From cff714c07e5e2c0f11c121504500a554d60c08cc Mon Sep 17 00:00:00 2001
From: Mel <einebeere@gmail.com>
Date: Thu, 21 Oct 2021 23:46:01 +0200
Subject: Implement program walking.

---
 src/interpret/scope.rs | 45 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 src/interpret/scope.rs

(limited to 'src/interpret/scope.rs')

diff --git a/src/interpret/scope.rs b/src/interpret/scope.rs
new file mode 100644
index 0000000..de32692
--- /dev/null
+++ b/src/interpret/scope.rs
@@ -0,0 +1,45 @@
+use super::value::Value;
+use crate::parse::ast::nodes::Identifier;
+use std::collections::HashMap;
+
+pub struct Scope {
+    scopes: Vec<HashMap<Identifier, Value>>,
+}
+
+impl Scope {
+    pub fn new() -> Self {
+        Scope { scopes: Vec::new() }
+    }
+
+    pub fn nest(&mut self) {
+        self.scopes.push(HashMap::new());
+    }
+
+    pub fn unnest(&mut self) {
+        self.scopes.pop();
+    }
+
+    pub fn set_var(&mut self, ident: &Identifier, value: Value) {
+        for scope in self.scopes.iter_mut() {
+            if scope.contains_key(ident) {
+                scope.insert(ident.clone(), value);
+                return;
+            }
+        }
+
+        let inner_scope = self
+            .scopes
+            .last_mut()
+            .expect("Tried accessing scope after last frame is gone.");
+        inner_scope.insert(ident.clone(), value);
+    }
+
+    pub fn get_var(&self, ident: &Identifier) -> Option<Value> {
+        for scope in self.scopes.iter().rev() {
+            if let Some(value) = scope.get(ident) {
+                return Some(value.clone());
+            }
+        }
+        None
+    }
+}
-- 
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