/* This file is part of DarkFi (https://dark.fi)
 *
 * Copyright (C) 2020-2026 Dyne.org foundation
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as
 * published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

use std::{
    io::Cursor,
    sync::{Arc, Mutex as SyncMutex, OnceLock, Weak},
    time::UNIX_EPOCH,
};

use async_trait::async_trait;
use darkfi::{
    event_graph::{
        self,
        proto::{EventPut, ProtocolEventGraph},
        EventGraph, EventGraphPtr,
    },
    net::{
        session::SESSION_DEFAULT,
        settings::{MagicBytes, NetworkProfile, Settings as NetSettings},
        ChannelPtr, P2p, P2pPtr,
    },
    system::{sleep, Subscription},
    Result as DarkFiResult,
};
use darkfi_serial::{
    deserialize_async, serialize, serialize_async, AsyncEncodable, Decodable, Encodable,
    SerialDecodable, SerialEncodable,
};
use sled_overlay::sled;

use crate::{
    error::{Error, Result},
    prop::{BatchGuardPtr, PropertyAtomicGuard, PropertyStr, Role},
    scene::{MethodCallSub, Pimpl, SceneNode, SceneNodePtr, SceneNodeType, SceneNodeWeak, Slot},
    ui::{
        chatview::{MessageId, Timestamp},
        OnModify,
    },
    ExecutorPtr,
};

use super::PluginSettings;

const P2P_RETRY_TIME: u64 = 20;
const COOLOFF_SLEEP_TIME: u64 = 20;
const COOLOFF_SYNC_ATTEMPTS: usize = 6;
const SYNC_MIN_PEERS: usize = 2;

const P2P_OUTBOUND_ACTIVE: usize = 6;
const P2P_OUTBOUND_SLEEP: usize = 1;

/// Due to drift between different machine's clocks, if the message timestamp is recent
/// then we will just correct it to the current time so messages appear sequential in the UI.
const RECENT_TIME_DIST: u64 = 25_000;

#[cfg(target_os = "android")]
mod paths {
    use crate::android::{get_appdata_path, get_external_storage_path};
    use std::path::PathBuf;

    pub fn get_evgrdb_path() -> PathBuf {
        get_external_storage_path().join("evgr")
    }
    pub fn get_use_tor_filename() -> PathBuf {
        get_external_storage_path().join("use_tor.txt")
    }

    pub fn nick_filename() -> PathBuf {
        get_appdata_path().join("/nick.txt")
    }

    pub fn p2p_datastore_path() -> PathBuf {
        get_appdata_path().join("darkirc_p2p")
    }
    pub fn hostlist_path() -> PathBuf {
        get_appdata_path().join("hostlist.tsv")
    }
}

#[cfg(not(target_os = "android"))]
mod paths {
    use std::path::PathBuf;

    pub fn get_evgrdb_path() -> PathBuf {
        dirs::data_local_dir().unwrap().join("darkfi/app/evgr")
    }
    pub fn get_use_tor_filename() -> PathBuf {
        dirs::data_local_dir().unwrap().join("darkfi/app/use_tor.txt")
    }

    pub fn nick_filename() -> PathBuf {
        dirs::cache_dir().unwrap().join("darkfi/app/nick.txt")
    }

    pub fn p2p_datastore_path() -> PathBuf {
        dirs::cache_dir().unwrap().join("darkfi/app/darkirc_p2p")
    }
    pub fn hostlist_path() -> PathBuf {
        dirs::cache_dir().unwrap().join("darkfi/app/hostlist.tsv")
    }
}

use paths::*;

macro_rules! t { ($($arg:tt)*) => { trace!(target: "plugin::darkirc", $($arg)*); } }
macro_rules! d { ($($arg:tt)*) => { debug!(target: "plugin::darkirc", $($arg)*); } }
macro_rules! i { ($($arg:tt)*) => { info!(target: "plugin::darkirc", $($arg)*); } }
macro_rules! e { ($($arg:tt)*) => { error!(target: "plugin::darkirc", $($arg)*); } }
macro_rules! w { ($($arg:tt)*) => { warn!(target: "plugin::darkirc", $($arg)*); } }

