use common::{
    comp::{
        aura::{AuraChange, AuraKey, AuraKind, AuraTarget},
        buff::{self, BuffCategory},
        group::Group,
        Auras, BuffKind, Buffs, CharacterState, Health, Pos,
    },
    event::{EventBus, ServerEvent},
    resources::DeltaTime,
    uid::{Uid, UidAllocator},
};
use common_ecs::{Job, Origin, Phase, System};
use specs::{
    saveload::MarkerAllocator, shred::ResourceId, Entities, Join, Read, ReadStorage, SystemData,
    World, WriteStorage,
};
use std::time::Duration;

#[derive(SystemData)]
pub struct ReadData<'a> {
    entities: Entities<'a>,
    dt: Read<'a, DeltaTime>,
    server_bus: Read<'a, EventBus<ServerEvent>>,
    uid_allocator: Read<'a, UidAllocator>,
    positions: ReadStorage<'a, Pos>,
    char_states: ReadStorage<'a, CharacterState>,
    healths: ReadStorage<'a, Health>,
    groups: ReadStorage<'a, Group>,
    uids: ReadStorage<'a, Uid>,
}

#[derive(Default)]
pub struct Sys;
impl<'a> System<'a> for Sys {
    type SystemData = (
        ReadData<'a>,
        WriteStorage<'a, Auras>,
        WriteStorage<'a, Buffs>,
    );

    const NAME: &'static str = "aura";
    const ORIGIN: Origin = Origin::Common;
    const PHASE: Phase = Phase::Create;

    fn run(_job: &mut Job<Self>, (read_data, mut auras, mut buffs): Self::SystemData) {
        let mut server_emitter = read_data.server_bus.emitter();
        let dt = read_data.dt.0;

        auras.set_event_emission(false);
        buffs.set_event_emission(false);

        // Iterate through all buffs, on any buffs that are from an aura, sets the check
        // for whether the buff recently set by aura to false
        for (_, mut buffs_comp) in (&read_data.entities, &mut buffs).join() {
            for (_, buff) in buffs_comp.buffs.iter_mut() {
                if let Some(cat_id) = buff
                    .cat_ids
                    .iter_mut()
                    .find(|cat_id| matches!(cat_id, BuffCategory::FromAura(true)))
                {
                    *cat_id = BuffCategory::FromAura(false);
                }
            }
        }

        // Iterate through all entities with an aura
        for (entity, pos, mut auras_comp) in
            (&read_data.entities, &read_data.positions, &mut auras).join()
        {
            let mut expired_auras = Vec::<AuraKey>::new();
            // Iterate through the auras attached to this entity
            for (key, aura) in auras_comp.auras.iter_mut() {
                // Tick the aura and subtract dt from it
                if let Some(remaining_time) = &mut aura.duration {
                    if let Some(new_duration) =
                        remaining_time.checked_sub(Duration::from_secs_f32(dt))
                    {
                        *remaining_time = new_duration;
                    } else {
                        *remaining_time = Duration::default();
                        expired_auras.push(key);
                    }
                }
                for (target, target_pos, mut target_buffs, health, target_uid) in (
                    &read_data.entities,
                    &read_data.positions,
                    &mut buffs,
                    &read_data.healths,
                    &read_data.uids,
                )
                    .join()
                {
                    // Ensure entity is within the aura radius
                    if target_pos.0.distance_squared(pos.0) < aura.radius.powi(2) {
                        if let AuraTarget::GroupOf(uid) = aura.target {
                            let same_group = read_data
                                .uid_allocator
                                .retrieve_entity_internal(uid.into())
                                .and_then(|e| read_data.groups.get(e))
                                .map_or(false, |owner_group| {
                                    Some(owner_group) == read_data.groups.get(target)
                                })
                                || *target_uid == uid;

                            if !same_group {
                                continue;
                            }
                        }

                        // TODO: When more aura kinds (besides Buff) are
                        // implemented, match on them here
                        match aura.aura_kind {
                            AuraKind::Buff {
                                kind,
                                data,
                                category,
                                source,
                            } => {
                                let apply_buff = match kind {
                                    BuffKind::CampfireHeal => {
                                        matches!(
                                            read_data.char_states.get(target),
                                            Some(CharacterState::Sit)
                                        ) && health.current() < health.maximum()
                                    },
                                    // Add other specific buff conditions here
                                    _ => true,
                                };
                                if apply_buff {
                                    // Checks that target is not already receiving a buff from an
                                    // aura, where the buff is of the same kind, and is of at least
                                    // the same strength and of at least the same duration
                                    // If no such buff is present, adds the buff
                                    let emit_buff = !target_buffs.buffs.iter().any(|(_, buff)| {
                                        buff.cat_ids.iter().any(|cat_id| {
                                            matches!(cat_id, BuffCategory::FromAura(_))
                                        }) && buff.kind == kind
                                            && buff.data.strength >= data.strength
                                            && buff.time.map_or(true, |dur| {
                                                data.duration.map_or(false, |dur_2| dur >= dur_2)
                                            })
                                    });
                                    if emit_buff {
                                        use buff::*;
                                        server_emitter.emit(ServerEvent::Buff {
                                            entity: target,
                                            buff_change: BuffChange::Add(Buff::new(
                                                kind,
                                                data,
                                                vec![category, BuffCategory::FromAura(true)],
                                                source,
                                            )),
                                        });
                                    }
                                    // Finds all buffs on target that are from an aura, are of the
                                    // same buff kind, and are of at most the same strength
                                    // For any such buffs, marks it as recently applied
                                    for (_, buff) in
                                        target_buffs.buffs.iter_mut().filter(|(_, buff)| {
                                            buff.cat_ids.iter().any(|cat_id| {
                                                matches!(cat_id, BuffCategory::FromAura(_))
                                            }) && buff.kind == kind
                                                && buff.data.strength <= data.strength
                                        })
                                    {
                                        if let Some(cat_id) =
                                            buff.cat_ids.iter_mut().find(|cat_id| {
                                                matches!(cat_id, BuffCategory::FromAura(false))
                                            })
                                        {
                                            *cat_id = BuffCategory::FromAura(true);
                                        }
                                    }
                                }
                            },
                        }
                    }
                }
            }
            if !expired_auras.is_empty() {
                server_emitter.emit(ServerEvent::Aura {
                    entity,
                    aura_change: AuraChange::RemoveByKey(expired_auras),
                });
            }
        }
        auras.set_event_emission(true);
        buffs.set_event_emission(true);
    }
}