-- Simple class for xxx in Lua 5.0
-- by Philippe Lhoste <PhiLho(a)GMX.net> http://Phi.Lho.free.fr

-- Implementation of the LTN7: Modules & Packages by Roberto Ierusalimschy
-- http://www.lua.org/notes/ltn007.html
-- Replace ThisClass by the actual name of the class...
-- This is a skeleton of class, you have to change the samples given below
-- to something meaningful.

-- Avoid to load this file twice
if ThisClass ~= nil then return end

local Public, Private, Meta = {}, {}, {}

ThisClass = Public


--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--
-- Private generic functions

function Private.GetRaw(a, b)
	return a * 256 + b
end

function Private.GetParts(x)
	local p = math.floor(x / 256)
	return p, x - p * 256
end

-- Fill data with missing fields
function Private.Update(data)
	local raw = data.raw
	data.hb, data.lb = Private.GetParts(raw)
end

function Private.IsOK(o)
	return type(o) == "table" and type(o.raw) == "number"
end


--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--
-- Meta functions

-- All accesses to instance objects will redirect to ThisClass if not overloaded
Meta.__index = ThisClass

-- Return a string representation
function Meta.__tostring(self)
	return string.format("%02x %02x", self.hb, self.lb)
end

-- Compute the difference
function Meta.__sub(a, b)
	if Private.IsOK(a) and Private.IsOK(b) then
		return a.raw - b.raw
	else
		error("Can only subtract ThisClass objects")
	end
end

-- Compare two ThisClass objects (less or equal)
function Meta.__le(a, b)
	if Private.IsOK(a) and Private.IsOK(b) then
		return a.raw <= b.raw
	else
		error("Can only compare two ThisClass objects")
	end
end

-- Compare two ThisClass objects (less than)
function Meta.__lt(a, b)
	if Private.IsOK(a) and Private.IsOK(b) then
		return a.raw < b.raw
	else
		error("Can only compare two ThisClass objects")
	end
end

-- Compare two ThisClass objects (equal)
function Meta.__eq(a, b)
	if Private.IsOK(a) and Private.IsOK(b) then
		return a.raw == b.raw
	else
		error("Can only compare two ThisClass objects")
	end
end

-- Set a field, but update the raw value and all related fields
function Meta.__newindex(self, key, value)
print("=== NewIndex: ", key, value)
	if key == "R" or key == "raw" then
		self.raw = value
	elseif key == "L" or key == "lb" then
		self.raw = self.raw + (value - self.lb)
	elseif key == "H" or key == "hb" then
		self.raw = self.raw + (value - self.hb) * 256
	else	-- Unknown additional field
		rawset(self, key, value)
		return
	end
	Private.Update(self)
end


--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--
-- Public generic functions

function Public.Invert(x)
	local a, b = Private.GetParts(x)
	return a + b * 256
end


--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--
-- Member functions

function Public:Incr(p)
	p = string.lower(p or '')
	if p == 'h' then
		self.raw = self.raw + 256
	else
		self.raw = self.raw + 1
	end
	Private.Update(self)
end

function Public:Decr(p)
	p = string.lower(p or '')
	if p == 'h' then
		self.raw = self.raw - 256
	else
		self.raw = self.raw - 1
	end
	Private.Update(self)
end


--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--==--
-- Constructors

-- Normal constructor
function Public:New(a, b)
	local obj =
	{
		-- Private data
		raw = Private.GetRaw(a, b),
	}
	-- Compute the missing fields in data table
	Private.Update(obj)

	-- Attach metamethods to object
	setmetatable(obj, Meta)
	return obj
end

-- Other constructor
function Public:Parse(s)
	if type(s) ~= "string" then
		error("Can only parse a string!")
	end
	local a, b
	_, _, a, b = string.find(s, "(%x%x).-(%x%x)")
	a, b = tonumber(a, 16), tonumber(b, 16)
	return Public:New(a, b)
end