init service: base structure, some api-methods, migrations

src/main/kotlin/com/example/demo/AppConfig.kt

@@ -0,0 +1,14 @@
+package com.example.demo
+
+import com.example.demo.provider.MockedShopProvider
+import com.example.demo.provider.ShopProvider
+import org.springframework.context.annotation.Bean
+import org.springframework.context.annotation.Configuration
+
+@Configuration
+class AppConfig {
+    @Bean
+    fun shopProvider(): ShopProvider{
+        return MockedShopProvider()
+    }
+}

src/main/kotlin/com/example/demo/DemoApplication.kt

@@ -0,0 +1,11 @@
+package com.example.demo
+
+import org.springframework.boot.autoconfigure.SpringBootApplication
+import org.springframework.boot.runApplication
+
+@SpringBootApplication
+class DemoApplication
+
+fun main(args: Array<String>) {
+	runApplication<DemoApplication>(*args)
+}

src/main/kotlin/com/example/demo/controllers/GreetingController.kt

@@ -0,0 +1,18 @@
+package com.example.demo.controllers
+
+import com.example.demo.provider.html.renderProductTable
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+class GreetingController {
+    @GetMapping("/greeting")
+    fun greet(): String {
+        return "Hello World!"
+    }
+
+    @GetMapping("/example/html")
+    fun exampleHtml(): String {
+        return renderProductTable()
+    }
+}

src/main/kotlin/com/example/demo/controllers/ShopController.kt

@@ -0,0 +1,39 @@
+package com.example.demo.controllers
+
+import com.example.demo.provider.ShopProvider
+import jakarta.servlet.http.HttpServletResponse
+import kotlinx.serialization.json.Json
+import kotlinx.serialization.json.encodeToJsonElement
+import org.springframework.beans.factory.annotation.Autowired
+import org.springframework.http.HttpStatus
+import org.springframework.web.bind.annotation.GetMapping
+import org.springframework.web.bind.annotation.ResponseBody
+import org.springframework.web.bind.annotation.RestController
+
+@RestController
+class ShopController (
+    @field:Autowired private val shopProvider: ShopProvider,
+) {
+    @GetMapping(value = ["/shop/common-info"], produces = ["application/json"] )
+    @ResponseBody
+    fun commonInfo(response: HttpServletResponse): String {
+        response.contentType = "application/json"
+
+        val shop = shopProvider.getRandomShop()
+
+        if (shop == null) {
+            response.status = HttpStatus.NOT_FOUND.value()
+
+            return "not found"
+        }
+
+        return Json.encodeToJsonElement(value = mapOf(
+            "customers" to mapOf(
+                "withMoreUndeliveredOrdersThanDelivered" to shop.getCustomersWithMoreUndeliveredOrdersThanDelivered().map { cus -> cus.name }
+            ),
+            "products" to mapOf(
+                "orderedByAllCustomers" to shop.getSetOfProductsOrderedByEveryCustomer().map { pr -> pr.name },
+            )
+        )).toString()
+    }
+}

src/main/kotlin/com/example/demo/models/City.kt

@@ -0,0 +1,3 @@
+package com.example.demo.models
+
+data class City(val name: String)

src/main/kotlin/com/example/demo/models/Customer.kt

@@ -0,0 +1,16 @@
+package com.example.demo.models
+
+data class Customer(val name: String, val city: City, val orders: List<Order>) {
+    /**
+     * Return the most expensive product among all delivered products
+     */
+    fun getMostExpensiveDeliveredProduct(): Product? = orders.filter { ord -> ord.isDelivered }
+        .flatMap { ord -> ord.products }
+        .maxByOrNull { pr -> pr.price }
+
+    fun getMostExpensiveOrderedProduct(): Product? = orders.flatMap { ord -> ord.products }.maxByOrNull { pr -> pr.price }
+
+    fun getOrderedProducts(): Set<Product> = orders.flatMap { order -> order.products }.toSet()
+
+    fun getTotalOrderPrice(): Double = orders.flatMap { ord -> ord.products }.sumOf { pr -> pr.price }
+}

src/main/kotlin/com/example/demo/models/Order.kt

@@ -0,0 +1,3 @@
+package com.example.demo.models
+
+data class Order(val products: List<Product>, val isDelivered: Boolean)

src/main/kotlin/com/example/demo/models/Product.kt

@@ -0,0 +1,3 @@
+package com.example.demo.models
+
+data class Product(val name: String, val price: Double)

