nc_extended_rotating/state.lua

local math_round, minetest, vector
    = math.round, minetest, vector

local fix_rotatable_facedir       = nc_extended_rotating.registry.fix_rotatable_facedir;
local is_rotatable                = nc_extended_rotating.registry.is_rotatable;
local rotate_facedir              = nc_extended_rotating.rotate.rotate_facedir;
local rotation_vector_from_lookat = nc_extended_rotating.utility.rotation_vector_from_lookat;

-- Distance at which we want to rotate by "pushing" on an edge.
local EDGE_DISTANCE = 2.5 / 16 -- texels (at 16² texture resolution)


-- Contains a per-player state that holds information, created by a raycast
-- done in `playerstep`, about the node this player might rotate. This is used
-- to update the their HUD and to decide what to do when a rightclick occurs.
local rotating_state = {}

-- Calculates the state for the specified `player` and player `data`.
-- This state contains information about how the player would rotate a block.
local function calculate_rotating_state(player, data)
    local state = {}

    local pointed_thing = data.raycast()
    if (not pointed_thing) or pointed_thing.type ~= "node" then return nil end

    state.pos  = pointed_thing.under
    state.node = minetest.get_node(state.pos)
    if not is_rotatable(state.node) then return nil end

    if vector.equals(pointed_thing.above, pointed_thing.under) then return nil end
    state.face = pointed_thing.above - pointed_thing.under

    -- When player is sneaking, must be empty-handed for rotating to work.
    local is_sneaking = player:get_player_control().sneak
    if is_sneaking and (not player:get_wielded_item():is_empty()) then return nil end

    local degrees = 90
    local r = rotation_vector_from_lookat(state.node, pointed_thing, EDGE_DISTANCE)
    state.axis = r

    local num = math_round(r.x * r.x + r.y * r.y + r.z * r.z) -- Squared length.
    if     num == 1 then state.mode = "face"
    elseif num == 2 then state.mode = "edge"; state.axis = state.face:cross(r)
    elseif num == 3 then state.mode = "mirror"; degrees = 120
    end

    -- Sneaking causes the direction of the rotation to be inverted.
    if is_sneaking then degrees = -degrees end
    state.invert = is_sneaking

    state.facedir = rotate_facedir(state.node.param2, state.axis, -degrees)
    state.facedir = fix_rotatable_facedir(state.node, state.facedir)
    state.success = state.facedir and state.facedir ~= state.node.param2

    return state
end

minetest.register_on_leaveplayer(function(player)
    local name = player:get_player_name()
    rotating_state[name] = nil
end)


local state = {}

function state.update_rotating_state(player, data)
    local rot_state = calculate_rotating_state(player, data)
    rotating_state[player:get_player_name()] = rot_state
    return rot_state
end

function state.get_rotating_state(player, pos, node)
    if not minetest.is_player(player) then return nil end
    local rot_state = rotating_state[player:get_player_name()]
    if not rot_state then return nil end

    if not vector.equals(pos, rot_state.pos) then return nil end
    if node.name ~= rot_state.node.name or node.param2 ~= rot_state.node.param2 then return nil end

    return rot_state
end

return state