//! Login/logout and the mapping between network clients and characters.

use std::collections::{BTreeMap, HashMap, VecDeque};

use bevy::prelude::*;
use bevy_replicon::prelude::*;
use game_core::{
    GameData,
    components::*,
    protocol::{AdminStatus, Chat, GameLog, Login, Rejected, Welcome},
};

use crate::{
    ServerSettings,
    commands::{self, CommandSource},
    config::ServerConfig,
    movement::MoveIntent,
    persistence::SavedCharacter,
    world::{SpawnPoint, WorldLayout, find_free_tile},
};

/// Which client controls a character. Server-only.
#[derive(Component, Clone, Copy, Debug)]
pub struct Controller(pub ClientId);

/// The player owning a character (a UUID sent by the client). Server-only.
#[derive(Component, Clone, Debug, PartialEq, Eq)]
pub struct PlayerId(pub String);

/// Marks characters of players with admin rights. Server-only.
#[derive(Component, Clone, Copy, Debug)]
pub struct Admin;

/// Online characters by client.
#[derive(Resource, Default)]
pub struct Players {
    pub by_client: HashMap<ClientId, Entity>,
}

/// Characters that are currently offline, by player id. Persisted with the world.
#[derive(Resource, Default)]
pub struct CharacterStore(pub BTreeMap<String, SavedCharacter>);

pub const MAX_NAME_LEN: usize = 24;

pub fn tell(commands: &mut Commands, client: ClientId, text: impl Into<String>) {
    commands.server_trigger(ToClients {
        targets: SendTargets::Single(client),
        message: GameLog { text: text.into() },
    });
}

pub fn valid_name(name: &str) -> bool {
    let len = name.chars().count();
    (1..=MAX_NAME_LEN).contains(&len)
        && name.trim() == name
        && name
            .chars()
            .all(|c| c.is_alphanumeric() || c == ' ' || c == '_' || c == '-')
}

/// Everything [`check_access`] needs to know about a login attempt.
#[derive(Clone, Copy, Debug)]
pub struct AccessRequest<'a> {
    pub player_id: &'a str,
    /// Character name (the stored one for returning players).
    pub name: &'a str,
    pub password: &'a str,
    /// Host of an embedded server or a local client; bypasses all restrictions.
    pub owner: bool,
    pub online: usize,
    pub id_online: bool,
    pub new_character: bool,
    /// Another player's character already uses this name.
    pub name_taken: bool,
}

/// Whether a player may join. Pure so the rules can be tested in isolation.
pub fn check_access(config: &ServerConfig, req: &AccessRequest) -> Result<(), String> {
    if uuid::Uuid::parse_str(req.player_id).is_err() {
        return Err("Invalid player id.".into());
    }
    let admin = req.owner || is_listed(&config.access.admins, req.player_id, req.name);
    if !req.owner {
        if !config.password.is_empty() && req.password != config.password {
            return Err(if req.password.is_empty() {
                "This server requires a password.".into()
            } else {
                "Wrong password.".into()
            });
        }
        if is_listed(&config.access.banned, req.player_id, req.name) {
            return Err("You are banned from this server.".into());
        }
        if config.access.whitelist_enabled
            && !admin
            && !is_listed(&config.access.whitelist, req.player_id, req.name)
        {
            return Err("You are not on the whitelist.".into());
        }
        if req.online >= config.max_players && !admin {
            return Err("The server is full.".into());
        }
    }
    if req.id_online {
        return Err("You are already logged in.".into());
    }
    if req.new_character {
        if !valid_name(req.name) {
            return Err(format!(
                "Invalid character name. Use 1-{MAX_NAME_LEN} letters, digits, spaces, `_` or `-`."
            ));
        }
        if req.name_taken {
            return Err("That name belongs to another player.".into());
        }
    }
    Ok(())
}

/// Whether a ban/whitelist/admin entry matches a player id or (case-insensitively) a name.
pub fn is_listed(list: &[String], player_id: &str, name: &str) -> bool {
    list.iter()
        .any(|e| e == player_id || (!name.is_empty() && e.eq_ignore_ascii_case(name)))
}

/// Whether a player has admin rights.
pub fn is_admin(
    world_owner: Option<&str>,
    config: &ServerConfig,
    client: ClientId,
    id: &str,
) -> bool {
    client == ClientId::Server
        || world_owner == Some(id)
        || config.access.admins.iter().any(|a| a == id)
}

