diff --git a/CHANGELOG.md b/CHANGELOG.md
index d23c0da..f27d01f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,7 @@
 ## [Unreleased]
+### Added
+- Tokenizer and AST
+
 ## 0.0.0+dev.0 - 2020-07-24
 ### Added
 - Basic design draft
diff --git a/lib/jessie.dart b/lib/jessie.dart
index 82130dd..ce0a1fd 100644
--- a/lib/jessie.dart
+++ b/lib/jessie.dart
@@ -1,8 +1,4 @@
 /// JSONPath for Dart
 library jessie;
 
-export 'package:jessie/src/field.dart';
-export 'package:jessie/src/filter.dart';
-export 'package:jessie/src/index.dart';
-export 'package:jessie/src/neutral.dart';
-export 'package:jessie/src/tokenizer.dart';
+export 'package:jessie/src/json_path.dart';
diff --git a/lib/src/ast.dart b/lib/src/ast.dart
new file mode 100644
index 0000000..74cb7d8
--- /dev/null
+++ b/lib/src/ast.dart
@@ -0,0 +1,38 @@
+class Node {
+  Node(this.value);
+
+  static Node build(List<String> tokens) {
+    final root = Node(r'$');
+    if (tokens.isEmpty) {
+      return root;
+    }
+    final reversed = [...tokens.reversed];
+    if (reversed.last == r'$') {
+      reversed.removeLast();
+    }
+    final stack = <Node>[root];
+    while (reversed.isNotEmpty) {
+      final token = reversed.removeLast();
+      if (token == '[') {
+        stack.add(Node(token));
+        continue;
+      }
+      if (token == ']' || token == ')') {
+        final search = token == ']' ? '[' : '(';
+        final children = <Node>[];
+        while (stack.last.value != search) {
+          children.add(stack.removeLast());
+        }
+        final brackets = stack.removeLast();
+        brackets.children.addAll(children);
+        stack.last.children.add(brackets);
+        continue;
+      }
+      stack.last.children.add(Node(token));
+    }
+    return stack.last;
+  }
+
+  final String value;
+  final children = <Node>[];
+}
diff --git a/lib/src/field.dart b/lib/src/field.dart
index e24334d..55428f0 100644
--- a/lib/src/field.dart
+++ b/lib/src/field.dart
@@ -1,4 +1,5 @@
 import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/match.dart';
 
 class Field extends Filter {
   Field(this.name);
@@ -6,9 +7,9 @@ class Field extends Filter {
   final String name;
 
   @override
-  Iterable call(Iterable nodes) => nodes
-      .where((node) => node is Map && node.containsKey(name))
-      .map((node) => node[name]);
+  Iterable<PathMatch> call(Iterable<PathMatch> matches) => matches
+      .where((m) => m.value is Map && m.value.containsKey(name))
+      .map((m) => PathMatch(m.value[name], m.path + toString()));
 
   @override
   String toString() => "['$name']";
diff --git a/lib/src/filter.dart b/lib/src/filter.dart
index 733cbc8..f4d8e03 100644
--- a/lib/src/filter.dart
+++ b/lib/src/filter.dart
@@ -1,8 +1,10 @@
+import 'package:jessie/src/match.dart';
+
 abstract class Filter {
   const Filter();
 
-  /// Applies this JSONPath to the [nodes]
-  Iterable call(Iterable nodes);
+  /// Applies this filter to the [matches]
+  Iterable<PathMatch> call(Iterable<PathMatch> matches);
 
   /// The string expression without leading `$`
   @override
@@ -23,7 +25,8 @@ class _Chain extends Filter {
   final Filter second;
 
   @override
-  Iterable call(Iterable nodes) => second(first(nodes));
+  Iterable<PathMatch> call(Iterable<PathMatch> matches) =>
+      second(first(matches));
 
