From d125a844da7c00e3684e047cd1d06761eaf8ad11 Mon Sep 17 00:00:00 2001
From: Simon Binder <oss@simonbinder.eu>
Date: Sun, 16 Jun 2019 21:23:33 +0200
Subject: [PATCH] Start implementing SELECT statements for parser

---
 sqlparser/lib/src/ast/ast.dart                | 15 ++++++-
 sqlparser/lib/src/ast/clauses/limit.dart      | 17 ++++++++
 .../lib/src/ast/expressions/expressions.dart  |  2 +-
 .../lib/src/ast/expressions/literals.dart     |  6 +--
 sqlparser/lib/src/ast/expressions/simple.dart |  5 +--
 sqlparser/lib/src/ast/statements/select.dart  | 16 +++++++
 sqlparser/lib/src/reader/parser/parser.dart   | 42 +++++++++++++++++--
 sqlparser/lib/src/reader/tokenizer/token.dart |  6 +++
 sqlparser/lib/src/utils/ast_equality.dart     |  1 -
 sqlparser/pubspec.yaml                        |  2 +-
 sqlparser/test/parser/expression_test.dart    |  3 +-
 11 files changed, 96 insertions(+), 19 deletions(-)
 create mode 100644 sqlparser/lib/src/ast/clauses/limit.dart
 create mode 100644 sqlparser/lib/src/ast/statements/select.dart

diff --git a/sqlparser/lib/src/ast/ast.dart b/sqlparser/lib/src/ast/ast.dart
index f6c5630e..d5c8c539 100644
--- a/sqlparser/lib/src/ast/ast.dart
+++ b/sqlparser/lib/src/ast/ast.dart
@@ -1,5 +1,12 @@
-import 'package:sqlparser/src/ast/expressions/literals.dart';
-import 'package:sqlparser/src/ast/expressions/simple.dart';
+import 'package:sqlparser/src/reader/tokenizer/token.dart';
+
+part 'clauses/limit.dart';
+
+part 'expressions/expressions.dart';
+part 'expressions/literals.dart';
+part 'expressions/simple.dart';
+
+part 'statements/select.dart';
 
 abstract class AstNode {
   Iterable<AstNode> get childNodes;
@@ -7,6 +14,10 @@ abstract class AstNode {
 }
 
 abstract class AstVisitor<T> {
+  T visitSelectStatement(SelectStatement e);
+
+  T visitLimit(Limit e);
+
   T visitBinaryExpression(BinaryExpression e);
   T visitUnaryExpression(UnaryExpression e);
   T visitIsExpression(IsExpression e);
diff --git a/sqlparser/lib/src/ast/clauses/limit.dart b/sqlparser/lib/src/ast/clauses/limit.dart
new file mode 100644
index 00000000..9acf9641
--- /dev/null
+++ b/sqlparser/lib/src/ast/clauses/limit.dart
@@ -0,0 +1,17 @@
+part of '../ast.dart';
+
+class Limit extends AstNode {
+  Expression count;
+  Token offsetSeparator; // can either be OFFSET or just a comma
+  Expression offset;
+
+  Limit({this.count, this.offsetSeparator, this.offset});
+
+  @override
+  T accept<T>(AstVisitor<T> visitor) {
+    return visitor.visitLimit(this);
+  }
+
+  @override
+  Iterable<AstNode> get childNodes => [count, if (offset != null) offset];
+}
diff --git a/sqlparser/lib/src/ast/expressions/expressions.dart b/sqlparser/lib/src/ast/expressions/expressions.dart
index ab458506..66a50d07 100644
--- a/sqlparser/lib/src/ast/expressions/expressions.dart
+++ b/sqlparser/lib/src/ast/expressions/expressions.dart
@@ -1,4 +1,4 @@
-import 'package:sqlparser/src/ast/ast.dart';
+part of '../ast.dart';
 
 abstract class Expression implements AstNode {
   const Expression();
diff --git a/sqlparser/lib/src/ast/expressions/literals.dart b/sqlparser/lib/src/ast/expressions/literals.dart
index a8998e42..ad029421 100644
--- a/sqlparser/lib/src/ast/expressions/literals.dart
+++ b/sqlparser/lib/src/ast/expressions/literals.dart
@@ -1,8 +1,4 @@
-import 'package:sqlparser/src/ast/ast.dart';
-import 'package:sqlparser/src/reader/tokenizer/token.dart';
-
-import 'expressions.dart';
-
+part of '../ast.dart';
 // https://www.sqlite.org/syntax/literal-value.html
 
 abstract class Literal extends Expression {
diff --git a/sqlparser/lib/src/ast/expressions/simple.dart b/sqlparser/lib/src/ast/expressions/simple.dart
index 8dcc5ef2..0c9ef4a4 100644
--- a/sqlparser/lib/src/ast/expressions/simple.dart
+++ b/sqlparser/lib/src/ast/expressions/simple.dart
@@ -1,7 +1,4 @@
-import 'package:sqlparser/src/ast/ast.dart';
-import 'package:sqlparser/src/reader/tokenizer/token.dart';
-
-import 'expressions.dart';
+part of '../ast.dart';
 
