// Command createuser inserts a users row with an operator-chosen id, bypassing
// the normal users_id_seq auto-assignment. This works because users.id is
// GENERATED BY DEFAULT AS IDENTITY (not GENERATED ALWAYS) -- an explicit id in
// the INSERT is honored, the same mechanism ensureOfficialSystemUserWithDB
// (internal/store/postgres/message_send.go) already relies on to seed the
// built-in system accounts (ChatBot, BotFather, ...) at their fixed ids.
//
// Normal signup (auth.signUp) never lets a caller pick an id, so this exists
// purely for local/dev tooling -- reserving a specific low id (below
// OfficialSystemUserID=777000, say) for a test account.
//
// Usage:
//
//	createuser -id 1000 [-first-name Test] [-last-name User] [-username testuser] -phone "15550001234"
//	createuser -id 1000 [-first-name Test] [-last-name User] [-username testuser] -email "test@example.com"
//
// -phone and -email are mutually exclusive: an email-signup account never
// stores the address in users.phone directly (see internal/domain/emailphone.go)
// -- it gets a synthetic "888"-prefixed display phone instead (the same one
// assignEmailSignupDisplayPhone hands a real email-signup account), with the
// real address recorded separately in signup_email.
//
// Reads TELESRV_POSTGRES_DSN the same way the server does (internal/config).
package main

import (
	"context"
	"crypto/rand"
	"encoding/binary"
	"errors"
	"flag"
	"fmt"
	"os"
	"time"

	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"
	"github.com/jackc/pgx/v5/pgxpool"

	"telesrv/internal/config"
	"telesrv/internal/domain"
)

// maxEmailSignupPhoneAttempts bounds the display-phone collision-retry loop,
// mirroring internal/app/auth/service.go's own constant of the same name.
const maxEmailSignupPhoneAttempts = 20

func randomInt64() (int64, error) {
	var b [8]byte
	if _, err := rand.Read(b[:]); err != nil {
		return 0, fmt.Errorf("rand: %w", err)
	}
	return int64(binary.LittleEndian.Uint64(b[:])), nil
}

func main() {
	id := flag.Int64("id", 0, "user id to create (required)")
	firstName := flag.String("first-name", "Test", "first name")
	lastName := flag.String("last-name", "", "last name")
	username := flag.String("username", "", "username, without @ (optional)")
	phone := flag.String("phone", "", "phone number (optional; mutually exclusive with -email)")
	email := flag.String("email", "", "email address for an email-signup account (optional; mutually exclusive with -phone)")
	force := flag.Bool("force", false, "skip the reserved-id / sequence-collision safety checks")
	flag.Parse()

	if *id <= 0 {
		fmt.Fprintln(os.Stderr, "createuser: -id is required and must be positive")
		os.Exit(2)
	}
	if *phone != "" && *email != "" {
		fmt.Fprintln(os.Stderr, "createuser: -phone and -email are mutually exclusive")
		os.Exit(2)
	}
	if !*force {
		if domain.IsSystemUserID(*id) {
			fmt.Fprintf(os.Stderr, "createuser: %d is a reserved built-in system account id (see internal/domain/system.go) - refusing, pass -force to override\n", *id)
			os.Exit(2)
		}
		if *id >= domain.UserIDSequenceBase {
			fmt.Fprintf(os.Stderr, "createuser: %d is >= UserIDSequenceBase (%d) - a future organic signup could eventually collide with it; pass -force to proceed anyway (then consider bumping users_id_seq yourself)\n", *id, domain.UserIDSequenceBase)
			os.Exit(2)
		}
	}

	cfg, err := config.Load()
	if err != nil {
		fmt.Fprintf(os.Stderr, "createuser: load config: %v\n", err)
		os.Exit(1)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Second)
	defer cancel()

	pool, err := pgxpool.New(ctx, cfg.PostgresDSN)
	if err != nil {
		fmt.Fprintf(os.Stderr, "createuser: connect: %v\n", err)
		os.Exit(1)
	}
	defer pool.Close()