/// Recent rejected logins, for admins.
#[derive(Resource, Default)]
pub struct RejectedLogins(pub VecDeque<String>);

const REJECTED_HISTORY: usize = 20;

/// Tells a client why, then disconnects it.
pub fn disconnect(commands: &mut Commands, client: ClientId, reason: impl Into<String>) {
    commands.server_trigger(ToClients {
        targets: SendTargets::Single(client),
        message: Rejected {
            reason: reason.into(),
        },
    });
    if let ClientId::Client(entity) = client {
        commands.write_message(DisconnectRequest { client: entity });
    }
}

/// Sends a message to every online admin.
pub fn tell_admins(world: &mut World, text: &str) {
    let mut q = world.query_filtered::<&Controller, With<Admin>>();
    let admins: Vec<ClientId> = q.iter(world).map(|c| c.0).collect();
    let mut commands = world.commands();
    for client in admins {
        tell(&mut commands, client, text);
    }
    world.flush();
}

/// Name of the character a player id owns in this world, online or stored.
pub fn character_name(world: &mut World, player_id: &str) -> Option<String> {
    let mut q = world.query::<(&Character, &PlayerId)>();
    if let Some((c, _)) = q.iter(world).find(|(_, id)| id.0 == player_id) {
        return Some(c.name.clone());
    }
    world
        .resource::<CharacterStore>()
        .0
        .get(player_id)
        .map(|c| c.name.clone())
}

/// Player id owning a character name (case-insensitive), online or stored.
pub fn find_player_by_name(world: &mut World, name: &str) -> Option<String> {
    let mut q = world.query::<(&Character, &PlayerId)>();
    if let Some((_, id)) = q
        .iter(world)
        .find(|(c, _)| c.name.eq_ignore_ascii_case(name))
    {
        return Some(id.0.clone());
    }
    world
        .resource::<CharacterStore>()
        .0
        .iter()
        .find(|(_, c)| c.name.eq_ignore_ascii_case(name))
        .map(|(id, _)| id.clone())
}

pub fn on_login(login: On<FromClient<Login>>, mut commands: Commands) {
    let client = login.client_id;
    let login = login.message.clone();
    commands.queue(move |world: &mut World| handle_login(world, client, login));
}

fn handle_login(world: &mut World, client: ClientId, login: Login) {
    if world.resource::<Players>().by_client.contains_key(&client) {
        return;
    }
    let player_id = login.player_id.trim().to_lowercase();
    let stored_name = character_name(world, &player_id);
    let new_character = stored_name.is_none();
    let name = stored_name.unwrap_or_else(|| login.name.trim().to_owned());
    let name_taken =
        new_character && find_player_by_name(world, &name).is_some_and(|owner| owner != player_id);
    let owner = world.resource::<ServerSettings>().owner.as_deref() == Some(player_id.as_str())
        || client == ClientId::Server;
    let id_online = world
        .query::<&PlayerId>()
        .iter(world)
        .any(|id| id.0 == player_id);
    let request = AccessRequest {
        player_id: &player_id,
        name: &name,
        password: &login.password,
        owner,
        online: world.resource::<Players>().by_client.len(),
        id_online,
        new_character,
        name_taken,
    };
    if let Err(reason) = check_access(world.resource::<ServerConfig>(), &request) {
        let entry = format!("{name} ({player_id}): {reason}");
        warn!("rejected login of {entry}");
        tell_admins(world, &format!("[admin] Rejected {entry}"));
        let mut log = world.resource_mut::<RejectedLogins>();
        if log.0.len() >= REJECTED_HISTORY {
            log.0.pop_front();
        }
        log.0.push_back(entry);
        disconnect(&mut world.commands(), client, reason);
        world.flush();
        return;
    }

