gstack/make-pdf/test/diagram-prepass.test.ts

/**
 * Unit tests for the diagram pre-pass: fence extraction, info-string parsing,
 * slot substitution, diagnostic blocks, image inlining policy, and the
 * byte-level image dimension prober, and the bundle runner's script shape
 * (render function injected). No live Aside required — `run: null` makes
 * downscale paths no-ops.
 */
import { afterAll, describe, expect, test } from "bun:test";
import * as fs from "node:fs";
import * as os from "node:os";
import * as path from "node:path";
import zlib from "node:zlib";

import {
  type BundleCall,
  type BundleResult,
  StrictModeError,
  buildDiagnosticBlock,
  bundleRunner,
  buildDiagramFigure,
  contentWidthInches,
  dimToInches,
  extractDiagramFences,
  inlineLocalImages,
  landscapeContentBox,
  parseInfoString,
  rasterizeDiagramFigures,
  renderFenceSlots,
  resolveBundlePath,
  substituteSlots,
  decodeFigureSource,
} from "../src/diagram-prepass";
import { imageDims } from "../src/image-size";
import type { RenderResult, RenderSpec } from "../../lib/aside-render";

// ─── fence extraction ─────────────────────────────────────────────────

describe("extractDiagramFences", () => {
  test("extracts a mermaid fence and replaces it with a token paragraph", () => {
    const md = "# T\n\n```mermaid\ngraph LR\n  A --> B\n```\n\ntail";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(1);
    expect(fences[0].lang).toBe("mermaid");
    expect(fences[0].source).toBe("graph LR\n  A --> B");
    expect(markdown).toContain(fences[0].token);
    expect(markdown).not.toContain("```mermaid");
  });

  test("extracts excalidraw fences", () => {
    const md = '```excalidraw\n{"type":"excalidraw","elements":[]}\n```';
    const { fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(1);
    expect(fences[0].lang).toBe("excalidraw");
  });

  test("render=false keeps the fence as code and strips the flag", () => {
    const md = "```mermaid render=false\ngraph LR\n  X --> Y\n```";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(0);
    expect(markdown).toContain("```mermaid\ngraph LR");
    expect(markdown).not.toContain("render=false");
  });

  test("title is captured from the info string", () => {
    const md = '```mermaid title="Auth flow"\ngraph LR\n  A --> B\n```';
    const { fences } = extractDiagramFences(md);
    expect(fences[0].title).toBe("Auth flow");
  });

  test("non-diagram fences pass through untouched", () => {
    const md = "```js\nconst a = 1;\n```";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(0);
    expect(markdown).toBe(md);
  });

  test("a mermaid example inside a plain fence is never extracted", () => {
    const md = "````\n```mermaid\ngraph LR\n```\n````";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(0);
    expect(markdown).toBe(md);
  });

  test("tilde fences work", () => {
    const md = "~~~mermaid\ngraph TD\n  A --> B\n~~~";
    const { fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(1);
  });

  test("unclosed fence at EOF replays verbatim", () => {
    const md = "```mermaid\ngraph LR\n  A --> B";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(0);
    expect(markdown).toBe(md);
  });

  test("multiple fences get distinct ordinals and tokens", () => {
    const md = "```mermaid\nA\n```\n\nmiddle\n\n```mermaid\nB\n```";
    const { fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(2);
    expect(fences[0].ordinal).toBe(1);
    expect(fences[1].ordinal).toBe(2);
    expect(fences[0].token).not.toBe(fences[1].token);
  });
});

describe("parseInfoString", () => {
  test("plain language", () => {
    expect(parseInfoString("mermaid")).toEqual({ lang: "mermaid", render: true, title: undefined });
  });
  test("render=false", () => {
    expect(parseInfoString("mermaid render=false").render).toBe(false);
  });
  test("single-quoted title", () => {
    expect(parseInfoString("mermaid title='Hi there'").title).toBe("Hi there");
  });
});

