Implement delete

example/lib/example.dart

@@ -21,6 +21,6 @@ class Users extends Table {
 class ShopDb extends SallyDb with _$ShopDbMixin {
 
   Future<List<User>> allUsers() => users.select().get();
-  Future<User> userByName(String name) => users.select().where((u) => u.name.equals(name)).single();
+  Future<User> userByName(String name) => (users.select()..where((u) => u.name.equals(name))).single();
 
 }

example/lib/example.g.dart

@@ -8,6 +8,10 @@ class _$ShopDbMixin implements QueryExecutor {
     return null;
   }
 
+  Future<int> executeDelete(String sql, [dynamic params]) {
+    return null;
+  }
+
 }
 
 class StructuredUsersTable extends Users with TableStructure<Users, User> {

sally/lib/src/database.dart

@@ -7,6 +7,7 @@ class UseData {
 
 abstract class QueryExecutor {
   Future<List<Map<String, dynamic>>> executeQuery(String sql, [dynamic params]);
+  Future<int> executeDelete(String sql, [dynamic params]);
 }
 
 abstract class SallyDb {}

sally/lib/src/dsl/columns.dart

@@ -7,18 +7,18 @@ class Column<T> {
   Predicate equals(T compare) => null;
 }
 
-class IntColumn extends Column<int> {
-  Predicate isBiggerThan(int i) => null;
-  Predicate isSmallerThan(int i) => null;
+abstract class IntColumn extends Column<int> {
+  Predicate isBiggerThan(int i);
+  Predicate isSmallerThan(int i);
 }
 
-class BoolColumn extends Column<bool> {
-  Predicate isTrue() => null;
-  Predicate isFalse() => null;
+abstract class BoolColumn extends Column<bool> {
+  Predicate isTrue();
+  Predicate isFalse();
 }
 
-class TextColumn extends Column<String> {
-  Predicate like(String regex) => null;
+abstract class TextColumn extends Column<String> {
+  Predicate like(String regex);
 }
 
 class ColumnBuilder<T> {

sally/lib/src/queries/expressions/variable.dart

@@ -13,3 +13,16 @@ class Variable extends SqlExpression {
     context.buffer.write('? ');
   }
 }
+
+class HardcodedConstant extends SqlExpression {
+
+  final dynamic value;
+
+  HardcodedConstant(this.value);
+
+  @override
+  void writeInto(GenerationContext context) {
+    context.buffer.write(context.harcodedSqlValue(value));
+  }
+
+}

sally/lib/src/queries/generation_context.dart

@@ -5,4 +5,8 @@ class GenerationContext {
   void addBoundVariable(dynamic data) {
     boundVariables.add(data);
   }
+
+  String harcodedSqlValue(dynamic value) {
+    return value.toString();
+  }
 }

sally/lib/src/queries/statement/delete.dart

@@ -0,0 +1,25 @@
+import 'package:sally/src/queries/expressions/expressions.dart';
+import 'package:sally/src/queries/statement/statements.dart';
+import 'package:sally/src/queries/table_structure.dart';
+
+class DeleteStatement<Table> with Limitable, WhereFilterable<Table, dynamic> {
+
+  DeleteStatement(TableStructure<Table, dynamic> table) {
+    super.table = table;
+  }
+
+  /// Deletes all records matched by the optional where and limit statements.
+  /// Returns the amount of deleted rows.
+  Future<int> performDelete() {
+    GenerationContext context = GenerationContext();
+    context.buffer.write('DELETE FROM ');
+    context.buffer.write(table.sqlTableName);
+    context.buffer.write(' ');
+
+    if (hasWhere) whereExpression.writeInto(context);
+    if (hasLimit) limitExpression.writeInto(context);
+
+    return table.executor.executeDelete(context.buffer.toString(), context.boundVariables);
+  }
+
+}

