feat: add support for conditional code

Close #43

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/demo/SourceCodeView.java

@@ -24,18 +24,28 @@
 import com.vaadin.flow.component.dependency.NpmPackage;
 import com.vaadin.flow.component.html.Div;
 import com.vaadin.flow.dom.Element;
+import elemental.json.Json;
+import elemental.json.JsonObject;
+import java.util.Map;
 
 @SuppressWarnings("serial")
 @JsModule("./code-viewer.ts")
 @NpmPackage(value = "lit", version = "2.5.0")
 class SourceCodeView extends Div implements HasSize {
 
+  private final Element codeViewer;
+
   public SourceCodeView(String sourceUrl) {
+    this(sourceUrl, null);
+  }
+
+  public SourceCodeView(String sourceUrl, Map<String, String> properties) {
     String url = translateSource(sourceUrl);
-    Element codeViewer = new Element("code-viewer");
+    codeViewer = new Element("code-viewer");
     getElement().appendChild(codeViewer);
     getElement().getStyle().set("display", "flex");
     codeViewer.getStyle().set("flex-grow", "1");
+    setProperties(properties);
     addAttachListener(
         ev -> {
           codeViewer.executeJs("this.fetchContents($0,$1)", url, "java");
@@ -49,4 +59,16 @@ private static String translateSource(String url) {
     }
     return url;
   }
+
+  private void setProperties(Map<String, String> properties) {
+    if (properties != null) {
+      JsonObject env = Json.createObject();
+      properties.forEach((k, v) -> {
+        if (v != null) {
+          env.put(k, Json.create(v));
+        }
+      });
+      codeViewer.setPropertyJson("env", env);
+    }
+  }
 }

src/main/java/com/flowingcode/vaadin/addons/demo/SplitLayoutDemo.java

@@ -23,6 +23,9 @@
 import com.vaadin.flow.component.Composite;
 import com.vaadin.flow.component.splitlayout.SplitLayout;
 import com.vaadin.flow.component.splitlayout.SplitLayout.Orientation;
+import com.vaadin.flow.server.Version;
+import java.util.HashMap;
+import java.util.Map;
 
 @SuppressWarnings("serial")
 class SplitLayoutDemo extends Composite<SplitLayout> {
@@ -31,8 +34,12 @@ class SplitLayoutDemo extends Composite<SplitLayout> {
 
   public SplitLayoutDemo(Component demo, String sourceUrl) {
     getContent().setOrientation(Orientation.HORIZONTAL);
-    code = new SourceCodeView(sourceUrl);
 
+    Map<String, String> properties = new HashMap<>();
+    properties.put("vaadin", VaadinVersion.getVaadinVersion());
+    properties.put("flow", Version.getFullVersion());
+
+    code = new SourceCodeView(sourceUrl, properties);
     getContent().addToPrimary(demo);
     getContent().addToSecondary(code);
     getContent().setSizeFull();

src/main/java/com/flowingcode/vaadin/addons/demo/VaadinVersion.java

@@ -0,0 +1,27 @@
+package com.flowingcode.vaadin.addons.demo;
+
+import com.vaadin.flow.server.Version;
+import java.util.Objects;
+import java.util.Properties;
+import org.slf4j.LoggerFactory;
+
+public class VaadinVersion {
+
+  private VaadinVersion() {
+    throw new UnsupportedOperationException();
+  }
+
+  public static String getVaadinVersion() {
+    try {
+      Properties pom = new Properties();
+      pom.load(VaadinVersion.class
+          .getResourceAsStream("/META-INF/maven/com.vaadin/vaadin-core/pom.properties"));
+      return Objects.requireNonNull((String) pom.get("version"));
+    } catch (Exception e) {
+      LoggerFactory.getLogger(Version.class.getName())
+          .warn("Unable to determine Vaadin version number", e);
+      return null;
+    }
+  }
+
+}

