Add tokenizer and AST

CHANGELOG.md

@@ -1,4 +1,7 @@
 ## [Unreleased]
+### Added
+- Tokenizer and AST
+
 ## 0.0.0+dev.0 - 2020-07-24
 ### Added
 - Basic design draft

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';

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>[];
+}

lib/src/field.dart

@@ -1,14 +1,15 @@
 import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/match.dart';
 
 class Field extends Filter {
   Field(this.name);
 
   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']";

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';

lib/src/index.dart

@@ -1,14 +1,15 @@
 import 'package:jessie/src/filter.dart';
+import 'package:jessie/src/match.dart';
 
 class Index extends Filter {
   Index(this.index);
 
   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]';

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();
+}

lib/src/match.dart

@@ -0,0 +1,7 @@
+class PathMatch<T> {
+  PathMatch(this.value, this.path);
+
+  final T value;
+
+  final String path;
+}

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'$';
+}

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)));
+  }
+}

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 = ['..', '&&', '||'];