[TYPO3-dev] Typo3 extension: how to build a extension to load image/media from my cloud site

[jim cai]

hi,
i want to implement a Typo3 extension: load image/media from my cloud site, and insert into Typo3 web page.
but i am a very new comer of Typo3. i want to learn how to build my extension. could someone tell me the guideline or a sample extension which is similiar as my extension? i read Typo3 site, but it hard to understand and the sample extension do not match my extension purpose, so i can not refer it much.

the extension features are:
1. i have a DAM(Digital Assets Management) system to store lots of images/medias. i want to use OAuth protocol to connect to my DAM system. so my extension should plug in someplace to let me connect to my OAuth site. on that setting page, i should able to input my OAuth APP_ID, APP_Secret, then i should to open a dialog to connect to my OAuth site, and input my account info. later, i should be able to store the OAuth access token in some DB.
2. i want my extension appear in some places in Typo3, wherever i can insert a image/media. whenever user want to insert a image/media, the extension will launch a page/frame to my DAM system, and i can choose a image to insert into Typo3 page.
when i create a image element in Typo3 site, in the Images tab/section, it has 2 buttons "Add Image" and "Select & upload files", here i guess my extension should create the 3rd button named "From Cloud". this new "From Cloud" button is used to show all my images/medias on my DAM system. and when user click this button, it will popup up a dialog. that popup dialog will show all images/medias on my DAM system, and let user select some images, and insert into current Typo3 page. this dialog contains a folder tree on left panel, to show my DAM structure. the dialog show all images/medias on right panel. it also has some Typo3 own button to insert images into web page.

because i am very new comer for Typo3, read docs.typo3.org/typo3cms/ExtbaseFluidBook/4-FirstExtension/1-the-example-extension.html is already hard for me. the major block is how to insert the "From Cloud" button in Typo3 own page.
could someone give me suggestion/guideline about my extension? or a similiar extension to let me download and study?
many thanks!