package customerverification

import (
	"context"
	"errors"
	"fmt"
	"io"

	"github.com/google/uuid"
)

var (
	ErrUnsupportedType = errors.New("unsupported file type")
	ErrInvalidSide     = errors.New("side must be 'front' or 'back'")
)

type Service struct {
	repo    Repository
	storage *Storage
}

func NewService(repo Repository, storage *Storage) *Service {
	return &Service{repo: repo, storage: storage}
}

type DocumentInput struct {
	Reader      io.Reader
	ContentType string
}

// Submit stores the front/back document images and (re)creates the
// customer's verification record in "pending" status -- including on
// resubmission after a rejection, so admins always review the latest pair.
func (s *Service) Submit(ctx context.Context, userID uuid.UUID, front, back DocumentInput) (*CustomerVerification, error) {
	frontExt, ok := allowedTypes[front.ContentType]
	if !ok {
		return nil, ErrUnsupportedType
	}
	backExt, ok := allowedTypes[back.ContentType]
	if !ok {
		return nil, ErrUnsupportedType
	}

	frontKey := uuid.NewString() + frontExt
	if err := s.storage.Save(frontKey, front.Reader); err != nil {
		return nil, fmt.Errorf("save front document: %w", err)
	}
	backKey := uuid.NewString() + backExt
	if err := s.storage.Save(backKey, back.Reader); err != nil {
		_ = s.storage.Delete(frontKey)
		return nil, fmt.Errorf("save back document: %w", err)
	}

	v := &CustomerVerification{
		ID:       uuid.New(),
		UserID:   userID,
		FrontKey: frontKey,
		BackKey:  backKey,
		Status:   StatusPending,
	}
	if err := s.repo.Upsert(ctx, v); err != nil {
		_ = s.storage.Delete(frontKey)
		_ = s.storage.Delete(backKey)
		return nil, err
	}
	return v, nil
}

func (s *Service) GetByUser(ctx context.Context, userID uuid.UUID) (*CustomerVerification, error) {
	return s.repo.FindByUserID(ctx, userID)
}

func (s *Service) Get(ctx context.Context, id uuid.UUID) (*CustomerVerification, error) {
	return s.repo.FindByID(ctx, id)
}

func (s *Service) List(ctx context.Context, status string) ([]*CustomerVerification, error) {
	return s.repo.List(ctx, status)
}

func (s *Service) Review(ctx context.Context, id uuid.UUID, status, adminNote string) (*CustomerVerification, error) {
	if !ValidStatuses[status] {
		return nil, fmt.Errorf("invalid status %q", status)
	}
	return s.repo.UpdateStatus(ctx, id, status, adminNote)
}

// IsApproved satisfies orders.VerificationChecker: an unsubmitted customer
// (no row at all) is simply "not approved yet", not an error.
func (s *Service) IsApproved(ctx context.Context, userID uuid.UUID) (bool, error) {
	v, err := s.repo.FindByUserID(ctx, userID)
	if errors.Is(err, ErrNotFound) {
		return false, nil
	}
	if err != nil {
		return false, err
	}
	return v.Status == StatusApproved, nil
}

// DocumentPath resolves which side of a verification record to read from
// disk, for the handler to stream after checking the caller is authorized.
func (s *Service) DocumentPath(v *CustomerVerification, side string) (string, error) {
	switch side {
	case "front":
		return s.storage.Path(v.FrontKey), nil
	case "back":
		return s.storage.Path(v.BackKey), nil
	default:
		return "", ErrInvalidSide
	}
}