initial walkable implementation

src/renderer/mod.rs

@@ -3,8 +3,10 @@
 mod errors;
 mod renderable;
 mod renderer;
+mod walkable;
 
 pub use renderable::Renderable;
 pub use renderer::compile_template;
 pub use renderer::CompiledTemplate;
 pub use renderer::DustRenderer;
+pub use walkable::Walkable;

src/renderer/renderer.rs

@@ -5,6 +5,7 @@ use crate::parser::TemplateElement;
 use crate::renderer::errors::CompileError;
 use crate::renderer::errors::RenderError;
 use crate::renderer::renderable::Renderable;
+use crate::renderer::walkable::Walkable;
 use std::collections::HashMap;
 use std::ops::Index;
 
@@ -93,3 +94,42 @@ impl<'a> DustRenderer<'a> {
         Ok("".to_owned())
     }
 }
+
+fn walk_path<'a, C>(context: &'a C, path: &Vec<&str>) -> &'a C
+where
+    C: Walkable<Output = C>,
+{
+    let mut output: &C = context;
+
+    for elem in path.iter() {
+        output = context.walk(elem);
+    }
+
+    output
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    impl<'a> Walkable for HashMap<&str, &str> {
+        type Output = str;
+
+        fn walk(&self, segment: &str) -> &str {
+            self.get(segment).unwrap()
+        }
+    }
+
+    #[test]
+    fn test_walk_path() {
+        let context: HashMap<&str, &str> = [
+            ("cat", "kitty"),
+            ("dog", "doggy"),
+            ("tiger", "murder kitty"),
+        ]
+        .iter()
+        .cloned()
+        .collect();
+        assert_eq!(context.walk("cat"), "kitty");
+    }
+}