wip: hier walker

Cargo.lock

@@ -1042,6 +1042,12 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "fallible-iterator"
+version = "0.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2acce4a10f12dc2fb14a218589d4f1f62ef011b2d0cc4b3cb1bba8e94da14649"
+
 [[package]]
 name = "fastrand"
 version = "2.0.0"
@@ -3202,6 +3208,7 @@ dependencies = [
  "chrono",
  "diesel",
  "diesel_migrations",
+ "fallible-iterator",
  "filebuffer",
  "lazy_static",
  "lexpr",

db/Cargo.toml

@@ -59,6 +59,7 @@ tree_magic_mini = { version = "3.0.2", features = ["with-gpl-data"] }
 nonempty = "0.6.0"
 
 shadow-rs = { version = "0.23", default-features = false }
+fallible-iterator = "0.3.0"
 
 [build-dependencies]
 shadow-rs = { version = "0.23", default-features = false }

db/src/hierarchies.rs

@@ -1,7 +1,10 @@
+use std::collections::HashSet;
 use std::convert::TryFrom;
+use std::iter::{self, FromIterator};
 use std::sync::{Arc, Mutex};
 
 use anyhow::{anyhow, Result};
+use fallible_iterator::FallibleIterator;
 use lru::LruCache;
 use tracing::trace;
 use uuid::Uuid;
@@ -82,6 +85,57 @@ pub fn list_roots(connection: &UpEndConnection) -> Result<Vec<Address>> {
         .collect())
 }
 
+pub type AddressPath = (Vec<Address>, Address);
+
+pub struct HierWalker {
+    connection: UpEndConnection,
+    current: Vec<AddressPath>,
+    seen: HashSet<Address>,
+}
+
+impl HierWalker {
+    pub fn new(connection: UpEndConnection, start: Address) -> Self {
+        Self {
+            connection,
+            current: vec![(vec![], start.clone())],
+            seen: HashSet::from_iter(iter::once(start)),
+        }
+    }
+}
+
+impl FallibleIterator for HierWalker {
+    type Item = AddressPath;
+    type Error = anyhow::Error;
+
+    fn next(&mut self) -> Result<Option<Self::Item>, Self::Error> {
+        while let Some((path, address)) = self.current.pop() {
+            let children: Vec<Address> = self
+                .connection
+                .query(Query::SingleQuery(QueryPart::Matches(PatternQuery {
+                    entity: QueryComponent::Variable(None),
+                    attribute: QueryComponent::Exact(ATTR_IN.into()),
+                    value: QueryComponent::Exact(address.clone().into()),
+                })))?
+                .into_iter()
+                .map(|e| e.entity)
+                .collect();
+
+            let path: Vec<Address> = path.into_iter().chain(iter::once(address.clone())).collect();
+
+            for child in children {
+                if !self.seen.contains(&child) {
+                    self.seen.insert(child.clone());
+                    self.current.push((path.clone(), child));
+                }
+            }
+
+            return Ok(Some((path, address)));
+        }
+
+        Ok(None)
+    }
+}
+
 lazy_static! {
     static ref FETCH_CREATE_LOCK: Mutex<()> = Mutex::new(());
 }