#![feature(label_break_value, duration_float)]

pub mod error;

// Reexports
pub use crate::error::Error;
pub use specs::join::Join;
pub use specs::Entity as EcsEntity;

use common::{
    comp,
    msg::{ClientMsg, ClientState, ServerMsg},
    net::PostBox,
    state::State,
};
use std::{
    collections::HashMap,
    net::SocketAddr,
    time::{Duration, Instant},
};

use threadpool::ThreadPool;
use vek::*;

const SERVER_TIMEOUT: f64 = 20.0; // Seconds

pub enum Event {
    Chat(String),
    Disconnect,
}

pub struct Client {
    client_state: ClientState,
    thread_pool: ThreadPool,

    last_ping: f64,
    postbox: PostBox<ClientMsg, ServerMsg>,

    last_server_ping: Instant,
    last_ping_delta: f64,

    tick: u64,
    state: State,
    entity: EcsEntity,
    view_distance: Option<u32>,

    pending_chunks: HashMap<Vec2<i32>, Instant>,
}

impl Client {
    /// Create a new `Client`.
    #[allow(dead_code)]
    pub fn new<A: Into<SocketAddr>>(addr: A, view_distance: Option<u32>) -> Result<Self, Error> {
        let mut client_state = ClientState::Connected;
        let mut postbox = PostBox::to(addr)?;

        // Wait for initial sync
        let (mut state, entity) = match postbox.next_message() {
            Some(ServerMsg::InitialSync {
                ecs_state,
                entity_uid,
            }) => {
                let mut state = State::from_state_package(ecs_state);
                let entity = state
                    .ecs()
                    .entity_from_uid(entity_uid)
                    .ok_or(Error::ServerWentMad)?;
                (state, entity)
            }
            _ => return Err(Error::ServerWentMad),
        };

        Ok(Self {
            client_state,
            thread_pool: threadpool::Builder::new()
                .thread_name("veloren-worker".into())
                .build(),

            last_ping: state.get_time(),
            postbox,

            last_server_ping: Instant::now(),
            last_ping_delta: 0.0,

            tick: 0,
            state,
            entity,
            view_distance,

            pending_chunks: HashMap::new(),
        })
    }

    /// Request a state transition to `ClientState::Registered`.
    pub fn register(&mut self, player: comp::Player) {
        self.postbox.send_message(ClientMsg::Register { player });
        self.client_state = ClientState::Pending;
    }

    /// Request a state transition to `ClientState::Character`.
    pub fn request_character(&mut self, name: String, body: comp::Body) {
        self.postbox
            .send_message(ClientMsg::Character { name, body });
        self.client_state = ClientState::Pending;
    }

    pub fn set_view_distance(&mut self, view_distance: u32) {
        self.view_distance = Some(view_distance.max(1).min(25));
        self.postbox
            .send_message(ClientMsg::SetViewDistance(self.view_distance.unwrap())); // Can't fail
    }

    /// Send a chat message to the server.
    #[allow(dead_code)]
    pub fn send_chat(&mut self, msg: String) {
        self.postbox.send_message(ClientMsg::Chat(msg))
    }

    /// Jump locally, the new positions will be synced to the server
    #[allow(dead_code)]
    pub fn jump(&mut self) {
        if self.client_state != ClientState::Character {
            return;
        }
        self.state.write_component(self.entity, comp::Jumping);
    }

    /// Start to glide locally, animation will be synced
    #[allow(dead_code)]
    pub fn glide(&mut self, state: bool) {
        if self.client_state != ClientState::Character {
            return;
        }
        if state {
            self.state.write_component(self.entity, comp::Gliding);
        } else {
            self.state
                .ecs_mut()
                .write_storage::<comp::Gliding>()
                .remove(self.entity);
        }
    }

    /// Start to attack
    #[allow(dead_code)]
    pub fn attack(&mut self) {
        if self.client_state != ClientState::Character {
            return;
        }
        // TODO: Test if attack is possible using timeout
        self.state
            .write_component(self.entity, comp::Attacking::start());
        self.postbox.send_message(ClientMsg::Attack);
    }

    /// Tell the server the client wants to respawn.
    #[allow(dead_code)]
    pub fn respawn(&mut self) {
        if self.client_state != ClientState::Dead {
            return;
        }
        self.postbox.send_message(ClientMsg::Respawn)
    }

    /// Remove all cached terrain
    #[allow(dead_code)]
    pub fn clear_terrain(&mut self) {
        self.state.clear_terrain();
        self.pending_chunks.clear();
    }