	accessHash, err := randomInt64()
	if err != nil {
		fmt.Fprintf(os.Stderr, "createuser: %v\n", err)
		os.Exit(1)
	}

	displayPhone := *phone
	signupEmail := ""
	if *email != "" {
		signupEmail = domain.NormalizeEmailForPhone(*email)
		displayPhone, err = assignEmailSignupDisplayPhone(ctx, pool)
		if err != nil {
			fmt.Fprintf(os.Stderr, "createuser: %v\n", err)
			os.Exit(1)
		}
	}

	// phone/username/signup_email all sit under partial unique indexes that
	// exclude '', so leaving any of them blank never collides with another
	// blank-valued account.
	row := pool.QueryRow(ctx, `
		INSERT INTO users (id, access_hash, phone, signup_email, first_name, last_name, username, country_code)
		VALUES ($1, $2, $3, $4, $5, $6, $7, '')
		ON CONFLICT (id) DO NOTHING
		RETURNING id`,
		*id, accessHash, displayPhone, signupEmail, *firstName, *lastName, *username)

	var createdID int64
	if err := row.Scan(&createdID); err != nil {
		fmt.Fprintln(os.Stderr, describeInsertFailure(*id, *username, displayPhone, signupEmail, err))
		os.Exit(1)
	}

	fmt.Printf("created user id=%d access_hash=%d first_name=%q last_name=%q username=%q phone=%q signup_email=%q\n",
		createdID, accessHash, *firstName, *lastName, *username, displayPhone, signupEmail)
}

// describeInsertFailure turns the INSERT's failure into a message naming the
// actual thing that collided, instead of "id already exists" for every case:
// ON CONFLICT (id) DO NOTHING only covers the id itself, so a duplicate
// username/phone/signup_email surfaces here as a distinct unique-violation
// error (pgx.ErrNoRows only means the id itself was the conflict).
func describeInsertFailure(id int64, username, phone, signupEmail string, err error) string {
	var pgErr *pgconn.PgError
	if errors.As(err, &pgErr) && pgErr.Code == "23505" {
		switch pgErr.ConstraintName {
		case "users_username_lower_unique_idx":
			return fmt.Sprintf("createuser: username %q is already taken", username)
		case "users_phone_unique_idx":
			return fmt.Sprintf("createuser: phone %q is already in use", phone)
		case "users_signup_email_lower_unique_idx":
			return fmt.Sprintf("createuser: email %q is already in use by another account", signupEmail)
		default:
			return fmt.Sprintf("createuser: unique constraint %q violated: %v", pgErr.ConstraintName, err)
		}
	}
	if errors.Is(err, pgx.ErrNoRows) {
		return fmt.Sprintf("createuser: id %d already exists", id)
	}
	return fmt.Sprintf("createuser: insert failed: %v", err)
}

// assignEmailSignupDisplayPhone mirrors internal/app/auth/service.go's method
// of the same name: pick a random "888"-prefixed display phone and re-roll on
// the astronomically unlikely collision with an existing account's phone.
func assignEmailSignupDisplayPhone(ctx context.Context, pool *pgxpool.Pool) (string, error) {
	for range maxEmailSignupPhoneAttempts {
		candidate, err := domain.NewEmailSignupDisplayPhone(domain.EmailPhonePrefix)
		if err != nil {
			return "", err
		}
		var exists bool
		if err := pool.QueryRow(ctx, `SELECT EXISTS (SELECT 1 FROM users WHERE phone = $1)`, candidate).Scan(&exists); err != nil {
			return "", fmt.Errorf("check display phone collision: %w", err)
		}
		if !exists {
			return candidate, nil
		}
	}
	return "", fmt.Errorf("assign email signup display phone: exhausted %d attempts", maxEmailSignupPhoneAttempts)
}