Add spring boot demo application version 2.7.18 (#14)

The goal is to build a demo application using spring boot that is equivalent to the kotlin one built with ktor.

- https://start.spring.io/ by default supports spring boot version 3.x. 3.x is not compatible with Java 8, so we downgraded the generated  app to 2.7.18 which is compatible. https://www.marcobehler.com/guides/spring-and-spring-boot-versions
- We changed the toolchain for `inngest-core` to Java 8 so that Java 8 apps can consume it. This meant we couldn't use Java httpclient which [was introduced in Java 11](https://openjdk.org/groups/net/httpclient/intro.html).
- We evaluated a couple of Http clients and went with OkHttp because its API resembles the Java 11 Http client the most (Other clients were Google Http client and Apache Http client)
- The current state is that the app syncs correctly to the dev server but when a function is called it fails on steps execution because of two issues that we'll be looking into next:
```
  Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Handler dispatch failed; nested exception is java.lang.NoClassDefFoundError: kotlin/enums/EnumEntriesKt] with root cause

java.lang.ClassNotFoundException: kotlin.enums.EnumEntriesKt
	at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:641) ~[na:na]
	at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:188) ~[na:na]
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[na:na]
	at com.inngest.OpCode.<clinit>(Function.kt:26) ~[main/:na]
	at com.inngest.InngestFunction.call(Function.kt:124) ~[main/:na]
	at com.inngest.CommHandler.callFunction(Comm.kt:85) ~[main/:na]
	at com.inngest.springbootdemo.InngestController.handleRequest(InngestController.java:40) ~[main/:na]
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:104) ~[na:na]
	at java.base/java.lang.reflect.Method.invoke(Method.java:578) ~[na:na]
	at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205) 
```
- The second issue is that reified inline functions [cannot be called from Java](https://stackoverflow.com/a/42742119) and `step.run` currently is. 
https://github.com/inngest/inngest-kt/blob/e9a6a15498d742a775a8a5bbd107cada10d9bb31/inngest-core/src/main/kotlin/com/inngest/Step.kt#L28

inngest-core/build.gradle.kts

@@ -10,7 +10,10 @@ repositories {
 dependencies {
     implementation("com.beust:klaxon:5.5")
     implementation("com.fasterxml.jackson.core:jackson-core:2.16.1")
+
     implementation("com.fasterxml.jackson.core:jackson-databind:2.16.1")
+    implementation("com.squareup.okhttp3:okhttp:4.12.0")
+
     testImplementation(kotlin("test"))
 }
 
@@ -20,4 +23,6 @@ tasks.named<Test>("test") {
 }
 
 // TODO - Move this to share conventions gradle file
-java { toolchain { languageVersion.set(JavaLanguageVersion.of(20)) } }
+java {
+    toolchain { languageVersion.set(JavaLanguageVersion.of(8)) }
+}

inngest-core/src/main/kotlin/com/inngest/Comm.kt

@@ -2,10 +2,11 @@ package com.inngest
 
 import com.beust.klaxon.Json
 import com.beust.klaxon.Klaxon
-import java.net.URI
-import java.net.http.HttpClient
-import java.net.http.HttpRequest
-import java.net.http.HttpResponse
+import okhttp3.MediaType.Companion.toMediaType
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import okhttp3.RequestBody.Companion.toRequestBody
+import java.io.IOException
 
 data class ExecutionRequestPayload(
     val ctx: ExecutionContext,
@@ -125,17 +126,30 @@ class CommHandler(val functions: HashMap<String, InngestFunction>) {
                 v = "0.0.1",
                 functions = getFunctionConfigs(),
             )
-        val requestBody = Klaxon().toJsonString(requestPayload)
+        val jsonRequestBody = Klaxon().toJsonString(requestPayload)
+
+        val client = OkHttpClient()
+
+        val jsonMediaType = "application/json".toMediaType()
+        val requestBody = jsonRequestBody.toRequestBody(jsonMediaType)
 