// ─── slots ────────────────────────────────────────────────────────────

describe("substituteSlots", () => {
  test("replaces the <p>-wrapped token with slot HTML", () => {
    const slots = new Map([["gstack-diagram-slot-ab-1", "<figure>X</figure>"]]);
    const html = "<h1>T</h1>\n<p>gstack-diagram-slot-ab-1</p>\n<p>tail</p>";
    const out = substituteSlots(html, slots);
    expect(out).toContain("<figure>X</figure>");
    expect(out).not.toContain("gstack-diagram-slot");
    expect(out).not.toContain("<p><figure>");
  });
});

describe("diagnostic + figure blocks", () => {
  const fence = {
    lang: "mermaid", source: "graph LR\n  A --> B", render: true,
    token: "t", ordinal: 3, title: undefined,
  };
  test("diagnostic block escapes error content and names the lang", () => {
    const block = buildDiagnosticBlock(fence, 'Parse <error> "quoted"');
    expect(block).toContain("diagram-error");
    expect(block).toContain("Diagram failed to render (mermaid)");
    expect(block).toContain("Parse &lt;error&gt;");
    expect(block).not.toContain("<error>");
  });
  test("figure carries role=img and ordinal-based aria-label fallback", () => {
    const fig = buildDiagramFigure(fence, "<svg></svg>");
    expect(fig).toContain('role="img"');
    expect(fig).toContain('aria-label="diagram 3"');
    expect(fig).toContain("<svg></svg>");
  });
  test("figure strips scripts from SVG (sanitizer second layer)", () => {
    const fig = buildDiagramFigure(fence, "<svg><script>alert(1)</script><g/></svg>");
    expect(fig).not.toContain("<script>");
  });
  test("title becomes aria-label and caption", () => {
    const fig = buildDiagramFigure({ ...fence, title: "Auth flow" }, "<svg></svg>");
    expect(fig).toContain('aria-label="Auth flow"');
    expect(fig).toContain("diagram-caption");
  });
  test("embedded source round-trips mermaid arrows exactly", () => {
    const source = "graph LR\n  A --> B\n  B -->|label with $& and `ticks`| C";
    const fig = buildDiagramFigure({ ...fence, source }, "<svg></svg>");
    expect(decodeFigureSource(fig)).toBe(source);
  });
  test("slot substitution is immune to $-replacement patterns in labels", () => {
    const slotHtml = `<figure>label says $' and $& here</figure>`;
    const out = substituteSlots("<p>tok-x</p><p>tail</p>", new Map([["tok-x", slotHtml]]));
    expect(out).toContain("label says $' and $& here");
    expect(out).toContain("<p>tail</p>");
    expect(out).not.toContain("tailtail"); // $' expansion would duplicate the tail
  });
});

// ─── image dimension probing ──────────────────────────────────────────

function tinyPng(w: number, h: number): Buffer {
  const chunk = (t: string, d: Buffer) => {
    const body = Buffer.concat([Buffer.from(t, "ascii"), d]);
    const len = Buffer.alloc(4);
    len.writeUInt32BE(d.length);
    const crc = Buffer.alloc(4);
    crc.writeUInt32BE(zlib.crc32 ? zlib.crc32(body) : 0);
    return Buffer.concat([len, body, crc]);
  };
  const ihdr = Buffer.alloc(13);
  ihdr.writeUInt32BE(w, 0);
  ihdr.writeUInt32BE(h, 4);
  ihdr[8] = 8; ihdr[9] = 2;
  const raw = Buffer.concat(
    Array.from({ length: h }, () => Buffer.concat([Buffer.from([0]), Buffer.alloc(w * 3, 0x80)])),
  );
  return Buffer.concat([
    Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]),
    chunk("IHDR", ihdr),
    chunk("IDAT", zlib.deflateSync(raw)),
    chunk("IEND", Buffer.alloc(0)),
  ]);
}

describe("imageDims", () => {
  test("PNG", () => {
    expect(imageDims(tinyPng(640, 480))).toEqual({ width: 640, height: 480, mime: "image/png" });
  });
  test("GIF", () => {
    const b = Buffer.alloc(13);
    b.write("GIF89a", 0, "ascii");
    b.writeUInt16LE(320, 6);
    b.writeUInt16LE(200, 8);
    expect(imageDims(b)).toEqual({ width: 320, height: 200, mime: "image/gif" });
  });
  test("JPEG (SOF0)", () => {
    const b = Buffer.from([
      0xff, 0xd8,                                  // SOI
      0xff, 0xe0, 0x00, 0x04, 0x00, 0x00,          // APP0 len 4
      0xff, 0xc0, 0x00, 0x0b, 0x08, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x00, 0x00, // SOF0 h=256 w=512
    ]);
    expect(imageDims(b)).toEqual({ width: 512, height: 256, mime: "image/jpeg" });
  });
  test("SVG via width/height attrs", () => {
    const b = Buffer.from('<svg xmlns="x" width="800" height="400"></svg>');
    expect(imageDims(b)).toEqual({ width: 800, height: 400, mime: "image/svg+xml" });
  });
  test("SVG via viewBox", () => {
    const b = Buffer.from('<svg viewBox="0 0 1200 600"></svg>');
    expect(imageDims(b)).toEqual({ width: 1200, height: 600, mime: "image/svg+xml" });
  });
  test("unknown bytes → null", () => {
    expect(imageDims(Buffer.from("definitely not an image, sorry"))).toBeNull();
  });
});

