local has_doc = minetest.get_modpath(minetest.get_current_modname())

mcl_cauldrons.registered_cauldrons = {}


-- symbolic constants.
mcl_cauldrons.BUCKET_FILL_LEVELS = 3
mcl_cauldrons.BOTTLE_FILL_LEVELS = 1


-- list of substances accepted by cauldron.
-- N.B. hopefully this will be obsoleted by the liquids API.
mcl_cauldrons.substances = {
	"cauldron_water",
	"cauldron_river_water",
}


-- Find cauldron from registered cauldrons -> string, table
--  `substance` == nil for any cauldron content (incl. empty), "" = only empty.
--  `fill_level` == nil for any/first fill level satisfying `substance`.
-- e.g. find_cauldron("cauldron_water", 2) -> "mcl_cauldrons:cauldron_water_2"
-- Returns 2 values: node_name:string, node_definition:table;
-- if nothing else matches, returns empty cauldron ("mcl_cauldrons:cauldron").
function mcl_cauldrons.find_cauldron(substance, fill_level)
	local empty_nodename = "mcl_cauldrons:cauldron"
	local empty_nodedef = mcl_cauldrons.registered_cauldrons[empty_nodename]
	if (substance == "") then
		return empty_nodename, empty_nodedef
	end
	for nodename, nodedef in pairs(mcl_cauldrons.registered_cauldrons) do
		-- matched on substance: 'any', or exact match from .groups.
		local match_substance = (substance == nil) or (nodedef.groups[substance] and (nodedef.groups[substance] ~= 0))
		-- matched on fill_level: 'any', or exact match from .groups.
		local match_level = (fill_level == nil) or (nodedef.groups.cauldron_filled == fill_level)
		if match_substance and match_level then
			return nodename, nodedef
		end
	end
	-- no match, use empty.
	return empty_nodename, empty_nodedef
end

-- Test: node describes a cauldron -> boolean
function mcl_cauldrons.is_cauldron(node)
	return (minetest.get_item_group(node.name, "cauldron") ~= 0)
end

-- Test: cauldron node contains specified substance -> boolean
function mcl_cauldrons.has_substance(node, substance)
	return (minetest.get_item_group(node.name, substance) ~= 0)
end

-- list of supported substances -> table
function mcl_cauldrons.list_substances()
	return mcl_cauldron.substances
end

-- Get substance inside cauldron -> string or nil
function mcl_cauldrons.get_substance(node)
	local nodename = node.name
	-- data-driven to avoid if-cascade.
	-- until liquids API is available, the substance name matches the group key in the node definition (e.g. "cauldron_water").
	for i, probe_key in ipairs(mcl_cauldrons.substances) do
		if minetest.get_item_group(node.name, probe_key) ~= 0 then
			return probe_key
		end
	end
	-- claim cauldron is empty.
	return nil
end

-- Get maximum number of levels available for cauldron node -> number
-- Optionally specify `substance` (mainly to determine a change in cauldron substance, e.g. filling a full one with bucket of something else)
-- substance == nil to ignore substance criteria
function mcl_cauldrons.get_maximum(node, substance)
	local nodename
	if substance == nil then
		nodename = node.name
	else
		nodename = mcl_cauldrons.find_cauldron(substance, nil)
	end
	return minetest.get_item_group(nodename, "cauldron_maximum")
end

-- Get current level of cauldron -> number
-- Optionally specify `substance`, substance==nil to indicate current content.
function mcl_cauldrons.get_level(node, substance)
	if substance and (minetest.get_item_group(node.name, substance) == 0) then
		return 0
	end
	return minetest.get_item_group(node.name, "cauldron_filled")
end

-- Test: cauldron is empty -> boolean
-- (i.e. fill level is 0, or contents is empty)
function mcl_cauldrons.is_empty(node)
	if not mcl_cauldrons.is_cauldron(node) then
		error("not a cauldron", node.name)
	end
	if minetest.get_item_group(node.name, "cauldron_filled") == 0 then
		return true
	end
	return false
end

-- Test: cauldron is full -> boolean
-- (i.e. current fill level matches maximum level.
function mcl_cauldrons.is_full(node)
	local maximum = mcl_cauldrons.get_maximum(node)
	local current = mcl_cauldrons.get_level(node)
	return (current >= maximum)
end

-- Set fill level, bypassing game rules -> table
-- Optionally indicate substance (to change cauldron content); nil to preserve.
-- returns a node table as accepted by minetest.set_node()
function mcl_cauldrons.set_level(node, fill_level, substance)
	if substance == nil then
		-- determine current substance.
		substance = mcl_cauldrons.get_substance(node)
	end
	local nodename, nodedef = mcl_cauldrons.find_cauldron(substance, fill_level)
	local newnode = { name = nodename, param1 = node.param1, param2 = node.param2 }
	return newnode
end

-- Change content of cauldron by number of levels with indicated substance -> table
-- Subject to game rules (delegated to node definition's on_fill callback)
-- returns a node table as accepted by minetest.set_node()
function mcl_cauldrons.fill_levels(node, change_levels, substance)
	local nodedef = mcl_cauldrons.registered_cauldrons[node.name]
	local callback = nodedef._mcl_on_fill
	-- use callback if available, else revert.
	return callback and callback(node, change_levels, substance) or node
end

-- drain counterpart to fill_levels()
function mcl_cauldrons.drain_levels(node, change_levels, substance)
	local nodedef = mcl_cauldrons.registered_cauldrons[node.name]
	local callback = nodedef._mcl_on_drain
	-- use callback if available, else revert.
	return callback and callback(node, change_levels, substance) or node
end


-- Wrapper to register cauldron-specific nodes.
-- additional bookkeeping specific to mcl_cauldrons.
function mcl_cauldrons.register_cauldron_node(nodename, nodedef, doc_alias)
	mcl_cauldrons.registered_cauldrons[nodename] = nodedef
	minetest.register_node(nodename, nodedef)
	if doc_alias and has_doc then
		doc.add_entry_alias("nodes", doc_alias, "nodes", nodename)
	end
end