#!Lua-5.0.exe
-- FileSplitJoint.lua: Split a file in several smaller parts or joint parts of a file previously splitted.
--
-- It tries to be "smart" by checking which files are here:
-- If the given filename exists, it will split it in files with same name,
-- but with suffixes .001 .002 etc.
-- If the given filename.001 exists, it will joint the parts into filename.
-- If both exists, it issues an error.
--
-- by Philippe Lhoste <PhiLho(a)GMX.net> http://Phi.Lho.free.fr
-- v. 1.0 -- 2003/11/20

local filename  = arg and arg[1]

local partSize = 1024 * 1024	-- One megabyte fits well on a floppy disk...
--local partSize = 4 * 1024	-- For Test
local part
local partNb = 0

-- If file has no read access or doesn't exist, return nil.
-- Otherwise, return the size of the file, in bytes (can be 0).
function GetFileSize(filename)
	local res
	local f = io.open(filename, 'rb')
	if f == nil then
		return nil
	end
	res = f:seek('end')
	f:close()
	return res
end

function DoSplit(filenameIn)
	print("Splitting '" .. filenameIn .. "'...")
	local filenameOut, fo
	local fi = io.open(filenameIn, 'rb')
	if fi == nil then
		return nil, "Cannot open " .. filenameIn
	end
	repeat
		partNb = partNb + 1
		filenameOut = filenameIn .. "." .. string.format("%03d", partNb)
		part = fi:read(partSize)
		if part ~= nil then
			fo = io.open(filenameOut, 'wb')
			if fo == nil then
				return nil, "Cannot open '" .. filenameOut .. "'"
			end
			print("Writing '" .. filenameOut .. "' (" .. string.len(part) .. " bytes)")
			fo:write(part)
			fo:close()
		end
	until part == nil
	fi:close()
	return true
end

function DoJoint(filenameOut)
	print("Joining files to '" .. filenameOut .. "'...")
	local filenameIn, fi
	local fo = io.open(filenameOut, 'wb')
	if fo == nil then
		return nil, "Cannot open " .. filenameOut
	end
	repeat
		partNb = partNb + 1
		filenameIn = filenameOut .. "." .. string.format("%03d", partNb)
		fi = io.open(filenameIn, 'rb')
		if fi == nil then
			fo:close()
			if partNb == 1 then	-- Not even a first file?
				return nil, "Cannot find '" .. filenameIn .. "'"
			end
			return true	-- No more files
		end
		-- Read whole file
		part = fi:read('*a')
		print("Read: '" .. filenameIn .. "' (" .. string.len(part) .. " bytes)")
		fi:close()
		if part ~= nil and part ~= "" then
			fo:write(part)
		end
	until part == nil or part == ""
	fo:close()
	return true
end

function FindAction(filename)
	if filename == nil then
		return nil, "I need a file name!"
	end

	local toSplit = GetFileSize(filename)
	local toJoint = GetFileSize(filename .. ".001")

	if toSplit == nil and toJoint == nil then
		return nil, "Cannot find '" .. filename .. "' nor '" .. filename .. ".001' in current path."
	end
	if toSplit ~= nil and toJoint ~= nil then
		return nil, "Both '" .. filename .. "' and '" .. filename .. ".001' exist in current path, I don't know what to do!"
	end
	if toSplit ~= nil then
		if toSplit <= partSize then
			return nil, "'" .. filename .. "' is smaller (" .. toSplit .." bytes) than the split size (" .. partSize .." bytes), nothing to do!"
		else
			return "split"
		end
	else
		toJoint = GetFileSize(filename .. ".002")
		if toJoint == nil then
			return nil, "'" .. filename .. ".002' not found in current path, I need at least two files to joint!"
		else
			return "joint"
		end
	end
end

action, err = FindAction(filename)
if action == "split" then
	result, err = DoSplit(filename)
elseif action == "joint" then
	result, err = DoJoint(filename)
else	-- Error in FindAction
	result = nil
end
if not result then
	print("Error: " .. (err or '?'))
else
	print("Done.")
end