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service.go
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service.go
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package dna
import (
"context"
"strings"
"github.com/pkg/errors"
)
// Service describes the expected behavior of the DNA sequence service.
// Users can add their DNA, and check if subsequences exist.
type Service interface {
Add(ctx context.Context, user, token, sequence string) error
Check(ctx context.Context, user, token, subsequence string) error
}
// DefaultService provides our DNA sequence business logic.
type DefaultService struct {
repo Repository
valid Validator
}
var (
// ErrSubsequenceNotFound is returned by Check on a failure.
ErrSubsequenceNotFound = errors.New("subsequence doesn't appear in the DNA sequence")
// ErrBadAuth is returned if a user validation check fails.
ErrBadAuth = errors.New("bad auth")
// ErrInvalidSequence is returned if an invalid sequence is added.
ErrInvalidSequence = errors.New("invalid DNA sequence")
)
// Repository is a client-side interface, which models
// the concrete e.g. SQLiteRepository.
type Repository interface {
Insert(ctx context.Context, user, sequence string) error
Select(ctx context.Context, user string) (sequence string, err error)
}
// Validator is a client-side interface, which models
// the parts of the auth service that we use.
type Validator interface {
Validate(ctx context.Context, user, token string) error
}
// NewDefaultService returns a usable service, wrapping a repository.
func NewDefaultService(r Repository, v Validator) *DefaultService {
return &DefaultService{
repo: r,
valid: v,
}
}
// Add a user and their DNA sequence to the database.
func (s *DefaultService) Add(ctx context.Context, user, token, sequence string) (err error) {
if err := s.valid.Validate(ctx, user, token); err != nil {
return ErrBadAuth
}
if !validSequence(sequence) {
return ErrInvalidSequence
}
if err := s.repo.Insert(ctx, user, sequence); err != nil {
return errors.Wrap(err, "error adding new user")
}
return nil
}
// Check returns true if the given subsequence is present in the user's DNA.
func (s *DefaultService) Check(ctx context.Context, user, token, subsequence string) (err error) {
if err := s.valid.Validate(ctx, user, token); err != nil {
return ErrBadAuth
}
sequence, err := s.repo.Select(ctx, user)
if err != nil {
return errors.Wrap(err, "error reading DNA sequence from repository")
}
if !strings.Contains(sequence, subsequence) {
return ErrSubsequenceNotFound
}
return nil
}
func validSequence(sequence string) bool {
for _, r := range sequence {
switch r {
case 'g', 'a', 't', 'c':
continue
default:
return false
}
}
return true
}