diff --git a/PyTeX/format/macros.py b/PyTeX/format/macros.py
new file mode 100644
index 0000000..23f9bd9
--- /dev/null
+++ b/PyTeX/format/macros.py
@@ -0,0 +1,25 @@
+from typing import List, Union
+from enum import Enum
+
+
+class MacroReplacement(Enum):
+    author = 'author'
+    shortauthor = 'shortauthor'
+    date = 'date'
+    year = 'year'
+    version = 'version',
+    file_name = 'file_name'
+    name = 'name'  # class or package name
+    repo_version = 'repo_version'
+    pytex_version = 'pytex_version'
+
+
+class Macro:
+    def __init__(self):
+        raise NotImplementedError
+
+    def matches(self, line: str) -> bool:
+        raise NotImplementedError
+
+    def apply(self, line: str, *args, **kwargs) -> Union[str, List[str]]:
+        raise NotImplementedError
diff --git a/PyTeX/format/tex_formatter.py b/PyTeX/format/tex_formatter.py
index f1249d5..7ca259d 100644
--- a/PyTeX/format/tex_formatter.py
+++ b/PyTeX/format/tex_formatter.py
@@ -1,4 +1,4 @@
-from typing import List, TextIO
+from typing import List, TextIO, Optional, Tuple, Dict
 from pathlib import Path
 from .pytex_formatter import PyTeXFormatter
 from .macros import Macro
@@ -9,6 +9,7 @@ class LineStream:
         self._file = filename
         self._handle = open(filename, 'r')
         self._cached_lines: List[str] = []
+        self._file_exhausted: bool = False
 
     def current_line(self):
         return self.future_line(0)
@@ -43,21 +44,66 @@ class LineStream:
             )
         if self._cached_lines[-1] == '':
             self._handle.close()
+            self._file_exhausted = True
 
+    @property
+    def exhausted(self) -> bool:
+        return self._file_exhausted & len(self._cached_lines) == 0
 
 
 class TexFormatter(PyTeXFormatter):
     def __init__(self, *args, **kwargs):
         super().__init__(*args, **kwargs)
         self._macros: List[Macro] = []
+        self._line_stream: LineStream = None
         self._output_file: TextIO = None
 
+    @property
+    def line_stream(self) -> LineStream:
+        if self._line_stream is None:
+            self._line_stream = LineStream(self.input_file)
+        return self._line_stream
+
+    @property
+    def macros(self) -> List[Macro]:
+        return self._macros
+
     def _handle_macro(self, macro: Macro):
-        self._current_line = macro.apply(self._current_line, self)
+        res = macro.apply(
+            self.line_stream.current_line(),
+            self
+        )
+        if isinstance(res, str):
+            self.line_stream.set_line(res)
+        else:
+            self.line_stream.pop_line()
+            self.line_stream.push_lines(res)
 
     def _shipout_line(self):
-        self.write_line(self._current_line.rstrip())
+        line = self.line_stream.pop_line().rstrip()
+        self.write_line(line)
 
     def write_line(self, line: str):
-        self._output_file.writelines([line])
+        self._output_file.write(line)
 
+    def open_output_stream(self):
+        raise NotImplementedError
+
+    @property
+    def future_config(self) -> Optional[List[Tuple[str, Dict]]]:
+        raise NotImplementedError
+
+    def format(self, build_dir: Path, overwrite: bool = False) -> Optional[List[Tuple[str, Dict]]]:
+        self.open_output_stream()
+        while not self.line_stream.exhausted:
+            recent_replacement = True
+            while recent_replacement:
+                recent_replacement = False
+                for macro in self.macros:
+                    if macro.matches(self.line_stream.current_line()):
+                        self._handle_macro(macro)
+                        recent_replacement = True
+                        break
+            self._shipout_line()
+        self._output_file.close()
+        return self.future_config