Add email validation.

Cargo.lock

@@ -2646,6 +2646,28 @@ dependencies = [
  "rand",
 ]
 
+[[package]]
+name = "validator"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "841d6937c33ec6039d8071bcf72933146b5bbe378d645d8fa59bdadabfc2a249"
+dependencies = [
+ "idna",
+ "lazy_static",
+ "regex",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "url",
+ "validator_types",
+]
+
+[[package]]
+name = "validator_types"
+version = "0.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ad9680608df133af2c1ddd5eaf1ddce91d60d61b6bc51494ef326458365a470a"
+
 [[package]]
 name = "vcpkg"
 version = "0.2.10"
@@ -2913,4 +2935,5 @@ dependencies = [
  "tracing-subscriber",
  "unicode-segmentation",
  "uuid",
+ "validator",
 ]

Cargo.toml

@@ -29,6 +29,7 @@ tracing-log = "0.1.1"
 tracing-actix-web = "0.2.0"
 serde-aux = "1.0.1"
 unicode-segmentation = "1.7.1"
+validator = "0.12.0"
 
 [dev-dependencies]
 reqwest = { version = "0.10.7", features = ["json"] }

src/domain/mod.rs

@@ -0,0 +1,6 @@
+mod subscriber_name;
+mod subscriber_email;
+mod new_subscriber;
+
+pub use subscriber_name::SubscriberName;
+pub use new_subscriber::NewSubscriber;

src/domain/new_subscriber.rs

@@ -0,0 +1,6 @@
+use crate::domain::subscriber_name::SubscriberName;
+
+pub struct NewSubscriber {
+    pub email: String,
+    pub name: SubscriberName,
+}

src/domain/subscriber_email.rs

@@ -0,0 +1,44 @@
+use validator::validate_email;
+
+#[derive(Debug)]
+pub struct SubscriberEmail(String);
+
+impl SubscriberEmail {
+    pub fn parse(s: String) -> Result<SubscriberEmail, String> {
+        if validate_email(&s) {
+            Ok(Self(s))
+        } else {
+            Err(format!("{} is not a valid subscriber email.", s))
+        }
+    }
+}
+
+impl AsRef<str> for SubscriberEmail {
+    fn as_ref(&self) -> &str {
+        &self.0
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::SubscriberEmail;
+    use claim::assert_err;
+
+    #[test]
+    fn empty_string_is_rejected() {
+        let email = "".to_string();
+        assert_err!(SubscriberEmail::parse(email));
+    }
+
+    #[test]
+    fn email_missing_at_symbol_is_rejected() {
+        let email = "ursuladomain.com".to_string();
+        assert_err!(SubscriberEmail::parse(email));
+    }
+
+    #[test]
+    fn email_missing_subject_is_rejected() {
+        let email = "@domain.com".to_string();
+        assert_err!(SubscriberEmail::parse(email));
+    }
+}

src/domain/subscriber_name.rs

@@ -1,16 +1,11 @@
 use unicode_segmentation::UnicodeSegmentation;
 
-pub struct NewSubscriber {
-    pub email: String,
-    pub name: SubscriberName,
-}
-
 #[derive(Debug)]
 pub struct SubscriberName(String);
 
 impl SubscriberName {
     /// Returns an instance of `SubscriberName` if the input satisfies all
-    /// our validation constraints on subscriber names.  
+    /// our validation constraints on subscriber names.
     /// It panics otherwise.
     pub fn parse(s: String) -> Result<SubscriberName, String> {
         // `.trim()` returns a view over the input `s` without trailing