// ─── content-box math ─────────────────────────────────────────────────

describe("content width", () => {
  test("letter with 1in margins = 6.5in", () => {
    expect(contentWidthInches({})).toBeCloseTo(6.5);
  });
  test("a4 with 25mm margins", () => {
    expect(contentWidthInches({ pageSize: "a4", margins: "25mm" })).toBeCloseTo(8.27 - 50 / 25.4, 2);
  });
  test("dimToInches parses pt/cm/mm/px", () => {
    expect(dimToInches("72pt", 1)).toBeCloseTo(1);
    expect(dimToInches("2.54cm", 1)).toBeCloseTo(1);
    expect(dimToInches("25.4mm", 1)).toBeCloseTo(1);
    expect(dimToInches("96px", 1)).toBeCloseTo(1);
    expect(dimToInches("garbage", 1.5)).toBe(1.5);
  });
});

// ─── image inlining ───────────────────────────────────────────────────

describe("inlineLocalImages", () => {
  const dir = fs.mkdtempSync(path.join(os.tmpdir(), "prepass-img-"));
  fs.writeFileSync(path.join(dir, "ok.png"), tinyPng(40, 20));
  afterAll(() => {
    try { fs.rmSync(dir, { recursive: true, force: true }); } catch { /* best-effort */ }
  });

  const base = {
    inputDir: dir,
    strict: false,
    allowNetwork: false,
    contentWidthIn: 6.5,
    run: null,
  };

  test("local image becomes a data URI with probed dimensions", async () => {
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="ok.png" alt="x">`, { ...base, warn: (m) => warnings.push(m) });
    expect(out).toContain("data:image/png;base64,");
    expect(out).toContain('data-gstack-px-width="40"');
    expect(out).toContain('data-gstack-px-height="20"');
    expect(warnings).toHaveLength(0);
  });

  test("missing image → visible placeholder + warning", async () => {
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="nope.png">`, { ...base, warn: (m) => warnings.push(m) });
    expect(out).toContain("image-missing");
    expect(out).toContain("nope.png");
    expect(warnings.length).toBe(1);
  });

  test("missing image + --strict → StrictModeError", async () => {
    await expect(
      inlineLocalImages(`<img src="nope.png">`, { ...base, strict: true, warn: () => {} }),
    ).rejects.toThrow(StrictModeError);
  });

  test("remote image is BLOCKED with a visible placeholder (offline posture)", async () => {
    // Leaving the tag would make Chromium fetch it at print time anyway —
    // the offline posture must remove the src, not just warn about it.
    const warnings: string[] = [];
    const tag = `<img src="https://example.com/x.png">`;
    const out = await inlineLocalImages(tag, { ...base, warn: (m) => warnings.push(m) });
    expect(out).not.toContain("https://example.com/x.png\"");
    expect(out).toContain("remote image blocked");
    expect(warnings[0]).toContain("offline");
  });

  test("symlink escaping the input dir is caught by the realpath check", async () => {
    const outside = fs.mkdtempSync(path.join(os.tmpdir(), "prepass-symlink-"));
    fs.writeFileSync(path.join(outside, "secret.png"), tinyPng(5, 5));
    const link = path.join(dir, "innocent.png");
    try {
      fs.symlinkSync(path.join(outside, "secret.png"), link);
      const warnings: string[] = [];
      await inlineLocalImages(`<img src="innocent.png">`, { ...base, warn: (m) => warnings.push(m) });
      expect(warnings.some((w) => w.includes("OUTSIDE the input directory"))).toBe(true);
    } finally {
      try { fs.unlinkSync(link); } catch { /* ignore */ }
      fs.rmSync(outside, { recursive: true, force: true });
    }
  });

