Add check for whether user needs content downloaded

persistence/user_queries.go

@@ -146,3 +146,42 @@ func (p Profile) GetUserByID(id scraper.UserID) (scraper.User, error) {
     }
     return ret, err
 }
+
+/**
+ * Returns `true` if content download is needed, `false` otherwise
+ *
+ * If:
+ * - the user isn't in the DB at all (first time scraping), OR
+ * - `is_content_downloaded` is false in the DB, OR
+ * - the banner / profile image URL has changed from what the DB has
+ * then it needs to be downloaded.
+ *
+ * The `user` object will always have `is_content_downloaded` = false on every scrape.  This is
+ * why the No Worsening Principle is needed.
+ */
+func (p Profile) CheckUserContentDownloadNeeded(user scraper.User) bool {
+    row := p.DB.QueryRow(`select is_content_downloaded, profile_image_url, banner_image_url from users where id = ?`, user.ID)
+
+    var is_content_downloaded bool
+    var profile_image_url string
+    var banner_image_url string
+    err := row.Scan(&is_content_downloaded, &profile_image_url, &banner_image_url)
+    if err != nil {
+        if err == sql.ErrNoRows {
+            return true
+        } else {
+            panic(err)
+        }
+    }
+
+    if !is_content_downloaded {
+        return true
+    }
+    if banner_image_url != user.BannerImageUrl {
+        return true
+    }
+    if profile_image_url != user.ProfileImageUrl {
+        return true
+    }
+    return false
+}

persistence/user_queries_test.go

@@ -81,3 +81,52 @@ func TestUserExists(t *testing.T) {
 		t.Errorf("It should exist, but it doesn't: %d", user.ID)
 	}
 }
+
+/**
+ * Test scenarios relating to user content downloading
+ */
+func TestCheckUserContentDownloadNeeded(t *testing.T) {
+	profile_path := "test_profiles/TestUserQueries"
+	profile := create_or_load_profile(profile_path)
+
+	user := create_dummy_user()
+
+	// If user is not in database, should be "yes" automatically
+	if profile.CheckUserContentDownloadNeeded(user) != true {
+		t.Errorf("Non-saved user should always require content download")
+	}
+
+	// Save the user, but `is_content_downloaded` is still "false"
+	user.BannerImageUrl = "banner url1"
+	user.ProfileImageUrl = "profile url1"
+	user.IsContentDownloaded = false
+	err := profile.SaveUser(user)
+	if err != nil {
+		panic(err)
+	}
+
+	// If is_content_downloaded is false, then it needs download
+	if profile.CheckUserContentDownloadNeeded(user) != true {
+		t.Errorf("Non-downloaded user should require download")
+	}
+
+	// Mark `is_content_downloaded` as "true" again
+	user.IsContentDownloaded = true
+	err = profile.SaveUser(user)
+	if err != nil {
+		panic(err)
+	}
+
+	// If everything is up to date, no download should be required
+	if profile.CheckUserContentDownloadNeeded(user) != false {
+		t.Errorf("Up-to-date user shouldn't need a download")
+	}
+
+	// Change an URL, but don't save it-- needs to be different from what's in the DB
+	user.BannerImageUrl = "banner url2"
+
+	// Download needed for new banner image
+	if profile.CheckUserContentDownloadNeeded(user) != true {
+		t.Errorf("If banner image changed, user should require another download")
+	}
+}