initial

_pdf_build/mermaid_render.py

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+"""Render Mermaid diagram sources to PNG for PDF embedding (mermaid-cli + Chromium)."""
+
+from __future__ import annotations
+
+import hashlib
+import subprocess
+import tempfile
+from pathlib import Path
+
+from reportlab.lib.units import cm
+from reportlab.lib.utils import ImageReader
+from reportlab.platypus import Image, Paragraph, Spacer
+
+BUILD_DIR = Path(__file__).resolve().parent
+CONFIG = BUILD_DIR / "mermaid-config.json"
+CACHE_DIR = BUILD_DIR / "mermaid_cache"
+MERMAID_CLI = ("npx", "--yes", "@mermaid-js/mermaid-cli@11.4.0")
+
+MAX_DIAGRAM_WIDTH_CM = 15.8
+MAX_DIAGRAM_HEIGHT_CM = 17.0
+CAPTION_STYLE_NAME = "DiagramCaption"
+
+
+def _content_hash(content: str) -> str:
+    return hashlib.sha256(content.strip().encode("utf-8")).hexdigest()[:16]
+
+
+def estimate_mermaid_pixels(content: str) -> tuple[int, int, int]:
+    """Return (width_px, height_px, scale) heuristics for flowchart layout."""
+    lines = [ln for ln in content.splitlines() if ln.strip() and not ln.strip().startswith("%%")]
+    n_edges = sum(1 for ln in lines if "-->" in ln or "---" in ln or "-.->" in ln)
+    n_nodes = sum(
+        1
+        for ln in lines
+        if "[" in ln or "(" in ln or "{" in ln or (ln.strip() and "-->" not in ln and "subgraph" not in ln.lower())
+    )
+    n_sub = sum(1 for ln in lines if "subgraph" in ln.lower())
+    lr = any("flowchart LR" in ln or "graph LR" in ln for ln in lines)
+
+    scale = 2
+    if lr:
+        width = 2200 + min(n_nodes, 12) * 120
+        height = 650 + n_sub * 180 + min(n_edges, 10) * 30
+    else:
+        width = 1700 + min(n_sub, 4) * 200
+        height = 650 + n_edges * 70 + n_sub * 220 + min(n_nodes, 14) * 25
+
+    width = int(min(max(width, 1200), 3600))
+    height = int(min(max(height, 550), 3400))
+    return width, height, scale
+
+
+def render_mermaid_to_png(content: str, dest: Path, *, width: int, height: int, scale: int) -> None:
+    if not CONFIG.exists():
+        raise FileNotFoundError(f"mermaid config missing: {CONFIG}")
+    dest.parent.mkdir(parents=True, exist_ok=True)
+    with tempfile.NamedTemporaryFile("w", suffix=".mmd", delete=False, encoding="utf-8") as tmp:
+        tmp.write(content.strip() + "\n")
+        mmd_path = Path(tmp.name)
+    try:
+        subprocess.run(
+            [
+                *MERMAID_CLI,
+                "-i",
+                str(mmd_path),
+                "-o",
+                str(dest),
+                "-c",
+                str(CONFIG),
+                "-b",
+                "white",
+                "-w",
+                str(width),
+                "-H",
+                str(height),
+                "-s",
+                str(scale),
+            ],
+            cwd=str(BUILD_DIR.parents[1]),
+            check=True,
+            timeout=180,
+            capture_output=True,
+            text=True,
+        )
+    except subprocess.CalledProcessError as exc:
+        msg = (exc.stderr or exc.stdout or str(exc)).strip()
+        raise RuntimeError(f"mermaid-cli failed: {msg}") from exc
+    finally:
+        mmd_path.unlink(missing_ok=True)
+    if not dest.is_file() or dest.stat().st_size == 0:
+        raise RuntimeError(f"mermaid-cli produced no PNG: {dest}")
+
+
+def cached_mermaid_png(content: str) -> Path:
+    """Render or reuse cached PNG for Mermaid source."""
+    CACHE_DIR.mkdir(parents=True, exist_ok=True)
+    key = _content_hash(content)
+    png = CACHE_DIR / f"{key}.png"
+    if png.is_file() and png.stat().st_size > 0:
+        return png
+    w, h, scale = estimate_mermaid_pixels(content)
+    render_mermaid_to_png(content, png, width=w, height=h, scale=scale)
+    return png
+
+
+def diagram_flowables(
+    png_path: Path,
+    styles,
+    *,
+    caption: str = "",
+    max_width_cm: float = MAX_DIAGRAM_WIDTH_CM,
+    max_height_cm: float = MAX_DIAGRAM_HEIGHT_CM,
+) -> list:
+    """ReportLab flowables: image (+ optional caption) sized to fit A4 body."""
+    reader = ImageReader(str(png_path))
+    w_px, h_px = reader.getSize()
+    max_w = max_width_cm * cm
+    max_h = max_height_cm * cm
+    scale = min(max_w / w_px, max_h / h_px)
+    img = Image(str(png_path), width=w_px * scale, height=h_px * scale)
+    img.hAlign = "CENTER"
+    out: list = [Spacer(1, 0.12 * cm), img, Spacer(1, 0.06 * cm)]
+    if caption:
+        cap = styles[CAPTION_STYLE_NAME] if CAPTION_STYLE_NAME in styles else styles["Normal"]
+        out.insert(0, Spacer(1, 0.06 * cm))
+        out.append(Paragraph(f"<i>{caption}</i>", cap))
+    out.append(Spacer(1, 0.1 * cm))
+    return out
+
+
+def ensure_diagram_caption_style(styles) -> None:
+    from reportlab.lib.styles import ParagraphStyle
+    from reportlab.lib import colors
+
+    if CAPTION_STYLE_NAME not in styles:
+        styles.add(
+            ParagraphStyle(
+                CAPTION_STYLE_NAME,
+                parent=styles["Normal"],
+                fontSize=7,
+                textColor=colors.grey,
+                alignment=1,
+                spaceAfter=4,
+            )
+        )