PDF generation

src/helpers/simple-pdf-writer.ts

@@ -0,0 +1,166 @@
+type PdfTextRun = {
+  pageIndex: number;
+  x: number;
+  y: number;
+  fontSize: number;
+  bold: boolean;
+  text: string;
+};
+
+/** Minimal PDF 1.4 writer (Helvetica) — no external dependencies. */
+export class SimplePdfWriter {
+  private readonly pageWidth = 595.28;
+  private readonly pageHeight = 841.89;
+  private readonly marginX = 50;
+  private readonly marginTop = 50;
+  private readonly marginBottom = 50;
+  private runs: PdfTextRun[] = [];
+  private pageCount = 1;
+  private cursorY = this.pageHeight - this.marginTop;
+  private pageIndex = 0;
+
+  private ensureSpace(lineHeight: number): void {
+    if (this.cursorY - lineHeight < this.marginBottom) {
+      this.pageIndex += 1;
+      this.pageCount += 1;
+      this.cursorY = this.pageHeight - this.marginTop;
+    }
+  }
+
+  private addRun(text: string, fontSize: number, bold = false): void {
+    const lineHeight = fontSize + 4;
+    this.ensureSpace(lineHeight);
+    this.runs.push({
+      pageIndex: this.pageIndex,
+      x: this.marginX,
+      y: this.cursorY,
+      fontSize,
+      bold,
+      text,
+    });
+    this.cursorY -= lineHeight;
+  }
+
+  addTitle(text: string): void {
+    this.addRun(text, 16, true);
+    this.cursorY -= 4;
+  }
+
+  addSection(text: string): void {
+    this.cursorY -= 6;
+    this.addRun(text, 13, true);
+    this.cursorY -= 2;
+  }
+
+  addLine(text: string): void {
+    this.addRun(text, 10, false);
+  }
+
+  addKeyValue(label: string, value?: string | number | null): void {
+    const v =
+      value === undefined || value === null || value === ""
+        ? "-"
+        : String(value);
+    this.addLine(`${label}: ${v}`);
+  }
+
+  addBlank(): void {
+    this.cursorY -= 8;
+  }
+
+  toBuffer(): Buffer {
+    const chunkById: string[] = [];
+    const offsets: number[] = [0];
+    let size = Buffer.byteLength("%PDF-1.4\n", "utf8");
+
+    const addObj = (content: string): number => {
+      const id = chunkById.length;
+      offsets.push(size);
+      const block = `${id} 0 obj\n${content}\nendobj\n`;
+      chunkById.push(block);
+      size += Buffer.byteLength(block, "utf8");
+      return id;
+    };
+
+    chunkById.push("%PDF-1.4\n");
+
+    const fontRegularId = addObj(
+      "<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica /Encoding /WinAnsiEncoding >>",
+    );
+    const fontBoldId = addObj(
+      "<< /Type /Font /Subtype /Type1 /BaseFont /Helvetica-Bold /Encoding /WinAnsiEncoding >>",
+    );
+
+    const contentIds: number[] = [];
+    for (let p = 0; p < this.pageCount; p++) {
+      const pageRuns = this.runs.filter((r) => r.pageIndex === p);
+      const cmds: string[] = [];
+      for (const run of pageRuns) {
+        const font = run.bold ? "F2" : "F1";
+        cmds.push("BT");
+        cmds.push(`/${font} ${run.fontSize} Tf`);
+        cmds.push(`1 0 0 1 ${run.x.toFixed(2)} ${run.y.toFixed(2)} Tm`);
+        cmds.push(`${encodePdfText(run.text)} Tj`);
+        cmds.push("ET");
+      }
+      const stream = cmds.join("\n");
+      contentIds.push(
+        addObj(
+          `<< /Length ${Buffer.byteLength(stream, "utf8")} >>\nstream\n${stream}\nendstream`,
+        ),
+      );
+    }
+
+    const pagesKidsToken = "__PAGES_KIDS__";
+    const pagesId = addObj(
+      `<< /Type /Pages /Kids [${pagesKidsToken}] /Count ${this.pageCount} >>`,
+    );
+    const pageIds: number[] = [];
+    for (let p = 0; p < this.pageCount; p++) {
+      pageIds.push(
+        addObj(
+          `<< /Type /Page /Parent ${pagesId} 0 R /Resources << /Font << /F1 ${fontRegularId} 0 R /F2 ${fontBoldId} 0 R >> >> /MediaBox [0 0 ${this.pageWidth} ${this.pageHeight}] /Contents ${contentIds[p]} 0 R >>`,
+        ),
+      );
+    }
+
+    const catalogId = addObj(`<< /Type /Catalog /Pages ${pagesId} 0 R >>`);
+
+    chunkById[pagesId] = chunkById[pagesId].replace(
+      pagesKidsToken,
+      pageIds.map((id) => `${id} 0 R`).join(" "),
+    );
+
+    const body = chunkById.join("");
+    const bodyBuf = Buffer.from(body, "utf8");
+    const xrefAt = bodyBuf.length;
+    const xref: string[] = [
+      `xref\n0 ${offsets.length}\n0000000000 65535 f \n`,
+    ];
+    for (let i = 1; i < offsets.length; i++) {
+      xref.push(`${String(offsets[i]).padStart(10, "0")} 00000 n \n`);
+    }
+    const trailer = `trailer\n<< /Size ${offsets.length} /Root ${catalogId} 0 R >>\nstartxref\n${xrefAt}\n%%EOF\n`;
+    return Buffer.concat([bodyBuf, Buffer.from(xref.join("") + trailer, "utf8")]);
+  }
+}
+
+/** PDF literal string for Helvetica (WinAnsi) — Latin text only. */
+function encodePdfText(input: string): string {
+  const text = input.normalize("NFC");
+  const safe = [...text]
+    .map((ch) => {
+      const code = ch.charCodeAt(0);
+      if (code >= 0x20 && code <= 0x7e) return ch;
+      if (ch === "—" || ch === "–") return "-";
+      if (/\s/.test(ch)) return " ";
+      return "";
+    })
+    .join("")
+    .replace(/\s+/g, " ")
+    .trim();
+  return `(${safe
+    .replace(/\\/g, "\\\\")
+    .replace(/\(/g, "\\(")
+    .replace(/\)/g, "\\)")})`;
+}