[graph] Add edge from index #245

.github/workflows/pr.yaml

@@ -44,7 +44,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: taiki-e/install-action@cargo-llvm-cov
       - run: rustup component add llvm-tools-preview
-      - run: cargo llvm-cov --fail-uncovered-regions 127 --fail-uncovered-functions 0 --fail-uncovered-lines 2
+      - run: cargo llvm-cov --fail-uncovered-regions 128 --fail-uncovered-functions 0 --fail-uncovered-lines 3
 
   test:
     runs-on: ubuntu-latest

src/graph.rs

@@ -1,9 +1,9 @@
+use self::graph_edge::GraphEdge;
 use self::graph_node::GraphNode;
 use self::graph_node_iterator::GraphNodeIterator;
 use crate::DbError;
 
 mod graph_edge;
-mod graph_element;
 mod graph_node;
 mod graph_node_iterator;
 
@@ -27,6 +27,14 @@ impl Graph {
         }
     }
 
+    pub(crate) fn edge(&self, index: i64) -> Option<GraphEdge> {
+        if self.validate_edge(index).is_err() {
+            return None;
+        }
+
+        Some(GraphEdge { graph: self, index })
+    }
+
     pub(crate) fn insert_edge(&mut self, from: i64, to: i64) -> Result<i64, DbError> {
         self.validate_node(from)?;
         self.validate_node(to)?;
@@ -80,6 +88,16 @@ impl Graph {
         None
     }
 
+    fn validate_edge(&self, index: i64) -> Result<(), DbError> {
+        if let Some(meta) = self.from_meta.get((-index) as usize) {
+            if 0 <= *meta {
+                return Ok(());
+            }
+        }
+
+        Err(DbError::from(format!("'{}' is not a valid edge", index)))
+    }
+
     fn validate_node(&self, index: i64) -> Result<(), DbError> {
         if let Some(meta) = self.from_meta.get(index as usize) {
             if 0 <= *meta {
@@ -95,6 +113,23 @@ impl Graph {
 mod tests {
     use super::*;
 
+    #[test]
+    fn edge_from_index() {
+        let mut graph = Graph::new();
+        let from = graph.insert_node();
+        let to = graph.insert_node();
+        let index = graph.insert_edge(from, to).unwrap();
+
+        assert_eq!(graph.edge(index).unwrap().index(), index);
+    }
+
+    #[test]
+    fn edge_from_index_missing() {
+        let graph = Graph::new();
+
+        assert!(graph.edge(-3).is_none());
+    }
+
     #[test]
     fn insert_edge() {
         let mut graph = Graph::new();

src/graph/graph_edge.rs

@@ -1,12 +1,14 @@
-#[allow(dead_code)]
-pub(crate) struct GraphEdge {}
+use super::Graph;
 
-#[cfg(test)]
-mod tests {
-    use super::*;
+#[allow(dead_code)]
+pub(crate) struct GraphEdge<'a> {
+    pub(crate) graph: &'a Graph,
+    pub(crate) index: i64,
+}
 
-    #[test]
-    fn new() {
-        let _edge = GraphEdge {};
+#[allow(dead_code)]
+impl<'a> GraphEdge<'a> {
+    pub(crate) fn index(&self) -> i64 {
+        self.index
     }
 }