    let saved = match world.resource_mut::<CharacterStore>().0.remove(&player_id) {
        Some(saved) => saved,
        None => {
            let spawn = world.resource::<SpawnPoint>().0;
            new_character_data(world.resource::<GameData>(), &name, spawn)
        }
    };
    let mut buildings =
        world.query_filtered::<(&GridPos, &BuildingState), (With<Building>, Without<Character>)>();
    let pos = find_free_tile(
        saved.pos,
        &world.resource::<WorldLayout>().0,
        &buildings.query(world),
    );
    let config = world.resource::<ServerConfig>().clone();
    let owner_id = world.resource::<ServerSettings>().owner.clone();
    let admin = is_admin(owner_id.as_deref(), &config, client, &player_id);
    let mut entity = world.spawn((
        Replicated,
        Character { name: name.clone() },
        pos,
        Facing(saved.facing),
        saved.vitals,
        saved.inventory,
        saved.skills,
        Controller(client),
        PlayerId(player_id.clone()),
        MoveIntent::default(),
    ));
    if admin {
        entity.insert(Admin);
    }
    let entity = entity.id();
    world
        .resource_mut::<Players>()
        .by_client
        .insert(client, entity);
    info!(
        "{name} logged in (player id {player_id}, {client:?}{})",
        if admin { ", admin" } else { "" }
    );
    let greeting = if new_character {
        format!("Welcome to the station, {name}. Press H for help.")
    } else {
        format!("Welcome back, {name}.")
    };
    let mut commands = world.commands();
    commands.server_trigger(ToClients {
        targets: SendTargets::Single(client),
        message: Welcome {
            server_name: config.name.clone(),
            motd: config.motd.clone(),
            character: name,
            admin,
        },
    });
    tell(&mut commands, client, greeting);
    if !config.motd.is_empty() {
        tell(&mut commands, client, config.motd);
    }
    world.flush();
}

/// Longest accepted chat message, in characters.
pub const MAX_CHAT_LEN: usize = 200;

/// Chat messages and `/commands` from players.
pub fn on_chat(chat: On<FromClient<Chat>>, mut commands: Commands) {
    let client = chat.client_id;
    let text: String = chat
        .message
        .text
        .chars()
        .filter(|c| !c.is_control())
        .take(MAX_CHAT_LEN)
        .collect();
    commands.queue(move |world: &mut World| handle_chat(world, client, text.trim()));
}

fn handle_chat(world: &mut World, client: ClientId, text: &str) {
    let Some(&entity) = world.resource::<Players>().by_client.get(&client) else {
        return;
    };
    if text.is_empty() {
        return;
    }
    if let Some(command) = text.strip_prefix('/') {
        let player_id = world.get::<PlayerId>(entity).map(|id| id.0.clone());
        let owner = client == ClientId::Server
            || player_id
                .is_some_and(|id| world.resource::<ServerSettings>().owner.as_deref() == Some(&id));
        let source = CommandSource::Player {
            client,
            admin: world.get::<Admin>(entity).is_some(),
            owner,
        };
        let name = world
            .get::<Character>(entity)
            .map(|c| c.name.clone())
            .unwrap_or_default();
        info!("{name} ran `/{command}`");
        let reply = commands::execute(world, source, command);
        let mut cmds = world.commands();
        for line in reply {
            tell(&mut cmds, client, line);
        }
        world.flush();
        return;
    }
    let Some(name) = world.get::<Character>(entity).map(|c| c.name.clone()) else {
        return;
    };
    let line = format!("<{name}> {text}");
    info!(target: "chat", "{line}");
    world.commands().server_trigger(ToClients {
        targets: SendTargets::All,
        message: GameLog { text: line },
    });
    world.flush();
}

/// Applies access list changes to online players: kicks banned and no longer
/// whitelisted players and updates admin rights.
pub fn enforce_access(world: &mut World) {
    let config = world.resource::<ServerConfig>().clone();
    let owner = world.resource::<ServerSettings>().owner.clone();
    let mut q = world.query::<(Entity, &Character, &PlayerId, &Controller, Has<Admin>)>();
    let online: Vec<_> = q
        .iter(world)
        .map(|(e, c, id, ctrl, admin)| (e, c.name.clone(), id.0.clone(), ctrl.0, admin))
        .collect();
    for (entity, name, id, client, was_admin) in online {
        let admin = is_admin(owner.as_deref(), &config, client, &id);
        let privileged =
            admin || client == ClientId::Server || owner.as_deref() == Some(id.as_str());
        let reason = if privileged {
            None
        } else if is_listed(&config.access.banned, &id, &name) {
            Some("You have been banned from this server.")
        } else if config.access.whitelist_enabled
            && !is_listed(&config.access.whitelist, &id, &name)
        {
            Some("You are not on the whitelist.")
        } else {
            None
        };
        let mut commands = world.commands();
        if let Some(reason) = reason {
            info!("disconnecting {name}: {reason}");
            disconnect(&mut commands, client, reason);
        } else if admin != was_admin {
            if admin {
                commands.entity(entity).insert(Admin);
            } else {
                commands.entity(entity).remove::<Admin>();
            }
            commands.server_trigger(ToClients {
                targets: SendTargets::Single(client),
                message: AdminStatus { admin },
            });
            tell(
                &mut commands,
                client,
                if admin {
                    "You are now an admin."
                } else {
                    "You are no longer an admin."
                },
            );
        }
        world.flush();
    }
}

