challenge-1-validate.diff

diff --git a/internal/dna/service.go b/internal/dna/service.go
index a23237a..9a58af8 100644
--- a/internal/dna/service.go
+++ b/internal/dna/service.go
@@ -6,6 +6,7 @@ import (
        "strings"
 
        "github.com/pkg/errors"
+       "regexp"
 )
 
 var (
@@ -14,6 +15,8 @@ var (
 
        // ErrBadAuth is returned if a user validation check fails.
        ErrBadAuth = errors.New("bad auth")
+
+       ErrValidationFailed = errors.New("sequence does not appear to be a valid DNA sequence")
 )
 
 // Service provides the API.
@@ -72,6 +75,17 @@ func (s *Service) Check(user, token, subsequence string) error {
        return nil
 }
 
+func (s *Service) Validate(user, token, sequence string) error {
+       if err := s.valid.Validate(user, token); err != nil {
+               return ErrBadAuth
+       }
+       validationRE := regexp.MustCompile(`^[atgc]+$`)
+       if !validationRE.MatchString(sequence) {
+               return ErrValidationFailed
+       }
+       return nil
+}
+
 // ServeHTTP implements http.Handler in a very naïve way.
 func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
        var (
@@ -111,6 +125,23 @@ func (s *Service) ServeHTTP(w http.ResponseWriter, r *http.Request) {
                        http.Error(w, err.Error(), http.StatusInternalServerError)
                }
 
+       case method == "GET" && first == "validate":
+               var (
+                       user        = r.URL.Query().Get("user")
+                       token       = r.URL.Query().Get("token")
+                       sequence = r.URL.Query().Get("sequence")
+               )
+               switch err := s.Validate(user, token, sequence); true {
+               case err == nil:
+                       fmt.Fprintln(w, "Sequence is valid")
+               case err == ErrValidationFailed:
+                       http.Error(w, err.Error(), http.StatusNotAcceptable)
+               case err == ErrBadAuth:
+                       http.Error(w, err.Error(), http.StatusUnauthorized)
+               default:
+                       http.Error(w, err.Error(), http.StatusInternalServerError)
+               }
+
        default:
                http.NotFound(w, r)
        }
diff --git a/internal/dna/service_test.go b/internal/dna/service_test.go
index e73f576..db84859 100644
--- a/internal/dna/service_test.go
+++ b/internal/dna/service_test.go
@@ -38,6 +38,27 @@ func TestFlow(t *testing.T) {
        }
 }
 
+func TestService_Validate(t *testing.T) {
+       var (
+               repo  = newMockRepo()
+               user  = "vincent"
+               token = "some_token"
+               valid = newMockValidator(user, token)
+               s     = NewService(repo, valid)
+       )
+
+       for sequence, want := range map[string]error {
+               "": ErrValidationFailed,
+               "a": nil,
+               "acgt": nil,
+               "acgtx": ErrValidationFailed,
+       }{
+               if have := s.Validate(user, token, sequence); want != have {
+                       t.Errorf("Validate(%q): want %v, have %v", sequence, want, have)
+               }
+       }
+}
+
 type mockRepo struct {
        dna map[string]string
 }