From 70938253e8abf6fed3b1e1d222af2c9d24437ff6 Mon Sep 17 00:00:00 2001
From: Tan Yin Loo <tianhai82@yahoo.com>
Date: Sun, 24 Nov 2024 08:18:52 +0800
Subject: [PATCH] simple tx engine implementation

---
 coredb/txengine/tx_engine.go | 139 +++++++++++++++++++++++++++++++++++
 1 file changed, 139 insertions(+)
 create mode 100644 coredb/txengine/tx_engine.go

diff --git a/coredb/txengine/tx_engine.go b/coredb/txengine/tx_engine.go
new file mode 100644
index 0000000..6bb0168
--- /dev/null
+++ b/coredb/txengine/tx_engine.go
@@ -0,0 +1,139 @@
+package txengine
+
+import (
+	"context"
+	"database/sql"
+	"errors"
+	"fmt"
+
+	"github.com/olachat/gola/v2/coredb"
+	"github.com/olachat/gola/v2/golalib/testdata/blogs"
+	"github.com/olachat/gola/v2/golalib/testdata/users"
+)
+
+type TypedTx[T any] sql.Tx
+type Tx sql.Tx
+
+func WithTypedTx[T any](tx *sql.Tx) *TypedTx[T] {
+	return (*TypedTx[T])(tx)
+}
+
+func WithTx(tx *sql.Tx) *Tx {
+	return (*Tx)(tx)
+}
+
+func StartTx(ctx context.Context, tx *sql.Tx, fn func(ctx context.Context, sqlTx *sql.Tx) error) (err error) {
+	defer func() {
+		//nolint:gocritic
+		if r := recover(); r != nil {
+			_ = tx.Rollback()
+			var ok bool
+			err, ok = r.(error)
+			if !ok {
+				err = fmt.Errorf("%v", r)
+			}
+		} else if err != nil {
+			errRollback := tx.Rollback()
+			if errors.Is(errRollback, sql.ErrTxDone) && ctx.Err() != nil {
+				errRollback = nil
+			}
+			if errRollback != nil {
+				err = fmt.Errorf("%v encountered. but rollback failed: %w", err, errRollback)
+			}
+		} else {
+			err = tx.Commit()
+		}
+	}()
+
+	err = fn(ctx, tx)
+
+	return err
+}
+
+func Example() {
+	ctxOuter := context.Background()
+	tx, _ := coredb.BeginTx(ctxOuter, "test_db", &coredb.DefaultTxOpts)
+	var count int
+	_ = StartTx(ctxOuter, tx, func(ctx context.Context, sqlTx *sql.Tx) error {
+		userRec, err := WithTypedTx[users.User](sqlTx).FindOne(ctx, users.TableName, coredb.NewWhere("where uid=?", 1))
+		if err != nil {
+			return fmt.Errorf("findOne user uid:%d failed: %w", 1, err)
+		}
+		if userRec == nil {
+			return fmt.Errorf("user:%d not found", 1)
+		}
+		ct, err := WithTx(sqlTx).QueryInt(ctx, blogs.DBName, "select count(*) from blogs")
+		if err != nil {
+			return fmt.Errorf("QueryInt error: %w", err)
+		}
+		count = ct
+		return nil
+	})
+	fmt.Println(count)
+}
+
+// FindOne returns a row from given table type with where query.
+// If no rows found, *T will be nil. No error will be returned.
+func (o *TypedTx[T]) FindOne(ctx context.Context, tableName string, where coredb.WhereQuery) (*T, error) {
+	u := new(T)
+	columnsNames := coredb.GetColumnsNames[T]()
+	data := coredb.StrutForScan(u)
+	whereSQL, params := where.GetWhere()
+	query := fmt.Sprintf("SELECT %s FROM `%s` %s", columnsNames,
+		tableName, whereSQL)
+	err2 := (*sql.Tx)(o).QueryRowContext(ctx, query, params...).Scan(data...)
+
+	if err2 != nil {
+		// It's on purpose the hide the error
+		// But should re-consider later
+		if err2 == sql.ErrNoRows {
+			return nil, nil
+		}
+
+		return nil, err2
+	}
+
+	return u, nil
+}
+
+// Exec given query with given db info & params
+func (o *Tx) Exec(ctx context.Context, query string, params ...any) (sql.Result, error) {
+	return (*sql.Tx)(o).ExecContext(ctx, query, params...)
+}
+
+// Find returns rows from given table type with where query
+func (o *TypedTx[T]) Find(ctx context.Context, tableName string, where coredb.WhereQuery) ([]*T, error) {
+	columnsNames := coredb.GetColumnsNames[T]()
+	whereSQL, params := where.GetWhere()
+	query := fmt.Sprintf("SELECT %s FROM `%s` %s", columnsNames,
+		tableName, whereSQL)
+
+	return o.Query(ctx, query, params...)
+}
+
+// QueryInt single int result by query, handy for count(*) querys
+func (o *Tx) QueryInt(ctx context.Context, query string, params ...any) (result int, err error) {
+	err = (*sql.Tx)(o).QueryRowContext(ctx, query, params...).Scan(&result)
+	return
+}
+
+// Query rows from given table type with where query & params
+func (o *TypedTx[T]) Query(ctx context.Context, query string, params ...any) (result []*T, err error) {
+	rows, err := (*sql.Tx)(o).QueryContext(ctx, query, params...)
+	if err != nil {
+		return
+	}
+
+	var u *T
+	for rows.Next() {
+		u = new(T)
+		data := coredb.StrutForScan(u)
+		err = rows.Scan(data...)
+		if err != nil {
+			return
+		}
+		result = append(result, u)
+	}
+
+	return
+}