Mutations (#5)

.github/workflows/dart.yml

@@ -23,4 +23,4 @@ jobs:
       - name: Analyzer
         run: dartanalyzer --fatal-infos --fatal-warnings lib test example
       - name: Tests
-        run: pub run test
+        run: pub run test_coverage --no-badge --print-test-output --min-coverage 100

.gitignore

@@ -19,3 +19,8 @@ doc/api/
 *.js_
 *.js.deps
 *.js.map
+
+# test_coverage
+test/.test_coverage.dart
+coverage
+coverage_badge.svg

CHANGELOG.md

@@ -1,4 +1,12 @@
 ## [Unreleased]
+## [0.1.0] - 2020-09-05
+### Added
+- JsonPath.set() method to alter the JSON object in a non-destructive way
+
+### Changed
+- **BREAKING!** `Result` renamed to `JsonPathMatch`
+- **BREAKING!**  `JsonPath.filter()` renamed to `read()`
+
 ## [0.0.2] - 2020-09-01
 ### Fixed
 - Last element of array was not selected (regression #1)
@@ -41,7 +49,8 @@
 ### Added
 - Basic design draft
 
-[Unreleased]: https://github.com/f3ath/jessie/compare/0.0.2...HEAD
+[Unreleased]: https://github.com/f3ath/jessie/compare/0.1.0...HEAD
+[0.1.0]: https://github.com/f3ath/jessie/compare/0.0.2...0.1.0
 [0.0.2]: https://github.com/f3ath/jessie/compare/0.0.1...0.0.2
 [0.0.1]: https://github.com/f3ath/jessie/compare/0.0.0+dev.7...0.0.1
 [0.0.0+dev.7]: https://github.com/f3ath/jessie/compare/0.0.0+dev.6...0.0.0+dev.7

README.md

@@ -45,17 +45,45 @@ void main() {
 }  
   ''');
 
