sum_airship/balloon.lua

local mod_name = minetest.get_current_modname()
local mod_path = minetest.get_modpath(mod_name)

local me = sum_hot_air_balloon

me.vars = {
    lift = 4,
    speed = 3,
    fuel_time = 30,
}

function me.on_activate(self, staticdata, dtime_s)
	local data = minetest.deserialize(staticdata)
	if type(data) == "table" then
		self._itemstring = data.itemstring
        if data._driver then
            self._driver = minetest.get_player_by_name((data._driver:get_player_name()))
        else
            self._driver = nil
        end
        self._flags = data._flags
        if self._driver then me.detach(self) end
	end
    self.object:set_animation({x=0, y=149}, 24)
end

function me.get_staticdata(self)
	return minetest.serialize({
		itemstring = self._itemstring,
        _driver = ((self._driver and self._driver:is_player())
            and self._driver:get_player_name()) or nil,
        _flags = self._flags,
	})
end

function me.attach(self, player)
    if not (player and player:is_player()) then
        return false
    end
	self._driver = player
    self._driver:set_attach(self.object, "",
		{x = 0, y = -3.0, z = 0}, {x = 0, y = 0, z = 0})
    self._driver:set_look_horizontal(self.object:get_yaw())
end

function me.detach(self)
    if not self._driver then return false end
    self._driver:set_detach()
    self._driver = nil
    return true
end


function me.on_death(self, killer)
	if killer and killer:is_player()
    and not minetest.is_creative_enabled(killer:get_player_name()) then
		local inv = killer:get_inventory()
		inv:add_item("main", self._itemstring)
	else
		minetest.add_item(self.object:get_pos(), self._itemstring)
	end
    me.detach(self)
	self._driver = nil
end

function me.on_rightclick(self, clicker)
	local item = clicker:get_wielded_item()
	local item_name = item:get_name()
	if clicker and item and item_name
    and (string.find(item_name, ":coal")
	or string.find(item_name, ":charcoal")) then
		if not minetest.is_creative_enabled(clicker:get_player_name()) then
			item:take_item()
			clicker:set_wielded_item(item)
		end
	else
		me.attach(self, clicker)
	end
end


-- 10, 5, 5
-- this system ensures collision kind of works with balloons.
-- does not include entity to entity collisions
local balloon = {}
balloon.offset = 4.5
balloon.length = 3
balloon.height = 2.5
local balloon_nodes = {}
balloon_nodes[0] = { -- top
	p = vector.new(0, balloon.offset + balloon.height, 0),
	dir = vector.new(0, -5, 0),}
balloon_nodes[1] = { -- front
	p = vector.new(0, balloon.offset, balloon.length),
	dir = vector.new(0, -0.5, -1),}
balloon_nodes[2] = { -- back
	p = vector.new(0, balloon.offset, -balloon.length),
	dir = vector.new(0, 0, 1),}
balloon_nodes[3] = { -- left or right
	p = vector.new(balloon.length, balloon.offset, 0),
	dir = vector.new(-1, 0, 0),}
balloon_nodes[4] = { -- left or right
	p = vector.new(-balloon.length, balloon.offset, 0),
	dir = vector.new(1, 0, 0),}
-- diagonals
local vdiag = 0.7
balloon_nodes[5] = {
	p = vector.new(-balloon.length*vdiag, balloon.offset, -balloon.length*vdiag),
	dir = vector.new(vdiag, 0, vdiag),}
balloon_nodes[6] = {
	p = vector.new(balloon.length*vdiag, balloon.offset, -balloon.length*vdiag),
	dir = vector.new(-vdiag, 0, vdiag),}
balloon_nodes[7] = {
	p = vector.new(-balloon.length*vdiag, balloon.offset, balloon.length*vdiag),
	dir = vector.new(vdiag, 0, -vdiag),}
balloon_nodes[8] = {
	p = vector.new(balloon.length*vdiag, balloon.offset, balloon.length*vdiag),
	dir = vector.new(-vdiag, 0, -vdiag),}

function me.get_balloon_collide(self)
	local force = vector.new()
	local o = self.object:get_pos()
	for _, check in pairs(balloon_nodes) do
		local n = minetest.get_node(vector.add(check.p, o))
		-- minetest.add_particle({
		-- 	pos = vector.add(o, check.p),
		-- 	velocity = vector.new(0, 1, 0),
		-- 	expirationtime = math.random(0.5, 2),
		-- 	size = math.random(0.1, 4),
		-- 	texture = "sum_wood_ash_planks.png",
		-- })
		if n and minetest.registered_nodes[n.name]
		and minetest.registered_nodes[n.name].walkable then
			force = vector.add(force, check.dir)
		end
	end
	return force
end

function me.on_step(self, dtime, moveresult)
    local exit = false
    local ctrl = nil
    -- allow to exit
    if self._driver and self._driver:is_player() then
        local name = self._driver:get_player_name()
        ctrl = player_info.p[name]
        exit = ctrl.just_pressed.sneak
    end
    if exit then
        me.detach(self)
        return false
    end