    /// Execute a single client tick, handle input and update the game state by the given duration.
    #[allow(dead_code)]
    pub fn tick(&mut self, control: comp::Control, dt: Duration) -> Result<Vec<Event>, Error> {
        // This tick function is the centre of the Veloren universe. Most client-side things are
        // managed from here, and as such it's important that it stays organised. Please consult
        // the core developers before making significant changes to this code. Here is the
        // approximate order of things. Please update it as this code changes.
        //
        // 1) Collect input from the frontend, apply input effects to the state of the game
        // 2) Handle messages from the server
        // 3) Go through any events (timer-driven or otherwise) that need handling and apply them
        //    to the state of the game
        // 4) Perform a single LocalState tick (i.e: update the world and entities in the world)
        // 5) Go through the terrain update queue and apply all changes to the terrain
        // 6) Sync information to the server
        // 7) Finish the tick, passing actions of the main thread back to the frontend

        // 1) Handle input from frontend.
        // Pass character actions from frontend input to the player's entity.
        // TODO: Only do this if the entity already has a Inputs component!
        if self.client_state == ClientState::Character {
            self.state.write_component(self.entity, control.clone());
        }

        // 2) Build up a list of events for this frame, to be passed to the frontend.
        let mut frontend_events = Vec::new();

        // Handle new messages from the server.
        frontend_events.append(&mut self.handle_new_messages()?);

        // 3)

        // 4) Tick the client's LocalState
        self.state.tick(dt);

        // 5) Terrain
        let pos = self
            .state
            .read_storage::<comp::phys::Pos>()
            .get(self.entity)
            .cloned();
        if let (Some(pos), Some(view_distance)) = (pos, self.view_distance) {
            let chunk_pos = self.state.terrain().pos_key(pos.0.map(|e| e as i32));

            // Remove chunks that are too far from the player.
            let mut chunks_to_remove = Vec::new();
            self.state.terrain().iter().for_each(|(key, _)| {
                if (Vec2::from(chunk_pos) - Vec2::from(key))
                    .map(|e: i32| e.abs() as u32)
                    .reduce_max()
                    > view_distance
                {
                    chunks_to_remove.push(key);
                }
            });
            for key in chunks_to_remove {
                self.state.remove_chunk(key);
            }

            // Request chunks from the server.
            // TODO: This is really inefficient.
            'outer: for dist in 0..=view_distance as i32 {
                for i in chunk_pos.x - dist..=chunk_pos.x + dist {
                    for j in chunk_pos.y - dist..=chunk_pos.y + dist {
                        let key = Vec2::new(i, j);
                        if self.state.terrain().get_key(key).is_none()
                            && !self.pending_chunks.contains_key(&key)
                        {
                            if self.pending_chunks.len() < 4 {
                                self.postbox
                                    .send_message(ClientMsg::TerrainChunkRequest { key });
                                self.pending_chunks.insert(key, Instant::now());
                            } else {
                                break 'outer;
                            }
                        }
                    }
                }
            }

            // If chunks are taking too long, assume they're no longer pending.
            let now = Instant::now();
            self.pending_chunks
                .retain(|_, created| now.duration_since(*created) < Duration::from_secs(10));
        }

        // Send a ping to the server once every second
        if Instant::now().duration_since(self.last_server_ping) > Duration::from_secs(1) {
            self.postbox.send_message(ClientMsg::Ping);
            self.last_server_ping = Instant::now();
        }

        // 6) Update the server about the player's physics attributes.
        match (
            self.state.read_storage().get(self.entity).cloned(),
            self.state.read_storage().get(self.entity).cloned(),
            self.state.read_storage().get(self.entity).cloned(),
        ) {
            (Some(pos), Some(vel), Some(dir)) => {
                self.postbox
                    .send_message(ClientMsg::PlayerPhysics { pos, vel, dir });
            }
            _ => {}
        }

        // Update the server about the player's current animation.
        if let Some(mut animation_info) = self
            .state
            .ecs_mut()
            .write_storage::<comp::AnimationInfo>()
            .get_mut(self.entity)
        {
            if animation_info.changed {
                self.postbox
                    .send_message(ClientMsg::PlayerAnimation(animation_info.clone()));
            }
        }

        // 7) Finish the tick, pass control back to the frontend.

