Work with google analytics API

Steps: I have some websites in my webmaster google account, so i have a code for each google analytics account. 1. i need a script that can see if there is a google analytics API code stored in a plain text and log automatically to display the graphics information this graphics are provided by the google API 2. is there is no stored information i need that script show a button to open a modal and request to login to google account and select wich account i want to use you can see the video for more information [login to view URL] 3. after the user select the account to use i want that code stored in a plain text and in the next load it will display the information related to that google analytics account 3.1 this script is for place in backoffice that i already have (you don´t need to develop any backoffice) 3.2 i need code commented to add more graphs ok? i need creat like a dashboard for add more graphs, for start i need at least 3 graphics visitors of current date, visitors of month, where they came from that kind of charts that are available on the API 4. i need a secund script that see the code that i stored in the plain text and load the tracking code for give the informatio to the google this script is to place in the public page / frontoffice