+  final prices = JsonPath(r'$..price');
+
+  print('All prices in the store:');
+
   /// The following code will print:
   ///
   /// $['store']['book'][0]['price']:	8.95
   /// $['store']['book'][1]['price']:	12.99
   /// $['store']['book'][2]['price']:	8.99
   /// $['store']['book'][3]['price']:	22.99
   /// $['store']['bicycle']['price']:	19.95
-  JsonPath(r'$..price')
-      .filter(json)
+  prices
+      .read(json)
       .map((result) => '${result.path}:\t${result.value}')
       .forEach(print);
+
+  print('\n');
+
+  final bikeColor = JsonPath(r'$.store.bicycle.color');
+
+  print('A copy of the store with repainted bike:');
+  print(bikeColor.set(json, 'blue'));
+
+  print('\n');
+
+  print('Note, that the bike in the original store is still red:');
+  bikeColor
+      .read(json)
+      .map((result) => '${result.path}:\t${result.value}')
+      .forEach(print);
+
+  print('\n');
+
+  print('It is also possible to modify json in place:');
+  final someBooks = JsonPath(r'$.store.book[::2]');
+  someBooks.read(json).forEach((match) {
+    result.value['title'] = 'Banana';
+  });
+  print(json);
 }
 
 ```
@@ -89,7 +117,7 @@ Instead, use the callback-kind of filters.
 ```dart
 /// Select all elements with price under 20
 JsonPath(r'$.store..[?discounted]', filter: {
-  'discounted': (e) => e is Map && e['price'] is num && e['price'] < 20
+  'discounted': (e) => e['price'] < 20
 });
 ``` 
 

example/main.dart

@@ -42,15 +42,44 @@ void main() {
 }  
   ''');
 
+  final prices = JsonPath(r'$..price');
+
+  print('All prices in the store:');
+
   /// The following code will print:
   ///
   /// $['store']['book'][0]['price']:	8.95
   /// $['store']['book'][1]['price']:	12.99
   /// $['store']['book'][2]['price']:	8.99
   /// $['store']['book'][3]['price']:	22.99
   /// $['store']['bicycle']['price']:	19.95
-  JsonPath(r'$..price')
-      .filter(json)
+  prices
+      .read(json)
+      .map((match) => '${match.path}:\t${match.value}')
+      .forEach(print);
+
+  print('\n');
+
+  final bikeColor = JsonPath(r'$.store.bicycle.color');
+
+  print('A copy of the store with repainted bike:');
+  print(bikeColor.set(json, 'blue'));
+
+  print('\n');
+
+  print('Note, that the bike in the original store is still red:');
+  bikeColor
+      .read(json)
       .map((result) => '${result.path}:\t${result.value}')
       .forEach(print);
+
+  print('\n');
+
+  print('It is also possible to modify json in place '
+      'as long as the matching value is an object or a list:');
+  final someBooks = JsonPath(r'$.store.book[::2]');
+  someBooks.read(json).forEach((match) {
+    match.value['title'] = 'Banana';
+  });
+  print(json);
 }

lib/json_path.dart

@@ -2,4 +2,5 @@
 library json_path;
 
 export 'package:json_path/src/json_path.dart';
-export 'package:json_path/src/result.dart';
+export 'package:json_path/src/json_path_match.dart';
+export 'package:json_path/src/predicate.dart';

lib/src/ast/ast.dart

@@ -0,0 +1,25 @@
+import 'package:json_path/src/ast/node.dart';
+
+/// The Abstract Syntax Tree
+class AST {
+  AST(Iterable<String> tokens) {
+    tokens.skipWhile((_) => _ == r'$').forEach(_processToken);
+  }
+
+  /// The children of the root node
+  Iterable<Node> get nodes => _stack.last.children;
+
+  final _stack = <Node>[Node('')];
+
+  void _processToken(String token) {
+    if (token == '[') {
+      _stack.add(Node(token));
+    } else if (token == ']') {
+      final node = _stack.removeLast();
+      if (node.value != '[') throw FormatException('Mismatching brackets');
+      _stack.last.children.add(node);
+    } else {
+      _stack.last.children.add(Node(token));
+    }
+  }
+}

lib/src/node.dart → lib/src/ast/node.dart

@@ -1,7 +1,5 @@
 class Node {
-  Node(this.value, [Iterable<Node> children]) {
-    if (children != null) this.children.addAll(children);
-  }
+  Node(this.value);
 
   final String value;
   final children = <Node>[];

lib/src/ast/tokenize.dart

@@ -0,0 +1,17 @@
+Iterable<String> tokenize(String expr) =>
+    _tokens.allMatches(expr).map((match) => match.group(0));
+
+final _tokens = RegExp([
+  r'\$', // root
+  r'\[', // left bracket
+  r'\]', // right bracket
+  r'\.\.', // recursion
+  r'\.', // child
+  r'\*', // wildcard
+  r'\:', // slice
+  r'\,', // union
+  r'\?', // filter
+  r"'(?:[^'\\]|\\.)*'", // quoted string
+  r'-?\d+', // number
+  r'([A-Za-z_-][A-Za-z_\d-]*)', // field
+].join('|'));

lib/src/json_path.dart

@@ -1,19 +1,40 @@
-import 'package:json_path/src/parser.dart';
+import 'package:json_path/src/ast/ast.dart';
+import 'package:json_path/src/ast/tokenize.dart';
+import 'package:json_path/src/json_path_match.dart';
+import 'package:json_path/src/parsing_state.dart';
 import 'package:json_path/src/predicate.dart';
-import 'package:json_path/src/result.dart';
+import 'package:json_path/src/selector/root.dart';
 import 'package:json_path/src/selector/selector.dart';
 
 /// A JSONPath expression
 class JsonPath {
-  /// Creates an instance from string
-  JsonPath(String expression, {Map<String, Predicate> filter})
-      : _selector = const Parser().parse(expression, filter ?? {});
+  /// Creates an instance from string. The [expression] is parsed once, and
+  /// the instance may be used many times after that.
+  ///
+  /// The [filter] arguments may contain the named filters used
+  /// in the [expression].
+  ///
+  /// Throws [FormatException] if the [expression] can not be parsed.
+  factory JsonPath(String expression, {Map<String, Predicate> filter}) {
+    if (expression.isEmpty) throw FormatException('Empty expression');
+    ParsingState state = Ready(RootSelector());
+    AST(tokenize(expression)).nodes.forEach((node) {
+      state = state.process(node, filter ?? {});
+    });
+    return JsonPath._(state.selector);
+  }
+
+  JsonPath._(this._selector);
 
   final Selector _selector;
 
-  /// Filters the given [json] object.
-  /// Returns an Iterable of all elements found
-  Iterable<Result> filter(json) => _selector.filter([Result(json, '')]);
+  /// Reads the given [json] object returning an Iterable of all matches found.
+  Iterable<JsonPathMatch> read(json) =>
+      _selector.read([JsonPathMatch(json, '')]);
+
+  /// Returns a copy of [json] with all matching values replaced with [value].
+  dynamic set(dynamic json, dynamic value) =>
+      _selector.replace(json, (_) => value);
 
   @override
   String toString() => _selector.expression();

lib/src/result.dart → lib/src/json_path_match.dart

@@ -1,6 +1,6 @@
 /// A single matching result
-class Result<T> {
-  Result(this.value, this.path);
+class JsonPathMatch<T> {
+  JsonPathMatch(this.value, this.path);
 
   /// The value
   final T value;