Hi, this is a straight forward job that would require downloading desired file and parsing paths that can be easily done using regular expressions.
The process would go this way: launch the app, enter page url, after that application downloads and process html file. All paths in html matched by the content type and tags would be processed so relative paths would be replaced with the absolute ones using the following rules:
/ - root, fetched from original page url, recognized whether actual page is in some subfolder or not, avoiding // for web hosted files
./ - current folder, that one is clear
../ - previous folder, fetched from the page url as well
Please be free to contact me to discuss the project in more details.
Best regards,
Nemanja