-        val client = HttpClient.newBuilder().build()
         // TODO - Add headers?
         val request =
-            HttpRequest.newBuilder()
-                .uri(URI.create(registrationUrl))
-                .POST(HttpRequest.BodyPublishers.ofString(requestBody))
+            Request.Builder()
+                .url(registrationUrl).addHeader("Content-Type", "application/json")
+                .post(requestBody)
                 .build()
-        val response = client.send(request, HttpResponse.BodyHandlers.ofString())
-        // TODO - Decode response and relay any message
+
+        client.newCall(request).execute().use { response ->
+            if (!response.isSuccessful) throw IOException("Unexpected code $response")
+
+            // TODO - Decode response and relay any message
+//            for ((name, value) in response.headers) {
+//                println("$name: $value")
+//            }
+//
+//            println(response.body!!.string())
+        }
 
         // TODO - Add headers to output
         val body: Map<String, Any?> = mapOf()

inngest-spring-boot-demo/build.gradle.kts

@@ -0,0 +1,28 @@
+plugins {
+    java
+    id("org.springframework.boot") version "2.7.18"
+    id("io.spring.dependency-management") version "1.1.4"
+}
+
+group = "com.inngest"
+version = "0.0.1"
+
+java {
+    sourceCompatibility = JavaVersion.VERSION_1_8
+}
+
+repositories {
+    mavenCentral()
+}
+
+dependencies {
+    implementation(project(":inngest-core"))
+
+    implementation("org.springframework.boot:spring-boot-starter-web")
+    testImplementation("org.springframework.boot:spring-boot-starter-test")
+}
+
+tasks.withType<Test> {
+    useJUnitPlatform()
+}
+

inngest-spring-boot-demo/src/main/java/com/inngest/springbootdemo/InngestController.java

@@ -0,0 +1,49 @@
+package com.inngest.springbootdemo;
+
+import com.inngest.CommResponse;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpStatus;
+import org.springframework.http.MediaType;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.*;
+
+@RestController
+@RequestMapping(value = "/api", produces = MediaType.APPLICATION_JSON_VALUE)
+public class InngestController {
+
+    private static final HttpHeaders commonHeaders = new HttpHeaders();
+
+    static {
+        String inngestSdk = "inngest-kt:v0.0.1";
+        commonHeaders.add("x-inngest-sdk", inngestSdk);
+    }
+
+    @GetMapping("/inngest")
+    public ResponseEntity<String> index() {
+        String response = InngestSingleton.getInstance().introspect();
+
+        return ResponseEntity.ok().headers(commonHeaders).body(response);
+    }
+
+    @PutMapping("/inngest")
+    public ResponseEntity<String> put() {
+        String response = InngestSingleton.getInstance().register();
+        return ResponseEntity.ok().headers(commonHeaders).body(response);
+    }
+
+    @PostMapping(value = "/inngest", produces = MediaType.APPLICATION_JSON_VALUE)
+    public ResponseEntity<String> handleRequest(
+        @RequestParam(name = "fnId") String functionId,
+        @RequestBody String body
+    ) {
+        try {
+            CommResponse response = InngestSingleton.getInstance().callFunction(functionId, body);
+
+            return ResponseEntity.status(response.getStatusCode().getCode()).headers(commonHeaders)
+                .body(response.getBody());
+        } catch (Exception e) {
+            return ResponseEntity.status(HttpStatus.INTERNAL_SERVER_ERROR)
+                .body(e.toString());
+        }
+    }
+}

inngest-spring-boot-demo/src/main/java/com/inngest/springbootdemo/InngestSingleton.java