src/main/kotlin/com/example/demo/models/Shop.kt

@@ -0,0 +1,48 @@
+package com.example.demo.models
+
+data class Shop(val name: String, val customers: List<Customer>) {
+    fun checkAllCustomersAreFrom(city: City): Boolean = customers.count { cus -> cus.city == city } == customers.count()
+
+    fun countCustomersFrom(city: City): Int = customers.count { cus -> cus.city == city }
+
+    fun getCitiesCustomersAreFrom(): Set<City> = customers.map { cus -> cus.city }.toSet()
+
+    fun findAnyCustomerFrom(city: City): Customer? = customers.firstOrNull { cus -> cus.city == city }
+
+    fun getAllOrderedProducts(): Set<Product> = customers.flatMap { cus -> cus.getOrderedProducts() }.toSet()
+
+    fun getCustomersFrom(city: City): List<Customer> = customers.filter { cus -> cus.city == city }
+
+    fun getCustomersSortedByNumberOfOrders(): List<Customer> = customers.sortedBy { cus -> cus.orders.count() }
+
+    fun getCustomerWithMaximumNumberOfOrders(): Customer? = customers.maxByOrNull { cus -> cus.orders.count() }
+
+    /**
+     * Return customers who have more undelivered orders than delivered
+     */
+    fun getCustomersWithMoreUndeliveredOrdersThanDelivered(): Set<Customer> = customers.partition(predicate = fun (cus): Boolean {
+        val (del, undel) = cus.orders.partition { ord -> ord.isDelivered }
+
+        return del.count() < undel.count()
+    }).first.toSet()
+
+    fun getNumberOfTimesProductWasOrdered(product: Product): Int = customers
+        .flatMap { cus -> cus.orders.flatMap { ord -> ord.products } }
+        .count { pr -> pr.name == product.name }
+
+    /**
+     * Return the set of products that were ordered by every customer.
+     * Note: a customer may order the same product for several times.
+     */
+    fun getSetOfProductsOrderedByEveryCustomer(): Set<Product> {
+        val products = customers.flatMap { cus -> cus.orders.flatMap { ord -> ord.products } }.toSet()
+
+        return customers.fold(products) { orderedProducts, cus ->
+            orderedProducts.intersect(cus.orders.flatMap { ord -> ord.products }.toSet())
+        }.toSet()
+    }
+
+    fun groupCustomersByCity(): Map<City, List<Customer>> = customers.groupBy { cus -> cus.city }
+
+    fun hasCustomerFrom(city: City): Boolean = customers.any { cus -> cus.city == city }
+}

src/main/kotlin/com/example/demo/provider/MockedShopProvider.kt

@@ -0,0 +1,28 @@
+package com.example.demo.provider
+
+import com.example.demo.models.*
+
+class MockedShopProvider: ShopProvider {
+    override fun getRandomShop(): Shop? {
+        return Shop(name="shop", customers= listOf(
+            Customer(
+                name = "Foo-1",
+                city = City(name= "Bar"),
+                orders = listOf(
+                    Order(products = listOf(Product(name = "one", price = 11.2)), isDelivered = false),
+                    Order(products = listOf(Product(name = "two", price = 13.2)), isDelivered = false),
+                    Order(products = listOf(Product(name = "three", price = 15.2)), isDelivered = true),
+                )
+            ),
+            Customer(
+                name = "Foo-2",
+                city = City(name= "Bar"),
+                orders = listOf(
+                    Order(products = listOf(Product(name = "one", price = 12.2)), isDelivered = false),
+                    Order(products = listOf(Product(name = "two", price = 13.2)), isDelivered = true),
+                    Order(products = listOf(Product(name = "four", price = 14.2)), isDelivered = true),
+                )
+            ),
+        ))
+    }
+}

src/main/kotlin/com/example/demo/provider/ShopProvider.kt

@@ -0,0 +1,7 @@
+package com.example.demo.provider
+
+import com.example.demo.models.Shop
+
+interface ShopProvider {
+    fun getRandomShop(): Shop?
+}

src/main/kotlin/com/example/demo/provider/html/Attribute.kt

@@ -0,0 +1,5 @@
+package com.example.demo.provider.html
+
+class Attribute(val name : String, val value : String) {
+    override fun toString() = """$name="$value" """
+}

src/main/kotlin/com/example/demo/provider/html/Center.kt

@@ -0,0 +1,3 @@
+package com.example.demo.provider.html
+
+class Center: Tag("center")

src/main/kotlin/com/example/demo/provider/html/Html.kt

@@ -0,0 +1,12 @@
+package com.example.demo.provider.html
+
+class Html: Tag("html")
+
+fun html(init: Html.() -> Unit): Html {
+    val tag = Html()
+    tag.init()
+    return tag
+}
+
+fun Html.table(init : Table.() -> Unit) = doInit(Table(), init)
+fun Html.center(init : Center.() -> Unit) = doInit(Center(), init)

