how to develop an app for a website which don't provide API

I want to develop an iphone app for a website which don't provide api.I hava a solution like this:

1.I used opensource TFHpple lib Analysis website to get request parameters in post method and the results in get method 2. Custom made an api for the website 3. call the api

but by this way ,I found it‘s a little Complex and Unreliable.could someone have some other way to implement，in my opinion if i can develop a json api for this website.but i have no enough experience for this .thanks for your advice