From 47a1b9de22d9372b93bd173edb36876860d171f8 Mon Sep 17 00:00:00 2001
From: lqs <lqs@lqs.me>
Date: Wed, 1 Jul 2020 19:54:03 +0800
Subject: [PATCH] support for multiple dialects

---
 database.go      |  4 ++--
 database_test.go |  1 +
 dialect.go       | 30 ++++++++++++++++++++++++++++++
 expression.go    | 14 ++++++++++++++
 field.go         | 20 +++++++++++++++-----
 utils_test.go    |  6 ++++--
 6 files changed, 66 insertions(+), 9 deletions(-)
 create mode 100644 dialect.go

diff --git a/database.go b/database.go
index ddbab55..8f7e06c 100644
--- a/database.go
+++ b/database.go
@@ -36,7 +36,7 @@ type database struct {
 	db               *sql.DB
 	tx               *sql.Tx
 	logger           func(sql string, durationNano int64)
-	dialect          string
+	dialect          dialect
 	retryPolicy      func(error) bool
 	enableCallerInfo bool
 	interceptor      InterceptorFunc
@@ -67,7 +67,7 @@ func Open(driverName string, dataSourceName string) (db Database, err error) {
 		}
 	}
 	db = &database{
-		dialect: driverName,
+		dialect: getDialectFromDriverName(driverName),
 		db:      sqlDB,
 	}
 	return
diff --git a/database_test.go b/database_test.go
index ccf7da6..15d3fd0 100644
--- a/database_test.go
+++ b/database_test.go
@@ -30,6 +30,7 @@ func newMockDatabase() Database {
 	if err != nil {
 		panic(err)
 	}
+	db.(*database).dialect = dialectMySQL
 	return db
 }
 
diff --git a/dialect.go b/dialect.go
new file mode 100644
index 0000000..66ac3c7
--- /dev/null
+++ b/dialect.go
@@ -0,0 +1,30 @@
+package sqlingo
+
+type dialect int
+
+const (
+	dialectUnknown dialect = iota
+	dialectMySQL
+	dialectSqlite3
+	dialectPostgres
+	dialectMSSQL
+
+	dialectCount
+)
+
+type dialectArray [dialectCount]string
+
+func getDialectFromDriverName(driverName string) dialect {
+	switch driverName {
+	case "mysql":
+		return dialectMySQL
+	case "sqlite3":
+		return dialectSqlite3
+	case "postgres":
+		return dialectPostgres
+	case "sqlserver", "mssql":
+		return dialectMSSQL
+	default:
+		return dialectUnknown
+	}
+}
diff --git a/expression.go b/expression.go
index 66804be..7003e9c 100644
--- a/expression.go
+++ b/expression.go
@@ -174,6 +174,20 @@ func (e expression) GetSQL(scope scope) (string, error) {
 	return e.builder(scope)
 }
 
+func quoteIdentifier(identifier string) (result dialectArray) {
+	for dialect := dialect(0); dialect < dialectCount; dialect++ {
+		switch dialect {
+		case dialectMySQL:
+			result[dialect] = "`" + identifier + "`"
+		case dialectMSSQL:
+			result[dialect] = "[" + identifier + "]"
+		default:
+			result[dialect] = "\"" + identifier + "\""
+		}
+	}
+	return
+}
+
 func quoteString(s string) string {
 	bytes := []byte(s)
 	buf := make([]byte, len(s)*2+2)
diff --git a/field.go b/field.go
index 2018da7..7e75132 100644
--- a/field.go
+++ b/field.go
@@ -19,14 +19,24 @@ type StringField interface {
 }
 
 func newFieldExpression(tableName string, fieldName string) expression {
-	shortFieldNameSql := getSQLForName(fieldName)
-	fullFieldNameSql := getSQLForName(tableName) + "." + shortFieldNameSql
+	tableNameSqlArray := quoteIdentifier(tableName)
+	fieldNameSqlArray := quoteIdentifier(fieldName)
+
+	var fullFieldNameSqlArray dialectArray
+	for dialect := dialect(0); dialect < dialectCount; dialect++ {
+		fullFieldNameSqlArray[dialect] = tableNameSqlArray[dialect] + "." + fieldNameSqlArray[dialect]
+	}
+
 	return expression{
 		builder: func(scope scope) (string, error) {
-			if len(scope.Tables) != 1 || scope.lastJoin != nil || scope.Tables[0].GetName() != tableName {
-				return fullFieldNameSql, nil
+			dialect := dialectUnknown
+			if scope.Database != nil {
+				dialect = scope.Database.dialect
 			}
-			return shortFieldNameSql, nil
+			if len(scope.Tables) != 1 || scope.lastJoin != nil || scope.Tables[0].GetName() != tableName {
+				return fullFieldNameSqlArray[dialect], nil
+			}
+			return fieldNameSqlArray[dialect], nil
 		},
 	}
 }
diff --git a/utils_test.go b/utils_test.go
index 952c51b..d21dbfa 100644
--- a/utils_test.go
+++ b/utils_test.go
@@ -2,9 +2,11 @@ package sqlingo
 
 import "testing"
 
+var dummyMySQLScope = scope{Database: &database{dialect: dialectMySQL}}
+
 func assertValue(t *testing.T, value interface{}, expectedSql string) {
 	t.Helper()
-	if generatedSql, _, _ := getSQL(scope{}, value); generatedSql != expectedSql {
+	if generatedSql, _, _ := getSQL(dummyMySQLScope, value); generatedSql != expectedSql {
 		t.Errorf("value [%v] generated [%s] expected [%s]", value, generatedSql, expectedSql)
 	}
 }
@@ -18,7 +20,7 @@ func assertLastSql(t *testing.T, expectedSql string) {
 
 func assertError(t *testing.T, value interface{}) {
 	t.Helper()
-	if generatedSql, _, err := getSQL(scope{}, value); err == nil {
+	if generatedSql, _, err := getSQL(dummyMySQLScope, value); err == nil {
 		t.Errorf("value [%v] generated [%s] expected error", value, generatedSql)
 	}
 }