local minetest, nodecore
    = minetest, nodecore

local registry = {}
local registered_rotatables = {}

-- Registered rotatable nodes will call this function when their `on_rightclick`
-- is triggered instead of their default implementation. Can be overwritten.
registry.custom_on_rightclick = function(pos, node, clicker, item_stack, pointed_thing) end

local function register_rotatable(name, facedir_lookup)
    local def = minetest.registered_nodes[name]
    if not def then error("Unknown node '" .. name .. "'") end
    if def.paramtype2 ~= "facedir" then error("Node '" .. name .. "' must be 'facedir'") end
    def.on_rightclick = function(...) registry.custom_on_rightclick(...) end
    registered_rotatables[name] = { lookup = facedir_lookup }
end
registry.register_rotatable = register_rotatable

-- Returns whether the specified `node` is rotatable by this mod.
local function is_rotatable(node)
    local name = node and node.name or ""
    return not not registered_rotatables[name]
end
registry.is_rotatable = is_rotatable

-- Fixes facedir for the specified `node` when rotated to `facedir`.
-- * Returns `nil` if the node can't rotate this way.
-- * Returns `facedir` when the node can rotate this way.
-- * Returns another facedir when the node should rotate another equivalent way.
local function fix_rotatable_facedir(node, facedir)
    local name  = node and node.name or ""
    local entry = registered_rotatables[name]
    if not entry then return nil end
    if not entry.lookup then return facedir end
    return entry.lookup[facedir]
end
registry.fix_rotatable_facedir = fix_rotatable_facedir


--------------------------------------------
-- Register rotatable nodes from NodeCore --
--------------------------------------------

local function nodecore_filtered_lookup(eq_func)
    local lookup = {}
    for i = 0, 23 do
        local facedir = nodecore.facedirs[i]
        for j = 0, #lookup - 1 do
            local other = nodecore.facedirs[lookup[j]]
            if eq_func(facedir, other) then lookup[i] = j; break end
        end
        lookup[i] = lookup[i] or i
    end
    return lookup
end

local LENS_FILTERED_LOOKUP = nodecore_filtered_lookup(
    function(a, b) return vector.equals(a.f, b.f) end)
local PRISM_FILTERED_LOOKUP = nodecore_filtered_lookup(
    function(a, b) return vector.equals(a.f, b.r) and vector.equals(a.r, b.f) end)
local PANEL_FILTERED_LOOKUP = nodecore_filtered_lookup(
    function(a, b) return vector.equals(a.f, b.r) and vector.equals(a.r, b.f) end)

for _, lens_state in ipairs({ "", "_on", "_glow", "_glow_start" }) do
    register_rotatable("nc_optics:lens" .. lens_state, LENS_FILTERED_LOOKUP) end
for _, prism_state in ipairs({ "", "_on", "_gated" }) do
    register_rotatable("nc_optics:prism" .. prism_state, PRISM_FILTERED_LOOKUP) end

register_rotatable("nc_doors:panel_plank" , PANEL_FILTERED_LOOKUP)
register_rotatable("nc_doors:panel_cobble", PANEL_FILTERED_LOOKUP)

return registry