refac: Create interface for CustomerRepo

- Add ICustomerRepo which is an interface that contains all the necessary methods for interacting with the database. The benefit here is that we could easily swap out the implementation if necessary. Another class can implement this interface and use any database technology to do so.
- Rename CustomerRepo to CustomerJpaRepo.
- Rename CustomerRepoFacade to CustomerRepo.

Author: thorlauridsen

apps/api/src/main/kotlin/com/github/thorlauridsen/service/CustomerService.kt

@@ -3,7 +3,7 @@ package com.github.thorlauridsen.service
 import com.github.thorlauridsen.model.Customer
 import com.github.thorlauridsen.model.CustomerInput
 import com.github.thorlauridsen.exception.CustomerNotFoundException
-import com.github.thorlauridsen.persistence.CustomerRepoFacade
+import com.github.thorlauridsen.persistence.ICustomerRepo
 import org.slf4j.LoggerFactory
 import org.springframework.stereotype.Service
 import java.util.UUID
@@ -13,10 +13,10 @@ import java.util.UUID
  * - Saving customers.
  * - Fetching customers.
  *
- * @param customerRepo [CustomerRepoFacade] to interact with the database.
+ * @param customerRepo [ICustomerRepo] to interact with the database.
  */
 @Service
-class CustomerService(private val customerRepo: CustomerRepoFacade) {
+class CustomerService(private val customerRepo: ICustomerRepo) {
 
     private val logger = LoggerFactory.getLogger(this::class.java)
 

modules/persistence/src/main/kotlin/com/github/thorlauridsen/persistence/CustomerJpaRepo.kt

@@ -0,0 +1,11 @@
+package com.github.thorlauridsen.persistence
+
+import java.util.UUID
+import org.springframework.data.jpa.repository.JpaRepository
+
+/**
+ * Customer repository interface.
+ * This is a JPA repository for the [CustomerEntity].
+ * It extends the [JpaRepository] interface which allows us to easily define CRUD methods.
+ */
+interface CustomerJpaRepo : JpaRepository<CustomerEntity, UUID>

modules/persistence/src/main/kotlin/com/github/thorlauridsen/persistence/CustomerRepo.kt

@@ -1,11 +1,46 @@
 package com.github.thorlauridsen.persistence
 
+import com.github.thorlauridsen.model.Customer
+import com.github.thorlauridsen.model.CustomerInput
 import java.util.UUID
-import org.springframework.data.jpa.repository.JpaRepository
+import kotlin.jvm.optionals.getOrNull
+import org.springframework.stereotype.Repository
 
 /**
- * Customer repository interface.
- * This is a JPA repository for the customer entity.
- * It extends the [JpaRepository] interface which allows us to easily define CRUD methods.
+ * Customer repository facade class.
+ *
+ * This class is a facade for the [CustomerJpaRepo].
+ * A service class can use this facade to easily interact with the
+ * repository without needing to know about the database entity [CustomerEntity].
+ *
+ * It is annotated with [Repository] to allow Spring to automatically
+ * detect it as a bean and inject it where needed.
+ *
+ * @param customerRepo [CustomerJpaRepo] to interact with the database.
  */
-interface CustomerRepo : JpaRepository<CustomerEntity, UUID>
+@Repository
+class CustomerRepo(private val customerRepo: CustomerJpaRepo) : ICustomerRepo {
+
+    /**
+     * Save a customer.
+     * @param customer [CustomerInput] to save.
+     * @return [Customer] retrieved from database.
+     */
+    override fun save(customer: CustomerInput): Customer {
+        val entity = CustomerEntity(
+            mail = customer.mail,
+        )
+        val created = customerRepo.save(entity)
+        return created.toModel()
+    }
+
+    /**
+     * Get a customer given an id.
+     * @param id [UUID] to fetch customer.
+     * @return [Customer] or null if not found.
+     */
+    override fun find(id: UUID): Customer? {
+        val entity = customerRepo.findById(id).getOrNull()
+        return entity?.toModel()
+    }
+}

modules/persistence/src/main/kotlin/com/github/thorlauridsen/persistence/CustomerRepoFacade.kt

@@ -0,0 +1,28 @@
+package com.github.thorlauridsen.persistence
+
+import com.github.thorlauridsen.model.Customer
+import com.github.thorlauridsen.model.CustomerInput
+import java.util.UUID
+
+/**
+ * Customer repository interface.
+ * This is an interface containing methods for interacting with the customer table.
+ * A repository class will implement this interface to provide the actual implementation.
+ * This interface makes it easier to swap out the implementation of the repository if needed.
+ */
+interface ICustomerRepo {
+
+    /**
+     * Save a customer to the database.
+     * @param customer [CustomerInput] to save.
+     * @return [Customer] retrieved from database.
+     */
+    fun save(customer: CustomerInput): Customer
+
+    /**
+     * Get a customer given an id.
+     * @param id [UUID] to fetch customer.
+     * @return [Customer] or null if not found.
+     */
+    fun find(id: UUID): Customer?
+}