@@ -0,0 +1,73 @@
+package com.inngest.springbootdemo;
+
+import com.inngest.*;
+import kotlin.jvm.functions.Function2;
+
+import java.time.Duration;
+import java.util.HashMap;
+
+import com.fasterxml.jackson.annotation.JsonProperty;
+
+
+class Result {
+    @JsonProperty("sum")
+    private final int sum;
+
+    public Result(@JsonProperty("sum") int sum) {
+        this.sum = sum;
+    }
+
+    public int getSum() {
+        return sum;
+    }
+}
+
+// NOTE: We probably don't need this singleton anymore
+// when revisiting the SDK's interface.
+public class InngestSingleton {
+    private static CommHandler instance;
+
+    public static synchronized CommHandler getInstance() {
+        if (instance == null) {
+            FunctionTrigger fnTrigger = new FunctionTrigger("user-signup", null, null);
+            FunctionTrigger[] triggers = {fnTrigger};
+            FunctionOptions fnConfig = new FunctionOptions("fn-id-slug", "My function!", triggers);
+
+            Function2<FunctionContext, Step, Void> handler = (ctx, step) -> {
+                int x = 10;
+
+                System.out.println("-> handler called " + ctx.getEvent().getName());
+
+                // Steps types are problematic for now as it's not possible to called
+                // reified types from Java.
+
+//                int y = step.run("add-ten", () -> x + 10);
+
+//                Result res = step.run("cast-to-type-add-ten", () -> {
+//                    System.out.println("-> running step 1!! " + x);
+//                    // throw new Exception("An error!");
+//                    return new Result(y + 10);
+//                });
+
+//                System.out.println("res" + res);
+//                int add = step.run("add-one-hundred", () -> {
+//                    System.out.println("-> running step 2 :) " + (res != null ? res.getSum() : ""));
+//                    return (res != null ? res.getSum() : 0) + 100;
+//                });
+
+                step.sleep("wait-one-sec", Duration.ofSeconds(2));
+
+//                step.run("last-step", () -> (res != null ? res.getSum() : 0) * add);
+
+                return null;
+            };
+            InngestFunction function = new InngestFunction(fnConfig, handler);
+
+            HashMap<String, InngestFunction> functions = new HashMap<>();
+            functions.put("fn-id-slug", function);
+
+            instance = new CommHandler(functions);
+        }
+        return instance;
+    }
+}

inngest-spring-boot-demo/src/main/java/com/inngest/springbootdemo/SpringBootDemoApplication.java

@@ -0,0 +1,12 @@
+package com.inngest.springbootdemo;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class SpringBootDemoApplication {
+
+    public static void main(String[] args) {
+        SpringApplication.run(SpringBootDemoApplication.class, args);
+    }
+}

inngest-spring-boot-demo/src/main/resources/application.yml

@@ -0,0 +1,4 @@
+server:
+  port: 8080 # We probably want to change this to 8081 to avoid port conflicts
+             # but I kept it for now because of the hardcoded URL that are sent
+             # to the inngest dev-server.

inngest-spring-boot-demo/src/test/java/com/inngest/springbootdemo/InngestControllerTest.java

@@ -0,0 +1,25 @@
+package com.inngest.springbootdemo;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
+import org.springframework.test.web.servlet.MockMvc;
+
+import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
+import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
+
+@WebMvcTest(InngestController.class)
+public class InngestControllerTest {
+
+    @Autowired
+    private MockMvc mockMvc;
+
+    @Test
+    public void shouldReturnSyncPayload() throws Exception {
+        mockMvc.perform(get("/api/inngest"))
+            .andExpect(status().isOk())
+            .andExpect(content().contentType("application/json"))
+            .andExpect(jsonPath("$.appName").value("my-app"))
+            .andExpect(jsonPath("$.sdk").value("kotlin"));
+    }
+}

inngest-spring-boot-demo/src/test/java/com/inngest/springbootdemo/SpringBootDemoApplicationTests.java

@@ -0,0 +1,13 @@
+package com.inngest.springbootdemo;
+
+import org.junit.jupiter.api.Test;
+import org.springframework.boot.test.context.SpringBootTest;
+
+@SpringBootTest
+class SpringBootDemoApplicationTests {
+
+	@Test
+	void contextLoads() {
+	}
+
+}

settings.gradle.kts

@@ -12,4 +12,4 @@ plugins {
 
 rootProject.name = "inngest-sdk"
 
-include("inngest-core", "inngest-test-server")
+include("inngest-core", "inngest-test-server", "inngest-spring-boot-demo")