  test("special files and oversized images degrade to placeholders, never hang", async () => {
    // Directory masquerading as an image — not a regular file.
    fs.mkdirSync(path.join(dir, "dir.png"), { recursive: true });
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="dir.png">`, { ...base, warn: (m) => warnings.push(m) });
    expect(out).toContain("image-missing");
    expect(warnings.some((w) => w.includes("not a regular file"))).toBe(true);
  });

  test("malformed percent-encoding degrades to missing-image, never throws", async () => {
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="foo%zz.png">`, { ...base, warn: (m) => warnings.push(m) });
    expect(out).toContain("image-missing");
  });

  test("remote image + --allow-network passes silently", async () => {
    const warnings: string[] = [];
    const tag = `<img src="https://example.com/x.png">`;
    const out = await inlineLocalImages(tag, { ...base, allowNetwork: true, warn: (m) => warnings.push(m) });
    expect(out).toBe(tag);
    expect(warnings).toHaveLength(0);
  });

  test("remote image + --strict → StrictModeError", async () => {
    await expect(
      inlineLocalImages(`<img src="https://example.com/x.png">`, { ...base, strict: true, warn: () => {} }),
    ).rejects.toThrow(StrictModeError);
  });

  test("existing data URI gets dimension annotations only", async () => {
    const uri = `data:image/png;base64,${tinyPng(33, 44).toString("base64")}`;
    const out = await inlineLocalImages(`<img src="${uri}">`, { ...base, warn: () => {} });
    expect(out).toContain('data-gstack-px-width="33"');
    expect(out).toContain('data-gstack-px-height="44"');
  });

  test("out-of-tree image reads warn (never silent) and still inline", async () => {
    const outside = fs.mkdtempSync(path.join(os.tmpdir(), "prepass-outside-"));
    fs.writeFileSync(path.join(outside, "ext.png"), tinyPng(10, 10));
    try {
      const warnings: string[] = [];
      const out = await inlineLocalImages(`<img src="${path.join(outside, "ext.png")}">`, {
        ...base, warn: (m) => warnings.push(m),
      });
      expect(out).toContain("data:image/png;base64,");
      expect(warnings.some((w) => w.includes("OUTSIDE the input directory"))).toBe(true);
    } finally {
      fs.rmSync(outside, { recursive: true, force: true });
    }
  });

  test("out-of-tree image + --strict → StrictModeError", async () => {
    const outside = fs.mkdtempSync(path.join(os.tmpdir(), "prepass-outside-"));
    fs.writeFileSync(path.join(outside, "ext.png"), tinyPng(10, 10));
    try {
      await expect(
        inlineLocalImages(`<img src="${path.join(outside, "ext.png")}">`, {
          ...base, strict: true, warn: () => {},
        }),
      ).rejects.toThrow(StrictModeError);
    } finally {
      fs.rmSync(outside, { recursive: true, force: true });
    }
  });

  test("Windows drive-letter src is treated as a local path, not a URL scheme", async () => {
    // C:/x.png matches the single-letter-scheme regex — it must reach the
    // local-path branch (and the missing-file placeholder), never silently
    // pass through as an unknown URL.
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="C:/missing/x.png">`, { ...base, warn: (m) => warnings.push(m) });
    expect(out).toContain("image-missing");
    // Two warnings: it's out-of-tree (resolved outside inputDir) AND missing.
    expect(warnings.some((w) => w.includes("image not found"))).toBe(true);
  });

  test("indented fences inside lists replay byte-for-byte (no list splitting)", () => {
    const md = "- item\n\n  ```js\n  code();\n  ```\n\n- next";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(0);
    expect(markdown).toBe(md);
  });

  test("indented mermaid fences are NOT extracted (column-0 placeholder would split the list)", () => {
    const md = "- item\n\n  ```mermaid\n  graph LR\n  ```\n";
    const { markdown, fences } = extractDiagramFences(md);
    expect(fences).toHaveLength(0);
    expect(markdown).toBe(md);
  });

  test("oversized raster without a tab inlines at full size with no downscale", async () => {
    // 6000px-wide PNG header (body irrelevant for probing; file must exist)
    fs.writeFileSync(path.join(dir, "wide.png"), tinyPng(6000, 100));
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="wide.png">`, { ...base, warn: (m) => warnings.push(m) });
    expect(out).toContain('data-gstack-px-width="6000"');
  });

