if (SpringESkinTunes ~= nil)
	return
end

//TODO:
//1. do the todo deliberately placed lower down

//DOWNLOAD THE README FROM THE SRB2 MESSAGE BOARD FOR AN IMPLEMENTATION GUIDE:
//<LINK GOES HERE ONCE HOSTED>

//BACK-END-----------------------------------------------
local function IsNumber(nbr) return nbr ~= nil and type(nbr) == "number" end

local function IsTable(tbl) return tbl ~= nil and type(tbl) == "table" end

local function IsString(str) return str ~= nil and type(str) == "string" end

local function TableHasValue(tbl, val)
	if(IsTable(tbl) ~= true)
		return 0
	end
	
	for k, v in pairs(tbl)
		if(v == val)
			return true
		end
	end
	
	return false
end

local function CountTable(tbl)
	if(IsTable(tbl) ~= true)
		return 0
	end
	
	local c = 0
	
	for k, v in pairs(tbl)
		c = $ + 1
	end
	
	return c
end

local function StringEmptyOrNil(str, freeType)
	if(freeType ~= true and IsString(str) ~= true)
		return true
	end
	
	if(str==nil)//'nil' can tostring() into "nil" but i don't want that
		return true
	end
	
	str = tostring(str)
	
	local nospaces=""
	
	for c in str.gmatch(str,".")//for every character in line ('.' matcher being 'any condition')
		if(c~=" ")
			nospaces = nospaces..c
		end
	end
	
	return string.len(nospaces) <= 0
end

local function IsBool(b)
	if(b==nil)
		return false
	end
	
	if(type(b) ~= "boolean")
		return false
	end
	
	return true
end

local function IsPlayer(p)
	if(p==nil)
		return false
	end
	
	if(type(p)~="userdata")
		return false
	end

	if(userdataType(p)~="player_t")
		return false
	end
	
	if(p.valid ~= true)
		return false
	end

	return true
end

//specially designed to circumvent the fact that dedicated servers count as a
//non-spectator player in players.iterate (yes, really)
local function PlayerPhysicallyExists(p)
	if(IsPlayer(p) ~= true)
		return false
	end
	
	if(p.spectator == true)
		return false
	end
	
	if(p.mo==nil)
		return false
	end
	
	if(type(p.mo)~="userdata")
		return false
	end
	
	if(userdataType(p.mo)~="mobj_t")
		return false
	end
	
	if(IsBool(p.mo.valid)~=true)
		return false
	end
	
	if(p.mo.valid~=true)
		return false
	end
	
	return true
end

//FRONT-END-----------------------------------------------------
local register = {}
local tuneInfo = {}
tuneInfo["invinc"] = {}
tuneInfo["invinc"]["origSong"] = "kinvnc"
tuneInfo["invinc"]["condition"] = function(p) return IsPlayer(p) == true and p.invincibilitytimer > 0 == true end
tuneInfo["grow"] = {}
tuneInfo["grow"]["origSong"] = "kgrow"
tuneInfo["grow"]["condition"] = function(p) return IsPlayer(p) == true and p.growshrinktimer > 0 == true end

//late joiners will match their registry to the host. this
//is only relevant if people decide to use the API calls
//non-deterministically which is entirely possible so might as well
//keep my mind open
addHook("NetVars", function(x)
	register = x($)
end)

addHook("PostThinkFrame", function()
	for tuneKey, tuneInfoSingular in pairs(tuneInfo)
		Music_Remap(tuneKey, tuneInfoSingular["origSong"])
	end
	
	//do it backwards to give port priority
	for i = 3, 0, -1
		local p = displayplayers[i]
		
		if(PlayerPhysicallyExists(p) ~= true)
			continue
		end
		
		for skin, tuneList in pairs(register)
			if(p.mo.skin ~= skin)
				continue
			end
			
			for tune, songsAndSeed in pairs(tuneList)
				if(tuneInfo[tune]["condition"](p) == true)
					Music_Remap(tune, songsAndSeed["songs"][(songsAndSeed["seed"] % CountTable(songsAndSeed["songs"])) + 1])
				else
					songsAndSeed["seed"] = leveltime
				end
			end
		end
	end
end)

local function Set(skinName, tuneInfoKey, tuneSongs)
	if(StringEmptyOrNil(skinName, false) == true)
		return false
	end
	