src/main/kotlin/com/example/demo/provider/html/HtmlProvider.kt

@@ -0,0 +1,38 @@
+package com.example.demo.provider.html
+
+fun getTitleColor() = "#b9c9fe"
+fun getCellColor(index: Int, row: Int) = if ((index + row) %2 == 0) "#dce4ff" else "#eff2ff"
+
+fun renderProductTable(): String {
+    return html {
+        table {
+            tr (color = getTitleColor()) {
+
+                td {
+                    text("Product")
+                }
+                td {
+                    text("Price")
+                }
+                td {
+                    text("Popularity")
+                }
+            }
+
+            val products = getProducts()
+            for ((i, product) in products.withIndex()) {
+                tr {
+                    td (color = getCellColor(0, i+1)) {
+                        text(product.description)
+                    }
+                    td (color = getCellColor(1, i+1)) {
+                        text(product.price)
+                    }
+                    td (color = getCellColor(2, i+1)) {
+                        text(product.popularity)
+                    }
+                }
+            }
+        }
+    }.toString()
+}

src/main/kotlin/com/example/demo/provider/html/Product.kt

@@ -0,0 +1,11 @@
+package com.example.demo.provider.html
+
+data class Product(val description: String, val price: Double, val popularity: Int)
+
+fun getProducts(): Set<Product> {
+    return setOf(
+        Product("one", 12.0, 12),
+        Product("two", 13.0, 20),
+        Product("three", 14.0, 50)
+    )
+}

src/main/kotlin/com/example/demo/provider/html/TD.kt

@@ -0,0 +1,3 @@
+package com.example.demo.provider.html
+
+class TD: Tag("td")

src/main/kotlin/com/example/demo/provider/html/TR.kt

@@ -0,0 +1,7 @@
+package com.example.demo.provider.html
+
+class TR: Tag("tr")
+
+fun TR.td(color: String? = null, align : String = "left", init : TD.() -> Unit) = doInit(TD(), init)
+    .set("align", align)
+    .set("bgcolor", color)

src/main/kotlin/com/example/demo/provider/html/Table.kt

@@ -0,0 +1,5 @@
+package com.example.demo.provider.html
+
+class Table: Tag("table")
+
+fun Table.tr(color: String? = null, init : TR.() -> Unit) = doInit(TR(), init).set("bgcolor", color)

src/main/kotlin/com/example/demo/provider/html/Tag.kt

@@ -0,0 +1,28 @@
+package com.example.demo.provider.html
+
+open class Tag(val name: String) {
+    val children: MutableList<Tag> = ArrayList()
+    val attributes: MutableList<Attribute> = ArrayList()
+
+    override fun toString(): String {
+        return "<$name" +
+                (if (attributes.isEmpty()) "" else attributes.joinToString(separator = "", prefix = " ")) + ">" +
+                (if (children.isEmpty()) "" else children.joinToString(separator = "")) +
+                "</$name>"
+    }
+}
+
+fun <T: Tag> T.set(name: String, value: String?): T {
+    if (value != null) {
+        attributes.add(Attribute(name, value))
+    }
+    return this
+}
+
+fun <T: Tag> Tag.doInit(tag: T, init: T.() -> Unit): T {
+    tag.init()
+    children.add(tag)
+    return tag
+}
+
+fun Tag.text(s : Any?) = doInit(Text(s.toString()), {})

src/main/kotlin/com/example/demo/provider/html/Text.kt

@@ -0,0 +1,5 @@
+package com.example.demo.provider.html
+
+class Text(val text: String): Tag("b") {
+    override fun toString() = text
+}

src/main/resources/application.yml

@@ -0,0 +1,16 @@
+---
+spring:
+  application:
+    name: Demo
+  datasource:
+    url: jdbc:postgresql://localhost:5432/demo?currentSchema=demo
+    username: postgres
+    password: postgres
+    driver-class-name: org.postgresql.Driver
+    hikari:
+      schema: demo
+  flyway: #flyway automatically uses the datasource from the application to connect to the DB
+    enabled: true # enables flyway database migration
+    locations: classpath:db/migration/structure, classpath:db/migration/data # the location where flyway should look for migration scripts
+    validate-on-migrate: true
+    default-schema: demo

src/main/resources/db/migration/data/V1.1__insert_product_data.sql

@@ -0,0 +1,4 @@
+insert into product (guid, name, description, price, created_at) values
+    (gen_random_uuid(), 'salt', 'simple salt', 1200, now()),
+    (gen_random_uuid(), 'pepper', 'black pepper', 2099, now()),
+    (gen_random_uuid(), 'sugar', 'sweet sugar', 3129, now());

src/main/resources/db/migration/structure/V1__create_product_table.sql

@@ -0,0 +1,9 @@
+create table product (
+    id          bigserial primary key,
+    guid        uuid not null,
+    name        varchar(255) not null,
+    description text,
+    price       bigint not null,
+    created_at  timestamptz not null,
+    updated_at  timestamptz
+)

src/test/kotlin/com/example/demo/DemoApplicationTests.kt

@@ -0,0 +1,13 @@
+package com.example.demo
+
+import org.junit.jupiter.api.Test
+import org.springframework.boot.test.context.SpringBootTest
+
+@SpringBootTest
+class DemoApplicationTests {
+
+	@Test
+	fun contextLoads() {
+	}
+
+}