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

.gitignore

@@ -0,0 +1,32 @@
+.gradle
+build/
+!gradle/wrapper/gradle-wrapper.jar
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### STS ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+bin/
+!**/src/main/**/bin/
+!**/src/test/**/bin/
+
+### IntelliJ IDEA ###
+.idea
+*.iws
+*.iml
+*.ipr
+out/
+!**/src/main/**/out/
+!**/src/test/**/out/
+
+### VS Code ###
+.vscode/
+
+### Kotlin ###
+.kotlin

build.gradle.kts

@@ -0,0 +1,46 @@
+import org.jetbrains.kotlin.gradle.tasks.KotlinCompile
+
+plugins {
+	id("org.springframework.boot") version "3.2.4"
+	id("io.spring.dependency-management") version "1.1.4"
+	kotlin("jvm") version "2.0.20"
+	kotlin("plugin.jpa") version "1.9.23"
+	kotlin("plugin.serialization") version "2.0.20"
+	kotlin("plugin.spring") version "1.9.23"
+}
+
+group = "com.example"
+version = "0.0.1-SNAPSHOT"
+
+java {
+	sourceCompatibility = JavaVersion.VERSION_17
+}
+
+repositories {
+	mavenCentral()
+}
+
+dependencies {
+	implementation("com.fasterxml.jackson.module:jackson-module-kotlin")
+	implementation("org.flywaydb:flyway-core")
+	implementation("org.jetbrains.kotlin:kotlin-reflect")
+	implementation("org.jetbrains.kotlinx:kotlinx-serialization-json")
+	implementation("org.springframework.boot:spring-boot-starter-jdbc")
+	implementation("org.springframework.boot:spring-boot-starter-mustache")
+	implementation("org.springframework.boot:spring-boot-starter-web")
+	developmentOnly("org.springframework.boot:spring-boot-devtools")
+	runtimeOnly("org.postgresql:postgresql")
+	testImplementation("org.jetbrains.kotlin:kotlin-test-junit5")
+	testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<KotlinCompile> {
+	kotlinOptions {
+		freeCompilerArgs += "-Xjsr305=strict"
+		jvmTarget = "17"
+	}
+}
+
+tasks.withType<Test> {
+	useJUnitPlatform()
+}

checklist.md

@@ -0,0 +1,11 @@
+Some simple checklist for this demo repo:
+- [x] connect to database
+- [x] make migrations
+- [ ] make repository and models
+- [ ] make crud api
+- [ ] make openapi documentation generation
+- [ ] connect to kafka to produce events
+- [ ] make kafka consumer
+- [ ] register prometheus metrics
+- [ ] expose prometheus metrics
+- [ ] add otel collector

gradle/wrapper/gradle-wrapper.properties

@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.7-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists

gradlew

@@ -0,0 +1,249 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"

gradlew.bat

@@ -0,0 +1,92 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega

settings.gradle.kts

@@ -0,0 +1 @@
+rootProject.name = "demo"

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() {
+	}
+
+}