sally/lib/src/queries/statement/select.dart

@@ -0,0 +1,58 @@
+import 'package:sally/src/queries/expressions/expressions.dart';
+import 'package:sally/src/queries/statement/statements.dart';
+import 'package:sally/src/queries/table_structure.dart';
+
+class SelectStatement<Table, Result> with Limitable, WhereFilterable<Table, Result> {
+
+  SelectStatement(TableStructure<Table, Result> table) {
+    super.table = table;
+  }
+
+  GenerationContext _buildQuery() {
+    GenerationContext context = GenerationContext();
+    context.buffer.write('SELECT * FROM ');
+    context.buffer.write(table.sqlTableName);
+    context.buffer.write(' ');
+
+    if (hasWhere) whereExpression.writeInto(context);
+    if (hasLimit) limitExpression.writeInto(context);
+
+    return context;
+  }
+
+  /// Executes the select statement on the database and maps the returned rows
+  /// to the right dataclass.
+  Future<List<Result>> get() async {
+    final ctx = _buildQuery();
+    final sql = ctx.buffer.toString();
+    final vars = ctx.boundVariables;
+
+    final result = await table.executor.executeQuery(sql, vars);
+    return result.map(table.parse).toList();
+  }
+
+  /// Similar to [get], but it will only load one item by setting [limit()]
+  /// appropriately. This method will throw if no results where found. If you're
+  /// ok with no result existing, try [singleOrNull] instead.
+  Future<Result> single() async {
+    final element = singleOrNull();
+    if (element == null)
+      throw StateError("No item was returned by the query called with single()");
+
+    return element;
+  }
+
+  /// Similar to [get], but only uses one row of the result by setting the limit
+  /// accordingly. If no item was found, null will be returned instead.
+  Future<Result> singleOrNull() async {
+    // limit to one item, using the existing offset if it exists
+    limitExpression = LimitExpression(1, limitExpression.offset ?? 0);
+
+    final results = await get();
+    if (results.isEmpty)
+      return null;
+    return results.single;
+  }
+
+}
+

sally/lib/src/queries/statement/statements.dart

@@ -0,0 +1,45 @@
+import 'package:meta/meta.dart';
+import 'package:sally/src/queries/expressions/expressions.dart';
+import 'package:sally/src/queries/expressions/limit.dart';
+import 'package:sally/src/queries/expressions/where.dart';
+import 'package:sally/src/queries/predicates/predicate.dart';
+import 'package:sally/src/queries/table_structure.dart';
+
+/// Mixin for statements that allow a LIMIT operator
+class Limitable {
+
+  @protected
+  LimitExpression limitExpression;
+
+  void limit({int amount, int offset}) {
+    limitExpression = LimitExpression(amount, offset);
+  }
+
+  @protected
+  bool get hasLimit => limitExpression != null;
+
+}
+
+/// Mixin for statements that allow a WHERE operator on a specific table.
+class WhereFilterable<Table, Result> {
+
+  @protected
+  TableStructure<Table, Result> table;
+  @protected
+  WhereExpression whereExpression;
+
+  bool get hasWhere => whereExpression != null;
+
+  void where(Predicate filter(Table table)) {
+    final addedPredicate = filter(table.asTable);
+
+    if (hasWhere) {
+      // merge existing where expression together with new one by and-ing them
+      // together.
+      whereExpression = WhereExpression(whereExpression.predicate.and(addedPredicate));
+    } else {
+      whereExpression = WhereExpression(addedPredicate);
+    }
+  }
+
+}

sally/lib/src/queries/statements.dart

@@ -1,71 +0,0 @@
-import 'package:sally/src/queries/expressions/limit.dart';
-import 'package:sally/src/queries/expressions/where.dart';
-import 'package:sally/src/queries/generation_context.dart';
-import 'package:sally/src/queries/predicates/predicate.dart';
-import 'package:sally/src/queries/table_structure.dart';
-
-abstract class SqlStatement {
-  GenerationContext _buildQuery();
-}
-
-abstract class StatementForExistingData<Table, Result> extends SqlStatement {
-  final TableStructure<Table, Result> _table;
-
-  StatementForExistingData(this._table);
-
-  WhereExpression _where;
-  LimitExpression _limit;
-
-  Future<List<Result>> get() async {
-    final ctx = _buildQuery();
-    final sql = ctx.buffer.toString();
-    final vars = ctx.boundVariables;
-
-    final result = await _table.executor.executeQuery(sql, vars);
-    return result.map(_table.parse).toList();
-  }
-
-  Future<Result> single() async {
-    // limit to one item, using the existing offset if it exists
-    _limit = LimitExpression(1, _limit?.offset ?? 0);
-
-    return (await get()).single;
-  }
-
-  StatementForExistingData<Table, Result> where(
-      Predicate extractor(Table tbl)) {
-    final addedPredicate = extractor(_table.asTable);
-
-    if (_where != null) {
-      // merge existing where expression together with new one by and-ing them
-      // together.
-      _where = WhereExpression(_where.predicate.and(addedPredicate));
-    } else {
-      _where = WhereExpression(addedPredicate);
-    }
-
-    return this;
-  }
-
-  StatementForExistingData<Table, Result> limit({int amount, int offset}) {
-    _limit = LimitExpression(amount, offset);
-    return this;
-  }
-}
-
-class SelectStatement<T, R> extends StatementForExistingData<T, R> {
-  SelectStatement(TableStructure<T, R> table) : super(table);
-
-  @override
-  GenerationContext _buildQuery() {
-    GenerationContext context = GenerationContext();
-    context.buffer.write('SELECT * FROM ');
-    context.buffer.write(_table.sqlTableName);
-    context.buffer.write(' ');
-
-    if (_where != null) _where.writeInto(context);
-    if (_limit != null) _limit.writeInto(context);
-
-    return context;
-  }
-}