   @override
   String toString() => '$first$second';
diff --git a/lib/src/index.dart b/lib/src/index.dart
index a571f51..f1626c9 100644
--- a/lib/src/index.dart
+++ b/lib/src/index.dart
@@ -1,4 +1,5 @@
 import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/match.dart';
 
 class Index extends Filter {
   Index(this.index);
@@ -6,9 +7,9 @@ class Index extends Filter {
   final int index;
 
   @override
-  Iterable call(Iterable nodes) => nodes
-      .where((node) => node is List && node.length > index + 1)
-      .map((node) => node[index]);
+  Iterable<PathMatch> call(Iterable<PathMatch> matches) => matches
+      .where((m) => m.value is List && m.value.length > index + 1)
+      .map((m) => PathMatch(m.value[index], m.path + toString()));
 
   @override
   String toString() => '[$index]';
diff --git a/lib/src/json_path.dart b/lib/src/json_path.dart
new file mode 100644
index 0000000..c56932f
--- /dev/null
+++ b/lib/src/json_path.dart
@@ -0,0 +1,27 @@
+import 'package:jessie/src/ast.dart';
+import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/match.dart';
+import 'package:jessie/src/root.dart';
+import 'package:jessie/src/state.dart';
+import 'package:jessie/src/tokenize.dart';
+
+class JsonPath {
+  factory JsonPath(String expression) {
+    State state = Ready(Root());
+    for (final node in Node.build(tokenize(expression)).children) {
+      state = state.process(node);
+    }
+    return JsonPath._(state.filter);
+  }
+
+  JsonPath._(this._filter);
+
+  final Filter _filter;
+
+  /// Filters the given [json].
+  /// Returns an Iterable of all elements found
+  Iterable<PathMatch> filter(json) => _filter.call([PathMatch(json, '')]);
+
+  @override
+  String toString() => _filter.toString();
+}
diff --git a/lib/src/match.dart b/lib/src/match.dart
new file mode 100644
index 0000000..4182d65
--- /dev/null
+++ b/lib/src/match.dart
@@ -0,0 +1,7 @@
+class PathMatch<T> {
+  PathMatch(this.value, this.path);
+
+  final T value;
+
+  final String path;
+}
diff --git a/lib/src/neutral.dart b/lib/src/neutral.dart
deleted file mode 100644
index 60dc870..0000000
--- a/lib/src/neutral.dart
+++ /dev/null
@@ -1,11 +0,0 @@
-import 'package:jessie/jessie.dart';
-
-class Neutral extends Filter {
-  const Neutral();
-
-  @override
-  Iterable call(Iterable nodes) => nodes;
-
-  @override
-  String toString() => r'$';
-}
diff --git a/lib/src/root.dart b/lib/src/root.dart
new file mode 100644
index 0000000..3fdc028
--- /dev/null
+++ b/lib/src/root.dart
@@ -0,0 +1,13 @@
+import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/match.dart';
+
+class Root extends Filter {
+  const Root();
+
+  @override
+  Iterable<PathMatch> call(Iterable<PathMatch> matches) =>
+      matches.map((m) => PathMatch(m.value, toString()));
+
+  @override
+  String toString() => r'$';
+}
diff --git a/lib/src/state.dart b/lib/src/state.dart
new file mode 100644
index 0000000..88b59d4
--- /dev/null
+++ b/lib/src/state.dart
@@ -0,0 +1,40 @@
+import 'package:jessie/src/ast.dart';
+import 'package:jessie/src/field.dart';
+import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/index.dart';
+
+abstract class State {
+  State process(Node node);
+
+  Filter get filter;
+}
+
+class Ready implements State {
+  Ready(this.filter);
+
+  @override
+  final Filter filter;
+
+  @override
+  State process(Node node) {
+    if (node.value == '[') {
+      return Ready(filter.then(Index(int.parse(node.children.first.value))));
+    }
+    if (node.value == '.') {
+      return AwaitingField(filter);
+    }
