use crate::{utils, Error, Result};
use ruma::{
    events::{collections::only::Event as EduEvent, EventJson},
    identifiers::{RoomId, UserId},
};
use std::convert::TryFrom;

pub struct RoomEdus {
    pub(in super::super) roomuserid_lastread: sled::Tree, // RoomUserId = Room + User
    pub(in super::super) roomlatestid_roomlatest: sled::Tree, // Read Receipts, RoomLatestId = RoomId + Count + UserId
    pub(in super::super) roomactiveid_userid: sled::Tree, // Typing, RoomActiveId = RoomId + TimeoutTime + Count
    pub(in super::super) roomid_lastroomactiveupdate: sled::Tree, // LastRoomActiveUpdate = Count
}

impl RoomEdus {
    /// Adds an event which will be saved until a new event replaces it (e.g. read receipt).
    pub fn roomlatest_update(
        &self,
        user_id: &UserId,
        room_id: &RoomId,
        event: EduEvent,
        globals: &super::super::globals::Globals,
    ) -> Result<()> {
        let mut prefix = room_id.to_string().as_bytes().to_vec();
        prefix.push(0xff);

        // Remove old entry
        if let Some(old) = self
            .roomlatestid_roomlatest
            .scan_prefix(&prefix)
            .keys()
            .rev()
            .filter_map(|r| r.ok())
            .take_while(|key| key.starts_with(&prefix))
            .find(|key| {
                key.rsplit(|&b| b == 0xff)
                    .next()
                    .expect("rsplit always returns an element")
                    == user_id.to_string().as_bytes()
            })
        {
            // This is the old room_latest
            self.roomlatestid_roomlatest.remove(old)?;
        }

        let mut room_latest_id = prefix;
        room_latest_id.extend_from_slice(&globals.next_count()?.to_be_bytes());
        room_latest_id.push(0xff);
        room_latest_id.extend_from_slice(&user_id.to_string().as_bytes());

        self.roomlatestid_roomlatest.insert(
            room_latest_id,
            &*serde_json::to_string(&event).expect("EduEvent::to_string always works"),
        )?;

        Ok(())
    }

    /// Returns an iterator over the most recent read_receipts in a room that happened after the event with id `since`.
    pub fn roomlatests_since(
        &self,
        room_id: &RoomId,
        since: u64,
    ) -> Result<impl Iterator<Item = Result<EventJson<EduEvent>>>> {
        let mut prefix = room_id.to_string().as_bytes().to_vec();
        prefix.push(0xff);

        let mut first_possible_edu = prefix.clone();
        first_possible_edu.extend_from_slice(&(since + 1).to_be_bytes()); // +1 so we don't send the event at since

        Ok(self
            .roomlatestid_roomlatest
            .range(&*first_possible_edu..)
            .filter_map(|r| r.ok())
            .take_while(move |(k, _)| k.starts_with(&prefix))
            .map(|(_, v)| {
                Ok(serde_json::from_slice(&v).map_err(|_| {
                    Error::bad_database("Read receipt in roomlatestid_roomlatest is invalid.")
                })?)
            }))
    }

    /// Sets a user as typing until the timeout timestamp is reached or roomactive_remove is
    /// called.
    pub fn roomactive_add(
        &self,
        user_id: &UserId,
        room_id: &RoomId,
        timeout: u64,
        globals: &super::super::globals::Globals,
    ) -> Result<()> {
        let mut prefix = room_id.to_string().as_bytes().to_vec();
        prefix.push(0xff);

        let count = globals.next_count()?.to_be_bytes();

        let mut room_active_id = prefix;
        room_active_id.extend_from_slice(&timeout.to_be_bytes());
        room_active_id.push(0xff);
        room_active_id.extend_from_slice(&count);

        self.roomactiveid_userid
            .insert(&room_active_id, &*user_id.to_string().as_bytes())?;

        self.roomid_lastroomactiveupdate
            .insert(&room_id.to_string().as_bytes(), &count)?;

        Ok(())
    }

    /// Removes a user from typing before the timeout is reached.
    pub fn roomactive_remove(
        &self,
        user_id: &UserId,
        room_id: &RoomId,
        globals: &super::super::globals::Globals,
    ) -> Result<()> {
        let mut prefix = room_id.to_string().as_bytes().to_vec();
        prefix.push(0xff);

        let user_id = user_id.to_string();

        let mut found_outdated = false;

