>>/23628/
>  I'm not sure if endchan has this feature, but if it did, and even better if there was some API 

endchan is based on lynxchan and there is an api, take a look here:

https://gitgud.io/LynxChan/LynxChan/raw/master/doc/Json.txt recv
https://gitgud.io/LynxChan/LynxChan/raw/master/doc/Form.txt post