+    throw StateError('Got ${node.value} in $this');
+  }
+}
+
+class AwaitingField implements State {
+  AwaitingField(this.filter);
+
+  @override
+  final Filter filter;
+
+  @override
+  State process(Node node) {
+    return Ready(filter.then(Field(node.value)));
+  }
+}
diff --git a/lib/src/tokenize.dart b/lib/src/tokenize.dart
new file mode 100644
index 0000000..e8ce9e8
--- /dev/null
+++ b/lib/src/tokenize.dart
@@ -0,0 +1,49 @@
+List<String> tokenize(String expr) {
+  final tokens = <String>[];
+  var pos = 0;
+  while (pos < expr.length) {
+    var token = '';
+    while (pos < expr.length) {
+      if (_singles.contains(expr[pos])) {
+        if (token.isNotEmpty) {
+          break;
+        }
+        if (expr.length > pos + 1) {
+          final nextTwoChars = expr.substring(pos, pos + 1);
+          if (_doubles.contains(nextTwoChars)) {
+            token = nextTwoChars;
+            pos += 2;
+            break;
+          }
+        }
+        token = expr[pos++];
+        break;
+      }
+      token += expr[pos++];
+    }
+    tokens.add(token);
+  }
+  return tokens;
+}
+
+const _singles = [
+  r'$',
+  '[',
+  ']',
+  '(',
+  ')',
+  '?',
+  '.',
+  '*',
+  '@',
+  '<',
+  '>',
+  '-',
+  '=',
+  '&',
+  '|',
+  ':',
+  ' '
+];
+
+const _doubles = ['..', '&&', '||'];
diff --git a/lib/src/tokenizer.dart b/lib/src/tokenizer.dart
deleted file mode 100644
index d715a1c..0000000
--- a/lib/src/tokenizer.dart
+++ /dev/null
@@ -1,129 +0,0 @@
-List tokenize(String expression) {
-  final tokens = <Token>[];
-  var exp = expression;
-  while (exp.isNotEmpty) {
-    switch (exp[0]) {
-      case r'$':
-        tokens.add(const Root());
-        exp = exp.substring(1);
-        break;
-      case '*':
-        tokens.add(const Asterisk());
-        exp = exp.substring(1);
-        break;
-      case '[':
-        tokens.add(const LeftBracket());
-        exp = exp.substring(1);
-        break;
-      case ']':
-        tokens.add(const RightBracket());
-        exp = exp.substring(1);
-        break;
-      case '.':
-        if (exp.length > 1 && exp[1] == '.') {
-          tokens.add(const DoublePeriod());
-          exp = exp.substring(2);
-        } else {
-          tokens.add(const Period());
-          exp = exp.substring(1);
-        }
-        break;
-      default:
-        if (exp.startsWith(_digit)) {
-          final num = _allDigits.firstMatch(exp).group(0);
-          tokens.add(Number(int.parse(num)));
-          exp = exp.substring(num.length);
-        } else if (exp.startsWith(_char)) {
-          final text = _allAlphanumeric.firstMatch(exp).group(0);
-          tokens.add(Name(text));
-          exp = exp.substring(text.length);
-        } else {
-          throw 'Can not tokenize "$exp"';
-        }
-    }
-  }
-  return tokens;
-}
-
-final _char = RegExp(r'[a-zA-Z]');
-final _allAlphanumeric = RegExp(r'[a-zA-Z][a-zA-Z0-9]+');
-final _digit = RegExp(r'\d');
-final _allDigits = RegExp(r'\d+');
-
-abstract class Token {}
-
-class Root implements Token {
-  const Root();
-
-  @override
-  String toString() => r'$';
-}
-
-class Period implements Token {
-  const Period();
-
-  @override
-  String toString() => '.';
-}
-
-class DoublePeriod implements Token {
-  const DoublePeriod();
-
-  @override
-  String toString() => '..';
-}
-
-class Name implements Token {
-  const Name(this.value);
-
-  final String value;
-
-  @override
-  String toString() => value;
-}
-
-class Number implements Token {
-  const Number(this.value);
-
-  final int value;
