From 3f49519bea099787429de28a5deb364e1a8626e1 Mon Sep 17 00:00:00 2001
From: Tom Alexander <tom@fizz.buzz>
Date: Sun, 31 May 2020 15:44:09 -0400
Subject: [PATCH] Initial structure for new implementation of walking functions
 using the heterogeneous tree.

---
 src/renderer/breadcrumb_tree.rs |  4 ++--
 src/renderer/mod.rs             |  1 +
 src/renderer/tree_walking.rs    | 37 +++++++++++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 src/renderer/tree_walking.rs

diff --git a/src/renderer/breadcrumb_tree.rs b/src/renderer/breadcrumb_tree.rs
index 1faf0c3..3535983 100644
--- a/src/renderer/breadcrumb_tree.rs
+++ b/src/renderer/breadcrumb_tree.rs
@@ -7,7 +7,7 @@ pub trait BreadcrumbTree {
     fn get_parent(&self) -> Option<&dyn BreadcrumbTree>;
 }
 
-struct BreadcrumbTreeNode<'a, C: IntoContextElement> {
+pub struct BreadcrumbTreeNode<'a, C: IntoContextElement> {
     parent: Option<&'a dyn BreadcrumbTree>,
     element: BreadcrumbTreeNodeElement<'a, C>,
 }
@@ -44,7 +44,7 @@ impl<'a, C: IntoContextElement> BreadcrumbTree for BreadcrumbTreeNode<'a, C> {
     }
 }
 
-struct BreadcrumbTreeIterator<'a>(Option<&'a dyn BreadcrumbTree>);
+pub struct BreadcrumbTreeIterator<'a>(Option<&'a dyn BreadcrumbTree>);
 
 impl<'a> Iterator for BreadcrumbTreeIterator<'a> {
     type Item = &'a dyn IntoContextElement;
diff --git a/src/renderer/mod.rs b/src/renderer/mod.rs
index 3439bc5..7eecacb 100644
--- a/src/renderer/mod.rs
+++ b/src/renderer/mod.rs
@@ -7,6 +7,7 @@ mod inline_partial_tree;
 mod iteration_context;
 mod parameters_context;
 mod renderer;
+mod tree_walking;
 mod walking;
 
 pub use context_element::CloneIntoBoxedContextElement;
diff --git a/src/renderer/tree_walking.rs b/src/renderer/tree_walking.rs
new file mode 100644
index 0000000..5050652
--- /dev/null
+++ b/src/renderer/tree_walking.rs
@@ -0,0 +1,37 @@
+use crate::renderer::breadcrumb_tree::BreadcrumbTree;
+use crate::renderer::breadcrumb_tree::BreadcrumbTreeNode;
+use crate::renderer::context_element::IntoContextElement;
+use crate::renderer::WalkError;
+use std::borrow::Borrow;
+
+enum WalkResult<'a> {
+    NoWalk,
+    PartialWalk,
+    FullyWalked(&'a dyn IntoContextElement),
+}
+
+fn walk_path_from_single_level<'a, P, C>(context: &'a C, path: &[P]) -> WalkResult<'a>
+where
+    P: Borrow<str>,
+    C: Borrow<dyn IntoContextElement + 'a>,
+{
+    todo!()
+}
+
+pub fn walk_path<'a, B, P>(
+    maybe_breadcrumbs: Option<&'a BreadcrumbTreeNode<B>>,
+    path: &Vec<P>,
+) -> Result<&'a dyn IntoContextElement, WalkError>
+where
+    B: IntoContextElement,
+    P: Borrow<str>,
+{
+    match (maybe_breadcrumbs, path.first()) {
+        (None, _) => return Err(WalkError::CantWalk),
+        (Some(breadcrumbs), None) => return Ok(breadcrumbs.get_ice()),
+        (Some(breadcrumbs), Some(path_first)) if path_first.borrow() == "." => (),
+        (Some(breadcrumbs), Some(path_first)) => (),
+    }
+
+    Err(WalkError::CantWalk)
+}