 class UnaryExpression extends Expression {
   final Token operator;
diff --git a/sqlparser/lib/src/ast/statements/select.dart b/sqlparser/lib/src/ast/statements/select.dart
new file mode 100644
index 00000000..e3f43b9c
--- /dev/null
+++ b/sqlparser/lib/src/ast/statements/select.dart
@@ -0,0 +1,16 @@
+part of '../ast.dart';
+
+class SelectStatement extends AstNode {
+  final Expression where;
+  final Limit limit;
+
+  SelectStatement({this.where, this.limit});
+
+  @override
+  T accept<T>(AstVisitor<T> visitor) {
+    return visitor.visitSelectStatement(this);
+  }
+
+  @override
+  Iterable<AstNode> get childNodes => null;
+}
diff --git a/sqlparser/lib/src/reader/parser/parser.dart b/sqlparser/lib/src/reader/parser/parser.dart
index 730f45c0..a590620c 100644
--- a/sqlparser/lib/src/reader/parser/parser.dart
+++ b/sqlparser/lib/src/reader/parser/parser.dart
@@ -1,7 +1,5 @@
 import 'package:meta/meta.dart';
-import 'package:sqlparser/src/ast/expressions/expressions.dart';
-import 'package:sqlparser/src/ast/expressions/literals.dart';
-import 'package:sqlparser/src/ast/expressions/simple.dart';
+import 'package:sqlparser/src/ast/ast.dart';
 import 'package:sqlparser/src/reader/tokenizer/token.dart';
 
 const _comparisonOperators = [
@@ -72,6 +70,44 @@ class Parser {
     _error(message);
   }
 
+  /// Parses a [SelectStatement], or returns null if there is no select token
+  /// after the current position.
+  SelectStatement select() {
+    if (!_match(const [TokenType.select])) return null;
+
+    // todo parse result column
+
+    final where = _where();
+    final limit = _limit();
+
+    return SelectStatement(where: where, limit: limit);
+  }
+
+  /// Parses a where clause if there is one at the current position
+  Expression _where() {
+    if (_match(const [TokenType.where])) {
+      return expression();
+    }
+    return null;
+  }
+
+  /// Parses a [Limit] clause, or returns null if there is no limit token after
+  /// the current position.
+  Limit _limit() {
+    if (!_match(const [TokenType.limit])) return null;
+
+    final count = expression();
+    Token offsetSep;
+    Expression offset;
+
+    if (_match(const [TokenType.comma, TokenType.offset])) {
+      offsetSep = _previous;
+      offset = expression();
+    }
+
+    return Limit(count: count, offsetSeparator: offsetSep, offset: offset);
+  }
+
   /* We parse expressions here.
   * Operators have the following precedence:
   *  - + ~ NOT (unary)
diff --git a/sqlparser/lib/src/reader/tokenizer/token.dart b/sqlparser/lib/src/reader/tokenizer/token.dart
index a55760c5..c5023a61 100644
--- a/sqlparser/lib/src/reader/tokenizer/token.dart
+++ b/sqlparser/lib/src/reader/tokenizer/token.dart
@@ -45,9 +45,13 @@ enum TokenType {
   identifier,
 
   select,
+
   from,
   where,
 
+  limit,
+  offset,
+
   eof,
 }
 
@@ -55,6 +59,8 @@ const Map<String, TokenType> keywords = {
   'SELECT': TokenType.select,
   'FROM': TokenType.from,
   'WHERE': TokenType.where,
+  'LIMIT': TokenType.limit,
+  'OFFSET': TokenType.offset,
   'IS': TokenType.$is,
   'IN': TokenType.$in,
   'LIKE': TokenType.like,
diff --git a/sqlparser/lib/src/utils/ast_equality.dart b/sqlparser/lib/src/utils/ast_equality.dart
index 810d467f..21b96160 100644
--- a/sqlparser/lib/src/utils/ast_equality.dart
+++ b/sqlparser/lib/src/utils/ast_equality.dart
@@ -1,5 +1,4 @@
 import 'package:sqlparser/src/ast/ast.dart';
-import 'package:sqlparser/src/ast/expressions/simple.dart';
 
 /// Checks whether [a] and [b] are equal. If they aren't, throws an exception.
 void enforceEqual(AstNode a, AstNode b) {
diff --git a/sqlparser/pubspec.yaml b/sqlparser/pubspec.yaml
index 80cc4ec5..c41c5211 100644
--- a/sqlparser/pubspec.yaml
+++ b/sqlparser/pubspec.yaml
@@ -7,7 +7,7 @@ issue_tracker: https://github.com/simolus3/moor/issues
 author: Simon Binder <oss@simonbinder.eu>
 
 environment:
-  sdk: '>=2.2.0 <3.0.0'
+  sdk: '>=2.2.2 <3.0.0'
 
 dev_dependencies:
   test: ^1.0.0
diff --git a/sqlparser/test/parser/expression_test.dart b/sqlparser/test/parser/expression_test.dart
index 540c67a1..8b0a76be 100644
--- a/sqlparser/test/parser/expression_test.dart
+++ b/sqlparser/test/parser/expression_test.dart
@@ -1,5 +1,4 @@
-import 'package:sqlparser/src/ast/expressions/literals.dart';
-import 'package:sqlparser/src/ast/expressions/simple.dart';
+import 'package:sqlparser/src/ast/ast.dart';
 import 'package:sqlparser/src/reader/parser/parser.dart';
 import 'package:sqlparser/src/reader/tokenizer/scanner.dart';
 import 'package:sqlparser/src/reader/tokenizer/token.dart';