local minetest, vector, math_rad, math_random
    = minetest, vector, math.rad, math.random

local get_node_active_selection_box = nc_extended_rotating.utility.get_node_active_selection_box;

local TAU = math.pi * 2

local MOD_NAME = minetest.get_current_modname()
local ARROWS_FACE   = MOD_NAME .. ":arrows_face"
local ARROWS_EDGE   = MOD_NAME .. ":arrows_edge"
local ARROWS_CORNER = MOD_NAME .. ":arrows_corner"

local entities_per_player = {}

local function register_entity(name, mesh, rot_speed)
    minetest.register_entity(name, {
        initial_properties = {
            visual = "mesh",
            mesh   = mesh,
            textures = { "nc_extended_rotating_arrows.png^[opacity:192" },
            use_texture_alpha = true,
            pointable   = false, -- Can't be interacted with.
            static_save = false, -- Doesn't get saved.
            automatic_rotate = math_rad(rot_speed), -- Rotation in degrees per second.
        },
        on_deactivate = function(self, removal)
            if not self.player_name then return end
            entities_per_player[self.player_name] = nil
        end,
    })
end

register_entity(ARROWS_FACE  , "nc_extended_rotating_face.obj"  , 120)
register_entity(ARROWS_EDGE  , "nc_extended_rotating_edge.obj"  ,  60)
register_entity(ARROWS_CORNER, "nc_extended_rotating_corner.obj", 120)

minetest.register_on_leaveplayer(function(player, timed_out)
    local name   = player:get_player_name()
    local arrows = entities_per_player[name]
    if arrows then arrows.object:remove() end
end)

local entity = {}

function entity.update_entity_hint(player, state)
    local name   = player:get_player_name()
    local arrows = entities_per_player[name]

    if state then
        if arrows then
            if state.pos == arrows.prev_pos and state.axis == arrows.prev_axis and state.invert == arrows.prev_invert then
                -- No changes were made, so skip creating a new entity.
                return
            else
                -- Changes were made, delete the old entity.
                -- We do this to avoid rotation interpolation from `set_rotation`.
                arrows.object:remove()
                arrows = nil
            end
        end

        local ent, off
        if     state.mode == "face"   then ent, off = ARROWS_FACE  , state.axis / 1.85
        elseif state.mode == "edge"   then ent, off = ARROWS_EDGE  , vector.new(0, 0, 0)
        elseif state.mode == "corner" then ent, off = ARROWS_CORNER, state.axis / 2.65
        end

        local box = get_node_active_selection_box(state.node)
        local max = box.max - box.min
        local pos = state.pos + off:multiply(max)
        local rot = vector.dir_to_rotation(state.axis)
        rot.x = rot.x + (state.invert and -TAU/4 or TAU/4)

        arrows = minetest.add_entity(pos, ent):get_luaentity()
        arrows.object:set_properties({ visual_size = max })
        arrows.object:set_rotation(rot)

        arrows.player_name = name
        arrows.prev_pos    = state.pos
        arrows.prev_axis   = state.axis
        arrows.prev_invert = state.invert
        entities_per_player[name] = arrows

    elseif arrows then
        arrows.object:remove()
    end
end

return entity