File API w/ Seek

local binaryFile = {
    buffer = {},
    file = fileName,
    position = 1,
    write = function(self, ...)
        for i,v in ipairs(arg) do
            table.insert(self.buffer, self.position, v)
            self:seek("cur", 1)
        end
    end,
    read = function(self, bytes)
        bytes = bytes or 1
        local data = {unpack(self.buffer, self.position, self.position+bytes)}
        self:seek("cur", bytes+1)
        return data
    end,
    seek = function(self, whence, offset)
        if whence == "set" then
            whence = 1
        elseif whence == "cur" then
            whence = self.position
        elseif whence == "end" then
            whence = #self.buffer+1
        else
            whence = self.position
        end
        if not offset then
            offset = 0
        end

        if whence + offset > #self.buffer+1 then
            return false, "whence + offset > length of file"
        elseif whence+offset < 0 then
            return false, "whence + offset < 0"
        else
            self.position = whence+offset
            return self.position
        end
    end,
    flush = function(self)
        local handle = fs.open(self.file, "wb")
        for i,v in ipairs(self.buffer) do
            handle.write(v)
        end
        handle.close()
    end,
    update = function(self)
        if fs.exists(self.file) then
            local handle = fs.open(self.file, "rb")
            self.buffer = {}
            while true do
                local byte = handle.read()
                if byte then
                    table.insert(self.buffer, byte)
                else
                    return
                end
            end
            handle.close()
            return true
        end
        return false
    end,
    readAll = function(self)
        self:seek("end")
        return self.buffer
    end,
    clear = function(self)
        self.buffer = {}
    end,
    bytes = function(self)
        local i = 1
        return function()
            if i > #self.buffer then
                return
            end
            data = self.buffer[i]
            i = i+1
            return data
        end
    end,
    new = function(self, file)
        local object = {["file"] = file}
        setmetatable(object, self)
        self.__index = self
        object:update()
        return object
    end
}

local textFile = {
    position = 1,
    bufmode = 1,
    file = fileName,
    internalBuffer = "",
    writeToBuffer = function(self, data)
        local beforePosition = string.sub(self.internalBuffer, 1, self.position-1)
        local afterPosition = string.sub(self.internalBuffer, self.position)
        self.internalBuffer = beforePosition..data..afterPosition
    end,
    update = function(self)
        if fs.exists(self.file) then
            local handle = fs.open(self.file, "r")
            self.internalBuffer = handle.readAll()
            handle.close()
            return true
        end
        return false
    end,
    seek = function(self, whence, offset)
        if whence == "set" then
            whence = 1
        elseif whence == "cur" then
            whence = self.position
        elseif whence == "end" then
            whence = #self.internalBuffer+1
        else
            whence = self.position
        end
        if not offset then
            offset = 0
        end

        if whence + offset > #self.internalBuffer+1 then
            return false, "whence + offset > length of file"
        elseif whence+offset < 0 then
            return false, "whence + offset < 0"
        else
            self.position = whence+offset
            return self.position
        end
    end,
    flush = function(self)
        local internalHandle = fs.open(self.file, "w")
        internalHandle.write(self.internalBuffer)
        internalHandle.close()
    end,
    write = function(self, ...)
        for i,v in ipairs(arg) do
            self:writeToBuffer(v)
            if self.seekAfterWrite then
                self:seek("cur", #v+1)
            end
        end
    end,
    clear = function(self)
        self.internalBuffer = ""
    end,
    writeLine = function(self, ...)
        for i,v in ipairs(arg) do
            self:writeToBuffer(v.."\n")
            self:seek("cur", #v+2)
        end
    end,
    readLine = function(self)
        local nextNewLine = string.find(self.internalBuffer, "\n", self.position)
        if nextNewLine then
            local line = string.sub(self.internalBuffer, self.position, nextNewLine)
            self.position = nextNewLine+1
            return line
        end
    end,
    readAll = function(self)
        self:seek("end")
        return string.sub(self.internalBuffer, self.position)
    end,
    read = function(self, chars)
        chars = chars or 1
        local data = string.sub(self.internalBuffer, self.position, self.position+chars)
        self:seek("cur", chars+1)
        return data
    end,
    lines = function(self)
        local oldPos = self:seek()
        return function()
            local line = self:readLine()
            if line == nil then
                self:seek("set", oldPos)
            end
            return line
        end
    end,
    new = function(self, file)
        local object = {["file"] = file}
        setmetatable(object, self)
        self.__index = self
        object:update()
        return object
    end
}

function openBinary(fileName)
    return binaryFile:new(fileName)
end

function open(fileName)
    return textFile:new(fileName)
end