        // Cleanup
        self.state
            .ecs_mut()
            .write_storage::<comp::Jumping>()
            .remove(self.entity);

        self.tick += 1;
        Ok(frontend_events)
    }

    /// Clean up the client after a tick.
    #[allow(dead_code)]
    pub fn cleanup(&mut self) {
        // Cleanup the local state
        self.state.cleanup();
    }

    /// Handle new server messages.
    fn handle_new_messages(&mut self) -> Result<Vec<Event>, Error> {
        let mut frontend_events = Vec::new();

        // Step 1
        let new_msgs = self.postbox.new_messages();

        if new_msgs.len() > 0 {
            self.last_ping = self.state.get_time();

            for msg in new_msgs {
                match msg {
                    ServerMsg::InitialSync { .. } => return Err(Error::ServerWentMad),
                    ServerMsg::Shutdown => return Err(Error::ServerShutdown),
                    ServerMsg::Ping => self.postbox.send_message(ClientMsg::Pong),
                    ServerMsg::Pong => {
                        self.last_ping_delta = Instant::now()
                            .duration_since(self.last_server_ping)
                            .as_secs_f64()
                    }
                    ServerMsg::Chat(msg) => frontend_events.push(Event::Chat(msg)),
                    ServerMsg::SetPlayerEntity(uid) => {
                        self.entity = self.state.ecs().entity_from_uid(uid).unwrap()
                    } // TODO: Don't unwrap here!
                    ServerMsg::EcsSync(sync_package) => {
                        self.state.ecs_mut().sync_with_package(sync_package)
                    }
                    ServerMsg::EntityPhysics {
                        entity,
                        pos,
                        vel,
                        dir,
                    } => match self.state.ecs().entity_from_uid(entity) {
                        Some(entity) => {
                            self.state.write_component(entity, pos);
                            self.state.write_component(entity, vel);
                            self.state.write_component(entity, dir);
                        }
                        None => {}
                    },
                    ServerMsg::EntityAnimation {
                        entity,
                        animation_info,
                    } => match self.state.ecs().entity_from_uid(entity) {
                        Some(entity) => {
                            self.state.write_component(entity, animation_info);
                        }
                        None => {}
                    },
                    ServerMsg::TerrainChunkUpdate { key, chunk } => {
                        self.state.insert_chunk(key, *chunk);
                        self.pending_chunks.remove(&key);
                    }
                    ServerMsg::StateAnswer(Ok(state)) => {
                        self.client_state = state;
                    }
                    ServerMsg::StateAnswer(Err((error, state))) => {
                        self.client_state = state;
                    }
                    ServerMsg::ForceState(state) => {
                        self.client_state = state;
                    }
                    ServerMsg::Disconnect => {
                        frontend_events.push(Event::Disconnect);
                    }
                }
            }
        } else if let Some(err) = self.postbox.error() {
            return Err(err.into());
        } else if self.state.get_time() - self.last_ping > SERVER_TIMEOUT {
            return Err(Error::ServerTimeout);
        } else if self.state.get_time() - self.last_ping > SERVER_TIMEOUT * 0.5 {
            // Try pinging the server if the timeout is nearing.
            self.postbox.send_message(ClientMsg::Ping);
            self.last_server_ping = Instant::now();
        }

        Ok(frontend_events)
    }

    /// Get the player's entity.
    #[allow(dead_code)]
    pub fn entity(&self) -> EcsEntity {
        self.entity
    }

    /// Get the client state
    #[allow(dead_code)]
    pub fn get_client_state(&self) -> ClientState {
        self.client_state
    }

    /// Get the current tick number.
    #[allow(dead_code)]
    pub fn get_tick(&self) -> u64 {
        self.tick
    }

    #[allow(dead_code)]
    pub fn get_ping_ms(&self) -> f64 {
        self.last_ping_delta * 1000.0
    }

    /// Get a reference to the client's worker thread pool. This pool should be used for any
    /// computationally expensive operations that run outside of the main thread (i.e., threads that
    /// block on I/O operations are exempt).
    #[allow(dead_code)]
    pub fn thread_pool(&self) -> &threadpool::ThreadPool {
        &self.thread_pool
    }

    /// Get a reference to the client's game state.
    #[allow(dead_code)]
    pub fn state(&self) -> &State {
        &self.state
    }

    /// Get a mutable reference to the client's game state.
    #[allow(dead_code)]
    pub fn state_mut(&mut self) -> &mut State {
        &mut self.state
    }
}

impl Drop for Client {
    fn drop(&mut self) {
        self.postbox.send_message(ClientMsg::Disconnect);
    }
}