go__ent_demo/main.go

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"strings"
	"time"

	"code.osinet.fr/fgm/entdemo/ent"
	"code.osinet.fr/fgm/entdemo/ent/car"
	"code.osinet.fr/fgm/entdemo/ent/group"
	"code.osinet.fr/fgm/entdemo/ent/user"

	_ "github.com/mattn/go-sqlite3"
)

func CreateUser(ctx context.Context, client *ent.Client) (*ent.User, error) {
	u, err := client.User.
		Create().
		SetAge(30).
		SetName("a8m").
		Save(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed creating user: %w", err)
	}
	log.Println("user was created: ", u)
	return u, nil
}

func QueryUser(ctx context.Context, client *ent.Client) (*ent.User, error) {
	const name = "a8m"
	u, err := client.User.
		Query().
		Where(user.NameEQ(name)).
		// "Only" fails if no user found or more than 1 user returned.
		Only(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed querying user %s: %w", name, err)
	}
	log.Println("user returned: ", u)
	return u, nil
}

func CreateCars(ctx context.Context, client *ent.Client) (*ent.User, error) {
	var err error
	name := "tesla"
	tesla, err := client.Car.
		Create().
		SetModel(name).
		SetRegisteredAt(time.Now()).
		Save(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed creating %s car: %v", name, err)
	}
	log.Println("car was created: ", tesla)

	name = "ford"
	ford, err := client.Car.
		Create().
		SetModel(name).
		SetRegisteredAt(time.Now()).
		Save(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed creating %s car: %v", name, err)
	}
	log.Println("car was created: ", ford)

	u, err := QueryUser(ctx, client)
	if err != nil {
		return nil, fmt.Errorf("failed looking for user: %w", err)
	}
	u.Update().
		AddCars(tesla, ford).
		Save(ctx)
	if err != nil {
		return nil, fmt.Errorf("failed adding cards to user: %w", err)
	}
	return u, nil
}

func QueryCars(ctx context.Context, user *ent.User) error {
	cars, err := user.QueryCars().
		All(ctx)
	if err != nil {
		return fmt.Errorf("failed querying user %s cars: %w", user.Name, err)
	}
	log.Println("returned all cars: ", cars)

	ford, err := user.QueryCars().
		Where(car.ModelEQ("ford")).
		Only(ctx)
	if err != nil {
		return fmt.Errorf("failed searching for ford cars: %w", err)
	}
	log.Println("filtered cars: ", ford)
	return nil
}

func QueryCarUsers(ctx context.Context, u *ent.User) error {
	cars, err := u.QueryCars().All(ctx)
	if err != nil {
		return fmt.Errorf("failed querying user %s cars: %w", u.Name, err)
	}
	log.Println("returned all cars: ", cars)

	// query the inverse edge
	for _, car := range cars {
		owner, err := car.QueryOwner().Only(ctx)
		if err != nil {
			return fmt.Errorf("failed querying cat %s owner: %v", car.Model, err)
		}
		log.Printf("card %s owner: %q\n", car.Model, owner.Name)
	}
	return nil
}

func Open() (*ent.Client, error) {
	const db = "ent.db"
	err := os.Remove(db)
	if err != nil {
		pathErr, ok := err.(*os.PathError)
		if !ok {
			log.Fatalf("os.Remove returned a non-PathError: %w", err)
		}
		log.Printf("Error removing database: %s", pathErr.Error())
	}
	// Running client.Schema.Create will panic is DB exists already.
	client, err := ent.Open("sqlite3", strings.Join([]string{
		"file:",
		db,
		"?mode=rwc&cache=shared&_fk=1",
	},
		"",
	))
	// client, err := ent.Open("sqlite3", "file:ent?mode=memory&cache=shared&_fk=1")
	return client, err
}

func BasicDemo(ctx context.Context, client *ent.Client) {
	u, err := CreateUser(ctx, client)
	if err != nil {
		panic(err)
	}
	_, err = QueryUser(ctx, client)
	if err != nil {
		panic(err)
	}
	_, err = CreateCars(ctx, client)
	if err != nil {
		panic(err)
	}
	err = QueryCars(ctx, u)
	if err != nil {
		panic(err)
	}
	err = QueryCarUsers(ctx, u)
	if err != nil {
		panic(err)
	}
}