src/main/resources/META-INF/resources/frontend/code-viewer.ts

@@ -244,7 +244,54 @@ pre[class*="language-"] {
   }
 
   cleanupCode(text: string) : string {
-    return text.split('\n').map(line=>{
+    let lines  : (string|null)[] = text.split('\n');
+    let guards : (string|undefined)[] = [];
+    let stack  : string[] = [];
+    
+    let __elif = (guard:(string|undefined),value:(string|undefined)) => {
+        return guard=='isfalse' ? value : 'wastrue';
+    };
+    
+    let transition = (top:string, next:string) => {
+        let result = stack.pop()==top;
+        stack.push(result?next:'error'); 
+        return result;
+    };
+
+    for (let i=0;i<lines.length;i++) {
+        let m = lines[i]!.match("^\\s*//\\s*#(?<directive>\\w+)\\s*(?<line>.*)");
+        if (m && m.groups) {
+            let line = m.groups.line;
+            switch (m.groups.directive) {
+                case 'if':
+                    stack.push('if');
+                    guards.push(this.__eval(line));
+                    lines[i]=null;
+                    break;
+                case 'else':
+                    if (!transition('if', 'else')) break;
+                    guards.push(__elif(guards.pop(), 'istrue'));
+                    lines[i]=null;
+                    break;
+                case 'elif':
+                    if (!transition('if', 'if')) break;
+                    guards.push(__elif(guards.pop(), this.__eval(line)));
+                    lines[i]=null;
+                    break;
+                case 'endif':
+                    stack.pop();
+                    guards.pop();
+                    lines[i]=null;
+            }
+        }
+
+        if (!guards.every(x=>x=='istrue')) {
+            lines[i] = null;
+        }
+    }
+    
+    return lines.filter(line=>line!==null)
+    .map(line=>{
         let m= line!.match("^(?<spaces>\\s*)//\\s*show-source\\s(?<line>.*)");
         return m?m.groups!.spaces+m.groups!.line : line!;
     }).filter(line=>
@@ -268,4 +315,44 @@ pre[class*="language-"] {
       .replace(/'/g, "&#039;");
   }
 
+  __eval(line: string) : string|undefined {
+    let expr = line.split(' ');
+    if (expr.length==3) {
+        if (expr[0]!='vaadin') {
+            return 'isfalse';
+        }
+        
+        let op = (a:string,b:string) => { 
+            switch (expr[1]) {
+                case 'lt': return this.__compare(a,b)<0; 
+                case 'le': return this.__compare(a,b)<=0; 
+                case 'eq': return this.__compare(a,b)==0;
+                case 'ge': return this.__compare(a,b)>=0;
+                case 'gt': return this.__compare(a,b)>0;
+                case 'ne': return this.__compare(a,b)!=0;;
+                default: return undefined;
+        }};
+        
+        switch (op('23',expr[2])) {
+            case true: return 'istrue';
+            case false: return 'isfalse';
+        }
+    }
+    return undefined;
+  }
+  
+  __compare(a: string, b:string) : number {
+     let aa = a.split('.');
+     let bb = b.split('.');
+     for (let i=0; i<Math.min(aa.length,bb.length); i++) {
+         let ai = parseInt(aa[i]);
+         let bi = parseInt(bb[i]);
+         if (ai<bi) return -1;
+         if (ai>bi) return +1;
+     }
+     if (aa.length<bb.length) return -1;
+     if (aa.length<bb.length) return +1;
+     return 0;
+   }
+
 }

src/test/java/com/flowingcode/vaadin/addons/demo/SampleDemoDefault.java

@@ -33,5 +33,8 @@ public SampleDemoDefault() {
     add(new Span("Demo component with defaulted @DemoSource annotation"));
     //show-source System.out.println("this line will be displayed in the code snippet");
     this.getClass(); // hide-source (this line will not be displayed in the code snippet)
+    //#if vaadin ge 23
+    //show-source System.out.println("conditional code for Vaadin 23+");
+    //#endif
   }
 }