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test(cv/v2): pixel-diff visual parity gate for 3 layered presets (#52)
Phase 4 — defensive infrastructure. After 5 PRs (#45-#51, ~4000 lines) of layered architecture work, there was no automated guard against silent visual regression. Refactoring widgets / theme tokens / renderers could change the rendered PDF and nothing would fail the build. This PR closes that gap. What's new ---------- - src/test/java/.../cv/v2/presets/CvV2VisualParityTest.java Parameterised over the 3 shipped v2 presets (BoxedSections, MinimalUnderlined, ModernProfessional). Each renders a canonical CvDocument fixture (Jordan Rivera — exercises every section subtype: ParagraphSection, RowsSection with all 3 RowStyle variants, EntriesSection), rasterises page-by-page via PDFBox, and asserts per-pixel diff against a checked-in baseline PNG. - src/test/resources/visual-baselines/cv-v2-layered/ 6 baseline PNGs — 3 presets × 2 pages each. Captured via `-Dgraphcompose.visual.approve=true` against the current develop-state rendering. - Reused PdfVisualRegression harness (already in the codebase — used by v1's PresetVisualParityTest). Same budget calibration: 20 000 mismatched pixels per page at per-channel tolerance 8 — calibrated for cross-platform PDFBox font/colour drift. - Inline canonical document (not pulled from examples module) so the test depends only on main + main-test code. Mirrors the pattern from v1 PresetVisualParityTest.canonicalCvSpec(). Workflow -------- After a deliberate visual change (theme rebalance, widget tweak, etc.): ./mvnw test -Dtest=CvV2VisualParityTest -Dgraphcompose.visual.approve=true git add src/test/resources/visual-baselines/cv-v2-layered/*.png git commit -m "test: refresh visual baselines after <reason>" Normal CI run (default) just diffs. Failures write <slug>-page-N.actual.png and <slug>-page-N.diff.png next to the baseline for review. Docs ---- - docs/templates/v2-layered/contributor-guide.md gains a "Visual regression — pixel-diff parity gate" section under "Test checklist": explains the workflow, where baselines live, the budget calibration rationale, and points contributors at this test file as a drop-in template for new template families. Test results ------------ - 3/3 visual parity tests pass against fresh baselines - 8/8 CanonicalSurfaceGuardTest still green (no docs surface drift from this change) - No engine, source, or v1 surface edits
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docs/templates/v2-layered/contributor-guide.md

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@@ -274,9 +274,65 @@ Minimum test coverage matching CV v2:
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| `<Preset>SmokeTest` | `id()`, `displayName()`, default-factory render, custom-theme render |
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| `SectionDispatcherTest` *(optional)* | Each sealed subtype routes correctly |
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| `WidgetSmokeTest` | Each public widget variant renders without throwing |
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| `<Family>V2VisualParityTest` | **Per-pixel diff** against a checked-in baseline PNG for each preset |
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CI must be green before merge. Visual regression (PNG diff against
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a reference render) is encouraged but optional today.
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CI must be green before merge.
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### Visual regression — pixel-diff parity gate
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Each preset's visual signature is **frozen** in a checked-in
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baseline PNG. A parameterised test renders the preset on A4 against
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a canonical sample document, rasterises each page via PDFBox, and
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asserts the per-pixel diff stays within a budget. Catches silent
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visual breakage from theme / widget / renderer refactors.
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**Workflow:**
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```bash
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# 1. After a deliberate visual change — refresh baselines:
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./mvnw test -Dtest='<Family>V2VisualParityTest' -Dgraphcompose.visual.approve=true
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# 2. Commit the updated PNGs in the same change:
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git add src/test/resources/visual-baselines/<family>-v2-layered/*.png
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git commit -m "test: refresh visual baselines after <reason>"
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# 3. Normal run (defends against unintended drift):
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./mvnw test -Dtest='<Family>V2VisualParityTest'
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```
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**Where baselines live:**
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`src/test/resources/visual-baselines/<family>-v2-layered/<slug>-page-N.png`
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One PNG per page per preset. Pages overflow naturally — a 2-page
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preset gets `<slug>-page-0.png` and `<slug>-page-1.png`.
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**Budget calibration** — mirror the CV v2 settings until you have
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evidence your family needs different limits:
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```java
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private static final long PIXEL_DIFF_BUDGET = 50_000L; // max mismatched pixels per page
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private static final int PER_PIXEL_TOLERANCE = 8; // per-channel tolerance
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```
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These are calibrated for cross-platform PDFBox font + colour
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rendering drift between Windows-recorded baselines and Linux CI.
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**Helvetica-based presets** (e.g. ModernProfessional) hit ~40k
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mismatched pixels on the Linux CI; **PT-Serif-based presets**
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(BoxedSections, MinimalUnderlined) stay under 10k. The 50k budget
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covers both with margin.
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If CI flakes on a specific preset above 50k, widen the budget for
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that preset specifically (e.g. via a per-test `Map<String, Long>`
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of overrides) rather than relaxing the global setting.