#[derive(Clone, Debug, SerialEncodable, SerialDecodable)]
pub struct Privmsg {
    pub channel: String,
    pub nick: String,
    pub msg: String,
}

impl Privmsg {
    pub fn new(channel: String, nick: String, msg: String) -> Self {
        Self { channel, nick, msg }
    }

    pub fn msg_id(&self, timest: u64) -> MessageId {
        let mut hasher = blake3::Hasher::new();
        0u8.encode(&mut hasher).unwrap();
        0u8.encode(&mut hasher).unwrap();
        timest.encode(&mut hasher).unwrap();
        self.channel.encode(&mut hasher).unwrap();
        self.nick.encode(&mut hasher).unwrap();
        self.msg.encode(&mut hasher).unwrap();
        MessageId(hasher.finalize().into())
    }
}

struct SeenMsg {
    id: MessageId,
    is_self: bool,
    seen_times: usize,
}

struct SeenMessages {
    seen: Vec<SeenMsg>,
}

impl SeenMessages {
    fn new() -> Self {
        Self { seen: vec![] }
    }

    fn get_status(&self, id: &MessageId) -> Option<&SeenMsg> {
        self.seen.iter().find(|s| s.id == *id)
    }

    fn push(&mut self, id: MessageId, is_self: bool) {
        self.seen.push(SeenMsg { id, is_self, seen_times: 0 });
    }
}

pub type DarkIrcPtr = Arc<DarkIrc>;

pub struct DarkIrc {
    node: SceneNodeWeak,
    tasks: OnceLock<Vec<smol::Task<()>>>,

    p2p: P2pPtr,
    event_graph: EventGraphPtr,

    seen_msgs: SyncMutex<SeenMessages>,
    nick: PropertyStr,

    settings: PluginSettings,
}

impl DarkIrc {
    pub async fn new(node: SceneNodeWeak, sg_root: SceneNodePtr, ex: ExecutorPtr) -> Result<Pimpl> {
        let node_ref = &node.upgrade().unwrap();
        let nick = PropertyStr::wrap(node_ref, Role::Internal, "nick", 0).unwrap();

        let setting_root = Arc::new(SceneNode::new("setting", SceneNodeType::SettingRoot));
        node_ref.link(setting_root.clone());

        i!("Starting DarkIRC backend");
        let evgr_path = get_evgrdb_path();
        let db = match sled::open(&evgr_path) {
            Ok(db) => db,
            Err(err) => {
                e!("Sled database '{}' failed to open: {err}!", evgr_path.display());
                return Err(Error::SledDbErr)
            }
        };

        let setting_tree = db.open_tree("settings")?;
        let settings = PluginSettings { setting_root, sled_tree: setting_tree };

        let mut p2p_settings: NetSettings = Default::default();
        p2p_settings.magic_bytes = MagicBytes([251, 229, 199, 181]);
        p2p_settings.app_version = semver::Version::parse("0.5.0").unwrap();
        p2p_settings.app_name = "darkirc".to_string();
        if get_use_tor_filename().exists() {
            i!("Setup P2P network [tor]");
            let mut tor_profile = NetworkProfile::tor_default();
            tor_profile.outbound_connect_timeout = 60;
            p2p_settings.profiles.insert("tor".to_string(), tor_profile);
            p2p_settings.outbound_peer_discovery_cooloff_time = 60;

            p2p_settings.seeds.push(
                url::Url::parse(
                    "tor://g7fxelebievvpr27w7gt24lflptpw3jeeuvafovgliq5utdst6xyruyd.onion:25552",
                )
                .unwrap(),
            );
            p2p_settings.seeds.push(
                url::Url::parse(
                    "tor://yvklzjnfmwxhyodhrkpomawjcdvcaushsj6torjz2gyd7e25f3gfunyd.onion:25552",
                )
                .unwrap(),
            );
            p2p_settings.active_profiles = vec!["tor".to_string()];
        } else {
            i!("Setup P2P network [clearnet]");
            let mut profile = NetworkProfile::default();
            profile.outbound_connect_timeout = 40;
            profile.channel_handshake_timeout = 30;
            p2p_settings.profiles.insert("tcp+tls".to_string(), profile);

