cloaking/core.lua

--
-- Minetest player cloaking mod: Core functions
--
-- Copyright © 2018-2021 by luk3yx
--

cloaking = {}

-- Expose the real get_connected_players and get_player_by_name for mods that
--   can use them.
cloaking.get_player_by_name         = minetest.get_player_by_name
cloaking.get_objects_inside_radius  = minetest.get_objects_inside_radius
cloaking.get_objects_in_area        = minetest.get_objects_in_area
cloaking.get_server_status          = minetest.get_server_status

local cloaked_players = {}
local chatcommands_modified = false

-- Override built-in functions
function minetest.get_player_by_name(player)
    if cloaked_players[player] then
        return nil
    else
        return cloaking.get_player_by_name(player)
    end
end

local function remove_cloaked_players(list)
    for i = #list, 1, -1 do
        if cloaked_players[list[i]:get_player_name()] then
            table.remove(list, i)
        end
    end
end

function minetest.get_objects_inside_radius(pos, radius)
    local objs = cloaking.get_objects_inside_radius(pos, radius)
    remove_cloaked_players(objs)
    return objs
end

if cloaking.get_objects_in_area then
    function minetest.get_objects_in_area(pos1, pos2)
        local objs = cloaking.get_objects_in_area(pos1, pos2)
        remove_cloaked_players(objs)
        return objs
    end
end

local override_statusline = false
if minetest.settings:get_bool('show_statusline_on_connect') ~= nil then
    override_statusline = true
end

function minetest.get_server_status(name, joined)
    if override_statusline and joined == true then
        override_statusline = false
    end

    local status = cloaking.get_server_status(name, joined)
    if not status or status == "" then return status end
    local e = status:find('}', 1, true)
    if not e then return status end
    local motd = status:sub(e)
    status = status:sub(1, status:find('{', 1, true))
    local players = {}
    for _, player in ipairs(minetest.get_connected_players()) do
        table.insert(players, player:get_player_name())
    end
    players = table.concat(players, ', ')
    status = status .. players .. motd
    return status
end

-- Change the on-join status
if override_statusline then
    minetest.settings:set_bool('show_statusline_on_connect', false)
    minetest.register_on_joinplayer(function(player)
        if not override_statusline then return end

        local name   = player:get_player_name()
        local status = minetest.get_server_status(name, 'cloaking')

        if status and status ~= '' then
            minetest.chat_send_player(name, status)
        end
    end)
end

-- Don't allow chat or chatcommands in all commands that don't have the
--   allow_while_cloaked parameter set.
local delayed_uncloak
local function override_chatcommands()
    local chatcommands = minetest.registered_chatcommands
    for cmd_name, def in pairs(chatcommands) do
        if not def.allow_while_cloaked and not def._allow_while_cloaked then
            local real_cmd = def.func
            chatcommands[cmd_name].func = function(name, param)
                if cloaked_players[name] then
                    local pass, r1, r2
                    if def._disallow_while_cloaked then
                        pass = false
                    else
                        pass, r1, r2 = pcall(real_cmd, name, param)
                    end
                    if pass then
                        return r1, r2
                    else
                        return false, "You may not execute this chatcommand " ..
                            "while cloaked. Please use /uncloak if you want " ..
                            "to execute this chatcommand."
                    end
                else
                    return real_cmd(name, param)
                end
            end
        end
    end

    local c = 0
    for _, func in ipairs(minetest.registered_on_leaveplayers) do
        c = c + 1
        local f = func
        if f ~= delayed_uncloak then
            minetest.registered_on_leaveplayers[c] = function(p, t, cloaked)
                if cloaked ~= 'cloaking' and
                  cloaked_players[p:get_player_name()] then
                    return
                end
                return f(p, t)
            end
        end
    end
end

-- Handle chat messages
function cloaking.on_chat_message(name, message)
    if message:sub(1, 1) ~= "/" and cloaked_players[name] then
        minetest.chat_send_player(name, "You cannot use chat while cloaked." ..
            " Please use /uncloak if you want to use chat.")
        return true
    end
end

table.insert(minetest.registered_on_chat_messages, 1, cloaking.on_chat_message)
minetest.callback_origins[cloaking.on_chat_message] = {
    mod  = 'cloaking',
    name = 'on_chat_message'
}

-- Disallow some built-in commands.
for _, cmd in ipairs({'me', 'msg'}) do
    if minetest.chatcommands[cmd] then
        minetest.override_chatcommand(cmd, {
            _disallow_while_cloaked = true
        })
    end
end

-- Get player and name
local function player_and_name(player, n)
    if type(player) == "string" then
        player = cloaking.get_player_by_name(player)
    end
    local victim = player:get_player_name()

    if n then
        if cloaked_players[victim] then return false end
    elseif n ~= nil then
        if not cloaked_players[victim] then return false end
    end

    return player, victim
end

-- 0.4.X compatibility
local selectionbox = 'selectionbox'
if not minetest.features.object_independent_selectionbox then
    selectionbox = 'collisionbox'
end

-- "Hide" players
local hidden = {}
function cloaking.hide_player(player_or_name, preserve_attrs)
    -- Sanity check
    local player, victim = player_and_name(player_or_name, true)
    if not player then return end

    -- Save existing attributes
    if preserve_attrs or preserve_attrs == nil then
        if hidden[victim] then return end
        hidden[victim] = {
            player:get_properties(),
            player:get_nametag_attributes()
        }
    else
        hidden[victim] = nil
    end