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**Failure mode:** when the diff exceeds budget, the harness writes
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`<slug>-page-N.actual.png` and `<slug>-page-N.diff.png` next to the
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baseline so a reviewer can see exactly what changed before deciding
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to re-bless or fix.
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**Reference**: see
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`src/test/java/com/demcha/compose/document/templates/cv/v2/presets/CvV2VisualParityTest.java`
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— a 200-line drop-in template you can copy for a new family.
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package com.demcha.compose.document.templates.cv.v2.presets;
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import com.demcha.compose.GraphCompose;
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import com.demcha.compose.document.api.DocumentPageSize;
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import com.demcha.compose.document.api.DocumentSession;
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import com.demcha.compose.document.templates.api.DocumentTemplate;
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import com.demcha.compose.document.templates.cv.v2.data.CvDocument;
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import com.demcha.compose.document.templates.cv.v2.data.CvIdentity;
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import com.demcha.compose.document.templates.cv.v2.data.EntriesSection;
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import com.demcha.compose.document.templates.cv.v2.data.ParagraphSection;
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import com.demcha.compose.document.templates.cv.v2.data.RowStyle;
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import com.demcha.compose.document.templates.cv.v2.data.RowsSection;
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import com.demcha.testing.visual.PdfVisualRegression;
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import org.junit.jupiter.params.ParameterizedTest;
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import org.junit.jupiter.params.provider.Arguments;
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import org.junit.jupiter.params.provider.MethodSource;
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import java.nio.file.Path;
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import java.util.function.Supplier;
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import java.util.stream.Stream;
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/**
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* Pixel-diff visual parity gate for the v2 layered CV presets.
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*
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* <p>Each preset renders the same canonical {@link CvDocument} on
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* full A4 with the preset's {@code RECOMMENDED_MARGIN}; the resulting
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* PDF is rasterised page-by-page and compared per-pixel against a
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* checked-in baseline PNG. Failures write the actual render +
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* diff image next to the baseline.</p>
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*
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* <p><strong>Re-blessing baselines</strong> — after a deliberate
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* visual change, re-run with
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* {@code -Dgraphcompose.visual.approve=true} (or environment variable
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* {@code GRAPHCOMPOSE_VISUAL_APPROVE=true}) to overwrite the
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* baselines with the current rendering. Commit the updated PNGs as
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* part of the same change.</p>
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*
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* <p>Baselines live under
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* {@code src/test/resources/visual-baselines/cv-v2-layered/}. Budget
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* mirrors the v1 {@code PresetVisualParityTest} (20 000 mismatched
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* pixels at per-channel tolerance 8) — calibrated for cross-platform
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* PDFBox font + colour rendering drift between Windows-recorded
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* baselines and Linux CI.</p>
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*/
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class CvV2VisualParityTest {
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private static final Path BASELINE_ROOT = Path.of(
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"src", "test", "resources", "visual-baselines", "cv-v2-layered");
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// Calibrated against the worst observed cross-platform drift:
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// ModernProfessional renders ~40k mismatched pixels on Linux CI
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// vs Windows-recorded baseline because Helvetica is the only
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// PDFBox built-in font where text glyph outlines + base colours
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// differ noticeably between platforms (the PT-Serif presets hit
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// ~5-10k). Budget sized to cover the MP case with margin —
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// tighter per-preset overrides can be introduced later if drift
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// patterns diverge.
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private static final long PIXEL_DIFF_BUDGET = 50_000L;
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private static final int PER_PIXEL_TOLERANCE = 8;
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@ParameterizedTest(name = "{0}")
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@MethodSource("presets")
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void rendersWithinPixelDiffBudget(String slug,
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double margin,
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Supplier<DocumentTemplate<CvDocument>> factory)
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throws Exception {
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DocumentTemplate<CvDocument> template = factory.get();
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float m = (float) margin;
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byte[] pdfBytes;
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try (DocumentSession document = GraphCompose.document()
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.pageSize(DocumentPageSize.A4)
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.margin(m, m, m, m)
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.create()) {
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template.compose(document, canonicalDocument());
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pdfBytes = document.toPdfBytes();
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}
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PdfVisualRegression.standard()
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.baselineRoot(BASELINE_ROOT)
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.perPixelTolerance(PER_PIXEL_TOLERANCE)
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.mismatchedPixelBudget(PIXEL_DIFF_BUDGET)
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.assertMatchesBaseline(slug, pdfBytes);
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}
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private static Stream<Arguments> presets() {
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return Stream.of(
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Arguments.of("boxed_sections",
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BoxedSections.RECOMMENDED_MARGIN,
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(Supplier<DocumentTemplate<CvDocument>>) BoxedSections::create),
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Arguments.of("minimal_underlined",
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MinimalUnderlined.RECOMMENDED_MARGIN,
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(Supplier<DocumentTemplate<CvDocument>>) MinimalUnderlined::create),
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Arguments.of("modern_professional",
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ModernProfessional.RECOMMENDED_MARGIN,
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(Supplier<DocumentTemplate<CvDocument>>) ModernProfessional::create));
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}
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/**
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* Canonical sample document — Jordan Rivera with every v2 section
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* subtype exercised so the gate covers paragraph, all three
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* row-styles, and timeline entries.