            p2p_settings.outbound_connections = 5;
            p2p_settings.inbound_connections = 2;

            p2p_settings.seeds.push(url::Url::parse("tcp+tls://lilith0.dark.fi:25551").unwrap());
            p2p_settings.seeds.push(url::Url::parse("tcp+tls://lilith1.dark.fi:25551").unwrap());
            p2p_settings.active_profiles = vec!["tcp+tls".to_string()];
        }
        p2p_settings.p2p_datastore = p2p_datastore_path().into_os_string().into_string().ok();
        p2p_settings.hostlist = hostlist_path().into_os_string().into_string().ok();

        settings.add_p2p_settings(&p2p_settings);

        settings.load_settings();
        settings.update_p2p_settings(&mut p2p_settings);

        let p2p = match P2p::new(p2p_settings.clone(), ex.clone()).await {
            Ok(p2p) => p2p,
            Err(err) => {
                e!("Create p2p network failed: {err}!");
                return Err(Error::ServiceFailed)
            }
        };

        let event_graph = match EventGraph::new(
            p2p.clone(),
            db.clone(),
            std::path::PathBuf::new(),
            false,
            "darkirc_dag",
            1,
            ex.clone(),
        )
        .await
        {
            Ok(evgr) => evgr,
            Err(err) => {
                e!("Create event graph failed: {err}!");
                return Err(Error::ServiceFailed)
            }
        };

        if let Ok(prev_nick) = std::fs::read_to_string(nick_filename()) {
            nick.set(&mut PropertyAtomicGuard::none(), prev_nick);
        }

        let self_ = Arc::new(Self {
            node: node.clone(),
            tasks: OnceLock::new(),

            p2p,
            event_graph,

            seen_msgs: SyncMutex::new(SeenMessages::new()),
            nick,
            settings,
        });
        self_.clone().start(sg_root, ex).await;
        Ok(Pimpl::DarkIrc(self_))
    }

    async fn dag_sync(self: Arc<Self>, channel_sub: Subscription<DarkFiResult<ChannelPtr>>) {
        i!("Starting p2p network");
        while let Err(err) = self.p2p.clone().start().await {
            // This usually means we cannot listen on the inbound ports
            e!("Failed to start p2p network: {err}!");
            e!("Usually this means there is another process listening on the same ports.");
            e!("Trying again in {P2P_RETRY_TIME} secs");
            sleep(P2P_RETRY_TIME).await;
        }

        i!("Waiting for some P2P connections...");

        let mut sync_attempt = 0;
        loop {
            // Wait for a channel
            if let Err(err) = channel_sub.receive().await {
                w!("There was an error listening for channels. The service closed unexpectedly with error: {err}");
                continue
            }

            let peers_count = self.p2p.peers_count();
            self.notify_connect(peers_count, false).await;

            // Wait until we have enough connections
            if peers_count < SYNC_MIN_PEERS {
                i!("Connected to {peers_count} peers. Waiting for more connections.");
                continue
            }

            sync_attempt += 1;

            // Cool off periodically
            if sync_attempt > COOLOFF_SYNC_ATTEMPTS {
                i!("Wasn't able to sync yet. Cooling off for {COOLOFF_SLEEP_TIME} then will try again.");
                sleep(COOLOFF_SLEEP_TIME).await;
                sync_attempt = 0;
            }

            i!("Syncing event DAG (attempt #{sync_attempt})");
            match self.event_graph.dag_sync().await {
                Ok(()) => break,
                Err(e) => {
                    // TODO: Maybe at this point we should prune or something?
                    // TODO: Or maybe just tell the user to delete the DAG from FS.
                    w!("Failed DAG sync: ({e}). Waiting for more connections before retry.");
                }
            }
        }

        let peers_count = self.p2p.peers_count();
        self.notify_connect(peers_count, true).await;

        // Initial sync finished. Now just notify of connection changes
        loop {
            // Wait for a channel
            if let Err(err) = channel_sub.receive().await {
                w!("There was an error listening for channels. The service closed unexpectedly with error: {err}");
                continue
            }

            let peers_count = self.p2p.peers_count();
            self.notify_connect(peers_count, true).await;
        }
    }

    async fn notify_connect(&self, peers_count: usize, is_dag_synced: bool) {
        let node = self.node.upgrade().unwrap();
        node.trigger("connect", serialize(&(peers_count as u32, is_dag_synced))).await.unwrap();
    }

    async fn relay_events(self: Arc<Self>, ev_sub: Subscription<event_graph::Event>) {
        loop {
            let ev = ev_sub.receive().await;