    -- Hide the player
    player:set_properties({
        visual_size          = {x = 0, y = 0, z = 0},
        [selectionbox]       = {0,0,0,0,0,0},
        makes_footstep_sound = false,
        show_on_minimap      = false,
    })
    player:set_nametag_attributes({
        text = ' ',
        color = {r = 0, g = 0, b = 0, a = 0}
    })
end

-- Remove original attributes when players leave
minetest.register_on_leaveplayer(function(player)
    hidden[player:get_player_name()] = nil
end)

-- "Unhide" players
function cloaking.unhide_player(player_or_name)
    -- Sanity check
    local player, victim = player_and_name(player_or_name, true)
    if not player or hidden[victim] == nil then return end

    -- Get the data
    local data     = hidden[victim] or {}
    hidden[victim] = nil

    -- Use sensible defaults if the data does not exist.
    if not data[1] then
        local box = false
        if minetest.features.object_independent_selectionbox then
            box = player:get_properties().collisionbox
        end
        box = box or {-0.3,-1,-0.3,0.3,0.75,0.3}

        data = {{
            visual_size          = {x = 1, y = 2, z = 1},
            [selectionbox]       = box,
            makes_footstep_sound = true,
            show_on_minimap      = true,
        }}
    end

    -- Make the player visible
    player:set_properties(data[1])
    player:set_nametag_attributes(data[2] or {
        text = victim,
        color = {r = 255, g = 255, b = 255, a = 255}
    })
end

-- The cloak and uncloak functions
local use_areas = minetest.global_exists('areas') and areas.hud
function cloaking.cloak(player_or_name)
    if not chatcommands_modified then override_chatcommands() end

    local player, victim = player_and_name(player_or_name, true)
    if not player then return end

    cloaking.hide_player(player, false)

    local t = nil
    if use_areas and areas.hud[victim] then
        t = areas.hud[victim]
    end

    for _, f in ipairs(minetest.registered_on_leaveplayers) do
        if f ~= delayed_uncloak then
            f(player, false, 'cloaking')
        end
    end

    cloaked_players[victim] = true

    -- TODO: Get the highest ID somehow
    local t_id = t and t.areasId
    for id = 0, 100 do
        if id ~= t_id and player:hud_get(id) then
            player:hud_remove(id)
        end
    end

    if t then
        areas.hud[victim] = t
        player:hud_change(areas.hud[victim].areasId, "text", "Cloaked")
        areas.hud[victim].oldAreas = ""
    end

    minetest.log('verbose', victim .. ' was cloaked.')
end

function cloaking.uncloak(player_or_name)
    local player, victim = player_and_name(player_or_name, false)
    if not player then return end

    cloaked_players[victim] = nil
    hidden[victim] = false
    cloaking.unhide_player(player)

    -- In singleplayer, there is no joined the game message by default.
    if victim == "singleplayer" then
        minetest.chat_send_all("*** " .. victim .. " joined the game.")
    end

    for _, f in ipairs(minetest.registered_on_joinplayers) do
        f(player)
    end

    minetest.log('verbose', victim .. ' was uncloaked.')
end

-- API functions
cloaking.auto_uncloak = cloaking.uncloak

-- This function removes the player from the cloaked players table on the next
-- server step.
-- Defined as a local above override_chatcommands().
function delayed_uncloak(player)
    local victim = player:get_player_name()
    if cloaked_players[victim] then
        minetest.after(0, function()
            cloaked_players[victim] = nil
            if use_areas and areas.hud[victim] then
                areas.hud[victim] = nil
            end
        end)
    end
end

-- Register cloaking.delayed_uncloak "manually" so that the profiler can't
--   hijack it, preventing it from running.
table.insert(minetest.registered_on_leaveplayers, delayed_uncloak)
minetest.callback_origins[delayed_uncloak] = {
    mod  = 'cloaking',
    name = 'delayed_uncloak'
}


-- Override minetest.get_connected_players(), required for Minetest 5.2.0+.
local get_connected_players = minetest.get_connected_players
function minetest.get_connected_players()
    local res = get_connected_players()
    remove_cloaked_players(res)
    return res
end

-- There's currently no way to check if cloaked players will appear in the
-- unmodified minetest.get_connected_players().
function cloaking.get_connected_players()
    local players = minetest.get_connected_players()
    for name, cloaked in pairs(cloaked_players) do
        if cloaked then
            local player = cloaking.get_player_by_name(name)
            -- The player may be nil if they have just left but haven't been
            -- removed from the cloaked_players table yet.
            if player then
                players[#players + 1] = player
            end
        end
    end
    return players
end

function cloaking.get_cloaked_players()
    local players = {}
    for player, cloaked in pairs(cloaked_players) do
        if cloaked then
            table.insert(players, player)
        end
    end
    return players
end

-- Allow mods to get a list of cloaked and uncloaked player names.
function cloaking.get_connected_names()
    local a = cloaking.get_cloaked_players()
    for _, player in ipairs(minetest.get_connected_players()) do
        table.insert(a, player:get_player_name())
    end
    return a
end

function cloaking.is_cloaked(player)
    if type(player) ~= "string" then player = player:get_player_name() end
    return cloaked_players[player] and true or false
end

-- Prevent cloaked players dying
minetest.register_on_player_hpchange(function(player, hp_change)
    if player and hp_change < 0 then
        local name = player:get_player_name()
        if cloaked_players[name] then
            hp_change = 0
        end
    end
    return hp_change
end, true)