use std::sync::Arc;
use std::time::{Duration, Instant};

use elefren::debug::EventDisplay;
use elefren::debug::NotificationDisplay;
use elefren::debug::StatusDisplay;
use elefren::entities::account::Account;
use elefren::entities::event::Event;
use elefren::entities::notification::{Notification, NotificationType};
use elefren::entities::status::Status;
use elefren::status_builder::Visibility;
use elefren::{FediClient, StatusBuilder};
use futures::StreamExt;

use handle_mention::ProcessMention;

use crate::command::StatusCommand;
use crate::error::GroupError;
use crate::store::CommonConfig;
use crate::store::GroupConfig;
use crate::utils::{normalize_acct, LogError, VisExt};

mod handle_mention;

/// This is one group's config store capable of persistence
#[derive(Debug)]
pub struct GroupHandle {
    pub group_account: Account,
    pub client: FediClient,
    pub config: GroupConfig,
    pub cc: Arc<CommonConfig>,
}

// TODO move other options to common_config!

// // const DELAY_BEFORE_ACTION: Duration = Duration::from_millis(250);
// const DELAY_REOPEN_STREAM: Duration = Duration::from_millis(500);
// // higher because we can expect a lot of non-hashtag statuses here
// const SOCKET_ALIVE_TIMEOUT: Duration = Duration::from_secs(30);
// const SOCKET_RETIRE_TIME: Duration = Duration::from_secs(120);

macro_rules! grp_debug {
    ($self:ident, $f:expr) => {
        ::log::debug!(concat!("(@{}) ", $f), $self.config.get_acct());
    };
    ($self:ident, $f:expr, $($arg:tt)+) => {
        ::log::debug!(concat!("(@{}) ", $f), $self.config.get_acct(), $($arg)+);
    };
}

macro_rules! grp_info {
    ($self:ident, $f:expr) => {
        ::log::info!(concat!("(@{}) ", $f), $self.config.get_acct());
    };
    ($self:ident, $f:expr, $($arg:tt)+) => {
        ::log::info!(concat!("(@{}) ", $f), $self.config.get_acct(), $($arg)+);
    };
}

#[allow(unused)]
macro_rules! grp_trace {
    ($self:ident, $f:expr) => {
        ::log::trace!(concat!("(@{}) ", $f), $self.config.get_acct());
    };
    ($self:ident, $f:expr, $($arg:tt)+) => {
        ::log::trace!(concat!("(@{}) ", $f), $self.config.get_acct(), $($arg)+);
    };
}

macro_rules! grp_warn {
    ($self:ident, $f:expr) => {
        ::log::warn!(concat!("(@{}) ", $f), $self.config.get_acct());
    };
    ($self:ident, $f:expr, $($arg:tt)+) => {
        ::log::warn!(concat!("(@{}) ", $f), $self.config.get_acct(), $($arg)+);
    };
}

macro_rules! grp_error {
    ($self:ident, $f:expr) => {
        ::log::error!(concat!("(@{}) ", $f), $self.config.get_acct());
    };
    ($self:ident, $f:expr, $($arg:tt)+) => {
        ::log::error!(concat!("(@{}) ", $f), $self.config.get_acct(), $($arg)+);
    };
}

impl GroupHandle {
    #[allow(unused)]
    pub async fn save(&mut self) -> Result<(), GroupError> {
        grp_debug!(self, "Saving group state unconditionally");
        self.config.save(false).await?;
        Ok(())
    }

    pub async fn save_if_needed(&mut self) -> Result<(), GroupError> {
        if self.config.is_dirty() {
            grp_debug!(self, "Saving group state due to changes");
            self.config.save_if_needed(false).await?;
        }
        Ok(())
    }
}

trait NotifTimestamp {
    fn timestamp_millis(&self) -> u64;
}

impl NotifTimestamp for Notification {
    fn timestamp_millis(&self) -> u64 {
        self.created_at.timestamp_millis().max(0) as u64
    }
}

impl NotifTimestamp for Status {
    fn timestamp_millis(&self) -> u64 {
        // this may not work well for unseen status tracking,
        // if ancient statuses were to appear in the timeline :(
        self.created_at.timestamp_millis().max(0) as u64
    }
}

impl GroupHandle {
    pub async fn run(&mut self) -> Result<(), GroupError> {
        loop {
            match self.run_internal().await {
                Ok(()) => unreachable!(),
                Err(e @ GroupError::BadConfig(_)) => {
                    grp_error!(self, "ERROR in group handler, aborting! {}", e);
                    return Err(e);
                }
                Err(other) => {
                    grp_error!(self, "ERROR in group handler, will restart! {}", other);
                    tokio::time::sleep(Duration::from_secs_f64(self.cc.delay_reopen_error_s)).await;
                }
            }
        }
    }

    pub async fn run_internal(&mut self) -> Result<(), GroupError> {
        loop {
            grp_debug!(self, "Opening streaming API socket");

