1 files changed, 93 insertions, 0 deletions
diff --git a/crates/shirabe/src/dependency_resolver/rule_set_iterator.rs b/crates/shirabe/src/dependency_resolver/rule_set_iterator.rs
index 6012876..e2b67f4 100644
--- a/crates/shirabe/src/dependency_resolver/rule_set_iterator.rs
+++ b/crates/shirabe/src/dependency_resolver/rule_set_iterator.rs
@@ -1 +1,94 @@
 //! ref: composer/src/Composer/DependencyResolver/RuleSetIterator.php
+
+use indexmap::IndexMap;
+use crate::dependency_resolver::rule::Rule;
+
+/// Implements PHP \Iterator over a grouped rule set.
+#[derive(Debug)]
+pub struct RuleSetIterator {
+    pub(crate) rules: IndexMap<i64, Vec<Rule>>,
+    pub(crate) types: Vec<i64>,
+    pub(crate) current_offset: i64,
+    pub(crate) current_type: i64,
+    pub(crate) current_type_offset: i64,
+}
+
+impl RuleSetIterator {
+    pub fn new(rules: IndexMap<i64, Vec<Rule>>) -> Self {
+        let mut types: Vec<i64> = rules.keys().copied().collect();
+        types.sort();
+        let mut iter = Self {
+            rules,
+            types,
+            current_offset: 0,
+            current_type: -1,
+            current_type_offset: 0,
+        };
+        iter.rewind();
+        iter
+    }
+
+    pub fn current(&self) -> &Rule {
+        &self.rules[&self.current_type][self.current_offset as usize]
+    }
+
+    pub fn key(&self) -> i64 {
+        self.current_type
+    }
+
+    pub fn next(&mut self) {
+        self.current_offset += 1;
+
+        if !self.rules.contains_key(&self.current_type) {
+            return;
+        }
+
+        if self.current_offset >= self.rules[&self.current_type].len() as i64 {
+            self.current_offset = 0;
+
+            loop {
+                self.current_type_offset += 1;
+
+                if self.types.get(self.current_type_offset as usize).is_none() {
+                    self.current_type = -1;
+                    break;
+                }
+
+                self.current_type = self.types[self.current_type_offset as usize];
+
+                if self.rules[&self.current_type].len() != 0 {
+                    break;
+                }
+            }
+        }
+    }
+
+    pub fn rewind(&mut self) {
+        self.current_offset = 0;
+        self.current_type_offset = -1;
+        self.current_type = -1;
+
+        loop {
+            self.current_type_offset += 1;
+
+            if self.types.get(self.current_type_offset as usize).is_none() {
+                self.current_type = -1;
+                break;
+            }
+
+            self.current_type = self.types[self.current_type_offset as usize];
+
+            if self.rules[&self.current_type].len() != 0 {
+                break;
+            }
+        }
+    }
+
+    pub fn valid(&self) -> bool {
+        if let Some(rules) = self.rules.get(&self.current_type) {
+            rules.get(self.current_offset as usize).is_some()
+        } else {
+            false
+        }
+    }
+}