Remove no longer watched books from the feed

Cargo.lock

@@ -98,7 +98,7 @@ checksum = "35636a1494ede3b646cc98f74f8e62c773a38a659ebc777a2cf26b9b74171df9"
 
 [[package]]
 name = "bib-watcher"
-version = "0.2.0"
+version = "0.4.0"
 dependencies = [
  "chrono",
  "config",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "bib-watcher"
-version = "0.3.0"
+version = "0.4.0"
 edition = "2021"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

src/main.rs

@@ -2,7 +2,7 @@ use config::Config;
 use reqwest::header;
 use rss::{Channel, ChannelBuilder, GuidBuilder, ItemBuilder};
 use scraper::{Html, Selector};
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::{error::Error, fs::File, io::BufReader};
 
 use chrono::prelude::*;
@@ -42,6 +42,23 @@ fn main() -> Result<(), Box<dyn Error>> {
     for (title, url) in searches {
         search(url, title)?
     }
+    let urls = books.values().collect(); 
+    remove_old_books(&urls)?;
+
+    Ok(())
+}
+
+fn remove_old_books(urls: &HashSet<&String>) -> Result<(), Box<dyn Error>> {
+    let file = File::open(FILE_NAME)?;
+    let mut channel = Channel::read_from(BufReader::new(file))?;
+
+    let items: Vec<_> = channel.items
+        .iter()
+        .filter(|i|i.link.as_ref().is_some_and(|l|urls.contains(&l)))
+        .map(|i|i.clone())
+        .collect();
+        channel.set_items(items);
+    channel.pretty_write_to(File::create(FILE_NAME)?, b' ', 4)?;
     Ok(())
 }