use super::SysTimer;
use crate::client::{self, Client, RegionSubscription};
use common::{
    comp::{CharacterState, Ori, Player, Pos, Vel},
    msg::ServerMsg,
    region::{region_in_vd, regions_in_vd, Event as RegionEvent, RegionMap},
    state::Uid,
    terrain::TerrainChunkSize,
    vol::RectVolSize,
};
use specs::{Entities, Join, ReadExpect, ReadStorage, System, Write, WriteStorage};
use vek::*;

/// This system will update region subscriptions based on client positions
pub struct Sys;
impl<'a> System<'a> for Sys {
    type SystemData = (
        Entities<'a>,
        ReadExpect<'a, RegionMap>,
        Write<'a, SysTimer<Self>>,
        ReadStorage<'a, Uid>,
        ReadStorage<'a, Pos>,
        ReadStorage<'a, Vel>,
        ReadStorage<'a, Ori>,
        ReadStorage<'a, CharacterState>,
        ReadStorage<'a, Player>,
        WriteStorage<'a, Client>,
        WriteStorage<'a, RegionSubscription>,
    );

    fn run(
        &mut self,
        (
            entities,
            region_map,
            mut timer,
            uids,
            positions,
            velocities,
            orientations,
            character_states,
            players,
            mut clients,
            mut subscriptions,
        ): Self::SystemData,
    ) {
        timer.start();

        // To update subscriptions
        // 1. Iterate through clients
        // 2. Calculate current chunk position
        // 3. If chunk is the same return, otherwise continue (use fuzzyiness)
        // 4. Iterate through subscribed regions
        // 5. Check if region is still in range (use fuzzyiness)
        // 6. If not in range
        //     - remove from hashset
        //     - inform client of which entities to remove
        // 7. Determine list of regions that are in range and iterate through it
        //    - check if in hashset (hash calc) if not add it
        let mut regions_to_remove = Vec::new();
        for (client, subscription, pos, vd) in
            (&mut clients, &mut subscriptions, &positions, &players)
                .join()
                .filter_map(|(c, s, pos, player)| player.view_distance.map(|v| (c, s, pos, v)))
        {
            let chunk = (Vec2::<f32>::from(pos.0))
                .map2(TerrainChunkSize::RECT_SIZE, |e, sz| e as i32 / sz as i32);
            // Only update regions when moving to a new chunk
            // uses a fuzzy border to prevent rapid triggering when moving along chunk boundaries
            if chunk != subscription.fuzzy_chunk
                && (subscription
                    .fuzzy_chunk
                    .map2(TerrainChunkSize::RECT_SIZE, |e, sz| {
                        (e as f32 + 0.5) * sz as f32
                    })
                    - Vec2::from(pos.0))
                .map2(TerrainChunkSize::RECT_SIZE, |e, sz| {
                    e.abs() > (sz / 2 + client::CHUNK_FUZZ) as f32
                })
                .reduce_or()
            {
                // Update current chunk
                subscription.fuzzy_chunk = (Vec2::<f32>::from(pos.0))
                    .map2(TerrainChunkSize::RECT_SIZE, |e, sz| e as i32 / sz as i32);
                // Use the largest side length as our chunk size
                let chunk_size = TerrainChunkSize::RECT_SIZE.reduce_max() as f32;
                // Iterate through currently subscribed regions
                for key in &subscription.regions {
                    // Check if the region is not within range anymore
                    if !region_in_vd(
                        *key,
                        pos.0,
                        (vd as f32 * chunk_size)
                            + (client::CHUNK_FUZZ as f32 + client::REGION_FUZZ as f32 + chunk_size)
                                * 2.0f32.sqrt(),
                    ) {
                        // Add to the list of regions to remove
                        regions_to_remove.push(*key);
                    }
                }

                // Iterate through regions to remove
                for key in regions_to_remove.drain(..) {
                    // Remove region from this clients set of subscribed regions
                    subscription.regions.remove(&key);
                    // Tell the client to delete the entities in that region if it exists in the RegionMap
                    if let Some(region) = region_map.get(key) {
                        // Process entity left events since they won't be processed during phsyics sync because this region is no longer subscribed to
                        for event in region.events() {
                            match event {
                                RegionEvent::Entered(_, _) => {} // These don't need to be processed because this region is being thrown out anyway
                                RegionEvent::Left(id, maybe_key) => {
                                    // Lookup UID for entity
                                    if let Some(&uid) = uids.get(entities.entity(*id)) {
                                        if !maybe_key
                                            .as_ref()
                                            .map(|key| subscription.regions.contains(key))
                                            .unwrap_or(false)
                                        {
                                            client.notify(ServerMsg::DeleteEntity(uid.into()));
                                        }
                                    }
                                }
                            }
                        }
                        for (&uid, _) in (&uids, region.entities()).join() {
                            client.notify(ServerMsg::DeleteEntity(uid.into()))
                        }
                    }
                }

                for key in regions_in_vd(
                    pos.0,
                    (vd as f32 * chunk_size)
                        + (client::CHUNK_FUZZ as f32 + chunk_size) * 2.0f32.sqrt(),
                ) {
                    // Send client intial info about the entities in this region
                    if subscription.regions.insert(key) {
                        if let Some(region) = region_map.get(key) {
                            for (uid, pos, vel, ori, character_state, _) in (
                                &uids,
                                &positions,
                                velocities.maybe(),
                                orientations.maybe(),
                                character_states.maybe(),
                                region.entities(),
                            )
                                .join()
                            {
                                super::entity_sync::send_initial_unsynced_components(
                                    client,
                                    uid,
                                    pos,
                                    vel,
                                    ori,
                                    character_state,
                                );
                            }
                        }
                    }
                }
            }
        }

        timer.end();
    }
}