-- reimplementation of new_flow_logic branch: processing functions
-- written 2017 by thetaepsilon



local flowlogic = {}
flowlogic.helpers = {}
pipeworks.flowlogic = flowlogic



-- borrowed from above: might be useable to replace the above coords tables
local make_coords_offsets = function(pos, include_base)
	local coords = {
		{x=pos.x,y=pos.y-1,z=pos.z},
		{x=pos.x,y=pos.y+1,z=pos.z},
		{x=pos.x-1,y=pos.y,z=pos.z},
		{x=pos.x+1,y=pos.y,z=pos.z},
		{x=pos.x,y=pos.y,z=pos.z-1},
		{x=pos.x,y=pos.y,z=pos.z+1},
	}
	if include_base then table.insert(coords, pos) end
	return coords
end



-- local debuglog = function(msg) print("## "..msg) end



--local formatvec = function(vec) local sep="," return "("..tostring(vec.x)..sep..tostring(vec.y)..sep..tostring(vec.z)..")" end

-- new version of liquid check
-- accepts a limit parameter to only delete water blocks that the receptacle can accept,
-- and returns it so that the receptacle can update it's pressure values.
local check_for_liquids_v2 = function(pos, limit)
	local coords = make_coords_offsets(pos, false)
	local total = 0
	for index, tpos in ipairs(coords) do
		if total >= limit then break end
		local name = minetest.get_node(tpos).name
		if name == "default:water_source" then
			minetest.remove_node(tpos)
			total = total + 1
		end
	end
	--pipeworks.logger("check_for_liquids_v2@"..formatvec(pos).." total "..total)
	return total
end
flowlogic.check_for_liquids_v2 = check_for_liquids_v2



local label_pressure = "pipeworks.water_pressure"
local get_pressure_access = function(pos)
	local metaref = minetest.get_meta(pos)
	return {
		get = function()
			return metaref:get_float(label_pressure)
		end,
		set = function(v)
			metaref:set_float(label_pressure, v)
		end
	}
end


-- logging is unreliable when something is crashing...
local nilexplode = function(caller, label, value)
	if value == nil then
		error(caller..": "..label.." was nil")
	end
end



flowlogic.run = function(pos, node)
	local nodename = node.name
	-- get the current pressure value.
	local nodepressure = get_pressure_access(pos)
	local currentpressure = nodepressure.get()

	-- if node is an input: run intake phase
	local inputdef = pipeworks.flowables.inputs.list[nodename]
	if inputdef then
		currentpressure = flowlogic.run_input(pos, node, currentpressure, inputdef)
		--debuglog("post-intake currentpressure is "..currentpressure)
		--nilexplode("run()", "currentpressure", currentpressure)
	end

	-- balance pressure with neighbours
	currentpressure = flowlogic.balance_pressure(pos, node, currentpressure)

	-- if node is an output: run output phase
	local output = pipeworks.flowables.outputs.list[nodename]
	if output then
		currentpressure = flowlogic.run_output(
			pos,
			node,
			currentpressure,
			output.upper,
			output.lower,
			output.outputfn)
	end

	-- set the new pressure
	nodepressure.set(currentpressure)
end



flowlogic.balance_pressure = function(pos, node, currentpressure)
	-- debuglog("balance_pressure() "..node.name.." at "..pos.x.." "..pos.y.." "..pos.z)
	-- check the pressure of all nearby flowable nodes, and average it out.

	-- pressure handles to average over
	local connections = {}
	-- unconditionally include self in nodes to average over.
	-- result of averaging will be returned as new pressure for main flow logic callback
	local totalv = currentpressure
	local totalc = 1

	-- then handle neighbours, but if not a pressure node don't consider them at all
	for _, npos in ipairs(make_coords_offsets(pos, false)) do
		local nodename = minetest.get_node(npos).name
		-- for now, just check if it's in the simple table.
		-- TODO: the "can flow from" logic in flowable_node_registry.lua
		local haspressure = (pipeworks.flowables.list.simple[nodename])
		if haspressure then
			local neighbour = get_pressure_access(npos)
			--pipeworks.logger("balance_pressure @ "..formatvec(pos).." "..nodename.." "..formatvec(npos).." added to neighbour set")
			local n = neighbour.get()
			table.insert(connections, neighbour)
			totalv = totalv + n
			totalc = totalc + 1
		end
	end

	local average = totalv / totalc
	for _, target in ipairs(connections) do
		target.set(average)
	end

	return average
end



flowlogic.run_input = function(pos, node, currentpressure, inputdef)
	-- intakefn allows a given input node to define it's own intake logic.
	-- this function will calculate the maximum amount of water that can be taken in;
	-- the intakefn will be given this and is expected to return the actual absorption amount.

	local maxpressure = inputdef.maxpressure
	local intake_limit = maxpressure - currentpressure
	if intake_limit <= 0 then return currentpressure end

	local actual_intake = inputdef.intakefn(pos, intake_limit)
	--pipeworks.logger("run_input@"..formatvec(pos).." oldpressure "..currentpressure.." intake_limit "..intake_limit.." actual_intake "..actual_intake)
	if actual_intake <= 0 then return currentpressure end

	local newpressure = actual_intake + currentpressure
	--debuglog("run_input() end, oldpressure "..currentpressure.." intake_limit "..intake_limit.." actual_intake "..actual_intake.." newpressure "..newpressure)
	return newpressure
end



-- flowlogic output helper implementation:
-- outputs water by trying to place water nodes nearby in the world.
-- neighbours is a list of node offsets to try placing water in.
-- this is a constructor function, returning another function which satisfies the output helper requirements.
-- note that this does *not* take rotation into account.
flowlogic.helpers.make_neighbour_output_fixed = function(neighbours)
	return function(pos, node, currentpressure)
		local taken = 0
		for _, offset in pairs(neighbours) do
			local npos = vector.add(pos, offset)
			local name = minetest.get_node(npos).name
			if (name == "air") or (name == "default:water_flowing") then
				minetest.swap_node(npos, {name="default:water_source"})
				taken = taken + 1
			end
		end
		return taken
	end
end

-- complementary function to the above when using non-finite mode:
-- removes water sources from neighbor positions when the output is "off" due to lack of pressure.
flowlogic.helpers.make_neighbour_cleanup_fixed = function(neighbours)
	return function(pos, node, currentpressure)
		-- FIXME - this would indiscriminately take blocks while under-pressure, not just one time?
		for _, offset in pairs(neighbours) do
			local npos = vector.add(pos, offset)
			local name = minetest.get_node(npos).name
			if (name == "default:water_source") then
				minetest.remove_node(pos)
			end
		end
	end
end



flowlogic.run_output = function(pos, node, currentpressure, upper, lower, outputfn)
	-- processing step for water output devices.
	-- takes care of checking a minimum pressure value and updating the resulting pressure level
	-- the outputfn is provided the current pressure and returns the pressure "taken".
	-- as an example, using this with the above spigot function,
	-- the spigot function tries to output a water source if it will fit in the world.
	local result = currentpressure
	if currentpressure > lower then
		local takenpressure = outputfn(pos, node, currentpressure)
		local newpressure = currentpressure - takenpressure
		if newpressure < 0 then newpressure = 0 end
		result = newpressure
	end
	return result
end