  test("oversized raster WITH a runner: one __downscaleRaster batch, token swapped for the scaled bytes", async () => {
    fs.writeFileSync(path.join(dir, "wide2.png"), tinyPng(6000, 100));
    const calls: Array<{ fn: string; args: unknown[] }> = [];
    const run = async (batch: Array<{ fn: string; args: unknown[] }>) => {
      calls.push(...batch);
      return batch.map(() => ({ ok: true as const, value: "data:image/png;base64,U0NBTEVE" }));
    };
    const warnings: string[] = [];
    // Same image twice: read/downscaled once, both tags rewritten.
    const out = await inlineLocalImages(`<img src="wide2.png"> <img src="wide2.png" alt="b">`, { ...base, run, warn: (m) => warnings.push(m) });
    expect(calls).toHaveLength(1);
    expect(calls[0].fn).toBe("__downscaleRaster");
    expect(String(calls[0].args[0])).toStartWith("data:image/png;base64,");
    expect(calls[0].args[1]).toBe(1950); // 6.5in × 300dpi
    expect(out.match(/data:image\/png;base64,U0NBTEVE/g)).toHaveLength(2);
    expect(out).toContain('data-gstack-px-width="1950"');
    expect(out).not.toContain("gstack-downscale-slot");
    expect(warnings.some((w) => w.includes("downscaled wide2.png 6000px"))).toBe(true);
  });

  test("a failed downscale falls back to the full-size bytes with a warning", async () => {
    fs.writeFileSync(path.join(dir, "wide3.png"), tinyPng(6000, 100));
    const run = async (batch: unknown[]) => batch.map(() => ({ ok: false as const, error: "image decode failed" }));
    const warnings: string[] = [];
    const out = await inlineLocalImages(`<img src="wide3.png">`, { ...base, run, warn: (m) => warnings.push(m) });
    expect(out).toContain('data-gstack-px-width="6000"');
    expect(out).toContain("data:image/png;base64,");
    expect(out).not.toContain("gstack-downscale-slot");
    expect(warnings.some((w) => w.includes("downscale failed"))).toBe(true);
  });
});

// ─── bundle runner (script shape, injected render) ────────────────────

describe("bundleRunner", () => {
  const bundle = path.join(os.tmpdir(), `fake-bundle-${process.pid}.html`);
  fs.writeFileSync(bundle, "<!doctype html><div id=done>ready</div>");
  afterAll(() => { try { fs.unlinkSync(bundle); } catch { /* best-effort */ } });

  /** Fake Aside: asserts the spec shape and writes OK:/ERR: result files. */
  function fakeRender(script: (fn: string, args: unknown[]) => string) {
    const specs: RenderSpec[] = [];
    const render = async (spec: RenderSpec): Promise<RenderResult> => {
      specs.push(spec);
      for (const step of spec.steps) {
        if (step.kind !== "eval" || !step.out) throw new Error("expected eval steps with out files");
        const i = Number(step.expression.match(/call-(\d+)\.json/)![1]);
        const fn = step.expression.match(/window\["(__\w+)"\]/)![1];
        const args = JSON.parse(fs.readFileSync(path.join(spec.serveRoot!, `call-${i}.json`), "utf8"));
        let text: string;
        try { text = "OK:" + script(fn, args); } catch (e: any) { text = "ERR:" + e.message; }
        fs.writeFileSync(step.out, text);
      }
      return { ok: true, outputs: [], evals: {}, stdout: "" };
    };
    return { render, specs };
  }

  test("stages the bundle + one JSON args file per call in a served dir, waits for #done, reads results back", async () => {
    const { render, specs } = fakeRender((fn, args) => `${fn}(${args.join(",")})`);
    const run = bundleRunner({ bundlePath: bundle, render });
    const results = await run([
      { fn: "__renderMermaid", args: ["mermaid-fence-1", "graph LR"] },
      { fn: "__excalidrawToSvg", args: ["{}"] },
    ]);
    expect(results).toEqual([
      { ok: true, value: "__renderMermaid(mermaid-fence-1,graph LR)" },
      { ok: true, value: "__excalidrawToSvg({})" },
    ]);
    expect(specs).toHaveLength(1);
    const spec = specs[0];
    expect(spec.waitFor).toEqual({ selector: "#done", timeoutMs: 20_000 });
    expect(path.dirname(spec.file)).toBe(spec.serveRoot);
    expect(spec.steps).toHaveLength(2);
    // Payload rides the served dir, not argv: the expression stays tiny.
    for (const step of spec.steps) expect(step.kind === "eval" && step.expression.length < 300).toBe(true);
    // Private per-script dir is cleaned up.
    expect(fs.existsSync(spec.serveRoot!)).toBe(false);
  });

