log a textual representation

src/graph.rs

@@ -1,6 +1,8 @@
-use petgraph::Graph;
-use std::collections::HashMap;
+use petgraph::visit::Bfs;
+use petgraph::visit::EdgeRef;
+use petgraph::{Direction, Graph};
 use std::rc::Rc;
+use std::collections::HashMap;
 
 use crate::api::search::PullRequest;
 
@@ -19,3 +21,24 @@ pub fn build(prs: &Vec<Rc<PullRequest>>) -> Graph<Rc<PullRequest>, usize> {
 
     tree
 }
+
+/// Return a flattened list of graph nodes as tuples; each tuple is `(node, node's parent [if exists])`.
+pub fn log(graph: &Graph<Rc<PullRequest>, usize>) -> Vec<(Rc<PullRequest>, Option<Rc<PullRequest>>)> {
+    let roots: Vec<_> = graph.externals(Direction::Incoming).collect();
+    let mut out = Vec::new();
+
+    for root in roots {
+        let mut bfs = Bfs::new(&graph, root);
+        while let Some(node) = bfs.next(&graph) {
+            let parent = graph.edges_directed(node, Direction::Incoming).next();
+            let node: Rc<PullRequest> = graph[node].clone();
+
+            match parent {
+                Some(parent) => out.push((node, Some(graph[parent.source()].clone()))),
+                None => out.push((node, None)),
+            }
+        }
+    }
+
+    out
+}

src/main.rs

@@ -35,13 +35,14 @@ async fn main() -> Result<(), Box<dyn Error>> {
     let env: HashMap<String, String> = env::vars().collect();
     let args: Vec<String> = env::args().collect();
 
-    if args.len() > 3 {
-        println!("usage: gh-stack <pattern> <prelude_filename>");
+    if args.len() > 4 {
+        println!("usage: gh-stack <command=save|log> <pattern> <prelude_filename?>");
         process::exit(1);
     }
 
-    let pattern = &args[1];
-    let prelude = args.get(2);
+    let command = &args[1][..];
+    let pattern = &args[2];
+    let prelude = args.get(3);
 
     let token = env
         .get("GHSTACK_OAUTH_TOKEN")
@@ -52,6 +53,9 @@ async fn main() -> Result<(), Box<dyn Error>> {
     let prs = api::search::fetch_pull_requests_matching(&pattern, &credentials).await?;
     let prs = prs.into_iter().map(|pr| Rc::new(pr)).collect();
     let tree = graph::build(&prs);
+
+    match command {
+        "github" => {
             let table = markdown::build_table(tree, pattern);
 
             let output = match prelude {
@@ -68,6 +72,21 @@ async fn main() -> Result<(), Box<dyn Error>> {
                 "y" => persist::persist(&prs, &output, &credentials).await?,
                 _ => std::process::exit(1),
             }
+        }
+
+        "log" => {
+            let log = graph::log(&tree);
+            for (pr, maybe_parent) in log {
+                match maybe_parent {
+                    Some(parent) => println!("{} → {}", pr.head(), parent.head()),
+                    None => println!("{} → N/A", pr.head())
+                }
+            }
+        }
+
+        _ => { panic!("Invalid command!") }
+    };
+
 
     println!("Done!");
 
@@ -80,6 +99,7 @@ async fn main() -> Result<(), Box<dyn Error>> {
     - [x] Create markdown table
     - [x] Persist table back to Github
     - [x] Accept a prelude via STDIN
+    - [x] Log a textual representation of the graph
     - [ ] Panic on non-200s
     */
 }

src/markdown.rs

@@ -18,6 +18,7 @@ pub fn build_table(graph: Graph<Rc<PullRequest>, usize>, title: &str) -> String
     out.push_str("| PR | Title |  Merges Into  |\n");
     out.push_str("|:--:|:------|:-------------:|\n");
 
+    // TODO: Use graph::log to simplify this
     let roots: Vec<_> = graph.externals(Direction::Incoming).collect();
 
     for root in roots {