feat: add example picker dropdown to sample diagrams

Each diagram type in the Sample Diagrams panel is now a split button:
clicking the diagram name loads its default example, and a dropdown
arrow on the right (shown when a diagram has more than one example)
opens a popover listing all examples for that diagram.

- getSampleDiagrams now returns all examples per diagram with the
  default example first, instead of flattening to the default's code
- loadSampleDiagram analytics now include the chosen example title

https://claude.ai/code/session_015rUgHChBEkquLu77fMxmQ6

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/lib/components/Preset.svelte

@@ -1,13 +1,20 @@
 <script lang="ts">
   import Card from '$/components/Card/Card.svelte';
-  import { Button } from '$/components/ui/button';
-  import { getSampleDiagrams } from '$/util/mermaid';
+  import { Button, buttonVariants } from '$/components/ui/button';
+  import * as Popover from '$/components/ui/popover';
+  import { getSampleDiagrams, type SampleExample } from '$/util/mermaid';
   import { updateCode } from '$lib/util/state.svelte';
   import { logEvent } from '$lib/util/stats';
+  import { cn } from '$lib/utils';
   import ShapesIcon from '~icons/material-symbols/account-tree-outline-rounded';
+  import ChevronDownIcon from '~icons/material-symbols/keyboard-arrow-down-rounded';
 
-  const extras = {
-    ZenUML: `zenuml
+  const extras: Record<string, SampleExample[]> = {
+    ZenUML: [
+      {
+        title: 'Order Service',
+        isDefault: true,
+        code: `zenuml
     title Order Service
     @Actor Client #FFEBE6
     @Boundary OrderController #0747A6
@@ -31,15 +38,18 @@
       }
     }
     `
+      }
+    ]
   };
 
-  const samples = { ...getSampleDiagrams(), ...extras } as const;
-  const loadSampleDiagram = (diagramType: string): void => {
-    updateCode(samples[diagramType as keyof typeof samples], {
+  const samples = { ...getSampleDiagrams(), ...extras };
+
+  const loadSampleDiagram = (diagramType: string, example: SampleExample): void => {
+    updateCode(example.code, {
       resetPanZoom: true,
       updateDiagram: true
     });
-    logEvent('loadSampleDiagram', { diagramType });
+    logEvent('loadSampleDiagram', { diagramType, exampleTitle: example.title });
   };
 
   const mainDiagrams = [
@@ -62,12 +72,39 @@
 <Card title="Sample Diagrams" isOpen isStackable icon={{ component: ShapesIcon }}>
   <div class="flex h-fit max-h-52 flex-wrap gap-2 overflow-y-auto p-2">
     {#each diagramOrder as sample (sample)}
+      {@const examples = samples[sample]}
+      <div class="flex min-w-20 flex-grow">
         <Button
           size="sm"
-        class="w-fit min-w-20 flex-grow normal-case"
-        onclick={() => loadSampleDiagram(sample)}>
+          class={cn('flex-grow normal-case', examples.length > 1 && 'rounded-r-none')}
+          onclick={() => loadSampleDiagram(sample, examples[0])}>
           {sample}
         </Button>
+        {#if examples.length > 1}
+          <Popover.Root>
+            <Popover.Trigger
+              aria-label="Choose a {sample} example"
+              class={cn(
+                buttonVariants({ size: 'sm' }),
+                'rounded-l-none border-l border-primary-foreground/30 px-0.5 [&_svg]:size-5'
+              )}>
+              <ChevronDownIcon />
+            </Popover.Trigger>
+            <Popover.Content align="start" class="flex w-fit flex-col gap-1 p-1">
+              {#each examples as example (example.title)}
+                <Popover.Close
+                  class={cn(
+                    buttonVariants({ variant: 'ghost', size: 'sm' }),
+                    'justify-start normal-case'
+                  )}
+                  onclick={() => loadSampleDiagram(sample, example)}>
+                  {example.title}
+                </Popover.Close>
+              {/each}
+            </Popover.Content>
+          </Popover.Root>
+        {/if}
+      </div>
     {/each}
   </div>
 </Card>

src/lib/util/mermaid.test.ts

@@ -0,0 +1,23 @@
+import { describe, expect, it } from 'vitest';
+import { getSampleDiagrams } from './mermaid';
+
+describe('getSampleDiagrams', () => {
+  const samples = getSampleDiagrams();
+
+  it('should return at least one example per diagram', () => {
+    expect(Object.keys(samples).length).toBeGreaterThan(0);
+    for (const [name, examples] of Object.entries(samples)) {
+      expect(examples.length, `${name} should have at least one example`).toBeGreaterThan(0);
+      for (const example of examples) {
+        expect(example.title, `${name} has an example without a title`).toBeTruthy();
+        expect(example.code, `${name} example "${example.title}" has no code`).toBeTruthy();
+      }
+    }
+  });
+
+  it('should list the default example first', () => {
+    for (const [name, examples] of Object.entries(samples)) {
+      expect(examples[0].isDefault, `${name} should have its default example first`).toBe(true);
+    }
+  });
+});

src/lib/util/mermaid.ts

@@ -49,20 +49,20 @@ export const standardizeDiagramType = (diagramType: string) => {
 
 type DiagramDefinition = (typeof diagramData)[number];
 
+export type SampleExample = DiagramDefinition['examples'][number];
+
 const isValidDiagram = (diagram: DiagramDefinition): diagram is Required<DiagramDefinition> => {
   return Boolean(diagram.name && diagram.examples && diagram.examples.length > 0);
 };
 
-export const getSampleDiagrams = () => {
-  const diagrams = diagramData
-    .filter((d) => isValidDiagram(d))
-    .map(({ examples, ...rest }) => ({
-      ...rest,
-      example: examples?.filter(({ isDefault }) => isDefault)[0]
-    }));
-  const examples: Record<string, string> = {};
-  for (const diagram of diagrams) {
-    examples[diagram.name.replace(/ (Diagram|Chart|Graph)/, '')] = diagram.example.code;
+export const getSampleDiagrams = (): Record<string, SampleExample[]> => {
+  const samples: Record<string, SampleExample[]> = {};
+  for (const diagram of diagramData.filter((d) => isValidDiagram(d))) {
+    // The default example comes first, so it is loaded when clicking the
+    // diagram name and shown at the top of the example dropdown.
+    samples[diagram.name.replace(/ (Diagram|Chart|Graph)/, '')] = [...diagram.examples].sort(
+      (a, b) => Number(b.isDefault ?? false) - Number(a.isDefault ?? false)
+    );
   }
-  return examples;
+  return samples;
 };