From 527c79ad1c66225677c8e25342375da0929a3263 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vin=C3=ADcius=20Garcia?= <vingarcia00@gmail.com>
Date: Sat, 7 May 2022 22:26:27 -0300
Subject: [PATCH] Add an example repository showing how to use transactions

---
 examples/repo_with_transactions/models.go | 10 ++++
 examples/repo_with_transactions/users.go  | 63 +++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 examples/repo_with_transactions/models.go
 create mode 100644 examples/repo_with_transactions/users.go

diff --git a/examples/repo_with_transactions/models.go b/examples/repo_with_transactions/models.go
new file mode 100644
index 0000000..97a5ff5
--- /dev/null
+++ b/examples/repo_with_transactions/models.go
@@ -0,0 +1,10 @@
+package repo
+
+import "time"
+
+type User struct {
+	ID        int       `ksql:"id"`
+	Name      string    `ksql:"name"`
+	Email     string    `ksql:"email"`
+	CreatedAt time.Time `ksql:"created_at"`
+}
diff --git a/examples/repo_with_transactions/users.go b/examples/repo_with_transactions/users.go
new file mode 100644
index 0000000..fee0e9f
--- /dev/null
+++ b/examples/repo_with_transactions/users.go
@@ -0,0 +1,63 @@
+package repo
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/vingarcia/ksql"
+)
+
+var usersTable = ksql.NewTable("users", "id")
+
+// This function doesn't care if db is a transaction or not:
+func GetUser(ctx context.Context, db ksql.Provider, userId int) (User, error) {
+	var user User
+	err := db.QueryOne(ctx, &user, "FROM users WHERE id = ?", userId)
+	return user, err
+}
+
+// This function doesn't care if db is a transaction or not:
+func GetUserByEmail(ctx context.Context, db ksql.Provider, email string) (User, error) {
+	var user User
+	err := db.QueryOne(ctx, &user, "FROM users WHERE email = ?", email)
+	return user, err
+}
+
+// This function doesn't care if db is a transaction or not:
+func CreateUser(ctx context.Context, db ksql.Provider, user User) error {
+	user.CreatedAt = time.Now()
+	return db.Insert(ctx, usersTable, &user)
+}
+
+// This function doesn't care if db is a transaction or not:
+func UpdateUser(ctx context.Context, db ksql.Provider, user User) error {
+	return db.Patch(ctx, usersTable, &user)
+}
+
+// This function creates a transaction from the input db, if db was already a transaction
+// this operation will just keep working in the same transaction instead of creating a new one.
+func ChangeUserEmail(ctx context.Context, db ksql.Provider, userID int, newEmail string) error {
+	return db.Transaction(ctx, func(db ksql.Provider) error {
+		user, err := GetUser(ctx, db, userID)
+		if err != nil {
+			return err
+		}
+
+		// If there is nothing to do, just return:
+		if user.Email == newEmail {
+			return nil
+		}
+
+		_, err = GetUserByEmail(ctx, db, newEmail)
+		if err != ksql.ErrRecordNotFound {
+			return fmt.Errorf("can't change user email to '%s': this email is already used by other user", newEmail)
+		}
+		if err != nil {
+			return err
+		}
+
+		user.Email = newEmail
+		return UpdateUser(ctx, db, user)
+	})
+}