	//TODO: add check for skin existing if this gets merged: https://gitlab.com/kart-krew-dev/ring-racers/-/merge_requests/42
	
	if(StringEmptyOrNil(tuneInfoKey, false) == true)
		return false
	end
	
	if(IsString(tuneSongs) == true)
		tuneSongs = {tuneSongs}
	end
	
	if(IsTable(tuneSongs) ~= true)
		return false
	end
	
	local tuneInfoExists = false
	
	for k, v in pairs(tuneInfo)
		if(k == tuneInfoKey)
			tuneInfoExists = true
			break
		end
	end
	
	if(tuneInfoExists ~= true)
		return false
	end
	
	local tuneSongs_filtered = {}
	local tuneSongs_filtered_writeIndex = 1
	
	for k, v in pairs(tuneSongs)
		//can't check if 'v' (aka song in hardcode) is a real song
		//but the default response from the game is to just play silence
		//which i'm okay with
		if(StringEmptyOrNil(v, false) ~= true and TableHasValue(tuneSongs_filtered, v) ~= true)
			tuneSongs_filtered[tuneSongs_filtered_writeIndex] = v
			tuneSongs_filtered_writeIndex = $ + 1
		end
	end
	
	if(tuneSongs_filtered_writeIndex <= 1) //if no songs passed the filter
		return false
	end
	
	if(IsTable(register[skinName]) ~=true)
		register[skinName] = {}
	end
	
	if(IsTable(register[skinName][tuneInfoKey]) ~= true)
		register[skinName][tuneInfoKey] = {}
	end
	
	register[skinName][tuneInfoKey]["songs"] = tuneSongs_filtered
	register[skinName][tuneInfoKey]["seed"] = leveltime
	return true
end

local function Erase(skinKey, tuneInfoKey, tuneSongs)
	if(IsString(tuneSongs) == true)
		tuneSongs = {tuneSongs}
	end

	local skinExists = StringEmptyOrNil(skinKey, false) ~= true and register[skinKey] ~= nil
	local tuneInfoKeyExists = skinExists == true and StringEmptyOrNil(tuneInfoKey, false) ~= true and register[skinKey][tuneInfoKey] ~= nil
	local anyTuneSongExists = tuneInfoKeyExists == true and IsTable(tuneSongs) == true
	
	if(anyTuneSongExists == true)
		anyTuneSongExists = false
		
		for k, v in pairs(register[skinKey][tuneInfoKey]["songs"])
			if(StringEmptyOrNil(v, false) ~= true and TableHasValue(tuneSongs, v) == true)
				anyTuneSongExists = true
				break
			end
		end
	end
	
	local ret = {}
	ret[1] = false
	ret[2] = 0

	if(anyTuneSongExists)
		local newSongs = {}
		local newSongs_writeIndex = 1
		
		for k, v in pairs(register[skinKey][tuneInfoKey]["songs"])
			if(StringEmptyOrNil(v, false) ~= true and TableHasValue(tuneSongs, v) ~= true and TableHasValue(newSongs, v) ~= true)
				newSongs[newSongs_writeIndex] = v
				newSongs_writeIndex = $ + 1
			end
		end
		
		if(newSongs_writeIndex > 1)
			register[skinKey][tuneInfoKey]["songs"] = newSongs
			ret[2] = newSongs_writeIndex -1
		else
			local removeCount = CountTable(register[skinKey][tuneInfoKey])
			register[skinKey][tuneInfoKey] = nil //i'm pretty sure this outcome is impossible
			ret[2] = removeCount
		end
	elseif(tuneInfoKeyExists)
		if(IsTable(tuneSongs) ~= true)
			register[skinKey][tuneInfoKey] = nil
			ret[2] = 1
		else
			ret[2] = 0
		end
	elseif(skinExists)
		if(IsString(tuneInfoKey) ~= true and IsTable(tuneSongs) ~= true)
			register[skinKey] = nil
			ret[2] = 1
		else
			ret[2] = 0
		end
	else
		//wrapping outcomes in these conditionals because i don't want attempting to delete something that doesn't already exist to turn into falling backwards into deleting something more important (i.e. you try to delete the 'ana ng' skin but that skin doesn't exist so otherwise it'd just delete the whole table)
		if(IsString(skinKey) ~= true and IsString(tuneInfoKey) ~= true and IsTable(tuneSongs) ~= true)
			register = {}
			ret[2] = 1
		else
			ret[2] = 0
		end
	end
	
	ret[1] = ret[2] >= 1
	return ret
end

//not actually a part of the api nor used anywhere but i'm not getting rid of it bc
//it's really useful for debugging and i'm not giving just this item its own entire file
local function DBGRegistryToString()
	local ret = "REGISTRY AT TIC "..tostring(leveltime)..":\n"
	
	for skinName, skinInfo in pairs(register)
		ret = $..skinName..":\n"
		
		for tuneName, tuneInfo in pairs(skinInfo)
			ret = $.."    "..tuneName..":\n"
			
			for anonKey, songName in pairs(tuneInfo["songs"])
				ret = $.."        "..songName.."\n"
			end
		end
	end
	
	return ret
end

local skinTunes = {}
skinTunes.GetVersion = function() return 1 end //Advance this by 1 every time anything about this Lua file changes so that those relying on the script can conditionalize to the assumed state of the API
skinTunes.Set = Set
skinTunes.Erase = Erase

rawset(_G, "SpringESkinTunes", skinTunes)