1 files changed, 41 insertions, 0 deletions
diff --git a/src/path/mod.rs b/src/path/mod.rs
new file mode 100644
index 0000000..f889283
--- /dev/null
+++ b/src/path/mod.rs
@@ -0,0 +1,41 @@
+use std::str::FromStr;
+use nom::ErrorKind;
+use error::*;
+use value::{Value, ValueKind};
+
+mod parser;
+
+#[derive(Debug, Eq, PartialEq, Clone, Hash)]
+pub enum Expression {
+    Identifier(String),
+    Child(Box<Expression>, String),
+    Subscript(Box<Expression>, i32),
+}
+
+impl FromStr for Expression {
+    type Err = ConfigError;
+
+    fn from_str(s: &str) -> Result<Expression> {
+        parser::from_str(s).map_err(|kind| ConfigError::PathParse(kind))
+    }
+}
+
+impl Expression {
+    pub fn get<'a>(self, root: &'a Value) -> Option<&'a Value> {
+        match self {
+            Expression::Identifier(id) => {
+                match root.kind {
+                    // `x` access on a table is equivalent to: map[x]
+                    ValueKind::Table(ref map) => map.get(&id),
+
+                    // all other variants return None
+                    _ => None,
+                }
+            }
+
+            _ => {
+                unimplemented!();
+            }
+        }
+    }
+}