Add --bidi flag to path command

brood/src/commands/path.rs

@@ -3,6 +3,7 @@ use std::io;
 use crate::{
     algo::Dijkstra,
     data::Data,
+    graph::NodeIdx,
     util::{self, TitleNormalizer},
 };
 
@@ -11,6 +12,46 @@ use crate::{
 pub struct Cmd {
     start: String,
     goal: String,
+
+    // Search for a path in both directions.
+    #[arg(long, short)]
+    bidi: bool,
+}
+
+fn search_path(data: &Data, start: NodeIdx, goal: NodeIdx) -> Option<(u32, Vec<NodeIdx>)> {
+    println!("> Preparing dijkstra");
+    let mut dijkstra = Dijkstra::new(&data.graph);
+    println!("> Running dijkstra");
+    dijkstra.run(
+        start,
+        |node| node == goal,
+        |source, _edge, _target| !data.pages[source.usize()].redirect as u32,
+    );
+
+    if dijkstra.cost(goal) == u32::MAX {
+        return None;
+    }
+
+    println!("> Collecting path");
+    let cost = dijkstra.cost(goal);
+    let path = dijkstra.path(goal);
+    Some((cost, path))
+}
+
+fn print_path(data: &Data, start: NodeIdx, goal: NodeIdx, path: Option<(u32, Vec<NodeIdx>)>) {
+    let start = &data.pages[start.usize()].title;
+    let goal = &data.pages[goal.usize()].title;
+
+    let Some((cost, path)) = path else {
+        println!("No path found from {start} to {goal}");
+        return;
+    };
+
+    println!("Path found (cost {cost}, length {}):", path.len());
+
+    for page in path {
+        println!("{}", util::fmt_page(&data.pages[page.usize()]));
+    }
 }
 
 impl Cmd {
@@ -23,29 +64,22 @@ impl Cmd {
         println!("Start: {}", data.pages[start.usize()].title);
         println!("Goal:  {}", data.pages[goal.usize()].title);
 
-        println!(">> Find path");
-        println!("> Preparing dijkstra");
-        let mut dijkstra = Dijkstra::new(&data.graph);
-        println!("> Running dijkstra");
-        dijkstra.run(
-            start,
-            |node| node == goal,
-            |source, _edge, _target| !data.pages[source.usize()].redirect as u32,
-        );
-
-        if dijkstra.cost(goal) == u32::MAX {
-            println!("No path found");
-            return Ok(());
-        }
-
-        println!("> Collecting path");
-        let path = dijkstra.path(goal);
-        let cost = dijkstra.cost(goal);
+        if self.bidi {
+            println!(">> Find path forward");
+            let forward = search_path(&data, start, goal);
+            println!(">> Find path backward");
+            let backward = search_path(&data, goal, start);
 
             println!();
-        println!("Path found (cost {cost}, length {}):", path.len());
-        for page in path {
-            println!("{}", util::fmt_page(&data.pages[page.usize()]));
+            print_path(&data, start, goal, forward);
+            println!();
+            print_path(&data, goal, start, backward);
+        } else {
+            println!(">> Find path");
+            let path = search_path(&data, start, goal);
+
+            println!();
+            print_path(&data, start, goal, path);
         }
 
         Ok(())