package rest

import (
	"context"
	"crypto/rand"
	"log/slog"
	"math/big"
	"strings"

	"goAuth/internal/user"
)

const (
	AdminLogin            = "admin"
	adminPasswordLength   = 16
	adminPasswordAlphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789"
)

// seed creates the initial admin user with a random password, but only on the
// first startup when no users exist yet.
func seed(ctx context.Context, users *user.Service) error {
	count, err := users.CountUsers(ctx, true)
	if err != nil {
		return err
	}
	if count > 0 {
		return nil
	}

	password, err := generatePassword(adminPasswordLength)
	if err != nil {
		return err
	}

	admin, err := users.CreateAdmin(ctx, AdminLogin, password)
	if err != nil {
		return err
	}

	slog.Info("seeded admin user",
		slog.String("op", "rest.seed"),
		slog.Int64("user_id", admin.Id),
		slog.String("login", admin.Login),
		slog.String("password", password),
	)

	return nil
}

func generatePassword(length int) (string, error) {
	alphabetLen := big.NewInt(int64(len(adminPasswordAlphabet)))

	var builder strings.Builder
	builder.Grow(length)

	for range length {
		randIndex, err := rand.Int(rand.Reader, alphabetLen)
		if err != nil {
			slog.Error("generate admin password", slog.String("op", "rest.generatePassword"), slog.Any("error", err))
			return "", err
		}
		builder.WriteByte(adminPasswordAlphabet[randIndex.Int64()])
	}

	return builder.String(), nil
}