👍 add limit parser (#7)

okazaki-kk · web-flow · commit 12ebccf6bc4c · 2023-07-09T12:22:09.000+09:00
* add test

* add parser
diff --git a/internal/parser/ast/ast.go b/internal/parser/ast/ast.go
@@ -26,6 +26,7 @@ type SelectStatement struct {
 	From    *FromStatement
 	Where   *WhereStatement
 	OrderBy *OrderByStatement
+	Limit   *LimitStatement
 }
 
 // ResultStatement node represents a returning expression in a SELECT statement.
@@ -61,12 +62,17 @@ type OrderByStatement struct {
 	Direction token.TokenType
 }
 
+type LimitStatement struct {
+	Value Expression
+}
+
 func (s *SelectStatement) statementNode()      {}
 func (s *ResultStatement) statementNode()      {}
 func (s *FromStatement) statementNode()        {}
 func (s *WhereStatement) statementNode()       {}
 func (s *CreateTableStatement) statementNode() {}
 func (s *OrderByStatement) statementNode()     {}
+func (s *LimitStatement) statementNode()       {}
 
 // IdentExpr node represents an identifier.
 type IdentExpr struct {
diff --git a/internal/parser/parser.go b/internal/parser/parser.go
@@ -69,11 +69,17 @@ func (p *Parser) parseSelectStatement() (ast.Statement, error) {
 		return nil, err
 	}
 
+	limit, err := p.parseLimitStatement()
+	if err != nil {
+		return nil, err
+	}
+
 	selectStmt := ast.SelectStatement{
 		Result:  result,
 		From:    from,
 		Where:   where,
 		OrderBy: order,
+		Limit:   limit,
 	}
 
 	return &selectStmt, nil
@@ -271,6 +277,25 @@ func (p *Parser) parseOrderByStatement() (*ast.OrderByStatement, error) {
 	return &order, nil
 }
 
+func (p *Parser) parseLimitStatement() (*ast.LimitStatement, error) {
+	if p.token.Type != token.LIMIT {
+		return nil, nil
+	}
+	p.nextToken()
+
+	value, err := p.parseScalar(token.INT)
+	if err != nil {
+		return nil, err
+	}
+
+	p.nextToken()
+
+	limit := ast.LimitStatement{
+		Value: value,
+	}
+	return &limit, nil
+}
+
 func (p *Parser) parsePrimaryExpr() (ast.Expression, error) {
 	expr, err := p.parseExpr(LOWEST)
 	if err != nil {
diff --git a/internal/parser/parser_test.go b/internal/parser/parser_test.go
@@ -150,6 +150,52 @@ func TestParser_Select(t *testing.T) {
 				},
 			},
 		},
+		{
+			input: "SELECT id FROM customers WHERE id = 10 AND name = 'Tom' ORDER BY id ASC LIMIT 99",
+			stmt: &ast.SelectStatement{
+				Result: []ast.ResultStatement{
+					{
+						Expr: &ast.IdentExpr{
+							Name: "id",
+						},
+					},
+				},
+				From: &ast.FromStatement{
+					Table: "customers",
+				},
+				Where: &ast.WhereStatement{
+					Expr: &ast.ConditionExpr{
+						Left: &ast.ConditionExpr{
+							Left:     &ast.IdentExpr{Name: "id"},
+							Operator: token.EQ,
+							Right: &ast.ScalarExpr{
+								Type:    token.INT,
+								Literal: "10",
+							},
+						},
+						Operator: token.AND,
+						Right: &ast.ConditionExpr{
+							Left:     &ast.IdentExpr{Name: "name"},
+							Operator: token.EQ,
+							Right: &ast.ScalarExpr{
+								Type:    token.TEXT,
+								Literal: "Tom",
+							},
+						},
+					},
+				},
+				OrderBy: &ast.OrderByStatement{
+					Column:    "id",
+					Direction: token.ASC,
+				},
+				Limit: &ast.LimitStatement{
+					Value: &ast.ScalarExpr{
+						Type:    token.INT,
+						Literal: "99",
+					},
+				},
+			},
+		},
 	}
 
 	for _, test := range tests {
