local smt={}
smt.__index=smt
smt.proto=smt

local function round(x)
	return math.floor(x+.5)
end

function smt:bounds_and(a,b,c,...)
	if not a or not b then return false end
	local mi,ma
	mi=math.max(a[1],b[1])
	ma=math.min(a[2],b[2])
	if ma-mi<=0 then return false end
	if c then
		return self:bounds_and({mi,ma},c,...)
	end
	return {mi,ma}
end

function smt:bounds_or(a,b,c,...)
	local mi,ma=math.min(a[1],b[1]),math.max(a[2],b[2])
	if not a then return b end
	if not b then return a end
	if c then
		return self:bounds_or({mi,ma},c,...)
	end
	return {mi,ma}
end

function smt:new(fn,bounds)
	local obj={}
	obj.bounds=bounds
	if obj.bounds==nil then
		obj.bounds={-math.huge,math.huge}
	end
	obj.sample=fn
	return setmetatable(obj,self.proto)
end

function smt:sine()
	return self:new(function(self,t)
		return math.sin(t*math.pi*2)
	end)
end

function smt:square()
	return self:new(function(self,t)
		return (t%1)<=0.5 and -1 or 1
	end)
end

function smt:sawtooth()
	return self:new(function(self,t)
		return (t%1)*2-1
	end)
end

function smt:triangle()
	return self:new(function(self,t)
		--return ((t%1)<=0.5 and (t*2)%1 or 1-(t*2)%1)*2-1 -- sounds cool and glitchy but wrong
		local a=t%1
		if a>0.5 then
			return (1-(a*2-1))*2-1
		end
		return (a*2)*2-1
	end)
end

function smt:noise(y,z,x)
	return self:new(function(self,t)
		return love.math.noise(t,y,z,x)*2-1
	end)
end

function smt:silence(a)
	a=a or 0
	return smt:new(function()return a end)
end

local function rated_bounds(bounds,rate)
	local mi,ma=bounds[1],bounds[2]
	mi,ma=mi*rate,ma*rate
	mi,ma=round(mi),round(ma)-1
	return mi,ma
end

local function prefi(y)
	return math.min(1,math.max(-1,y))
end

function smt:compile(rate,bits,alt)
	rate=rate or 44100
	bits=bits or 16
	local bounds=self.bounds
	local mi,ma=rated_bounds(bounds,rate)
	if alt then
		bounds=self:bounds_and(bounds,alt.bounds)
		local mi,ma=rated_bounds(bounds,rate)
		local sdata=love.sound.newSoundData(ma-mi+1,rate,bits,2)
		for x=mi,ma do
			local x=x+mi
			sdata:setSample(x*2,prefi(self:sample(x/rate+0.5/rate)))
			sdata:setSample(x*2+1,prefi(alt:sample(x/rate+0.5/rate)))
		end
		return sdata
	end
	local sdata=love.sound.newSoundData(ma-mi+1,rate,bits,1)
	for x=mi,ma do
		local xx=x-mi
		sdata:setSample(xx,prefi(self:sample(x/rate+0.5/rate)))
	end
	return sdata
end

function smt:phase(p)
	local bb=self.bounds
	if bb then
		bb={bb[1]-p,bb[2]-p}
	end
	return self:new(function(obj,t)
		return self:sample(t+p)
	end,bb)
end

function smt:amp(a)
	return self:new(function(obj,t)
		return self:sample(t)*a
	end,self.bounds)
end

function smt:freq(f)
	local bb=self.bounds
	if bb then
		bb={bb[1]/f,bb[2]/f}
		if bb[2]<bb[1] then
			bb={bb[2],bb[1]}
		end
	end
	return self:new(function(obj,t)
		return self:sample(t*f)
	end,bb)
end

function smt:clamp(mi,ma)
	return self:new(function(nself,t)
		if t<mi or t>ma then return 0 end
		return self.sample(self,t)
	end,self:bounds_and(self.bounds,{mi,ma}))
end

function smt.am(car,mod,mi,ma)
	return smt:new(function(self,t)
		return car:sample(t)*((mod:sample(t)*0.5+0.5)*(ma-mi)+mi)
	end,car:bounds_and(car.bounds,mod.bounds))
end

function smt.pm(car,mod,mi,ma)
	assert(car.bounds
		and car.bounds[1]==-math.huge
		and car.bounds[2]==math.huge,
		"infinite carrier expected")
	mod=mod:add(mod:silence())
	return smt:new(function(self,t)
		return car:sample(t+((mod:sample(t)*0.5+0.5)*(ma-mi)+mi))
	end,car.bounds)
end

function smt.add(a,b,...)
	if not b then
		if not a then return smt:silence() end
		return a
	end
	local ls={a,b,...}
	local bbs={}
	for k,v in pairs(ls) do
		bbs[k]=v.bounds
	end
	return smt:new(function(self,t)
		local r=0
		for k,v in pairs(ls) do
			r=r+v:sample(t)
		end
		return r
	end,a:bounds_or(unpack(bbs)))
end

do
  local fwav=smt:sine():phase(0.75):freq(0.25)
  fwav=fwav:clamp(0,1)
  fwav=fwav:add(smt:silence(-1):clamp(-math.huge,0))
  function smt.fade(wave,ma,mi)
    local ff=fwav:freq(1/(mi-ma)):phase(-ma)
    return wave:am(ff,1,-1)
  end
end

function smt.fm(car,mod,rate,mi,ma) -- TODO
	local cframe,cache=0,{}
	return smt.new(function(self,t)
	end,mod.bounds)
end

return smt