1 files changed, 48 insertions, 0 deletions
diff --git a/crates/shirabe/src/dependency_resolver/rule_watch_chain.rs b/crates/shirabe/src/dependency_resolver/rule_watch_chain.rs
index aed4729..3d04f1c 100644
--- a/crates/shirabe/src/dependency_resolver/rule_watch_chain.rs
+++ b/crates/shirabe/src/dependency_resolver/rule_watch_chain.rs
@@ -1 +1,49 @@
 //! ref: composer/src/Composer/DependencyResolver/RuleWatchChain.php
+
+use crate::dependency_resolver::rule_watch_node::RuleWatchNode;
+
+/// An extension of SplDoublyLinkedList with seek and removal of current element.
+pub struct RuleWatchChain {
+    data: Vec<RuleWatchNode>,
+    current_offset: usize,
+}
+
+impl RuleWatchChain {
+    pub fn new() -> Self {
+        Self {
+            data: Vec::new(),
+            current_offset: 0,
+        }
+    }
+
+    fn rewind(&mut self) {
+        self.current_offset = 0;
+    }
+
+    fn next(&mut self) {
+        self.current_offset += 1;
+    }
+
+    fn key(&self) -> usize {
+        self.current_offset
+    }
+
+    fn offset_unset(&mut self, offset: usize) {
+        self.data.remove(offset);
+    }
+
+    /// Moves the internal iterator to the specified offset.
+    pub fn seek(&mut self, offset: usize) {
+        self.rewind();
+        for _ in 0..offset {
+            self.next();
+        }
+    }
+
+    /// Removes the current element from the list.
+    pub fn remove(&mut self) {
+        let offset = self.key();
+        self.offset_unset(offset);
+        self.seek(offset);
+    }
+}