access: bans

_continuum/banned/<node ID>: every node refuses the banned node's
changes from then on (judged as the ban stood) and leaves its
handshakes unanswered.

Auth plan M6.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/access/bans.rs b/src/access/bans.rs
new file mode 100644
index 0000000..339f6cf
--- /dev/null
+++ b/src/access/bans.rs
@@ -0,0 +1,18 @@
+//! Banned nodes (`_continuum/banned/<node ID>`, `{"by", "at", "reason"}`), written by a
+//! user who may write there, as any protocol data: a node refuses a banned node's
+//! handshake, so it neither syncs with it nor counts it a member (`swarm::peer`), and
+//! with the swarm's policy every node refuses the changes a banned node commits
+//! (`access::rules`, judged as the ban stood when they were made). Deleting the entry
+//! lifts the ban.
+
+use crate::document::{ReadDoc, meta, store};
+
+/// Where `node`'s ban is.
+pub(crate) fn path(node: &str) -> Vec<String> {
+    meta::path(&[meta::BANNED, node])
+}
+
+/// Whether `doc` bans `node`.
+pub(crate) fn banned(doc: &impl ReadDoc, node: &str) -> bool {
+    store::read_path(doc, &path(node)).ok().flatten().is_some()
+}