From bd2085ee8737f956f814e42d1e66b2adc87e088d Mon Sep 17 00:00:00 2001
From: Branden J Brown <zephyrtronium@gmail.com>
Date: Fri, 14 Mar 2025 23:09:08 -0400
Subject: [PATCH] implement leave command

---
 chord/client.go          |  2 ++
 chord/httpnode/client.go | 25 +++++++++++++++++++++++++
 chord/httpnode/server.go | 11 ++++++++++-
 main.go                  | 12 +++++++++++-
 test.bash                |  4 ++++
 5 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/chord/client.go b/chord/client.go
index 1cd4212..f6b52a0 100644
--- a/chord/client.go
+++ b/chord/client.go
@@ -18,6 +18,8 @@ type Client interface {
 	// Bye tells p that its predecessor or successor is leaving
 	// and had the given successor list.
 	Bye(ctx context.Context, p, n Peer, succ []Peer) error
+	// SayBye tells p to leave the network.
+	SayBye(ctx context.Context, p Peer) error
 
 	// Get asks s for a saved value.
 	Get(ctx context.Context, s Peer, id ID) (string, error)
diff --git a/chord/httpnode/client.go b/chord/httpnode/client.go
index ef096db..9bf667c 100644
--- a/chord/httpnode/client.go
+++ b/chord/httpnode/client.go
@@ -203,3 +203,28 @@ func (cl *Client) Bye(ctx context.Context, p, n chord.Peer, succ []chord.Peer) e
 	}
 	return nil
 }
+
+// SayBye tells p to leave the network.
+func (cl *Client) SayBye(ctx context.Context, p chord.Peer) error {
+	_, addr := p.Values()
+	if !addr.IsValid() {
+		return errors.New("SayBye with invalid peer")
+	}
+	url := url.URL{
+		Scheme: "http",
+		Host:   addr.String(),
+		Path:   path.Join("/", cl.APIBase),
+	}
+	req, err := http.NewRequestWithContext(ctx, "DELETE", url.String(), nil)
+	if err != nil {
+		return err
+	}
+	resp, err := cl.HTTP.Do(req)
+	if err != nil {
+		return err
+	}
+	if resp.StatusCode != http.StatusOK {
+		return errors.New(resp.Status)
+	}
+	return nil
+}
diff --git a/chord/httpnode/server.go b/chord/httpnode/server.go
index 060c789..443d327 100644
--- a/chord/httpnode/server.go
+++ b/chord/httpnode/server.go
@@ -57,6 +57,7 @@ func (n *Node) Router() http.Handler {
 	m.HandleFunc("POST /pred", n.notify)
 	m.HandleFunc("GET /neighbors", n.neighbors)
 	m.HandleFunc("POST /bye", n.bye)
+	m.HandleFunc("DELETE /", n.saybye)
 	return m
 }
 
@@ -170,6 +171,14 @@ func (n *Node) bye(w http.ResponseWriter, r *http.Request) {
 	}
 	n.self.Leave(p, s)
 	w.WriteHeader(http.StatusNoContent)
-	// Close the listener so that the server will shut down.
+}
+
+func (n *Node) saybye(w http.ResponseWriter, r *http.Request) {
+	err := chord.Leave(r.Context(), n.client, n.self)
+	if err != nil {
+		writeError(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+	w.WriteHeader(http.StatusOK)
 	n.l.Close()
 }
diff --git a/main.go b/main.go
index 8ec909b..eb13a6e 100644
--- a/main.go
+++ b/main.go
@@ -194,7 +194,17 @@ func cliJoin(ctx context.Context, cmd *cli.Command) error {
 	return srv.Shutdown(ctx)
 }
 
-func cliLeave(ctx context.Context, cmd *cli.Command) error  { return errors.New("not implemented") }
+func cliLeave(ctx context.Context, cmd *cli.Command) error {
+	// I'm not really clear on why this command takes a startup IP and port.
+	// All we need is the node to tell to leave.
+	n, err := netip.ParseAddrPort(cmd.String("n"))
+	if err != nil {
+		return err
+	}
+	cl := &httpnode.Client{HTTP: http.Client{Timeout: 5 * time.Second}}
+	return cl.SayBye(ctx, chord.Address(n))
+}
+
 func cliLookup(ctx context.Context, cmd *cli.Command) error { return errors.New("not implemented") }
 func cliPut(ctx context.Context, cmd *cli.Command) error    { return errors.New("not implemented") }
 func cliGet(ctx context.Context, cmd *cli.Command) error    { return errors.New("not implemented") }
diff --git a/test.bash b/test.bash
index f884f98..30021b8 100755
--- a/test.bash
+++ b/test.bash
@@ -16,4 +16,8 @@ THIRD=$!
 
 sleep 5
 # Each node logs its predecessor and successors. At this point, we see the ring.
+
+# Test leaving.
+./chord-node leave -n 127.0.0.1:3000
+
 kill $FIRST $SECOND $THIRD