implement some 0.2.0 features

src/trackers.rs

@@ -0,0 +1,20 @@
+use std::{collections::HashSet, str::FromStr};
+use url::Url;
+
+pub struct Trackers(HashSet<Url>);
+
+impl Trackers {
+    pub fn init(trackers: &Vec<String>) -> anyhow::Result<Self> {
+        let mut t = HashSet::with_capacity(trackers.len());
+        for tracker in trackers {
+            t.insert(Url::from_str(tracker)?);
+        }
+        Ok(Self(t))
+    }
+    pub fn is_empty(&self) -> bool {
+        self.0.is_empty()
+    }
+    pub fn clone(&self) -> HashSet<Url> {
+        self.0.clone()
+    }
+}