next().unwrap_or("").trim();

    match kind {
        "skip" => Some(ClaudeDoc::Skip),
        "thought" => {
            if body.is_empty() {
                None
            } else {
                Some(ClaudeDoc::Thought(body.to_owned()))
            }
        }
        "room" => {
            if body.is_empty() {
                return None;
            }
            let target = if arg.is_empty() {
                ResponseTarget::Room(default_room.clone())
            } else {
                match arg.parse::<OwnedRoomId>() {
                    Ok(rid) => ResponseTarget::Room(rid),
                    Err(_) => return None,
                }
            };
            Some(ClaudeDoc::Message {
                target,
                body: body.to_owned(),
            })
        }
        "dm" => {
            if body.is_empty() {
                return None;
            }
            match arg.parse::<OwnedUserId>() {
                Ok(uid) => Some(ClaudeDoc::Message {
                    target: ResponseTarget::Dm(uid),
                    body: body.to_owned(),
                }),
                Err(_) => None,
            }
        }
        _ => {
            // Unknown header - treat body as a thought so it doesn't leak to chat
            if body.is_empty() {
                None
            } else {
                Some(ClaudeDoc::Thought(format!(
                    "[unknown header '{header}'] {body}"
                )))
            }
        }
    }
}

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

    fn test_room() -> OwnedRoomId {
        "!test:example.com".parse().unwrap()
    }

    fn first_message(docs: &[ClaudeDoc]) -> (&ResponseTarget, &str) {
        for d in docs {
            if let ClaudeDoc::Message { target, body } = d {
                return (target, body.as_str());
            }
        }
        panic!("no message doc found");
    }

    fn assert_room(target: &ResponseTarget, expected: &str) {
        match target {
            ResponseTarget::Room(r) => assert_eq!(r.as_str(), expected),
            ResponseTarget::Dm(_) => panic!("expected room target, got dm"),
        }
    }

    #[test]
    fn parse_room_with_arg() {
        let raw = "=== room !other:server\nhello world";
        let docs = parse_response(raw, &test_room());
        let (target, body) = first_message(&docs);
        assert_room(target, "!other:server");
        assert_eq!(body, "hello world");
    }

    #[test]
    fn parse_room_no_arg_uses_default() {
        let raw = "=== room\nhi";
        let docs = parse_response(raw, &test_room());
        let (target, _) = first_message(&docs);
        assert_room(target, "!test:example.com");
    }

    #[test]
    fn parse_skip() {
        let raw = "=== skip";
        let docs = parse_response(raw, &test_room());
        assert_eq!(docs.len(), 1);
        assert!(matches!(docs[0], ClaudeDoc::Skip));
    }

    #[test]
    fn parse_plain_text_no_header() {
        let raw = "just a message";
        let docs = parse_response(raw, &test_room());
        let (target, body) = first_message(&docs);
        assert_room(target, "!test:example.com");
        assert_eq!(body, "just a message");
    }

    #[test]
    fn parse_empty() {
        assert!(parse_response("", &test_room()).is_empty());
        assert!(parse_response("   \n  ", &test_room()).is_empty());
    }

    #[test]
    fn parse_dm() {
        let raw = "=== dm @alice:example.com\nhi alice";
        let docs = parse_response(raw, &test_room());
        let (target, body) = first_message(&docs);
        match target {
            ResponseTarget::Dm(u) => assert_eq!(u.as_str(), "@alice:example.com"),
            ResponseTarget::Room(_) => panic!("expected dm target"),
        }
        assert_eq!(body, "hi alice");
    }

    #[test]
    fn parse_thought() {
        let raw = "=== thought\nthinking about whether to reply...";
        let docs = parse_response(raw, &test_room());
        assert_eq!(docs.len(), 1);
        match &docs[0] {
            ClaudeDoc::Thought(s) => assert_eq!(s, "thinking about whether to reply..."),
            _ => panic!("expected thought"),
        }
    }

    #[test]
    fn parse_multi_doc() {
        let raw = "\
=== thought
let me check notes

=== room !x:y
hi

=== dm @u:s
private

=== skip
";
        let docs = parse_response(raw, &test_room());
        assert_eq!(docs.len(), 4);
        assert!(matches!(docs[0], ClaudeDoc::Thought(_)));
        assert!(matches!(
            docs[1],
            ClaudeDoc::Message {
                target: ResponseTarget::Room(_),
                ..
            }
        ));
        assert!(matches!(
            docs[2],
            ClaudeDoc::Message {
                target: ResponseTarget::Dm(_),
                ..
            }
        ));
        assert!(matches!(docs[3], ClaudeDoc::Skip));
    }

    #[test]
    fn parse_preamble_becomes_thought() {
        let raw = "preamble line\n=== room !x:y\nhello";
        let docs = parse_response(raw, &test_room());
        assert_eq!(docs.len(), 2);
        assert!(matches!(docs[0], ClaudeDoc::Thought(_)));
        assert!(matches!(docs[1], ClaudeDoc::Message { .. }));
    }

    #[test]
    fn parse_unknown_header_becomes_thought() {
        let raw = "=== mystery foo\nbody";
        let docs = parse_response(raw, &test_room());
        assert_eq!(docs.len(), 1);
        assert!(matches!(docs[0], ClaudeDoc::Thought(_)));
    }
}