local EType = {}
EType.__index = EType

function EType:__eq(other)
	for k, v in pairs(self) do
		if rawget(other, k) ~= v then
			return false
		end
	end
	for k, v in pairs(other) do
		if rawget(self, k) ~= v then
			return false
		end
	end
	return true
end

function EType:__tostring()
	if self.kind == "scalar" then
		return (self.unsigned and "u" or "i") .. self.bits
	elseif self.kind == "func" then
		return (tostring(self.input) .. "->" .. tostring(self.output))
	elseif self.kind == "struct" then
		return ("(" .. table.concat(self.fields, ",") .. ")")
	elseif self.kind == "pointer" then
		return tostring(self.to) .. "*"
	elseif self.kind == "array" then
		return tostring(self.element_etype) .. "[" .. (self.length or "?") .. "]"
	elseif self.kind == "string" then
		return "string"
	end
	error("Unimplemented " .. self.kind)
end

function EType:byte_size()
	if self.kind == "scalar" then
		return (self.bits + 7) // 8
	end
	error("Unimplemented " .. self.kind)
end

local ETypes = {}

function ETypes.scalar(unsigned, bits)
	return setmetatable({kind = "scalar", bits = bits, unsigned = unsigned}, EType)
end

function ETypes.func(input_etype, output_etype)
	assert(input_etype ~= nil, "Nil function input")
	assert(output_etype ~= nil, "Nil function output")
	return setmetatable({kind = "func", input = input_etype, output = output_etype, modifiers = {}}, EType)
end

function ETypes.array(element_etype, length)
	return setmetatable({kind = "array", element_etype = element_etype, length = length}, EType)
end

function ETypes.struct(fields)
	return setmetatable({kind = "struct", fields = fields, modifiers = {}}, EType)
end

function ETypes.string()
	return setmetatable({kind = "string"}, EType)
end

function ETypes.ref(child)
	assert(child, "Nil pointee type")
	return setmetatable({kind = "pointer", to = child}, EType)
end

function ETypes.deref(ptr)
	assert(ptr and ptr.kind == "pointer", "Non-pointer type")
	return ptr.to
end

function ETypes.is(etype)
	return type(etype) == "table" and getmetatable(etype) == EType
end

return ETypes