package auth

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"errors"

	"codeberg.org/nextgo/dbots/internal/db"
	"codeberg.org/nextgo/dbots/internal/discord"
	"github.com/jackc/pgx/v5"
)

// todo: api keysssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssssss
// or sessions????????????
type Service struct {
	q      *db.Queries
	client *discord.Client
}

func NewService(q *db.Queries, client *discord.Client) *Service {
	return &Service{q: q, client: client}
}

// GenerateState produces a random OAuth state parameter.
func GenerateState() (string, error) {
	b := make([]byte, 16)
	if _, err := rand.Read(b); err != nil {
		return "", err
	}
	return base64.URLEncoding.EncodeToString(b), nil
}

// Callback handles the OAuth callback: exchanges the code, fetches the user,
// and upserts them in the database. Returns the local db.User.
func (s *Service) Callback(ctx context.Context, code string) (*db.User, error) {
	token, err := s.client.ExchangeCode(ctx, code)
	if err != nil {
		return nil, err
	}

	dUser, err := s.client.GetCurrentUser(ctx, token.AccessToken)
	if err != nil {
		return nil, err
	}

	user, err := s.q.UpdateUser(ctx, db.UpdateUserParams{
		ID:       dUser.ID,
		Username: &dUser.Username,
	})
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			user, err = s.q.CreateUser(ctx, db.CreateUserParams{
				ID:       dUser.ID,
				Username: dUser.Username,
			})
			if err != nil {
				return nil, err
			}
		}
		return nil, err
	}

	return user, nil
}