            // Try to deserialize the `Event`'s content into a `Privmsg`
            let privmsg: Privmsg = match deserialize_async(ev.content()).await {
                Ok(v) => v,
                Err(e) => {
                    e!("[IRC CLIENT] Failed deserializing incoming Privmsg event: {}", e);
                    continue
                }
            };

            let mut timest = ev.timestamp;
            let msg_id = privmsg.msg_id(timest);
            t!(
                "Relaying ev_id={:?}, ev={ev:?}, msg_id={msg_id}, privmsg={privmsg:?}, timest={timest}",
                ev.id(),
            );

            let is_self = {
                let mut is_self = false;
                let mut seen = self.seen_msgs.lock().unwrap();
                match seen.get_status(&msg_id) {
                    Some(msg) => {
                        is_self = msg.is_self;

                        if !msg.is_self || msg.seen_times > 1 {
                            warn!(target: "plugin::darkirc", "Skipping duplicate seen message: {msg_id}");
                            continue
                        }
                    }
                    None => {
                        seen.push(msg_id.clone(), false);
                    }
                }
                is_self
            };

            // This is a hack to make messages appear sequentially in the UI
            let now_timest = UNIX_EPOCH.elapsed().unwrap().as_millis() as u64;
            if !is_self && timest.abs_diff(now_timest) < RECENT_TIME_DIST {
                d!("Applied timestamp correction: <{timest}> => <{now_timest}>");
                timest = now_timest;
            }

            // Strip off starting #
            let mut channel = privmsg.channel;
            if channel.is_empty() {
                warn!(target: "plugin::darkirc", "Received privmsg with empty channel!");
                continue
            }
            if channel.chars().next().unwrap() != '#' {
                warn!(target: "plugin::darkirc", "Skipping encrypted channel: {channel}");
                continue
            }
            channel.remove(0);

            // Workaround for the chatview hack. This nick is off limits!
            let mut nick = privmsg.nick;
            if nick == "NOTICE" {
                nick = "noticer".to_string();
            }

            let mut arg_data = vec![];
            channel.encode(&mut arg_data).unwrap();
            timest.encode(&mut arg_data).unwrap();
            msg_id.encode(&mut arg_data).unwrap();
            nick.encode(&mut arg_data).unwrap();
            privmsg.msg.encode(&mut arg_data).unwrap();

            let node = self.node.upgrade().unwrap();
            node.trigger("recv", arg_data).await.unwrap();
        }
    }

    async fn process_send(me: &Weak<Self>, sub: &MethodCallSub) -> bool {
        let Ok(method_call) = sub.receive().await else {
            d!("Event relayer closed");
            return false
        };

        t!("method called: send({method_call:?})");
        assert!(method_call.send_res.is_none());

        fn decode_data(data: &[u8]) -> std::io::Result<(Timestamp, String, String)> {
            let mut cur = Cursor::new(&data);
            let timest = Timestamp::decode(&mut cur).unwrap();
            let channel = String::decode(&mut cur)?;
            let msg = String::decode(&mut cur)?;
            Ok((timest, channel, msg))
        }

        let Ok((timest, channel, msg)) = decode_data(&method_call.data) else {
            e!("send() method invalid arg data");
            return true
        };

        let Some(self_) = me.upgrade() else {
            // Should not happen
            panic!("self destroyed before send_method_task was stopped!");
        };

        self_.handle_send(timest, channel, msg).await;

        true
    }

    async fn handle_send(&self, timest: Timestamp, channel: String, msg: String) {
        let nick = self.nick.get();

        // Send text to channel
        d!("Sending privmsg: {timest} {channel}: <{nick}> {msg}");
        let msg = Privmsg::new(channel, nick, msg);
        let evgr = self.event_graph.clone();
        let mut event = event_graph::Event::new(serialize_async(&msg).await, &evgr).await;
        event.timestamp = timest;
        let msg_id = msg.msg_id(timest);