  test("a throwing call is an ERR result; the other calls in the script still succeed", async () => {
    const { render } = fakeRender((_fn, args) => {
      if (String(args[1]).includes("BROKEN")) throw new Error("Parse error on line 1");
      return "<svg/>";
    });
    const run = bundleRunner({ bundlePath: bundle, render });
    const results = await run([
      { fn: "__renderMermaid", args: ["a", "ok"] },
      { fn: "__renderMermaid", args: ["b", "BROKEN"] },
      { fn: "__renderMermaid", args: ["c", "ok"] },
    ]);
    expect(results.map((r) => r.ok)).toEqual([true, false, true]);
    expect(results[1]).toEqual({ ok: false, error: "Parse error on line 1" });
  });

  test("chunks at 40 calls per script (Aside's 120s script cap)", async () => {
    const { render, specs } = fakeRender(() => "x");
    const run = bundleRunner({ bundlePath: bundle, render });
    const results = await run(Array.from({ length: 85 }, (_, i) => ({ fn: "__renderMermaid", args: [`m${i}`, "g"] })));
    expect(results).toHaveLength(85);
    expect(specs.map((s) => s.steps.length)).toEqual([40, 40, 5]);
  });

  test("a whole-script failure fails every call in it with the renderer's message", async () => {
    const render = async (): Promise<RenderResult> => ({ ok: false, outputs: [], evals: {}, stdout: "", error: "aside repl did not run: spawn aside ENOENT" });
    const run = bundleRunner({ bundlePath: bundle, render });
    const results = await run([{ fn: "__renderMermaid", args: ["a", "g"] }, { fn: "__renderMermaid", args: ["b", "g"] }]);
    expect(results).toHaveLength(2);
    for (const r of results) {
      expect(r.ok).toBe(false);
      if (!r.ok) expect(r.error).toContain("diagram renderer: aside repl did not run");
    }
  });

  test("an unreadable bundle fails every call without touching Aside; zero calls run nothing", async () => {
    let rendered = 0;
    const render = async (): Promise<RenderResult> => { rendered++; return { ok: true, outputs: [], evals: {}, stdout: "" }; };
    const run = bundleRunner({ bundlePath: "/nonexistent/diagram-render.html", render });
    expect(await run([])).toEqual([]);
    const results = await run([{ fn: "__renderMermaid", args: ["a", "g"] }, { fn: "__renderMermaid", args: ["b", "g"] }]);
    expect(results.map((r) => r.ok)).toEqual([false, false]);
    if (!results[0].ok) expect(results[0].error).toContain("ENOENT");
    expect(rendered).toBe(0);
  });

});

/** Scripted BundleRun: a throwing script call becomes an ERR result, plus counters. */
function mockRun(script: (fn: string, ...args: unknown[]) => string) {
  const calls: string[] = [];
  let batches = 0;
  const run = async (batch: BundleCall[]): Promise<BundleResult[]> => {
    batches++;
    return batch.map((c) => {
      calls.push(c.fn);
      try {
        return { ok: true, value: script(c.fn, ...c.args) };
      } catch (e: any) {
        return { ok: false, error: e.message };
      }
    });
  };
  return { run, calls, batchCount: () => batches };
}

const fence = (over: Partial<{ lang: string; source: string; ordinal: number }>) => ({
  lang: "mermaid",
  source: "graph LR\n  A --> B",
  render: true as const,
  token: `tok-${over.ordinal ?? 1}`,
  ordinal: over.ordinal ?? 1,
  title: undefined,
  page: undefined,
  ...over,
});

