WIP: Refactor Exec implementations to be chainable

exec/select.go

@@ -0,0 +1,138 @@
+package exec
+
+import (
+	"database/sql"
+	"errors"
+	"reflect"
+
+	"git.gdulai.com/gdulai/simpleorm"
+	"git.gdulai.com/gdulai/simpleorm/schema"
+	log "gitlab.com/gdulai/simpleloglvl"
+)
+
+// Select execution which is translated to a select sql query.
+type Select[T any] struct {
+	target    schema.Table
+	whereStmt string
+	args      []any
+	limit     int64
+	offset    int64
+	ordering  []OrderBy
+	results   []T
+}
+
+// Creates the select query builder
+func CreateSelect[T any](orm *simpleorm.ORM) (Select[T], error) {
+	table, ok := orm.Cache().Get(reflect.TypeFor[T]().Name())
+	if !ok {
+		return Select[T]{}, errors.New("Failed to get table from schema cache")
+	}
+
+	return Select[T]{target: *table, limit: -1, offset: -1}, nil
+}
+
+// Sets the where part of the select query and the arguments
+// Returns the pointer of the Select instance
+func (s *Select[T]) Where(whereStmt string, args ...any) *Select[T] {
+	s.whereStmt = whereStmt
+	s.args = args
+	return s
+}
+
+// Sets the limit part of the select query
+// Returns the pointer of the Select instance
+func (s *Select[T]) Limit(limit int64) *Select[T] {
+	s.limit = limit
+	return s
+}
+
+// Sets the offset part of the select query
+// Returns the pointer of the Select instance
+func (s *Select[T]) Offset(offset int64) *Select[T] {
+	s.offset = offset
+	return s
+}
+
+// Sets the order by part of the select query
+// Returns the pointer of the Select instance
+func (s *Select[T]) OrderBy(ordering ...OrderBy) *Select[T] {
+	s.ordering = ordering
+	return s
+}
+
+// Returns the result of the select
+func (s *Select[T]) Results() []T {
+	return s.results
+}
+
+func (s *Select[T]) Execute(conn *simpleorm.DBConnection) error {
+	return s.execute(conn, nil)
+}
+
+func (s *Select[T]) execute(conn *simpleorm.DBConnection, tx *sql.Tx) error {
+	// Reinit the results, new execution
+	s.results = []T{}
+	dml, err := s.target.GetSelectDML()
+	if err != nil {
+		return err
+	}
+
+	if s.whereStmt != "" {
+		dml += " WHERE " + s.whereStmt
+	}
+
+	var effectiveArgs []any = s.args
+	if s.limit != -1 {
+		dml += " LIMIT ?"
+		effectiveArgs = append(effectiveArgs, s.limit)
+	}
+
+	if s.offset != -1 {
+		dml += " OFFSET ?"
+		effectiveArgs = append(effectiveArgs, s.offset)
+	}
+
+	log.LogDebug("Preparing sql: %s, with args: %s", dml, effectiveArgs)
+
+	var stmt *sql.Stmt
+	if tx != nil {
+		stmt, err = tx.Prepare(dml)
+	} else {
+		stmt, err = conn.Prepare(dml)
+	}
+
+	if err != nil {
+		return err
+	}
+	defer stmt.Close()
+
+	log.LogDebug("Executing statement: %s", stmt)
+
+	var rows *sql.Rows
+	if len(effectiveArgs) == 0 {
+		rows, err = stmt.Query()
+	} else {
+		// Flattent args to make sure it can be parsed correctly
+		var flatArgs []any
+		for _, a := range effectiveArgs {
+			if s, ok := a.([]any); ok {
+				flatArgs = append(flatArgs, s...)
+			} else {
+				flatArgs = append(flatArgs, a)
+			}
+		}
+		rows, err = stmt.Query(flatArgs...)
+
+	}
+
+	if err != nil {
+		return err
+	}
+
+	s.results, err = readRows[T](s.target, rows)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}