Improve the list of methods on the kbuilder.Query struct

Add the queryBuilder interface
Make the kbuilder.Query implement this interface
Add kbuilder.Query.Build() helper method for facilitating the usage if
the person prefers no to inject the kbuilder.Builder struct.

kbuilder/kbuilder.go

@@ -21,6 +21,10 @@ type Builder struct {
 	dialect ksql.Dialect
 }
 
+type queryBuilder interface {
+	BuildQuery(dialect ksql.Dialect) (sqlQuery string, params []interface{}, _ error)
+}
+
 // New creates a new Builder container.
 func New(driver string) (Builder, error) {
 	dialect, err := ksql.GetDriverDialect(driver)
@@ -31,48 +35,8 @@ func New(driver string) (Builder, error) {
 
 // Build receives a query builder struct, injects it with the configurations
 // build the query according to its arguments.
-func (builder *Builder) Build(query Query) (sqlQuery string, params []interface{}, _ error) {
-	var b strings.Builder
-
-	switch v := query.Select.(type) {
-	case string:
-		b.WriteString("SELECT " + v)
-	default:
-		selectQuery, err := buildSelectQuery(v, builder.dialect)
-		if err != nil {
-			return "", nil, errors.Wrap(err, "error reading the Select field")
-		}
-		b.WriteString("SELECT " + selectQuery)
-	}
-
-	b.WriteString(" FROM " + query.From)
-
-	if len(query.Where) > 0 {
-		var whereQuery string
-		whereQuery, params = query.Where.build(builder.dialect)
-		b.WriteString(" WHERE " + whereQuery)
-	}
-
-	if strings.TrimSpace(query.From) == "" {
-		return "", nil, fmt.Errorf("the From field is mandatory for every query")
-	}
-
-	if query.OrderBy.fields != "" {
-		b.WriteString(" ORDER BY " + query.OrderBy.fields)
-		if query.OrderBy.desc {
-			b.WriteString(" DESC")
-		}
-	}
-
-	if query.Limit > 0 {
-		b.WriteString(" LIMIT " + strconv.Itoa(query.Limit))
-	}
-
-	if query.Offset > 0 {
-		b.WriteString(" OFFSET " + strconv.Itoa(query.Offset))
-	}
-
-	return b.String(), params, nil
+func (builder *Builder) Build(query queryBuilder) (sqlQuery string, params []interface{}, _ error) {
+	return query.BuildQuery(builder.dialect)
 }
 
 // Query is is the struct template for building SELECT queries.
@@ -94,6 +58,62 @@ type Query struct {
 	OrderBy OrderByQuery
 }
 
+// Build is a utility function for finding the dialect based on the driver and
+// then calling BuildQuery(dialect)
+func (q Query) Build(driver string) (sqlQuery string, params []interface{}, _ error) {
+	dialect, err := ksql.GetDriverDialect(driver)
+	if err != nil {
+		return "", nil, err
+	}
+
+	return q.BuildQuery(dialect)
+}
+
+// BuildQuery implements the QueryBuilder interface
+func (q Query) BuildQuery(dialect ksql.Dialect) (sqlQuery string, params []interface{}, _ error) {
+	var b strings.Builder
+
+	switch v := q.Select.(type) {
+	case string:
+		b.WriteString("SELECT " + v)
+	default:
+		selectQuery, err := buildSelectQuery(v, dialect)
+		if err != nil {
+			return "", nil, errors.Wrap(err, "error reading the Select field")
+		}
+		b.WriteString("SELECT " + selectQuery)
+	}
+
+	b.WriteString(" FROM " + q.From)
+
+	if len(q.Where) > 0 {
+		var whereQuery string
+		whereQuery, params = q.Where.build(dialect)
+		b.WriteString(" WHERE " + whereQuery)
+	}
+
+	if strings.TrimSpace(q.From) == "" {
+		return "", nil, fmt.Errorf("the From field is mandatory for every query")
+	}
+
+	if q.OrderBy.fields != "" {
+		b.WriteString(" ORDER BY " + q.OrderBy.fields)
+		if q.OrderBy.desc {
+			b.WriteString(" DESC")
+		}
+	}
+
+	if q.Limit > 0 {
+		b.WriteString(" LIMIT " + strconv.Itoa(q.Limit))
+	}
+
+	if q.Offset > 0 {
+		b.WriteString(" OFFSET " + strconv.Itoa(q.Offset))
+	}
+
+	return b.String(), params, nil
+}
+
 // WhereQuery represents a single condition in a WHERE expression.
 type WhereQuery struct {
 	// Accepts any SQL boolean expression