            // wrapped in a timeout, this seems like the only place the group could hang
            // (https://git.ondrovo.com/MightyPork/group-actor/issues/8)
            let mut events = match tokio::time::timeout(Duration::from_secs(3), self.client.streaming_user()).await {
                Ok(Ok(events)) => events,
                Ok(Err(e)) => return Err(e.into()),
                Err(_) => {
                    return Err(GroupError::ApiTimeout);
                }
            };

            let socket_open_time = Instant::now();
            let mut last_rx = Instant::now();

            match self.catch_up_with_missed_notifications().await {
                Ok(true) => {
                    grp_debug!(self, "Some missed notifs handled");
                }
                Ok(false) => {
                    grp_debug!(self, "No notifs missed");
                }
                Err(e) => {
                    grp_error!(self, "Failed to handle missed notifs: {}", e);
                }
            }

            match self.catch_up_with_missed_statuses().await {
                Ok(true) => {
                    grp_debug!(self, "Some missed statuses handled");
                }
                Ok(false) => {
                    grp_debug!(self, "No statuses missed");
                }
                Err(e) => {
                    grp_error!(self, "Failed to handle missed statuses: {}", e);
                }
            }

            self.save_if_needed().await.log_error("Failed to save");

            'rx: loop {
                let remains_to_idle_close =
                    Duration::from_secs_f64(self.cc.socket_alive_timeout_s).saturating_sub(last_rx.elapsed());

                let remains_to_retire =
                    Duration::from_secs_f64(self.cc.socket_retire_time_s).saturating_sub(socket_open_time.elapsed());

                if remains_to_idle_close.is_zero() {
                    grp_warn!(self, "Socket idle too long, close");
                    break 'rx;
                }
                if remains_to_retire.is_zero() {
                    grp_debug!(self, "Socket open too long, closing");
                    break 'rx;
                }

                let timeout = remains_to_idle_close.min(remains_to_retire).max(Duration::from_secs(1)); // at least 1s

                grp_debug!(self, "Wait for message {:?}", timeout);
                match tokio::time::timeout(timeout, events.next()).await {
                    Ok(Some(event)) => {
                        last_rx = Instant::now();
                        grp_debug!(self, "(@{}) Event: {}", self.config.get_acct(), EventDisplay(&event));
                        match event {
                            Event::Update(status) => {
                                self.handle_status(status).await.log_error("Error handling a status");
                            }
                            Event::Notification(n) => {
                                self.handle_notification(n).await.log_error("Error handling a notification");
                            }
                            Event::Delete(_id) => {}
                            Event::FiltersChanged => {}
                            Event::Heartbeat => {}
                        }

                        self.save_if_needed().await.log_error("Failed to save");
                    }
                    Ok(None) => {
                        grp_warn!(self, "Group @{} socket closed, restarting...", self.config.get_acct());
                        break 'rx;
                    }
                    Err(_) => {
                        // Timeout so we can save if needed
                    }
                }
            }

            grp_warn!(self, "Notif stream closed, will reopen");
            tokio::time::sleep(Duration::from_secs_f64(self.cc.delay_reopen_closed_s)).await;
        }
    }

    async fn handle_notification(&mut self, n: Notification) -> Result<(), GroupError> {
        grp_debug!(self, "Handling notif #{}", n.id);
        let ts = n.timestamp_millis();
        self.config.set_last_notif(ts);

        let group_acct = self.config.get_acct().to_string();
        let notif_user_id = &n.account.id;
        let notif_acct = normalize_acct(&n.account.acct, &group_acct)?;

        if notif_acct == group_acct {
            grp_debug!(self, "This is our post, ignore that");
            return Ok(());
        }

        if self.config.is_banned(&notif_acct) {
            grp_warn!(self, "Notification actor {} is banned!", notif_acct);
            return Ok(());
        }

        match n.notification_type {
            NotificationType::Mention => {
                if let Some(status) = n.status {
                    self.handle_mention_status(status).await?;
                }
            }
            NotificationType::Follow => {
                grp_info!(self, "New follower!");
                // Just greet the user always
                self.handle_new_follow(&notif_acct, notif_user_id).await;
            }
            NotificationType::Favourite => {}
            NotificationType::Reblog => {}
            NotificationType::Other(_) => {}
        }

