Add cleaner handling for when entry is not found (#158)

* Add cleaner handling for when entry is not found

* Fix unit tests

handlers/paste.go

@@ -14,6 +14,7 @@ import (
 	"github.com/gorilla/mux"
 
 	"github.com/mtlynch/logpaste/random"
+	"github.com/mtlynch/logpaste/store"
 )
 
 const MaxPasteCharacters = 2 * 1000 * 1000
@@ -28,8 +29,12 @@ func (s defaultServer) pasteGet() http.HandlerFunc {
 		w.Header().Set("Content-Type", "text/plain; charset=UTF-8")
 		contents, err := s.store.GetEntry(id)
 		if err != nil {
-			log.Printf("Error retrieving entry with id %s: %v", id, err)
-			http.Error(w, "entry not found", http.StatusNotFound)
+			if _, ok := err.(store.EntryNotFoundError); ok {
+				http.Error(w, "entry not found", http.StatusNotFound)
+				return
+			}
+			log.Printf("failed to retrieve entry %s from datastore: %v", id, err)
+			http.Error(w, "failed to retrieve entry", http.StatusInternalServerError)
 			return
 		}
 		io.WriteString(w, contents)

handlers/paste_test.go

@@ -2,7 +2,6 @@ package handlers
 
 import (
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -11,6 +10,7 @@ import (
 	"testing"
 
 	"github.com/gorilla/mux"
+	"github.com/mtlynch/logpaste/store"
 )
 
 type mockStore struct {
@@ -21,7 +21,7 @@ func (ds mockStore) GetEntry(id string) (string, error) {
 	if contents, ok := ds.entries[id]; ok {
 		return contents, nil
 	}
-	return "", errors.New("not found")
+	return "", store.EntryNotFoundError{ID: id}
 }
 
 func (ds *mockStore) InsertEntry(id string, contents string) error {

store/sqlite/sqlite.go

@@ -52,6 +52,9 @@ func New() store.Store {
 func (d db) GetEntry(id string) (string, error) {
 	var contents string
 	if err := d.ctx.QueryRow("SELECT contents FROM entries WHERE id=?", id).Scan(&contents); err != nil {
+		if err == sql.ErrNoRows {
+			return "", store.EntryNotFoundError{ID: id}
+		}
 		return "", err
 	}
 	return contents, nil

store/store.go

@@ -1,6 +1,17 @@
 package store
 
+import "fmt"
+
 type Store interface {
 	GetEntry(id string) (string, error)
 	InsertEntry(id string, contents string) error
 }
+
+// EntryNotFoundError occurs when no entry exists with the given ID.
+type EntryNotFoundError struct {
+	ID string
+}
+
+func (f EntryNotFoundError) Error() string {
+	return fmt.Sprintf("could not find entry with ID=%v", f.ID)
+}