From 94a3f414e4df2f690563d2c631d250cb6028519a Mon Sep 17 00:00:00 2001
From: Gabriel Kaszewski <gabrielkaszewski@gmail.com>
Date: Thu, 14 May 2026 03:16:22 +0200
Subject: [PATCH] feat(domain): errors and value objects

---
 crates/domain/src/errors.rs        |  17 +++++
 crates/domain/src/lib.rs           |   3 +
 crates/domain/src/value_objects.rs | 117 +++++++++++++++++++++++++++++
 3 files changed, 137 insertions(+)
 create mode 100644 crates/domain/src/errors.rs
 create mode 100644 crates/domain/src/value_objects.rs

diff --git a/crates/domain/src/errors.rs b/crates/domain/src/errors.rs
new file mode 100644
index 0000000..f8a6af5
--- /dev/null
+++ b/crates/domain/src/errors.rs
@@ -0,0 +1,17 @@
+use thiserror::Error;
+
+#[derive(Debug, Error, Clone)]
+pub enum DomainError {
+    #[error("not found")]
+    NotFound,
+    #[error("unauthorized")]
+    Unauthorized,
+    #[error("forbidden")]
+    Forbidden,
+    #[error("conflict: {0}")]
+    Conflict(String),
+    #[error("invalid input: {0}")]
+    InvalidInput(String),
+    #[error("internal error: {0}")]
+    Internal(String),
+}
diff --git a/crates/domain/src/lib.rs b/crates/domain/src/lib.rs
index e69de29..fa5d165 100644
--- a/crates/domain/src/lib.rs
+++ b/crates/domain/src/lib.rs
@@ -0,0 +1,3 @@
+pub mod errors;
+pub mod value_objects;
+// remaining modules added in later tasks
diff --git a/crates/domain/src/value_objects.rs b/crates/domain/src/value_objects.rs
new file mode 100644
index 0000000..927b304
--- /dev/null
+++ b/crates/domain/src/value_objects.rs
@@ -0,0 +1,117 @@
+use uuid::Uuid;
+use crate::errors::DomainError;
+
+macro_rules! uuid_id {
+    ($name:ident) => {
+        #[derive(Debug, Clone, PartialEq, Eq, Hash, serde::Serialize, serde::Deserialize)]
+        pub struct $name(Uuid);
+        impl $name {
+            pub fn new() -> Self { Self(Uuid::new_v4()) }
+            pub fn from_uuid(u: Uuid) -> Self { Self(u) }
+            pub fn as_uuid(&self) -> Uuid { self.0 }
+        }
+        impl Default for $name {
+            fn default() -> Self { Self::new() }
+        }
+        impl std::fmt::Display for $name {
+            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+                write!(f, "{}", self.0)
+            }
+        }
+    };
+}
+
+uuid_id!(UserId);
+uuid_id!(ThoughtId);
+uuid_id!(LikeId);
+uuid_id!(BoostId);
+uuid_id!(ApiKeyId);
+uuid_id!(NotificationId);
+
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+pub struct Username(String);
+impl Username {
+    pub fn new(s: impl Into<String>) -> Result<Self, DomainError> {
+        let s = s.into();
+        if s.is_empty() || s.len() > 32 {
+            return Err(DomainError::InvalidInput("username: 1-32 chars".into()));
+        }
+        if !s.chars().all(|c| c.is_alphanumeric() || c == '_') {
+            return Err(DomainError::InvalidInput("username: alphanumeric or underscore only".into()));
+        }
+        Ok(Self(s))
+    }
+    pub fn from_trusted(s: String) -> Self { Self(s) }
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+impl std::fmt::Display for Username {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { write!(f, "{}", self.0) }
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+pub struct Email(String);
+impl Email {
+    pub fn new(s: impl Into<String>) -> Result<Self, DomainError> {
+        let s = s.into().to_lowercase();
+        if !s.contains('@') || s.len() > 255 {
+            return Err(DomainError::InvalidInput("invalid email".into()));
+        }
+        Ok(Self(s))
+    }
+    pub fn from_trusted(s: String) -> Self { Self(s) }
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+
+#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+pub struct PasswordHash(pub String);
+
+#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+pub struct Content(String);
+impl Content {
+    pub fn new_local(s: impl Into<String>) -> Result<Self, DomainError> {
+        let s = s.into();
+        if s.is_empty() || s.len() > 128 {
+            return Err(DomainError::InvalidInput("content: 1-128 chars".into()));
+        }
+        Ok(Self(s))
+    }
+    pub fn new_remote(s: impl Into<String>) -> Self { Self(s.into()) }
+    pub fn as_str(&self) -> &str { &self.0 }
+}
+impl std::fmt::Display for Content {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { write!(f, "{}", self.0) }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn username_rejects_empty() {
+        assert!(Username::new("").is_err());
+    }
+    #[test]
+    fn username_rejects_too_long() {
+        assert!(Username::new("a".repeat(33)).is_err());
+    }
+    #[test]
+    fn username_rejects_invalid_chars() {
+        assert!(Username::new("hello world").is_err());
+    }
+    #[test]
+    fn username_accepts_valid() {
+        assert!(Username::new("hello_123").is_ok());
+    }
+    #[test]
+    fn content_local_rejects_over_128() {
+        assert!(Content::new_local("a".repeat(129)).is_err());
+    }
+    #[test]
+    fn content_local_accepts_128() {
+        assert!(Content::new_local("a".repeat(128)).is_ok());
+    }
+    #[test]
+    fn email_rejects_no_at() {
+        assert!(Email::new("notanemail").is_err());
+    }
+}