pub fn new_character_data(data: &GameData, name: &str, spawn: GridPos) -> SavedCharacter {
    let mut inventory = Inventory::default();
    if data.items.contains_key("apple") {
        inventory.add("apple", 2, data);
    }
    SavedCharacter {
        name: name.to_owned(),
        pos: spawn,
        facing: Default::default(),
        vitals: Vitals::default(),
        inventory,
        skills: Skills::default(),
    }
}

/// Stores the character of a disconnecting client and removes it from the world.
pub fn on_disconnect(
    remove: On<Remove, ConnectedClient>,
    mut commands: Commands,
    mut players: ResMut<Players>,
    mut store: ResMut<CharacterStore>,
    characters: Query<(
        &Character,
        &PlayerId,
        &GridPos,
        &Facing,
        &Vitals,
        &Inventory,
        &Skills,
    )>,
) {
    let Some(entity) = players.by_client.remove(&ClientId::Client(remove.entity)) else {
        return;
    };
    if let Ok((c, id, pos, facing, vitals, inventory, skills)) = characters.get(entity) {
        info!("{} logged out", c.name);
        store.0.insert(
            id.0.clone(),
            SavedCharacter {
                name: c.name.clone(),
                pos: *pos,
                facing: facing.0,
                vitals: vitals.clone(),
                inventory: inventory.clone(),
                skills: skills.clone(),
            },
        );
    }
    commands.entity(entity).despawn();
}

#[cfg(test)]
mod tests {
    use super::*;

    const ID: &str = "4f1c0c56-1111-4a5e-9a1e-000000000001";

    fn request<'a>() -> AccessRequest<'a> {
        AccessRequest {
            player_id: ID,
            name: "Jane",
            password: "",
            owner: false,
            online: 0,
            id_online: false,
            new_character: true,
            name_taken: false,
        }
    }

    #[test]
    fn access_rules() {
        let mut config = ServerConfig::default();
        assert_eq!(check_access(&config, &request()), Ok(()));
        let bad_id = AccessRequest {
            player_id: "nope",
            ..request()
        };
        assert!(check_access(&config, &bad_id).is_err());

        config.password = "secret".into();
        assert!(check_access(&config, &request()).is_err());
        let with_password = AccessRequest {
            password: "secret",
            ..request()
        };
        assert_eq!(check_access(&config, &with_password), Ok(()));
        let owner = AccessRequest {
            owner: true,
            ..request()
        };
        assert_eq!(check_access(&config, &owner), Ok(()));
        config.password.clear();

        config.access.banned = vec!["JANE".into()];
        assert!(check_access(&config, &request()).is_err());
        config.access.banned = vec![ID.into()];
        assert!(check_access(&config, &request()).is_err());
        config.access.banned.clear();

        config.access.whitelist_enabled = true;
        assert!(check_access(&config, &request()).is_err());
        config.access.whitelist = vec!["jane".into()];
        assert_eq!(check_access(&config, &request()), Ok(()));
        config.access.whitelist.clear();
        config.access.admins = vec![ID.into()];
        assert_eq!(
            check_access(&config, &request()),
            Ok(()),
            "admins bypass the whitelist"
        );
        config.access.whitelist_enabled = false;
        config.access.admins.clear();

        config.max_players = 1;
        let full = AccessRequest {
            online: 1,
            ..request()
        };
        assert!(check_access(&config, &full).is_err());
        config.max_players = 32;

        for req in [
            AccessRequest {
                id_online: true,
                ..request()
            },
            AccessRequest {
                name_taken: true,
                ..request()
            },
            AccessRequest {
                name: "bad;name",
                ..request()
            },
        ] {
            assert!(check_access(&config, &req).is_err(), "{req:?}");
        }
        let returning = AccessRequest {
            name_taken: true,
            new_character: false,
            ..request()
        };
        assert_eq!(check_access(&config, &returning), Ok(()));
    }

    #[test]
    fn names() {
        assert!(valid_name("Jane Doe"));
        assert!(valid_name("x_1-2"));
        assert!(!valid_name(""));
        assert!(!valid_name(" padded"));
        assert!(!valid_name("semi;colon"));
        assert!(!valid_name(&"a".repeat(25)));
    }
}