// ─── renderFenceSlots: reset contract + excalidraw branches ───────────

describe("renderFenceSlots (mock runner)", () => {
  test("one batch for all fences: a failure is a diagnostic block and the NEXT fence still renders", async () => {
    const { run, batchCount } = mockRun((fn, ...args) => {
      if (String(args[1] ?? "").includes("BROKEN")) throw new Error("Parse error on line 1");
      return "<svg><g/></svg>";
    });
    const warnings: string[] = [];
    const slots = await renderFenceSlots(
      [
        fence({ ordinal: 1 }),
        fence({ ordinal: 2, source: "BROKEN" }),
        fence({ ordinal: 3 }),
      ],
      run,
      (m) => warnings.push(m),
    );
    expect(slots.get("tok-1")).toContain("<svg>");
    expect(slots.get("tok-2")).toContain("diagram-error");
    expect(slots.get("tok-2")).toContain("Parse error on line 1");
    expect(slots.get("tok-3")).toContain("<svg>"); // post-failure fence rendered
    expect(batchCount()).toBe(1);                  // one script for the whole document
    expect(warnings[0]).toContain("failed to render");
  });

  test("excalidraw fence renders via __excalidrawToSvg", async () => {
    const { run, calls } = mockRun(() => "<svg data-x><g/></svg>");
    const slots = await renderFenceSlots(
      [fence({ lang: "excalidraw", source: '{"type":"excalidraw","elements":[]}' })],
      run,
      () => {},
    );
    expect(calls).toEqual(["__excalidrawToSvg"]);
    expect(slots.get("tok-1")).toContain("<svg");
  });

  test("invalid excalidraw JSON fails fast into a diagnostic WITHOUT a bundle call", async () => {
    const { run, calls } = mockRun(() => "<svg/>");
    const warnings: string[] = [];
    const slots = await renderFenceSlots(
      [fence({ lang: "excalidraw", source: "{not json" })],
      run,
      (m) => warnings.push(m),
    );
    expect(calls).toEqual([]); // JSON.parse threw before any bundle call
    expect(slots.get("tok-1")).toContain("diagram-error");
    expect(warnings).toHaveLength(1);
  });
});

// ─── rasterizeDiagramFigures: svg-data-URI + error fallbacks ──────────

describe("rasterizeDiagramFigures (mock runner)", () => {
  const figure = `<figure class="diagram" role="img" aria-label="flow"><svg viewBox="0 0 10 10"><g/></svg></figure>`;

  test("figures and svg data-URI images rasterize to PNG in ONE batch", async () => {
    const svgUri = `data:image/svg+xml;base64,${Buffer.from("<svg/>").toString("base64")}`;
    const { run, calls, batchCount } = mockRun((_fn, svg) => `data:image/png;base64,${String(svg).includes("viewBox") ? "FIG" : "IMG"}`);
    const out = await rasterizeDiagramFigures(`${figure}<img src="${svgUri}" alt="v">`, run, 6.5, () => {});
    expect(calls).toEqual(["__rasterize", "__rasterize"]);
    expect(batchCount()).toBe(1);
    expect(out).toContain('<p><img src="data:image/png;base64,FIG" alt="flow"></p>');
    expect(out).toContain('src="data:image/png;base64,IMG" alt="v"');
    expect(out).not.toContain("gstack-raster-slot");
  });

  test("no rasterizable content → no bundle call at all", async () => {
    const { run, batchCount } = mockRun(() => "x");
    const html = `<p>plain</p><img src="data:image/png;base64,AAAA">`;
    expect(await rasterizeDiagramFigures(html, run, 6.5, () => {})).toBe(html);
    expect(batchCount()).toBe(0);
  });

  test("figure rasterization failure surfaces the SOURCE as text (never silent loss)", async () => {
    // Returning the figure unchanged would make the diagram vanish in DOCX
    // (the converter drops <figure>/<svg>) — the failure must be visible.
    const { run } = mockRun(() => { throw new Error("tainted"); });
    const warnings: string[] = [];
    const srcFigure = figure.replace(
      '<figure class="diagram"',
      `<figure class="diagram" data-gstack-source="${Buffer.from("graph LR\n  A --> B").toString("base64")}"`,
    );
    const out = await rasterizeDiagramFigures(srcFigure, run, 6.5, (m) => warnings.push(m));
    expect(out).toContain("could not be rasterized");
    expect(out).toContain("A --&gt; B"); // source visible (escaped), not dropped
    expect(out).not.toContain("<figure");
    expect(warnings[0]).toContain("rasterization failed");
  });

  test("svg data-URI rasterization failure keeps the original tag", async () => {
    const svgUri = `data:image/svg+xml;base64,${Buffer.from("<svg/>").toString("base64")}`;
    const { run } = mockRun(() => { throw new Error("decode failed"); });
    const tagIn = `<img src="${svgUri}">`;
    const out = await rasterizeDiagramFigures(tagIn, run, 6.5, () => {});
    expect(out).toBe(tagIn);
  });
});

