add purchase feature and completed purchases listing

src/main/kotlin/org/meliapp/backend/controller/PurchaseController.kt

@@ -0,0 +1,26 @@
+package org.meliapp.backend.controller
+
+import org.meliapp.backend.dto.ApiResponse
+import org.meliapp.backend.dto.purchase.PurchaseRequest
+import org.meliapp.backend.dto.purchase.PurchaseResponse
+import org.meliapp.backend.service.PurchaseService
+import org.springframework.http.ResponseEntity
+import org.springframework.web.bind.annotation.*
+
+@RestController
+@RequestMapping("/api/purchases")
+class PurchaseController(
+    private val purchaseService: PurchaseService
+) {
+
+    @PostMapping
+    fun buy(@RequestBody purchaseRequest: PurchaseRequest): ResponseEntity<ApiResponse<PurchaseResponse>> {
+        return ResponseEntity.ok(ApiResponse(purchaseService.buy(purchaseRequest)))
+    }
+
+    @GetMapping
+    fun purchases(): ResponseEntity<ApiResponse<List<PurchaseResponse>>> {
+        return ResponseEntity.ok(ApiResponse(purchaseService.purchases()))
+    }
+
+}

src/main/kotlin/org/meliapp/backend/dto/product/ProductPurchaseResponse.kt

@@ -0,0 +1,12 @@
+package org.meliapp.backend.dto.product
+
+import com.fasterxml.jackson.annotation.JsonProperty
+import java.math.BigDecimal
+
+data class ProductPurchaseResponse(
+    @JsonProperty("meli_id")
+    val meliId: String,
+    val title: String,
+    val thumbnail: String,
+    val price: BigDecimal,
+)

src/main/kotlin/org/meliapp/backend/dto/purchase/PurchaseRequest.kt

@@ -0,0 +1,9 @@
+package org.meliapp.backend.dto.purchase
+
+import com.fasterxml.jackson.annotation.JsonProperty
+
+data class PurchaseRequest(
+    @JsonProperty(value = "meli_id")
+    val meliId: String,
+    val quantity: Int
+)

src/main/kotlin/org/meliapp/backend/dto/purchase/PurchaseResponse.kt

@@ -0,0 +1,15 @@
+package org.meliapp.backend.dto.purchase
+
+import com.fasterxml.jackson.annotation.JsonProperty
+import org.meliapp.backend.dto.product.ProductPurchaseResponse
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+data class PurchaseResponse(
+    val id: Long,
+    val quantity: Int,
+    val product: ProductPurchaseResponse,
+    @JsonProperty("created_at")
+    val createdAt: LocalDateTime,
+    val total: BigDecimal,
+)

src/main/kotlin/org/meliapp/backend/model/Purchase.kt

@@ -0,0 +1,22 @@
+package org.meliapp.backend.model
+
+import jakarta.persistence.*
+import org.hibernate.annotations.CreationTimestamp
+import java.math.BigDecimal
+import java.time.LocalDateTime
+
+@Entity
+class Purchase {
+
+    @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    var id: Long = 0
+    @ManyToOne
+    lateinit var user: User
+    @ManyToOne
+    lateinit var product: Product
+    var quantity: Int = 0
+    @CreationTimestamp
+    var purchaseDate: LocalDateTime = LocalDateTime.now()
+    var totalPrice: BigDecimal = BigDecimal.ZERO
+}

src/main/kotlin/org/meliapp/backend/repository/PurchaseRepository.kt

@@ -0,0 +1,11 @@
+package org.meliapp.backend.repository
+
+import org.meliapp.backend.model.Purchase
+import org.springframework.data.jpa.repository.JpaRepository
+import org.springframework.data.jpa.repository.Query
+import org.springframework.data.repository.query.Param
+
+interface PurchaseRepository : JpaRepository<Purchase, Long> {
+    @Query("SELECT p FROM Purchase p WHERE p.user.id = :id")
+    fun findByUserId(@Param("id") id: Long): List<Purchase>
+}