-
-  @override
-  String toString() => value.toString();
-}
-
-class Asterisk implements Token {
-  const Asterisk();
-
-  @override
-  String toString() => '*';
-}
-
-class LeftBracket implements Token {
-  const LeftBracket();
-
-  @override
-  String toString() => '[';
-}
-
-class RightBracket implements Token {
-  const RightBracket();
-
-  @override
-  String toString() => ']';
-}
-
-//class LeftParenthesis implements Token {
-//  const LeftParenthesis();
-//}
-//
-//class RightParenthesis implements Token {
-//  const RightParenthesis();
-//}
-//
-//class Colon implements Token {
-//  const Colon();
-//}
-//
-//class Comma implements Token {
-//  const Comma();
-//}
diff --git a/test/functional_test.dart b/test/functional_test.dart
deleted file mode 100644
index 0996551..0000000
--- a/test/functional_test.dart
+++ /dev/null
@@ -1,49 +0,0 @@
-import 'dart:convert';
-import 'dart:io';
-
-import 'package:jessie/jessie.dart';
-import 'package:test/test.dart';
-
-void main() {
-  final store = jsonDecode(File('test/store.json').readAsStringSync());
-  group('Basic', () {
-    final path = JsonPath('store.book[0].title');
-    test('Filtering', () {
-      expect(path.filter(store).single, 'Sayings of the Century');
-    });
-    test('toString()', () {
-      expect(path.toString(), r"$['store']['book'][0]['title']");
-    });
-  });
-
-  group('Tokenizer', () {
-    test('Basic', () {
-      expect(tokenize('store.book[0].title').join(), 'store.book[0].title');
-    });
-  });
-}
-
-class JsonPath {
-  factory JsonPath(String path) {
-    final tokens = tokenize(path);
-    if (tokens.isNotEmpty && tokens.first == const Root()) {
-      tokens.removeAt(0);
-    }
-
-    var filter = const Neutral();
-
-    return JsonPath._(
-        Neutral() | Field('store') | Field('book') | Index(0) | Field('title'));
-  }
-
-  JsonPath._(this._filter);
-
-  final Filter _filter;
-
-  /// Filters the given [json].
-  /// Returns an Iterable of all elements found
-  Iterable filter(json) => _filter.call([json]);
-
-  @override
-  String toString() => _filter.toString();
-}
diff --git a/test/json_path_test.dart b/test/json_path_test.dart
new file mode 100644
index 0000000..7f0ecb2
--- /dev/null
+++ b/test/json_path_test.dart
@@ -0,0 +1,38 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:jessie/jessie.dart';
+import 'package:test/test.dart';
+
+void main() {
+  final store = jsonDecode(File('test/store.json').readAsStringSync());
+  group('Basic expressions', () {
+    test('Empty', () {
+      final path = JsonPath('');
+      expect(path.toString(), r'$');
+      expect(path.filter(store).single.value, store);
+      expect(path.filter(store).single.path, r'$');
+    });
+
+    test('Only root', () {
+      final path = JsonPath(r'$');
+      expect(path.toString(), r'$');
+      expect(path.filter(store).single.value, store);
+      expect(path.filter(store).single.path, r'$');
+    });
+
+    test('Single field', () {
+      final path = JsonPath(r'$.store');
+      expect(path.toString(), r"$['store']");
+      expect(path.filter(store).single.value, store['store']);
+      expect(path.filter(store).single.path, r"$['store']");
+    });
+
+    test('Path with an index', () {
+      final path = JsonPath(r'$.store.book[0].title');
+      expect(path.toString(), r"$['store']['book'][0]['title']");
+      expect(path.filter(store).single.value, 'Sayings of the Century');
+      expect(path.filter(store).single.path, r"$['store']['book'][0]['title']");
+    });
+  });
+}