// ─── image-size: WebP variants ────────────────────────────────────────

describe("imageDims WebP", () => {
  function riff(fmt: string, body: Buffer): Buffer {
    const b = Buffer.alloc(12 + 4 + body.length);
    b.write("RIFF", 0, "ascii");
    b.writeUInt32LE(4 + body.length + 4, 4);
    b.write("WEBP", 8, "ascii");
    b.write(fmt, 12, "ascii");
    body.copy(b, 16);
    return b;
  }

  test("VP8 (lossy)", () => {
    const body = Buffer.alloc(16);
    body.writeUInt16LE(800 & 0x3fff, 10); // width at chunk offset 26 = body offset 10
    body.writeUInt16LE(600 & 0x3fff, 12);
    expect(imageDims(riff("VP8 ", body))).toEqual({ width: 800, height: 600, mime: "image/webp" });
  });

  test("VP8L (lossless)", () => {
    const body = Buffer.alloc(10);
    body[4] = 0x2f; // signature at chunk offset 20 = body offset 4
    const w = 1023, h = 511;
    const bits = (w - 1) | ((h - 1) << 14);
    body.writeUInt32LE(bits >>> 0, 5);
    expect(imageDims(riff("VP8L", body))).toEqual({ width: 1023, height: 511, mime: "image/webp" });
  });

  test("VP8X (extended)", () => {
    const body = Buffer.alloc(14);
    const w = 4000 - 1, h = 250 - 1; // 24-bit minus-one at offsets 24/27 = body 8/11
    body[8] = w & 0xff; body[9] = (w >> 8) & 0xff; body[10] = (w >> 16) & 0xff;
    body[11] = h & 0xff; body[12] = (h >> 8) & 0xff; body[13] = (h >> 16) & 0xff;
    expect(imageDims(riff("VP8X", body))).toEqual({ width: 4000, height: 250, mime: "image/webp" });
  });

  test("unknown RIFF subtype → null", () => {
    expect(imageDims(riff("XXXX", Buffer.alloc(14)))).toBeNull();
  });
});

// ─── landscape geometry + slot fallback + bundle path + screen css ────

describe("landscape geometry, bare-token slots, bundle path", () => {
  test("landscapeContentBox letter defaults: 9in × 6.5in", () => {
    expect(landscapeContentBox({})).toEqual({ contentWIn: 9, contentHIn: 6.5 });
  });
  test("landscapeContentBox a4 + asymmetric margins", () => {
    const box = landscapeContentBox({ pageSize: "a4", marginLeft: "0.5in", marginRight: "0.5in", marginTop: "25mm", marginBottom: "1in" });
    expect(box.contentWIn).toBeCloseTo(11.69 - 1, 2);
    expect(box.contentHIn).toBeCloseTo(8.27 - 25 / 25.4 - 1, 2);
  });

  test("substituteSlots bare-token fallback (token not <p>-wrapped)", () => {
    const slots = new Map([["gstack-diagram-slot-x-1", "<figure>D</figure>"]]);
    const out = substituteSlots("<li>gstack-diagram-slot-x-1</li>", slots);
    expect(out).toBe("<li><figure>D</figure></li>");
  });

  test("resolveBundlePath honors the env override", () => {
    const tmp = path.join(os.tmpdir(), `bundle-override-${process.pid}.html`);
    fs.writeFileSync(tmp, "<!doctype html>");
    try {
      expect(resolveBundlePath({ GSTACK_DIAGRAM_BUNDLE: tmp } as NodeJS.ProcessEnv)).toBe(tmp);
    } finally {
      fs.unlinkSync(tmp);
    }
  });
  // NOTE: resolveBundlePath's not-found error shape is untestable from inside
  // this checkout (the repo-relative candidate always exists), and a vacuous
  // if-guarded assertion was worse than none. The env-override test above is
  // the honest coverage; the error path is exercised manually via
  // GSTACK_DIAGRAM_BUNDLE pointing at a missing file outside a repo.

});