1 files changed, 171 insertions, 0 deletions
diff --git a/src/types/repository.rs b/src/types/repository.rs
new file mode 100644
index 0000000..0bef30e
--- /dev/null
+++ b/src/types/repository.rs
@@ -0,0 +1,171 @@
+use async_trait::async_trait;
+use std::collections::HashMap;
+use std::sync::Mutex;
+use ulid::Generator;
+
+use super::*;
+
+#[derive(Debug, thiserror::Error)]
+pub enum RepoError {
+    #[error("parent account {0} not found")]
+    ParentNotFound(AccountId),
+}
+
+#[async_trait]
+pub trait AccountRepository: Send + Sync {
+    async fn create(&self, new: NewAccount) -> Result<Account, RepoError>;
+    async fn get(&self, id: AccountId) -> Result<Option<Account>, RepoError>;
+}
+
+#[derive(Default)]
+pub struct InMemoryAccountRepository {
+    accounts: Mutex<HashMap<AccountId, Account>>,
+    generator: Mutex<Generator>,
+}
+
+#[async_trait]
+impl AccountRepository for InMemoryAccountRepository {
+    async fn create(&self, new: NewAccount) -> Result<Account, RepoError> {
+        let id = {
+            let mut generator = self.generator.lock().unwrap();
+            // generate() is monotonic; on the rare same-tick random overflow,
+            // recover into a valid (incremented) Ulid rather than failing.
+            let ulid = generator
+                .generate()
+                .unwrap_or_else(|overflow| overflow.commit_overflow_increment());
+            AccountId::from_ulid(ulid)
+        };
+
+        let mut accounts = self.accounts.lock().unwrap();
+
+        let path = match new.parent {
+            Some(parent_id) => accounts
+                .get(&parent_id)
+                .ok_or(RepoError::ParentNotFound(parent_id))?
+                .path
+                .with_child(id),
+            None => MaterializedPath::root(id),
+        };
+
+        let account =
+            Account::from_parts(id, new.account_type, new.name, new.description, path);
+        accounts.insert(id, account.clone());
+        Ok(account)
+    }
+
+    async fn get(&self, id: AccountId) -> Result<Option<Account>, RepoError> {
+        Ok(self.accounts.lock().unwrap().get(&id).cloned())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn new_account(
+        account_type: AccountType,
+        name: &str,
+        parent: Option<AccountId>,
+    ) -> NewAccount {
+        NewAccount {
+            account_type,
+            name: name.into(),
+            description: String::new(),
+            parent,
+        }
+    }
+
+    // Seed the five standard chart-of-accounts roots, each with no parent.
+    async fn seed_roots(repo: &InMemoryAccountRepository) -> Vec<Account> {
+        let roots = [
+            (AccountType::Asset, "Assets"),
+            (AccountType::Liability, "Liabilities"),
+            (AccountType::Equity, "Equity"),
+            (AccountType::Revenue, "Revenue"),
+            (AccountType::Expense, "Expenses"),
+        ];
+        let mut created = Vec::new();
+        for (account_type, name) in roots {
+            let account = repo
+                .create(new_account(account_type, name, None))
+                .await
+                .unwrap();
+            created.push(account);
+        }
+        created
+    }
+
+    #[tokio::test]
+    async fn seeds_five_distinct_root_accounts() {
+        let repo = InMemoryAccountRepository::default();
+        let roots = seed_roots(&repo).await;
+
+        assert_eq!(roots.len(), 5);
+
+        // each root's path is just its own id — depth 1, no parent segment
+        for root in &roots {
+            assert_eq!(root.path.depth(), 1);
+        }
+
+        // all five ids are distinct
+        let mut ids: Vec<AccountId> = roots.iter().map(|a| a.id()).collect();
+        ids.sort();
+        ids.dedup();
+        assert_eq!(ids.len(), 5);
+    }
+
+    #[tokio::test]
+    async fn child_nests_under_its_parent() {
+        let repo = InMemoryAccountRepository::default();
+        let roots = seed_roots(&repo).await;
+        let assets = &roots[0];
+
+        let cash = repo
+            .create(new_account(AccountType::Asset, "Cash", Some(assets.id())))
+            .await
+            .unwrap();
+
+        // the child's path was built from the parent's
+        assert!(assets.path.is_ancestor_of(&cash.path));
+        assert_eq!(cash.path.depth(), assets.path.depth() + 1);
+
+        // and a grandchild nests under both
+        let checking = repo
+            .create(new_account(AccountType::Asset, "Checking", Some(cash.id())))
+            .await
+            .unwrap();
+
+        assert!(assets.path.is_ancestor_of(&checking.path));
+        assert!(cash.path.is_ancestor_of(&checking.path));
+        assert_eq!(checking.path.depth(), 3);
+    }
+
+    #[tokio::test]
+    async fn get_returns_a_created_account() {
+        let repo = InMemoryAccountRepository::default();
+        let roots = seed_roots(&repo).await;
+        let assets = &roots[0];
+
+        let fetched = repo.get(assets.id()).await.unwrap();
+        assert_eq!(fetched.map(|a| a.id()), Some(assets.id()));
+    }
+
+    #[tokio::test]
+    async fn create_under_missing_parent_fails() {
+        let repo = InMemoryAccountRepository::default();
+        seed_roots(&repo).await;
+
+        // an id minted by a *different* repo is guaranteed absent from `repo`
+        let other = InMemoryAccountRepository::default();
+        let stranger = other
+            .create(new_account(AccountType::Asset, "Elsewhere", None))
+            .await
+            .unwrap();
+
+        let result = repo
+            .create(new_account(AccountType::Asset, "Orphan", Some(stranger.id())))
+            .await;
+
+        assert!(matches!(result, Err(RepoError::ParentNotFound(_))));
+    }
+}