Implemented HTML endpoint that shows generated EPC QR Code in a simple web site

EpcQrCodeRest/src/main/kotlin/net/codinux/banking/epcqrcode/rest/EpcQrCodeResource.kt

@@ -3,6 +3,7 @@ package net.codinux.banking.epcqrcode.rest
 import net.codinux.banking.epcqrcode.rest.dto.GenerateEpcQrCodeRequest
 import net.codinux.banking.epcqrcode.rest.dto.GenerateEpcQrCodeResponse
 import net.codinux.banking.epcqrcode.rest.service.EpcQrCodeService
+import net.codinux.banking.epcqrcode.rest.service.HtmlService
 import org.eclipse.microprofile.openapi.annotations.Operation
 import org.eclipse.microprofile.openapi.annotations.media.Content
 import org.eclipse.microprofile.openapi.annotations.media.Schema
@@ -21,8 +22,8 @@ import javax.ws.rs.core.Response
 @Produces(MediaType.APPLICATION_JSON)
 @Tag(name = "EPC QR Code")
 class EpcQrCodeResource(
-    @Inject
+    @Inject private val service: EpcQrCodeService,
-    private val service: EpcQrCodeService
+    @Inject private val htmlService: HtmlService
 ) {
 
     private val log = LoggerFactory.getLogger(EpcQrCodeResource::class.java)
@@ -33,7 +34,7 @@ class EpcQrCodeResource(
         content = [ Content(mediaType = "application/json", schema = Schema(implementation = GenerateEpcQrCodeResponse::class)) ])
     @APIResponse(responseCode = "500", description = "An internal error occurred")
     @GET
-    fun createEpcQrCodeGet(@BeanParam request: GenerateEpcQrCodeRequest): Response {
+    fun createEpcQrCodeJsonGet(@BeanParam request: GenerateEpcQrCodeRequest): Response {
         return handleJsonRequest(request)
     }
 
@@ -43,13 +44,34 @@ class EpcQrCodeResource(
     @APIResponse(responseCode = "500", description = "An internal error occurred")
     @POST
     @Consumes(MediaType.APPLICATION_JSON)
-    fun createEpcQrCodePost(
+    fun createEpcQrCodeJsonPost(
         @RequestBody(content = [ Content(schema = Schema(implementation = GenerateEpcQrCodeRequest::class)) ])
         request: GenerateEpcQrCodeRequest
     ): Response {
         return handleJsonRequest(request)
     }
 
+    @Operation(summary = "Creates a EPC QR code (also marketed as GiroCode, scan2Code, ...)")
+    @APIResponse(responseCode = "200", description = "The generated EPC QR Code")
+    @APIResponse(responseCode = "500", description = "An internal error occurred")
+    @GET
+    @Produces(MediaType.TEXT_HTML)
+    fun createEpcQrCodeHtml(@BeanParam request: GenerateEpcQrCodeRequest): Response {
+        return try {
+            val qrCodeBytes = service.generateEpcQrCodeBase64EncodedString(request)
+
+            Response.ok(htmlService.createHtmlPage(request.imageHeightAndWidth, qrCodeBytes))
+                .header("Access-Control-Allow-Origin", "*")
+                .build()
+        } catch (e: Exception) {
+            log.error("Could not create QR code for $request", e)
+
+            Response.status(Response.Status.INTERNAL_SERVER_ERROR.statusCode, e.localizedMessage) // TODO: it's almost always a bad idea to pass exception message to the outside
+                .header("Access-Control-Allow-Origin", "*")
+                .build()
+        }
+    }
+
     private fun handleJsonRequest(request: GenerateEpcQrCodeRequest): Response {
         return try {
             val qrCodeBytes = service.generateEpcQrCodeBase64Encoded(request)

EpcQrCodeRest/src/main/kotlin/net/codinux/banking/epcqrcode/rest/service/EpcQrCodeService.kt

@@ -20,6 +20,12 @@ class EpcQrCodeService {
     return base64Encoder.encode(epcQrCode.bytes)
   }
 
+  fun generateEpcQrCodeBase64EncodedString(request: GenerateEpcQrCodeRequest): String {
+    val epcQrCode = generateEpcQrCode(request)
+
+    return base64Encoder.encodeToString(epcQrCode.bytes)
+  }
+
   private fun generateEpcQrCode(request: GenerateEpcQrCodeRequest): EpcQrCode {
     return epcQrCodeGenerator.generateEpcQrCode(mapToEpcQrCodeConfig(request))
   }

EpcQrCodeRest/src/main/kotlin/net/codinux/banking/epcqrcode/rest/service/HtmlService.kt

@@ -0,0 +1,26 @@
+package net.codinux.banking.epcqrcode.rest.service
+
+import javax.enterprise.context.ApplicationScoped
+
+@ApplicationScoped
+class HtmlService {
+
+  fun createHtmlPage(heightAndWidth: Int, qrCodeBase64Encoded: String): String {
+    return StringBuilder()
+      .appendLine("<!DOCTYPE html>")
+      .appendLine("<html>")
+      .appendLine("<head>")
+      .appendLine("<meta charset=\"UTF-8\">")
+      .appendLine("<title>EPC QR code (also marketed as GiroCode, scan2Code, ...)</title>")
+      .appendLine("</head>")
+      .appendLine("<body>")
+      .appendLine("<div style=\"height: 100vh; width: 100%; display: flex; justify-content: center; align-items: center;\">")
+      .appendLine("<img width=\"$heightAndWidth\" height=\"$heightAndWidth\" alt=\"EPC QR code (also marketed as GiroCode, scan2Code, ...)\" " +
+        "src=\"data:image/png;base64,$qrCodeBase64Encoded\" />")
+      .appendLine("</div>")
+      .appendLine("</body>")
+      .appendLine("</html>")
+      .toString()
+  }
+
+}