        Ok(())
    }

    /// Handle a non-mention status for tags
    async fn handle_status(&mut self, s: Status) -> Result<(), GroupError> {
        grp_debug!(self, "Handling status #{}", s.id);
        let ts = s.timestamp_millis();
        self.config.set_last_status(ts);

        let private = s.visibility.is_private();
        let has_hashtags = s.content.contains('#');
        let group_user = self.config.get_acct();
        let status_user = normalize_acct(&s.account.acct, group_user)?;
        let member_or_admin = self.config.is_member_or_admin(&status_user);
        let commands = crate::command::parse_slash_commands(&s.content);

        if status_user == group_user {
            grp_debug!(self, "This is our post, discard");
            return Ok(());
        }

        if self.config.is_banned(&status_user) {
            grp_debug!(self, "Status author @{} is banned, discard", status_user);
            return Ok(());
        }

        if self.config.is_optout(&status_user) && !member_or_admin {
            grp_debug!(self, "Status author @{} opted out, discard", status_user);
            return Ok(());
        }

        if commands.contains(&StatusCommand::Ignore) {
            grp_debug!(self, "Post has IGNORE command, discard");
            return Ok(());
        }

        // Sometimes notifications don't work, but we see the mentions as statuses
        for m in &s.mentions {
            let mentioned_user = normalize_acct(&m.acct, group_user)?;
            if mentioned_user == group_user {
                let notif_time = self.config.get_last_notif();

                if notif_time <= ts {
                    grp_debug!(
                        self,
                        "mentioned but status is older than last notif, can't be a valid notif, discard"
                    );
                    return Ok(());
                }

                if !commands.is_empty() {
                    grp_debug!(self, "Detected commands for this group, handle as notif");

                    return self
                        .handle_notification(Notification {
                            id: s.id.clone(), // ???
                            notification_type: NotificationType::Mention,
                            created_at: s.created_at,
                            account: s.account.clone(),
                            status: Some(s),
                        })
                        .await;
                } else if private {
                    grp_debug!(self, "mention in private without commands, discard, this is nothing");
                    return Ok(());
                }
            }
        }

        // optout does not work for members and admins, so don't check it

        if !member_or_admin {
            grp_debug!(self, "Status author @{} is not a member, discard", status_user);
            return Ok(());
        }

        if private {
            grp_debug!(self, "Status is private, discard");
            return Ok(());
        }

        if !has_hashtags {
            grp_debug!(self, "No hashtags, discard");
            return Ok(());
        }

        let tags = crate::command::parse_status_tags(&s.content);
        grp_debug!(self, "Tags in status: {:?}", tags);

        'tags: for t in tags {
            if self.config.is_tag_followed(&t) {
                grp_info!(self, "REBLOG #{} STATUS", t);
                self.client.reblog(&s.id).await.log_error("Failed to reblog");
                self.delay_after_post().await;
                break 'tags; // do not reblog multiple times!
            } else {
                grp_debug!(self, "#{} is not a group tag", t);
            }
        }

        Ok(())
    }

    async fn follow_user(&mut self, id: &str) -> Result<(), GroupError> {
        self.client.follow(id).await?;
        self.delay_after_post().await;
        Ok(())
    }

    /// Catch up with missed notifications, returns true if any were handled
    async fn catch_up_with_missed_notifications(&mut self) -> Result<bool, GroupError> {
        let last_notif = self.config.get_last_notif();

        let notifications = self.client.notifications().await?;
        let mut iter = notifications.items_iter();

        let mut notifs_to_handle = vec![];