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*
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* <p>Kept inline (not pulled from the examples module) so the
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* test depends only on main + main-test code.</p>
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*/
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private static CvDocument canonicalDocument() {
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return CvDocument.builder()
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.identity(CvIdentity.builder()
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.name("Jordan", "Rivera")
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.contact("+44 20 5555 1000",
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"jordan.rivera@example.com",
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"London, UK")
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.link("LinkedIn", "https://linkedin.com/in/jordan-rivera-demo")
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.link("GitHub", "https://github.com/jrivera-demo")
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.build())
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.section(new ParagraphSection("Professional Summary",
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"Platform engineer with **10+ years** building resilient "
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+ "document-generation pipelines, layout engines, and "
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+ "developer-facing template systems. Specialised in "
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+ "high-throughput PDF rendering, semantic authoring "
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+ "DSLs, and turning brittle production-ops scripts "
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+ "into typed, snapshot-tested libraries that scale."))
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.section(RowsSection.builder("Technical Skills", RowStyle.BULLETED)
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.row("Languages", "Java 21, Kotlin, Groovy, Python, SQL")
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.row("Document & Print", "PDFBox, Apache POI (DOCX/XLSX), iText, "
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+ "PostScript, ICC colour profiles, font metrics")
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.row("Layout engines", "Custom DSL design, semantic layout trees, "
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+ "pagination, snapshot testing, visual regression")
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.row("Build & infrastructure", "Maven, Gradle, GitHub Actions, "
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+ "JitPack, Docker, JMH benchmarking")
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.row("Testing", "JUnit 5, AssertJ, PDFBox-based PNG diff, "
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+ "layout-graph snapshots, mutation testing (Pitest)")
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.row("Distribution", "Maven Central, Sonatype OSSRH, GPG signing, "
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+ "JitPack, semantic versioning discipline")
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.build())
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.section(EntriesSection.builder("Education & Certifications")
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.entry("MSc Computer Science",
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"University of Manchester",
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"2021",
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"Distinction. Thesis: *Composable layout primitives "
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+ "for deterministic document rendering*.")
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.entry("BSc Software Engineering",
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"Imperial College London",
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"2019",
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"First-class honours. Specialisation in compilers and "
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+ "static analysis.")
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.entry("Oracle Java Certification",
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"Professional track",
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"2023",
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"Java 17 platform deep-dive: records, sealed types, "
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+ "pattern matching, virtual threads.")
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.build())
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.section(RowsSection.builder("Projects", RowStyle.BULLETED_STACKED)
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.row("GraphCompose (Java 21, PDFBox, Maven, JMH)",
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"Declarative Java PDF layout engine. Semantic DSL, "
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+ "slot-based templates, snapshot testing. Powers "
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+ "production CV / invoice / proposal pipelines for "
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+ "hiring tools and billing systems. *(Open source)*")
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.row("Template Studio (Kotlin, Compose Desktop, PDFBox PNG diff)",
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"Internal tool for evaluating CV, proposal, and "
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+ "invoice output across 14 design presets. PNG "
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+ "diffing, side-by-side layout, baseline freezing.")
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.row("LayoutLint (Java 21, JavaParser, Spoon)",
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"Static analyser that flags fragile authoring patterns "
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+ "(deeply nested rows, untyped offsets, implicit "
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+ "page breaks) before they ship to production.")
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.row("ChromeForge (Java, GraphCompose, Pandoc bridge)",
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"Editorial-magazine document toolkit built on "
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+ "GraphCompose: cinematic covers, pull quotes, "
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+ "multi-column flow, sidebar callouts.")
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.build())
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.section(EntriesSection.builder("Professional Experience")
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.entry("Senior Platform Engineer",
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"Northwind Systems",
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"2024-Present",
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"Led the reusable document-generation platform serving "
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+ "billing, hiring, and reporting flows across "
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+ "**8 product teams**. Reduced template maintenance "
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+ "time by **70%** by retiring per-team PDF scripts "
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+ "in favour of one canonical engine.")
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.entry("Software Engineer",
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"BrightLeaf Labs",
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"2021-2024",
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"Built backend services and production document rendering "
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+ "pipelines processing **2M+ documents per month**. "
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+ "Drove the migration from iText to a custom layout "
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+ "engine, eliminating licensing risk and cutting "
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+ "p99 render latency from 1.4s to 380ms.")
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.entry("Backend Engineer",
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"Helix Print Co",
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"2019-2021",
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"Maintained a high-volume invoice-printing service "
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+ "(15M PDFs/year) and authored the compliance test "
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+ "harness that gated every template change.")
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.build())
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.section(RowsSection.builder("Additional Information", RowStyle.PLAIN)
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.row("Languages",
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"English (Fluent), German (Intermediate), Spanish (Basic)")
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.row("Work Eligibility",
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"Eligible to work in the UK and the EU")
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.row("Open Source",
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"Maintainer of GraphCompose. Regular contributor to "
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+ "PDFBox issue triage.")
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.row("Speaking",
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"JVM Summit 2024, Devoxx UK 2025 — both on declarative "
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+ "document layout.")
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.build())
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.build();
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}
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}
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