func CreateGraph(ctx context.Context, client *ent.Client) error {
	ariel, err := client.User.
		Create().
		SetAge(30).
		SetName("ariel").
		Save(ctx)
	if err != nil {
		return err
	}
	neta, err := client.User.
		Create().
		SetAge(28).
		SetName("neta").
		Save(ctx)
	if err != nil {
		return err
	}
	// then, create the cars, and attach them to the users in the creation.
	_, err = client.Car.
		Create().
		SetModel("tesla").
		SetRegisteredAt(time.Now()). // ignore the time in the graph.
		SetOwner(ariel). // attach this graph to Ariel.
		Save(ctx)
	if err != nil {
		return err
	}
	_, err = client.Car.
		Create().
		SetModel("mazda").
		SetRegisteredAt(time.Now()). // ignore the time in the graph.
		SetOwner(ariel). // attach this graph to Ariel.
		Save(ctx)
	if err != nil {
		return err
	}
	_, err = client.Car.
		Create().
		SetModel("ford").
		SetRegisteredAt(time.Now()).
		SetOwner(neta).
		Save(ctx)
	if err != nil {
		return err
	}

	// create the groups, and add their users in the creation.
	_, err = client.Group.
		Create().
		SetName("GitLab").
		AddUsers(neta, ariel).
		Save(ctx)
	if err != nil {
		return err
	}
	_, err = client.Group.
		Create().
		SetName("GitHub").
		AddUsers(ariel).
		Save(ctx)
	if err != nil {
		return err
	}
	log.Println("The graph was created successfully")

	return nil
}

func QueryGithub(ctx context.Context, client *ent.Client) error {
	const name = "GitHub"
	cars, err := client.Group.
		Query().
		Where(group.Name(name)). // (Group(Name=GitHub),)
		QueryUsers(). // (User(Name=Ariel, Age=30),)
		QueryCars(). // (Car(Model=Tesla, RegisteredAt=<Time>), Car(Model=Mazda, RegisteredAt=<Time>),)
		All(ctx)
	if err != nil {
		return fmt.Errorf("failed getting %s cars: %w", name, err)
	}
	log.Println("cars returned: ", cars)
	// Output: (Car(Model=tesla, RegisteredAt=<Time>), Car(Model=mazda, RegisteredAt=<Time>),)
	return nil
}

// Get the cars of the users of all users in Ariel groups, except for the Mazda.
func QueryAriel(ctx context.Context, client *ent.Client) error {
	const name = "ariel"
	// First get user ariel
	ariel := client.User.
		Query().
		Where(
			user.HasCars(), // Useless ?
			user.Name(name),
		).
		OnlyX(ctx)

	cars, err := ariel.
		QueryGroups(). // Get Ariel's groups
		QueryUsers(). // Get the users in those groups
		QueryCars(). // Get the cars of the users in those groups
		Where(
			car.Not(
				car.ModelEQ("mazda"),
			),
		).
		All(ctx)
	if err != nil {
		return fmt.Errorf("failed getting %s cars: %w", name, err)
	}
	log.Println("cars returned: ", cars)
	// Output: (Car(Model=tesla, RegisteredAt=<Time>), Car(Model=ford, RegisteredAt=<Time>),)
	return nil
}

func QueryGroupsWithUsers(ctx context.Context, client *ent.Client) error {
	groups, err := client.Group.
		Query().
		Where(
			group.HasUsers(),
		).
		All(ctx)
	if err != nil {
		return fmt.Errorf("failed gettings groups with users: %w", err)
	}
	log.Println("groups with users: ", groups)
	return nil
}

func main() {
	client, err := Open()
	if err != nil {
		log.Fatalf("failed opening connection to sqlite: %v", err)
	}
	defer client.Close()

	// Run the auto-migration tool.
	if err := client.Schema.Create(context.Background()); err != nil {
		log.Fatalf("failed creating schema resources: %v", err)
	}

	bg := context.Background()
	// BasicDemo(bg, client)

	CreateGraph(bg, client)
	QueryGithub(bg, client)
	QueryAriel(bg, client)
	QueryGroupsWithUsers(bg, client)
}