1 files changed, 83 insertions, 0 deletions
diff --git a/src/interpreter/environment.ts b/src/interpreter/environment.ts
new file mode 100644
index 0000000..1c451aa
--- /dev/null
+++ b/src/interpreter/environment.ts
@@ -0,0 +1,83 @@
+import { UnknownSymbolError, InvalidType, type TracingLogger } from '@/utils';
+import { matchSignature, type Denotable } from '.';
+
+export class Environment {
+  private scope: Map<string, Denotable>;
+  private parent: Environment | null;
+  private logger: TracingLogger;
+
+  constructor(logger: TracingLogger, parent: Environment | null = null) {
+    this.logger = logger;
+    this.parent = parent;
+    this.scope = new Map();
+  }
+
+  public set(name: string, value: Denotable) {
+    this.scope.set(name, value);
+  }
+
+  public get(name: string): Denotable {
+    if (this.scope.has(name)) {
+      this.logger.debug(`Found Name=(${name}) in current scope`);
+      return this.scope.get(name)!;
+    }
+
+    if (this.parent) {
+      this.logger.debug(`Looking for Name=(${name}) in parent scope`);
+      return this.parent.get(name);
+    }
+
+    throw new UnknownSymbolError(`Undefined variable: ${name}`);
+  }
+
+  public has(name: string): boolean {
+    if (this.scope.has(name)) {
+      this.logger.debug(`Found Name=(${name}) in current scope`);
+      return true;
+    }
+
+    if (this.parent) {
+      this.logger.debug(`Found Name=(${name}) in current scope`);
+      return this.parent.has(name);
+    }
+
+    this.logger.debug(`Name=(${name}) not found in any scope`);
+    return false;
+  }
+
+  public createChild(): Environment {
+    return new Environment(this.logger.createChild('Env'), this);
+  }
+
+  public apply(name: string, args: Denotable[]): Denotable {
+    const fn = this.get(name);
+    if (typeof fn.value !== 'object' || !fn.value || !('body' in fn.value)) {
+      throw new InvalidType(name + ' is not a valid function');
+    }
+
+    const argTypes = args.map(arg => {
+      const { type, value } = arg;
+      const isFunction =
+        type === 'function' &&
+        typeof value === 'object' &&
+        value &&
+        'signatures' in value;
+      if (isFunction) {
+        return value.signatures;
+      }
+      return type;
+    });
+
+    const appliedSignature = matchSignature(argTypes, fn.value.signatures);
+    if (!appliedSignature) {
+      throw new InvalidType(`No matching signature for ${name}`);
+    }
+
+    this.logger.debug(
+      `Applying Function=(${name}) with Args=(${JSON.stringify(args)}) with Signature=(${JSON.stringify(appliedSignature)})`,
+    );
+
+    const value = fn.value.body.apply(this, args);
+    return { type: appliedSignature.return, value };
+  }
+}