src/main/kotlin/org/meliapp/backend/service/PurchaseService.kt

@@ -0,0 +1,59 @@
+package org.meliapp.backend.service
+
+import org.meliapp.backend.dto.product.ProductPurchaseResponse
+import org.meliapp.backend.dto.purchase.PurchaseRequest
+import org.meliapp.backend.dto.purchase.PurchaseResponse
+import org.meliapp.backend.model.Product
+import org.meliapp.backend.model.Purchase
+import org.meliapp.backend.repository.PurchaseRepository
+import org.springframework.stereotype.Service
+import java.math.BigDecimal
+
+@Service
+class PurchaseService(
+    private val purchaseRepository: PurchaseRepository,
+    private val authService: AuthService,
+    private val productService: ProductService
+) {
+
+    fun buy(purchaseRequest: PurchaseRequest): PurchaseResponse {
+        val user = authService.getUserAuthenticated()
+        val product = productService.findByMeliId(purchaseRequest.meliId)
+
+        val purchase = Purchase()
+        purchase.user = user
+        purchase.quantity = purchaseRequest.quantity
+        purchase.product = product
+        purchase.totalPrice = product.price * BigDecimal(purchaseRequest.quantity)
+
+        purchaseRepository.save(purchase)
+
+        return toPurchaseResponse(purchase)
+
+    }
+
+    fun purchases(): List<PurchaseResponse> {
+        val user = authService.getUserAuthenticated()
+        return purchaseRepository.findByUserId(user.id).map { toPurchaseResponse(it) }
+    }
+
+    private fun toPurchaseResponse(purchase: Purchase): PurchaseResponse {
+        return PurchaseResponse(
+            purchase.id,
+            purchase.quantity,
+            toProductPurchaseResponse(purchase.product),
+            purchase.purchaseDate,
+            purchase.totalPrice
+        )
+    }
+
+    private fun toProductPurchaseResponse(product: Product): ProductPurchaseResponse {
+        return ProductPurchaseResponse(
+            product.meliId,
+            product.title,
+            product.thumbnail,
+            product.price)
+    }
+
+
+}

src/test/kotlin/org/meliapp/backend/service/PurchaseServiceUnitTest.kt

@@ -0,0 +1,78 @@
+package org.meliapp.backend.service
+
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+import org.meliapp.backend.dto.purchase.PurchaseRequest
+import org.meliapp.backend.model.Product
+import org.meliapp.backend.model.Purchase
+import org.meliapp.backend.model.User
+import org.meliapp.backend.repository.PurchaseRepository
+import org.mockito.InjectMocks
+import org.mockito.Mock
+import org.mockito.kotlin.*
+import org.springframework.test.context.junit.jupiter.SpringExtension
+import java.math.BigDecimal
+import kotlin.test.assertEquals
+
+@ExtendWith(SpringExtension::class)
+class PurchaseServiceUnitTest {
+
+    @Mock
+    lateinit var purchaseRepository: PurchaseRepository
+
+    @Mock
+    lateinit var productService: ProductService
+
+    @Mock
+    lateinit var authService: AuthService
+
+    @InjectMocks
+    lateinit var purchaseService: PurchaseService
+
+    @BeforeEach
+    fun setup() {
+        val user: User = mock()
+        whenever(user.id).thenReturn(1)
+        whenever(authService.getUserAuthenticated()).thenReturn(user)
+    }
+
+    @AfterEach
+    fun cleanup() {
+        reset(purchaseRepository, productService, authService)
+    }
+
+    @Test
+    fun `can buy an existing product`() {
+        val meliId = "MELI_ID"
+        val productTitle = "TITLE"
+        val product: Product = mock()
+
+        whenever(product.meliId).thenReturn(meliId)
+        whenever(product.price).thenReturn(BigDecimal.ZERO)
+        whenever(product.title).thenReturn(productTitle)
+        whenever(productService.findByMeliId(meliId)).thenReturn(product)
+
+        val result = purchaseService.buy(PurchaseRequest(meliId, 1))
+
+        assertEquals(meliId, result.product.meliId)
+        assertEquals(productTitle, result.product.title)
+        assertEquals(BigDecimal.ZERO, result.product.price)
+        assertEquals(1, result.quantity)
+        assertEquals(BigDecimal.ZERO, result.total)
+
+        verify(purchaseRepository, times(1)).save(any<Purchase>())
+
+    }
+
+    @Test
+    fun `can get all the purchases from current user`() {
+        whenever(purchaseRepository.findByUserId(any())).thenReturn(listOf())
+
+        val result = purchaseService.purchases()
+
+        assertEquals(0, result.size)
+    }
+
+}