Add AstParser class for label parsing and error handling

README.md

@@ -5,3 +5,5 @@
 ### a nut
 
 #### a nut 
+
+test

chipnut/commands/compiler.py

@@ -19,6 +19,76 @@ class CompileContext:
     entry_path: Path
     output_name: str
 
+class BuildError(Exception):
+    pass
+
+class AstParser:
+    def __init__(self, file: Path):
+        self.file = self.read_file(file)
+        self.labels = []
+
+    def read_file(self, file: Path) -> str:
+        with file.open("r") as f:
+            return f.read()
+        
+    def parse_labels(self):
+        self.labels = []
+        current_label = None
+        current_sub_label = None
+
+        for line in self.file.splitlines():
+            stripped_line = line.strip()
+
+            if stripped_line.endswith(":"):
+                label_name = stripped_line[:-1].strip()
+                if not label_name:
+                    continue
+
+                if label_name.startswith("."):
+                    if current_label is None:
+                        raise BuildError(f"Sub-label '{label_name}:' found before any parent label.")
+
+                    sub_label_name = label_name[1:].strip()
+                    if not sub_label_name:
+                        continue
+
+                    current_sub_label = {
+                        "name": sub_label_name,
+                        "lines": [],
+                    }
+                    current_label["sub_labels"].append(current_sub_label)
+                    continue
+
+                if current_label is not None:
+                    self.labels.append(current_label)
+
+                current_label = {
+                    "name": label_name,
+                    "lines": [],
+                    "sub_labels": [],
+                }
+                current_sub_label = None
+                continue
+
+            if current_label is None:
+                continue
+
+            if stripped_line == "":
+                continue
+
+            if current_sub_label is not None:
+                current_sub_label["lines"].append(stripped_line)
+            else:
+                current_label["lines"].append(stripped_line)
+
+        if current_label is not None:
+            self.labels.append(current_label)
+
+        return self.labels
+
+    def parse(self):
+        return self.parse_labels()
+
 
 class Compiler:
     def __init__(self, context: CompileContext):