        // They are retrieved newest first, but we want oldest first for chronological handling

        let mut num = 0;
        let mut old_pn = 0;
        while let Some(n) = iter.next_item().await {
            let ts = n.timestamp_millis();
            if ts <= last_notif {
                break; // reached our last seen notif
            }

            grp_debug!(self, "Inspecting notif {}", NotificationDisplay(&n));
            notifs_to_handle.push(n);
            num += 1;
            if num > self.cc.max_catchup_notifs {
                grp_warn!(self, "Too many notifs missed to catch up!");
                break;
            }

            let pn = iter.page_num();
            if pn != old_pn {
                old_pn = pn;
                // sleep so we dont make the api angry
                tokio::time::sleep(Duration::from_secs_f64(self.cc.delay_fetch_page_s)).await;
            }
        }

        if notifs_to_handle.is_empty() {
            return Ok(false);
        }

        notifs_to_handle.reverse();

        grp_debug!(self, "{} notifications to catch up!", notifs_to_handle.len());

        for n in notifs_to_handle {
            grp_debug!(self, "Handling missed notification: {}", NotificationDisplay(&n));
            self.handle_notification(n).await.log_error("Error handling a notification");
        }

        Ok(true)
    }

    /// Catch up with missed statuses, returns true if any were handled
    async fn catch_up_with_missed_statuses(&mut self) -> Result<bool, GroupError> {
        let last_status = self.config.get_last_status();

        let statuses = self.client.get_home_timeline().await?;
        let mut iter = statuses.items_iter();

        let mut statuses_to_handle = vec![];

        // They are retrieved newest first, but we want oldest first for chronological handling

        let mut newest_status = None;

        let mut num = 0;
        let mut old_pn = 0;
        while let Some(s) = iter.next_item().await {
            let ts = s.timestamp_millis();
            if ts <= last_status {
                break; // reached our last seen status (hopefully there arent any retro-bumped)
            }

            grp_debug!(self, "Inspecting status {}", StatusDisplay(&s));

            if newest_status.is_none() {
                newest_status = Some(ts);
            }

            statuses_to_handle.push(s);
            num += 1;
            if num > self.cc.max_catchup_statuses {
                grp_warn!(self, "Too many statuses missed to catch up!");
                break;
            }

            let pn = iter.page_num();
            if pn != old_pn {
                old_pn = pn;
                // sleep so we dont make the api angry
                tokio::time::sleep(Duration::from_secs_f64(self.cc.delay_fetch_page_s)).await;
            }
        }

        if let Some(ts) = newest_status {
            self.config.set_last_status(ts);
        }

        if statuses_to_handle.is_empty() {
            grp_debug!(self, "No statuses to handle");
            return Ok(false);
        }

        statuses_to_handle.reverse();

        grp_debug!(self, "{} statuses to catch up!", statuses_to_handle.len());

        for s in statuses_to_handle {
            grp_debug!(self, "Handling missed status: {}", StatusDisplay(&s));
            self.handle_status(s).await.log_error("Error handling a status");
        }

        Ok(true)
    }

    async fn handle_mention_status(&mut self, status: Status) -> Result<(), GroupError> {
        let res = ProcessMention::run(self, status).await;

        self.save_if_needed().await.log_error("Failed to save");

        res
    }

    async fn handle_new_follow(&mut self, notif_acct: &str, notif_user_id: &str) {
        let mut follow_back = false;
        let text = if self.config.is_member_only() {
            // Admins are listed without @, so they won't become handles here.
            // Tagging all admins would be annoying.
            let mut admins = self.config.get_admins().cloned().collect::<Vec<_>>();
            admins.sort();

            format!(
                "\
                @{user} Welcome to the group! This group has posting restricted to members. \
                If you'd like to join, please ask one of the group admins:\n\
                {admins}",
                user = notif_acct,
                admins = admins.join(", ")
            )
        } else {
            follow_back = true;

            self.config.set_member(notif_acct, true).log_error("Fail add a member");

            format!(
                "\
                @{user} Welcome to the group! The group user will now follow you back to complete the sign-up. \
                To share a post, @ the group user or use a group hashtag.\n\n\
                Use /help for more info.",
                user = notif_acct
            )
        };

        let post = StatusBuilder::new()
            .status(text)
            .content_type("text/markdown")
            .visibility(Visibility::Direct)
            .build()
            .expect("error build status");

        self.client.new_status(post).await.log_error("Failed to post");
        self.delay_after_post().await;

        if follow_back {
            self.follow_user(notif_user_id).await.log_error("Failed to follow back");
        }
    }

    async fn delay_after_post(&self) {
        tokio::time::sleep(Duration::from_secs_f64(self.cc.delay_after_post_s)).await;
    }
}