    local climb = 0
    local right = 0
    local forward = 0
    local v = self.object:get_velocity()
    local p = self.object:get_pos()
    local node_below = minetest.get_node(vector.offset(p, 0, -0.8, 0)).name
	local is_on_floor = minetest.registered_nodes[node_below].walkable
	local in_water = minetest.get_item_group(minetest.get_node(p).name, "liquid") ~= 0
	local on_water = (minetest.get_item_group(minetest.get_node(vector.offset(p, 0, -0.2, 0)).name, "liquid") ~= 0 and not in_water)

    if ctrl then
        if ctrl.ctrl.up then forward = 1
        elseif ctrl.ctrl.down then forward = -1 end
        if ctrl.ctrl.jump then climb = 1
        elseif ctrl.ctrl.aux1 then climb = -1 end
        if ctrl.ctrl.right then right = 1
        elseif ctrl.ctrl.left then right = -1 end
        local yaw = self.object:get_yaw()
        local dir = minetest.yaw_to_dir(yaw)
        self.object:set_yaw(yaw - right * dtime)
        local added_vel = vector.multiply(dir, forward * dtime * me.vars.speed)
        added_vel.y = added_vel.y + (climb * dtime * me.vars.lift)
        v = vector.add(v, added_vel)
    end

	if self._driver then
		local collide_force = me.get_balloon_collide(self)
		-- collide_force = vector.normalize(collide_force)
		if collide_force ~= vector.new() then
			collide_force = vector.multiply(collide_force, 0.1)
			v = vector.multiply(v, 0.95)
		end
		v = vector.add(v, collide_force)
	end

    if not self._driver then
        v.y = v.y - dtime
    end

	if sum_air_currents ~= nil then
		if self._driver or not is_on_floor then
            local wind_vel = sum_air_currents.get_wind(p)
            wind_vel = vector.multiply(wind_vel, dtime)
			v = vector.add(wind_vel, v)
		end
	end
    if in_water then
        v.y = 1
    elseif on_water and not self._driver then
        v.y = 0
    end

    if (not self._driver) and is_on_floor then
        v.x = v.x * 0.8
        v.y = v.y * 0.95
        v.z = v.z * 0.8
    else
        v.x = v.x * (1 - (dtime * 0.5))
        v.y = v.y * (1 - (dtime * 0.5))
        v.z = v.z * (1 - (dtime * 0.5))
    end
    self.object:set_velocity(v)
end


minetest.register_entity("sum_hot_air_balloon:balloon_ENTITY", {
	physical = true,
	pointable = true,
	collisionbox = {-0.5, -0.5, -0.5, 0.5, 0.2, 0.5},
	selectionbox = {-0.5, -0.5, -0.5, 0.5, 0.2, 0.5},
	hp_max = 3,
	visual = "mesh",
	mesh = "sum_hot_air_balloon.b3d",
    backface_culling = false,
	textures = {
        "sum_hot_air_balloon_canvas.png",   -- balloon
        "sum_wood_ash_planks.png",          -- cradle
        "sum_wood_oak_plank.png",           -- lining
        "sum_wood_oak_plank.png",           -- strut
        "sum_wood_oak_plank.png",           -- strut
        "sum_hot_air_balloon_canvas.png",   -- burner
        "sum_wood_oak_plank.png",           -- small strut
        "sum_wood_oak_plank.png",           -- small strut
	},
    on_rightclick = me.on_rightclick,
    on_activate = me.on_activate,
    get_staticdata = me.get_staticdata,
    on_death = me.on_death,
    on_step = me.on_step,
	_driver = nil,
	_removed = false,
    _flags = {},
    _itemstring = "sum_hot_air_balloon:balloon_item",
})

minetest.register_craftitem("sum_hot_air_balloon:balloon_item", {
	description = "Hot air balloon",
    inventory_image = "sum_hot_air_balloon_item.png",
    groups = { vehicle = 1, airship = 1, transport = 1},
    on_place = function(itemstack, placer, pointed_thing)
        if pointed_thing.type ~= "node" then
            return itemstack
        end
        local node = minetest.get_node(pointed_thing.under)
        if placer and not placer:get_player_control().sneak then
            if minetest.registered_nodes[node.name] and minetest.registered_nodes[node.name].on_rightclick then
                return minetest.registered_nodes[node.name].on_rightclick(pointed_thing.under, node, placer, itemstack) or itemstack
            end
        end
        local pos = vector.offset(pointed_thing.above, 0, 0.5, 0)
        local self = minetest.add_entity(pos, "sum_hot_air_balloon:balloon_ENTITY"):get_luaentity()
        if not minetest.is_creative_enabled(placer:get_player_name()) then
            itemstack:take_item()
        end
        return itemstack
    end,
})