Build custom Minecraft
server gameplay in Lua.

--# nova syntax
-- Chest GUI shop: require library, build once, open for any player
local chestgui = require "chestgui"

-- Create a 3-row (27-slot) GUI
local gui = chestgui.create(3, "Shop")
local glass = mc.createItem("black_stained_glass_pane", { name = " " })

-- Decorate with glass border — no callback = stuck in place
for col = 1, 9 do
    gui:decorate(1, col, glass)
    gui:decorate(3, col, glass)
end

-- gui:set(row, col, item, callback) — clickable item
-- Returning false cancels the click (prevents item theft)
gui:set(2, 3, mc.createItem("diamond", { name = "Diamond", lore = { "10 coins" } })) \{ player ->
    -- player.data is per-player persistent storage (JSON, survives reloads)
    local coins = player.data.coins or 0
    if coins < 10 then
        player:sendMessage("Not enough coins!")
        return false
    end

    player.data.coins = coins - 10
    player:give(mc.createItem("diamond"))
    player:sendMessage("Bought a diamond! Coins: " .. (coins - 10))
    return false
}

register("shop") \{ ctx ->
    gui:open(ctx.player)
}

--# nova syntax
-- Live per-player sidebar refreshing every 2s, self-cleaning on disconnect
mc.on("player_join", function(player)
-- Per-player data persists as JSON across reloads
local visits = player.data.visits or 0
visits = visits + 1
player.data.visits = visits

if visits == 1 then
    player:give(mc.createItem("compass", 1))
end

-- Doesn't alter server scoreboards
player.sidebar = {
    title = "Stats",
    lines = {
        "HP " .. math.floor(player.health),
        "Visits " .. visits,
        "Online " .. mc.onlineCount,
    }
}

-- mc.scheduleRepeating(delay, interval, callback) — 20 ticks = 1 second
local id
id = mc.scheduleRepeating(40, 40) \{
    local sb = player.sidebar
    if sb then
        sb.lines = {
            "HP " .. math.floor(player.health),
            "Visits " .. visits,
            "Online " .. mc.onlineCount,
        }
    else
        mc.cancelTask(id)  -- sidebar destroyed, stop updating
    end
}

-- Clean up the repeating task when the player disconnects
mc.on("player_leave") \{ p ->
    if p.uuid == player.uuid then
        mc.cancelTask(id)
    end
}

--# nova syntax
-- Custom guard behaviour: patrol home, hunt players, return
mc.registerBehaviour("guard_beast") \{ self, state ->
    -- self: the mob wrapper; state: persists across server ticks per mob
    if not state.home then
        state.home = self.pos  -- remember spawn point on first tick
    end

    -- Throttle: only run every 10 ticks (0.5s) to avoid spam
    state.timer = (state.timer or 0) + 1
    if state.timer % 10 ~= 0 then return end

    -- Search for players within 10 blocks
    local players = self.world:getEntities(self.pos, 10, "minecraft:player")
    if #players > 0 then
        -- Navigate to nearest player, attack when in melee range
        self:navigateTo(players[1])
        if self:distanceTo(players[1]) < 2.5 then
            self:tryAttack(players[1])
        end
    else
        -- No threat — return to home position if drifted away
        local d = self:distanceTo(state.home)
        if d > 2 then
            self:navigateTo(state.home.x, state.home.y, state.home.z)
        end
    end
}

-- Spawn a zombie and assign the behaviour
local guard = world:spawn("minecraft:zombie", player.pos)
guard.customName = "Guard"
guard.health = 40
guard:setAI("guard_beast")

--# nova syntax
-- Simple: no arguments, no permission — anyone can use it
register("fly") \{ ctx ->
    ctx.player.isFlying = not ctx.player.isFlying
    ctx.player:sendMessage("Flight: " .. tostring(ctx.player.isFlying))
}

-- Complex: choice type (tab-completion), optional target, permission
register("kit <name:choice=warrior,archer,miner> [target:player]", \{ctx, name, target ->
    -- target is nil when omitted; fall back to the command sender
    local player = target or ctx.player
    player:clear()

    if name == "warrior" then
        -- mc.createItem(id, {components}) — name, unbreakable, lore, count...
        player:give(mc.createItem("iron_sword", { name = "Warrior Blade", unbreakable = true }))
        player:give(mc.createItem("iron_chestplate"))
    elseif name == "archer" then
        player:give(mc.createItem("bow", { name = "Longbow", unbreakable = true }))
        player:give(mc.createItem("arrow", 64))
    end
}, "px.ignis.admin")  -- only those with the permission

--# nova syntax
-- Three zones: lobby (auto-welcome), arena (PvP gate), boss (warning)
local lobby = world:createRegion(vec(0, 64, 0),   vec(100, 128, 100))
local arena = world:createRegion(vec(200, 64, 200), vec(300, 128, 300))
local boss  = world:createRegion(vec(400, 64, 400), vec(500, 96, 500))

-- enter/leave fire once per transition (not every tick)
lobby:on("player_enter") \{ p -> p:sendMessage("Welcome to the lobby!") }
lobby:on("player_leave") \{ p -> p:sendMessage("See you soon.") }

-- Gate PvP zone by permission; bounce unauthorised to lobby
arena:on("player_enter") \{ p ->
    if not p:hasPermission("px.ignis.pvp") then
        local a = lobby:getBounds().A
        p:teleport(a.x, a.y, a.z)
        p:sendMessage("PvP access denied.")
    end
}

-- Throttle: entity_move fires at most every 5 ticks (0.25s)
boss:on("entity_move", \{ e, from, to ->
    local d = to - from
    if d:length() > 0.5 then  -- moved more than half a block
        e:sendMessage("Boss room is small — slow down!")
    end
}, { throttle = 5 })

-- tick auto-subscribes: no enableTick() needed
lobby:on("tick") \{
    for _, p in ipairs(lobby.players) do
        p:sendActionBar("Online: " .. mc.onlineCount)
    end
}

-- Find regions at a position: returns {} when empty
mc.on("player_join") \{ p ->
    local zones = world:getRegionsAt(p.pos)
    p:sendMessage("You are in " .. #zones .. " zone(s).")
}

-- Resize at runtime — setBounds normalises corners, re-evaluates membership
arena:setBounds(vec(200, 64, 200), vec(350, 128, 300))