        // Keep track of our own messages so we don't apply timestamp correction to them
        // which messes up the msg id.
        {
            let mut seen = self.seen_msgs.lock().unwrap();
            seen.push(msg_id.clone(), true);
        }

        let mut arg_data = vec![];
        timest.encode_async(&mut arg_data).await.unwrap();
        msg_id.encode_async(&mut arg_data).await.unwrap();
        msg.nick.encode_async(&mut arg_data).await.unwrap();
        msg.msg.encode_async(&mut arg_data).await.unwrap();

        // Broadcast the msg

        if let Err(e) = evgr.dag_insert(&[event.clone()]).await {
            error!(target: "darkirc", "Failed inserting new event to DAG: {}", e);
        }

        self.p2p.broadcast(&EventPut(event)).await;
    }

    async fn apply_settings(self_: Arc<Self>, _: BatchGuardPtr) {
        self_.settings.save_settings();

        let p2p_settings = self_.p2p.settings();
        let mut write_guard = p2p_settings.write().await;
        self_.settings.update_p2p_settings(&mut write_guard);
    }

    async fn start(self: Arc<Self>, sg_root: SceneNodePtr, ex: ExecutorPtr) {
        i!("Registering EventGraph P2P protocol");
        let event_graph_ = Arc::clone(&self.event_graph);
        let registry = self.p2p.protocol_registry();
        registry
            .register(SESSION_DEFAULT, move |channel, _| {
                let event_graph_ = event_graph_.clone();
                async move { ProtocolEventGraph::init(event_graph_, channel).await.unwrap() }
            })
            .await;

        let me = Arc::downgrade(&self);

        let node = &self.node.upgrade().unwrap();

        let method_sub = node.subscribe_method_call("send").unwrap();
        let me2 = me.clone();
        let send_method_task =
            ex.spawn(async move { while Self::process_send(&me2, &method_sub).await {} });

        let mut on_modify = OnModify::new(ex.clone(), self.node.clone(), me.clone());
        async fn save_nick(self_: Arc<DarkIrc>, _batch: BatchGuardPtr) {
            let _ = std::fs::write(nick_filename(), self_.nick.get());
        }
        on_modify.when_change(self.nick.prop(), save_nick);

        // `apply_settings` is triggered if any setting changes
        for setting_node in self.settings.setting_root.get_children().iter() {
            on_modify.when_change(
                setting_node.get_property("value").clone().unwrap(),
                Self::apply_settings,
            );
        }

        let ev_sub = self.event_graph.event_pub.clone().subscribe().await;
        let ev_task = ex.spawn(self.clone().relay_events(ev_sub));

        // Sync the DAG
        let channel_sub = self.p2p.hosts().subscribe_channel().await;
        let dag_task = ex.spawn(self.clone().dag_sync(channel_sub));

        // Subscribe to window start/stop signals for dynamic outbound connections
        let window_node = sg_root.lookup_node("/window").unwrap();

        let (start_slot, start_recv) = Slot::new("app_start");
        window_node.register("start", start_slot).unwrap();
        let p2p = self.p2p.clone();
        let start_task = ex.spawn(async move {
            while let Ok(_) = start_recv.recv().await {
                i!("App started: set outbound connections to {P2P_OUTBOUND_ACTIVE}");
                p2p.settings().write().await.outbound_connections = P2P_OUTBOUND_ACTIVE;
                p2p.clone().reload().await;
            }
        });

        let (stop_slot, stop_recv) = Slot::new("app_stop");
        window_node.register("stop", stop_slot).unwrap();
        let p2p = self.p2p.clone();
        let stop_task = ex.spawn(async move {
            while let Ok(_) = stop_recv.recv().await {
                i!("App stopped: set outbound connections to {P2P_OUTBOUND_SLEEP}");
                p2p.settings().write().await.outbound_connections = P2P_OUTBOUND_SLEEP;
                p2p.clone().reload().await;
            }
        });

        let mut tasks = vec![send_method_task, ev_task, dag_task, start_task, stop_task];
        tasks.append(&mut on_modify.tasks);
        self.tasks.set(tasks).unwrap();
    }
}