sally/lib/src/queries/table_structure.dart

@@ -6,7 +6,8 @@ import 'package:sally/src/queries/generation_context.dart';
 import 'package:sally/src/queries/predicates/numbers.dart';
 import 'package:sally/src/queries/predicates/predicate.dart';
 import 'package:sally/src/queries/predicates/text.dart';
-import 'package:sally/src/queries/statements.dart';
+import 'package:sally/src/queries/statement/delete.dart';
+import 'package:sally/src/queries/statement/select.dart';
 
 abstract class TableStructure<UserSpecifiedTable, ResolvedType> {
   QueryExecutor executor;
@@ -18,6 +19,8 @@ abstract class TableStructure<UserSpecifiedTable, ResolvedType> {
 
   SelectStatement<UserSpecifiedTable, ResolvedType> select() =>
       SelectStatement<UserSpecifiedTable, ResolvedType>(this);
+
+  DeleteStatement<UserSpecifiedTable> delete() => DeleteStatement(this);
 }
 
 class StructuredColumn<T> implements SqlExpression, Column<T> {
@@ -51,14 +54,15 @@ class StructuredBoolColumn extends StructuredColumn<bool>
     implements BoolColumn {
   StructuredBoolColumn(String sqlName) : super(sqlName);
 
-  @override
-  Predicate isFalse() {
-    return not(isTrue());
-  }
+  // Booleans will be stored as integers, where 0 means false and 1 means true
 
+  @override
+  Predicate isFalse() {
+    return EqualityPredicate(this, HardcodedConstant(0));
+  }
   @override
   Predicate isTrue() {
-    return BooleanExpressionPredicate(this);
+    return EqualityPredicate(this, HardcodedConstant(1));
   }
 }
 

sally/test/queries_test.dart

@@ -56,25 +56,40 @@ void main() {
     });
 
     test("generates limit statements", () {
-      users.select().limit(amount: 10).get();
+      (users.select()..limit(amount: 10)).get();
       verify(executor.executeQuery("SELECT * FROM users LIMIT 10 ", any));
     });
 
     test("generates like expressions", () {
-      users.select().where((u) => u.name.like("Dash%")).get();
+      (users.select()..where((u) => u.name.like("Dash%"))).get();
       verify(executor
           .executeQuery("SELECT * FROM users WHERE name LIKE ? ", ["Dash%"]));
     });
 
     test("generates complex predicates", () {
-      users
-          .select()
-          .where((u) => not(u.name.equals("Dash")).and(u.id.isBiggerThan(12)))
+      (users.select()
+            ..where(
+                (u) => not(u.name.equals("Dash")).and(u.id.isBiggerThan(12))))
           .get();
 
       verify(executor.executeQuery(
           "SELECT * FROM users WHERE (NOT name = ? ) AND (id > ? ) ",
           ["Dash", 12]));
     });
+
+    test("generates expressions from boolean fields", () {
+      (users.select()..where((u) => u.isAwesome.isTrue())).get();
+
+      verify(executor.executeQuery(
+          "SELECT * FROM users WHERE is_awesome = 1", any));
+    });
+  });
+
+  group("Generates DELETE statements", () {
+    test("without any constaints", () {
+      users.delete().performDelete();
+
+      verify(executor.executeDelete("DELETE FROM users ", argThat(isEmpty)));
+    });
   });
 }