-- A game's own vocabulary:  a behaviour, a condition, and an action this game alone knows,
-- written as Author.singe writes its own manifest entries.  The description names this file
-- (vocabulary = "vocab.singe");  nothing else in Forge has heard of a bob.

-- A bob:  the entity rises and falls on a sine wave about where it was put.
AUTHOR.behaviours.bob = {
	help   = "Rises and falls about its place, height pixels either way, speed times a second.",
	params = { height = "number", speed = "number" },
	attach = function(instance, params)
		local _, y = authorPosition(instance)

		instance.bob = { height = params.height or 20, speed = params.speed or 2, base = y, at = 0 }
	end,
	step   = function(instance, dt)
		local bob     = instance.bob
		local x, _, z = authorPosition(instance)

		bob.at = bob.at + dt * bob.speed
		nodeSetPosition(instance.node, x, bob.base + math.sin(bob.at) * bob.height, z)
	end
}

-- Whether an instance bobs:  a condition of this game's own.
AUTHOR.conditions.bobbing = {
	help   = "An instance has a bob.",
	params = { entity = "entity" },
	emit   = function(p) return "vocabBobbing(" .. p.entity .. ")" end
}

-- Sets how high an instance bobs:  an action of this game's own.
AUTHOR.actions.setBob = {
	help   = "Changes how high an instance bobs.",
	params = { entity = "entity", height = "number" },
	emit   = function(p) return "vocabSetBob(" .. p.entity .. ", " .. p.height .. ")" end
}


function vocabBobbing(instance)
	return (instance ~= nil) and (instance.bob ~= nil)
end


function vocabSetBob(instance, height)
	if instance and instance.bob then
		instance.bob.height = height
	end
end