Add a pagination example

schema/ent/example/start.go

@@ -3,15 +3,18 @@ package main
 import (
 	"context"
 	"ersteller-lib/schema/ent/example/ent"
+	"ersteller-lib/schema/ent/example/ent/user"
 	"log"
 	"time"
 
+	"entgo.io/ent/dialect/sql"
 	_ "github.com/mattn/go-sqlite3"
 )
 
 func main() {
 	//client, err := ent.Open("sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
-	client, err := ent.Open("sqlite3", "/tmp/ersteller_ent_example.db?_fk=1")
+	client, err := ent.Open("sqlite3", "/tmp/ersteller_ent_example.db?_fk=1",
+		ent.Log(log.Println), ent.Debug())
 	if err != nil {
 		log.Fatalf("failed opening connection to sqlite: %v", err)
 	}
@@ -31,11 +34,59 @@ func main() {
 	}
 	log.Println("user was created: ", u)
 
-	time.Sleep(time.Second * 1)
-	u, err = client.User.UpdateOneID(u.ID).SetPassword("wtf").Save(ctx)
+	//time.Sleep(time.Second * 1)
+	//u, err = client.User.UpdateOneID(u.ID).SetPassword("wtf").Save(ctx)
+	//if err != nil {
+	//	log.Fatalf("failed updating user: %w", err)
+	//}j
+	//log.Println("user was updated", u)
+	users, nextId, hasNext, err := ListUsersAfterID(ctx, client, 0, 2)
 	if err != nil {
-		log.Fatalf("failed updating user: %w", err)
+		log.Fatalf("failed listing users: %w", err)
+	}
+	if hasNext {
+		log.Println("next id", nextId)
+		for _, u := range users {
+			log.Println("user", u.ID, u.Email, u.Password)
+		}
+	}
+	users, nextId, hasNext, err = ListUsersAfterID(ctx, client, nextId, 2)
+	if err != nil {
+		log.Fatalf("failed listing users: %w", err)
+	}
+	if hasNext {
+		log.Println("2 next id", nextId)
+		for _, u := range users {
+			log.Println("2 user", u.ID, u.Email, u.Password)
+		}
 	}
-	log.Println("user was updated", u)
 
 }
+
+// afterID is the last ID from the previous page. Use 0 for the first page.
+func ListUsersAfterID(ctx context.Context, client *ent.Client, afterID, limit int) ([]*ent.User, int, bool, error) {
+	q := client.User.Query().
+		Order(user.ByID(sql.OrderAsc())).
+		Limit(limit + 1) // fetch one extra to detect "has next"
+
+	if afterID > 0 {
+		q = q.Where(user.IDGT(afterID))
+	}
+
+	rows, err := q.All(ctx)
+	if err != nil {
+		return nil, -1, false, err
+	}
+
+	hasNext := len(rows) > limit
+	if hasNext {
+		rows = rows[:limit]
+	}
+
+	var next int
+	if len(rows) > 0 {
+		last := rows[len(rows)-1].ID
+		next = last
+	}
+	return rows, next, hasNext, nil
+}