1 files changed, 161 insertions, 0 deletions
diff --git a/src/path/mod.rs b/src/path/mod.rs
new file mode 100644
index 0000000..ff93287
--- /dev/null
+++ b/src/path/mod.rs
@@ -0,0 +1,161 @@
+use std::str::FromStr;
+use std::collections::HashMap;
+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(ConfigError::PathParse)
+    }
+}
+
+impl Expression {
+    pub fn get(self, root: &Value) -> Option<&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,
+                }
+            }
+
+            Expression::Child(expr, key) => {
+                match expr.get(root) {
+                    Some(value) => {
+                        match value.kind {
+                            // Access on a table is identical to Identifier, it just forwards
+                            ValueKind::Table(ref map) => map.get(&key),
+
+                            // all other variants return None
+                            _ => None,
+                        }
+                    }
+
+                    _ => None,
+                }
+            }
+
+            _ => {
+                unimplemented!();
+            }
+        }
+    }
+
+    pub fn get_mut<'a>(&self, root: &'a mut Value) -> Option<&'a mut Value> {
+        match *self {
+            Expression::Identifier(ref id) => {
+                match root.kind {
+                    ValueKind::Table(ref mut map) => {
+                        Some(map.entry(id.clone()).or_insert_with(|| Value::new(None, ValueKind::Nil)))
+                    }
+
+                    _ => None,
+                }
+            }
+
+            Expression::Child(ref expr, ref key) => {
+                match expr.get_mut(root) {
+                    Some(value) => {
+                        match value.kind {
+                            ValueKind::Table(ref mut map) => {
+                                Some(map.entry(key.clone()).or_insert_with(|| Value::new(None, ValueKind::Nil)))
+                            }
+
+                            _ => {
+                                *value = HashMap::<String, Value>::new().into();
+
+                                if let ValueKind::Table(ref mut map) = value.kind {
+                                    Some(map.entry(key.clone()).or_insert_with(|| Value::new(None, ValueKind::Nil)))
+                                } else {
+                                    println!("WHAT THE FUCK?");
+
+                                    unreachable!();
+                                }
+                            }
+                        }
+                    }
+
+                    _ => None,
+                }
+            }
+
+            _ => {
+                unimplemented!();
+            }
+        }
+    }
+
+    pub fn set<'a>(&self, root: &'a mut Value, value: Value) {
+        match *self {
+            Expression::Identifier(ref id) => {
+                // Ensure that root is a table
+                match root.kind {
+                    ValueKind::Table(_) => { }
+
+                    _ => {
+                        *root = HashMap::<String, Value>::new().into();
+                    }
+                }
+
+                match value.kind {
+                    ValueKind::Table(ref incoming_map) => {
+                        // Pull out another table
+                        let mut target = if let ValueKind::Table(ref mut map) = root.kind {
+                            map.entry(id.clone()).or_insert_with(|| HashMap::<String, Value>::new().into())
+                        } else {
+                            unreachable!();
+                        };
+
+                        // Continue the deep merge
+                        for (key, val) in incoming_map {
+                            Expression::Identifier(key.clone()).set(&mut target, val.clone());
+                        }
+                    }
+
+                    _ => {
+                        if let ValueKind::Table(ref mut map) = root.kind {
+                            // Just do a simple set
+                            map.insert(id.clone(), value);
+                        }
+                    }
+                }
+            }
+
+            Expression::Child(ref expr, ref key) => {
+                if let Some(parent) = expr.get_mut(root) {
+                    match parent.kind {
+                        ValueKind::Table(_) => {
+                            Expression::Identifier(key.clone()).set(parent, value);
+                        }
+
+                        _ => {
+                            // Didn't find a table. Oh well. Make a table and do this anyway
+                            *parent = HashMap::<String, Value>::new().into();
+
+                            Expression::Identifier(key.clone()).set(parent, value);
+                        }
+                    }
+                }
+            }
+
+            _ => {
+                unimplemented!();
+            }
+        }
+    }
+}