        // Maybe there are multiple ones from calling roomactive_add multiple times
        for outdated_edu in self
            .roomactiveid_userid
            .scan_prefix(&prefix)
            .filter_map(|r| r.ok())
            .filter(|(_, v)| v == user_id.as_bytes())
        {
            self.roomactiveid_userid.remove(outdated_edu.0)?;
            found_outdated = true;
        }

        if found_outdated {
            self.roomid_lastroomactiveupdate.insert(
                &room_id.to_string().as_bytes(),
                &globals.next_count()?.to_be_bytes(),
            )?;
        }

        Ok(())
    }

    /// Makes sure that typing events with old timestamps get removed.
    fn roomactives_maintain(
        &self,
        room_id: &RoomId,
        globals: &super::super::globals::Globals,
    ) -> Result<()> {
        let mut prefix = room_id.to_string().as_bytes().to_vec();
        prefix.push(0xff);

        let current_timestamp = utils::millis_since_unix_epoch();

        let mut found_outdated = false;

        // Find all outdated edus before inserting a new one
        for outdated_edu in self
            .roomactiveid_userid
            .scan_prefix(&prefix)
            .keys()
            .map(|key| {
                let key = key?;
                Ok::<_, Error>((
                    key.clone(),
                    utils::u64_from_bytes(key.split(|&b| b == 0xff).nth(1).ok_or_else(|| {
                        Error::bad_database("RoomActive has invalid timestamp or delimiters.")
                    })?)
                    .map_err(|_| Error::bad_database("RoomActive has invalid timestamp bytes."))?,
                ))
            })
            .filter_map(|r| r.ok())
            .take_while(|&(_, timestamp)| timestamp < current_timestamp)
        {
            // This is an outdated edu (time > timestamp)
            self.roomactiveid_userid.remove(outdated_edu.0)?;
            found_outdated = true;
        }

        if found_outdated {
            self.roomid_lastroomactiveupdate.insert(
                &room_id.to_string().as_bytes(),
                &globals.next_count()?.to_be_bytes(),
            )?;
        }

        Ok(())
    }

    /// Returns an iterator over all active events (e.g. typing notifications).
    pub fn last_roomactive_update(
        &self,
        room_id: &RoomId,
        globals: &super::super::globals::Globals,
    ) -> Result<u64> {
        self.roomactives_maintain(room_id, globals)?;

        Ok(self
            .roomid_lastroomactiveupdate
            .get(&room_id.to_string().as_bytes())?
            .map_or(Ok::<_, Error>(None), |bytes| {
                Ok(Some(utils::u64_from_bytes(&bytes).map_err(|_| {
                    Error::bad_database("Count in roomid_lastroomactiveupdate is invalid.")
                })?))
            })?
            .unwrap_or(0))
    }

    /// Returns an iterator over all active events (e.g. typing notifications).
    pub fn roomactives_all(&self, room_id: &RoomId) -> Result<ruma::events::typing::TypingEvent> {
        let mut prefix = room_id.to_string().as_bytes().to_vec();
        prefix.push(0xff);

        let mut user_ids = Vec::new();

        for user_id in self
            .roomactiveid_userid
            .scan_prefix(prefix)
            .values()
            .map(|user_id| {
                Ok::<_, Error>(
                    UserId::try_from(utils::string_from_bytes(&user_id?).map_err(|_| {
                        Error::bad_database("User ID in roomactiveid_userid is invalid unicode.")
                    })?)
                    .map_err(|_| {
                        Error::bad_database("User ID in roomactiveid_userid is invalid.")
                    })?,
                )
            })
        {
            user_ids.push(user_id?);
        }

        Ok(ruma::events::typing::TypingEvent {
            content: ruma::events::typing::TypingEventContent { user_ids },
            room_id: None, // Can be inferred
        })
    }

    /// Sets a private read marker at `count`.
    pub fn room_read_set(&self, room_id: &RoomId, user_id: &UserId, count: u64) -> Result<()> {
        let mut key = room_id.to_string().as_bytes().to_vec();
        key.push(0xff);
        key.extend_from_slice(&user_id.to_string().as_bytes());

        self.roomuserid_lastread.insert(key, &count.to_be_bytes())?;

        Ok(())
    }

    /// Returns the private read marker.
    pub fn room_read_get(&self, room_id: &RoomId, user_id: &UserId) -> Result<Option<u64>> {
        let mut key = room_id.to_string().as_bytes().to_vec();
        key.push(0xff);
        key.extend_from_slice(&user_id.to_string().as_bytes());

        self.roomuserid_lastread.get(key)?.map_or(Ok(None), |v| {
            Ok(Some(utils::u64_from_bytes(&v).map_err(|_| {
                Error::bad_database("Invalid private read marker bytes")
            })?))
        })
    }
}