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>,
}

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

#[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)]
struct ChatMessage {
    sender: OwnedUserId,
    body: String,
    is_self: bool,
    /// Unix seconds. 0 if unknown.
    ts: i64,
}

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,
}

const MAX_HISTORY: usize = 20;
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 (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,
    }));

    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());

        // Load recent history from matrix-sdk's persistent event cache
        let history = match load_recent_messages(&room, MAX_HISTORY).await {
            Ok(h) => h,
            Err(e) => {
                tracing::error!(room = %room_id, "failed to load history: {e}");
                continue;
            }
        };

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

        let chat_msgs: Vec<ChatMessage> = history
            .iter()
            .map(|(_, sender, body, ts)| ChatMessage {
                sender: sender.clone(),
                body: body.clone(),
                is_self: sender == &own_user,
                ts: *ts,
            })
            .collect();

        // Determine seen split: everything before (and including) prev_last_shown is "seen"
        let seen_idx = prev_last_shown
            .as_ref()
            .and_then(|id| history.iter().position(|(eid, _, _, _)| eid == id))
            .map_or(0, |pos| pos + 1);

        let new_last_event_id = history.last().map(|(eid, _, _, _)| eid.clone());

        match invoke_claude(&room_id, &room_name, &chat_msgs, seen_idx, &model).await {
            Ok(Some(response)) => {
                if let Some(target_room) = client.get_room(&response.room) {
                    let content = RoomMessageEventContent::text_plain(&response.body);
                    match target_room.send(content).await {
                        Ok(_) => {
                            let mut state = state.lock().await;
                            state.rate_budget = state.rate_budget.saturating_sub(1);
                            if let Some(eid) = new_last_event_id.clone() {
                                state.last_shown.insert(room_id.clone(), eid);
                            }
                            tracing::info!(
                                room = %response.room,
                                "sent response ({} budget remaining)",
                                state.rate_budget
                            );
                            drop(state);
                            send_read_receipt(&room, new_last_event_id.clone()).await;
                        }
                        Err(e) => tracing::error!("failed to send: {e}"),
                    }
                } else {
                    tracing::warn!(room = %response.room, "target room not found");
                }
            }
            Ok(None) => {
                tracing::debug!(room = %room_id, "claude chose to skip");
                {
                    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.clone()).await;
            }
            Err(e) => {
                tracing::error!(room = %room_id, "claude invocation failed: {e}");
            }
        }
    }
}

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 text messages from the room's persistent event cache.
/// Returns oldest-first list of (event_id, sender, body, ts_secs).
async fn load_recent_messages(
    room: &Room,
    limit: usize,
) -> anyhow::Result<Vec<(OwnedEventId, OwnedUserId, String, i64)>> {
    use matrix_sdk::ruma::events::AnySyncTimelineEvent;

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

    let mut out: Vec<(OwnedEventId, OwnedUserId, String, i64)> = Vec::new();
    for ev in events.iter().rev() {
        if out.len() >= limit {
            break;
        }
        let raw = ev.raw();
        let Ok(deserialized) = raw.deserialize() else {
            continue;
        };
        if let AnySyncTimelineEvent::MessageLike(msg) = deserialized {
            if let matrix_sdk::ruma::events::AnySyncMessageLikeEvent::RoomMessage(
                matrix_sdk::ruma::events::SyncMessageLikeEvent::Original(orig),
            ) = msg
            {
                if let MessageType::Text(text) = &orig.content.msgtype {
                    let ts_ms: u64 = orig.origin_server_ts.0.into();
                    let ts_secs: i64 = i64::try_from(ts_ms).unwrap_or(0) / 1000;
                    out.push((
                        orig.event_id.clone(),
                        orig.sender.clone(),
                        text.body.clone(),
                        ts_secs,
                    ));
                }
            }
        }
    }

    out.reverse();
    Ok(out)
}

struct ClaudeResponse {
    room: OwnedRoomId,
    body: String,
}

async fn invoke_claude(
    source_room: &OwnedRoomId,
    room_name: &str,
    history: &[ChatMessage],
    seen_idx: usize,
    model: &str,
) -> anyhow::Result<Option<ClaudeResponse>> {
    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 senders for per-person note discovery
    let mut senders: Vec<&OwnedUserId> = history
        .iter()
        .filter(|m| !m.is_self)
        .map(|m| &m.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(history.len());
    let (old, new) = history.split_at(seen);

    if !old.is_empty() {
        writeln!(prompt, "\n[previously seen messages — for context]").unwrap();
        for msg in old {
            let prefix = if msg.is_self { "(you) " } else { "" };
            let ts = format_ts(msg.ts);
            writeln!(prompt, "[{ts}] {prefix}{}: {}", msg.sender, msg.body).unwrap();
        }
    }

    writeln!(prompt, "\n[new messages — respond to these]").unwrap();
    if new.is_empty() {
        writeln!(prompt, "(none)").unwrap();
    } else {
        for msg in new {
            let prefix = if msg.is_self { "(you) " } else { "" };
            let ts = format_ts(msg.ts);
            writeln!(prompt, "[{ts}] {prefix}{}: {}", msg.sender, msg.body).unwrap();
        }
    }

    tracing::info!("invoking claude: {} new, {} seen", new.len(), 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))
}

fn parse_response(raw: &str, default_room: &OwnedRoomId) -> Option<ClaudeResponse> {
    let trimmed = raw.trim();

    if trimmed.starts_with("---") {
        let parts: Vec<&str> = trimmed.splitn(3, "---").collect();
        if parts.len() >= 3 {
            let frontmatter = parts[1].trim();
            let body = parts[2].trim();

            if frontmatter.contains("skip: true") || frontmatter.contains("skip:true") {
                return None;
            }

            let room = frontmatter
                .lines()
                .find(|l| l.starts_with("room:"))
                .and_then(|l| l.strip_prefix("room:"))
                .and_then(|r| r.trim().parse().ok())
                .unwrap_or_else(|| default_room.clone());

            if body.is_empty() {
                return None;
            }

            return Some(ClaudeResponse {
                room,
                body: body.to_owned(),
            });
        }
    }

    if trimmed.is_empty() {
        return None;
    }

    Some(ClaudeResponse {
        room: default_room.clone(),
        body: trimmed.to_owned(),
    })
}

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

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

    #[test]
    fn parse_frontmatter_response() {
        let raw = "---\nroom: !other:server\n---\nhello world";
        let resp = parse_response(raw, &test_room()).unwrap();
        assert_eq!(resp.room.as_str(), "!other:server");
        assert_eq!(resp.body, "hello world");
    }

    #[test]
    fn parse_skip_response() {
        let raw = "---\nskip: true\n---\n";
        assert!(parse_response(raw, &test_room()).is_none());
    }

    #[test]
    fn parse_plain_response() {
        let raw = "just a message";
        let resp = parse_response(raw, &test_room()).unwrap();
        assert_eq!(resp.room, test_room());
        assert_eq!(resp.body, "just a message");
    }

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

    #[test]
    fn parse_default_room() {
        let raw = "---\n---\nhello";
        let resp = parse_response(raw, &test_room()).unwrap();
        assert_eq!(resp.room, test_room());
    }
}