The script should be a Prestashop module, but can be a script running on its own and writing to the mysql database of the prestashop store.
It have to import a csv file form a given url on a given time (will run on chron job) and put the data, after manipulation, in the prestashop database without modifing the rest of the database structure or data.
The csv is a file with records of some products; one of this is the image url and it have to download the image to the server, it have to calculate the price starting from the one in the csv file and using some customizable options and it have to set to 0 or to delete the products no more showing up in the csv file.
Prestashop already have an import module and You can modify it, but probably the best result will be starting from scratch because it isn't able to import much products (e.g 3/400) wile the csv file is about 25000 records. Maybe an option to not overload the server is to check wich records have not benn modified since the last import and skip them.
The script will have to be customizable using a ini file or using a user interface.
The script will run on a linx server running apache and mysql.