
--[[

Copyright (C) 2016 - Auke Kok <sofar@foo-projects.org>

"lightning" is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as
published by the Free Software Foundation; either version 2.1
of the license, or (at your option) any later version.

--]]

lightning = {}

lightning.interval_low = 17
lightning.interval_high = 503
lightning.range_h = 100
lightning.range_v = 50
lightning.size = 100
lightning.effect_range = 400


local rng = PcgRandom(32321123312123)

local ps = {}
local ttl = 1

local revertsky = function()
	if ttl == 0 then
		return
	end
	ttl = ttl - 1
	if ttl > 0 then
		return
	end

	for playername, sky in pairs(ps) do
		local player = minetest.get_player_by_name(playername)
		-- check if the player is still online
		if player then
		   player:set_sky({type = "regular", sky_color = {sky.sky_color}})
		   player:override_day_night_ratio(sky.ratio)
		end
	end

	ps = {}
end



minetest.register_globalstep(revertsky)

-- select a random strike point, midpoint
local function choose_pos(pos)
	if not pos then
		local playerlist = minetest.get_connected_players()
		local playercount = table.getn(playerlist)

		-- nobody on
		if playercount == 0 then
			return nil, nil
		end

		local r = rng:next(1, playercount)
		local randomplayer = playerlist[r]
		pos = randomplayer:get_pos()

		-- avoid striking underground
		if pos.y < -20 then
			return nil, nil
		end

		pos.x = math.floor(pos.x - (lightning.range_h / 2) + rng:next(1, lightning.range_h))
		pos.y = pos.y + (lightning.range_v / 2)
		pos.z = math.floor(pos.z - (lightning.range_h / 2) + rng:next(1, lightning.range_h))
	end

	local b, pos2 = minetest.line_of_sight(pos, {x = pos.x, y = pos.y - lightning.range_v, z = pos.z}, 1)

	-- nothing but air found
	if b then
		return nil, nil
	end

	local n = minetest.get_node({x = pos2.x, y = pos2.y - 1/2, z = pos2.z})
	if n.name == "air" or n.name == "ignore" then
		return nil, nil
	end

	return pos, pos2
end

-- lightning strike API
-- * pos: optional, if not given a random pos will be chosen
-- * returns: bool - success if a strike happened
lightning.strike = function(pos, cosmetic)
	if lightning.auto then
		minetest.after(rng:next(lightning.interval_low, lightning.interval_high), lightning.strike)
	end

	local pos2
	pos, pos2 = choose_pos(pos)

	if not pos then
		return false
	end

	minetest.add_particlespawner({
		amount = 1,
		time = 0.2,
		-- make it hit the top of a block exactly with the bottom
		minpos = {x = pos2.x, y = pos2.y + (lightning.size / 2) + 1/2, z = pos2.z },
		maxpos = {x = pos2.x, y = pos2.y + (lightning.size / 2) + 1/2, z = pos2.z },
		minvel = {x = 0, y = 0, z = 0},
		maxvel = {x = 0, y = 0, z = 0},
		minacc = {x = 0, y = 0, z = 0},
		maxacc = {x = 0, y = 0, z = 0},
		minexptime = 0.2,
		maxexptime = 0.2,
		minsize = lightning.size * 10,
		maxsize = lightning.size * 10,
		collisiondetection = true,
		vertical = true,
		-- to make it appear hitting the node that will get set on fire, make sure
		-- to make the texture lightning bolt hit exactly in the middle of the
		-- texture (e.g. 127/128 on a 256x wide texture)
		texture = "lightning_lightning_" .. rng:next(1,3) .. ".png",
		-- 0.4.15+
		glow = 14,
	})

	minetest.sound_play({ pos = pos, name = "lightning_thunder", gain = 10, max_hear_distance = 500 })

	-- damage nearby objects, player or not
	if not cosmetic then
	   for _, obj in ipairs(minetest.get_objects_inside_radius(pos, 5)) do
		-- nil as param#1 is supposed to work, but core can't handle it.
		obj:punch(obj, 1.0, {full_punch_interval = 1.0, damage_groups = {fleshy=8}}, nil)
	   end
	end


	local playerlist = minetest.get_connected_players()
	for i = 1, #playerlist do
		local player = playerlist[i]
		local distance = vector.distance(player:get_pos(), pos)
		-- only affect players inside effect_range
		if distance < lightning.effect_range then
			local sky = {}
			sky.sky_color = player:get_sky(true)
			sky.ratio = player:get_day_night_ratio()

			local name = player:get_player_name()
			if ps[name] == nil then
				ps[name] = sky
				player:set_sky({type = "plain", base_color = "#CCFFFFFF"})
				player:override_day_night_ratio(1)
			end
		end
	end


	-- trigger revert of skybox
	ttl = 5

	if cosmetic == true then return end

	-- set the air node above it on fire
	pos2.y = pos2.y + 1/2
	if minetest.get_item_group(minetest.get_node({x = pos2.x, y = pos2.y - 1, z = pos2.z}).name, "liquid") < 1 then
		if minetest.get_node(pos2).name == "air" then
			-- only 1/4 of the time, something is changed
			if rng:next(1,4) > 1 then
				return
			end
			-- very rarely, potentially cause a fire
			if rng:next(1,200) == 1 then
				minetest.set_node(pos2, {name = "inferno:hungry_flame"})
			end
		end
	end

	-- perform block modifications
	if rng:next(1,10) > 1 then
		return
	end
	pos2.y = pos2.y - 1
	local n = minetest.get_node(pos2)
	if minetest.get_item_group(n.name, "tree") > 0 then
		minetest.swap_node(pos2, { name = "tech:large_wood_fire_smoldering"})
	--elseif minetest.get_item_group(n.name, "sand") > 0 then
		--minetest.set_node(pos2, { name = "default:glass"})
	--elseif minetest.get_item_group(n.name, "soil") > 0 then
	--	minetest.set_node(pos2, { name = "default:gravel"})
	end
end
