feat: autoplace fields from placeholders

package-lock.json

@@ -19,6 +19,7 @@
         "inngest-cli": "^0.29.1",
         "luxon": "^3.5.0",
         "mupdf": "^1.0.0",
+        "pdf2json": "^4.0.0",
         "react": "^18",
         "typescript": "5.6.2",
         "zod": "3.24.1"
@@ -27198,6 +27199,18 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/pdf2json": {
+      "version": "4.0.0",
+      "resolved": "https://registry.npmjs.org/pdf2json/-/pdf2json-4.0.0.tgz",
+      "integrity": "sha512-WkezNsLK8sGpuFC7+PPP0DsXROwdoOxmXPBTtUWWkCwCi/Vi97MRC52Ly6FWIJjOKIywpm/L2oaUgSrmtU+7ZQ==",
+      "license": "Apache-2.0",
+      "bin": {
+        "pdf2json": "bin/pdf2json.js"
+      },
+      "engines": {
+        "node": ">=20.18.0"
+      }
+    },
     "node_modules/pdfjs-dist": {
       "version": "3.11.174",
       "resolved": "https://registry.npmjs.org/pdfjs-dist/-/pdfjs-dist-3.11.174.tgz",

package.json

@@ -74,6 +74,7 @@
     "inngest-cli": "^0.29.1",
     "luxon": "^3.5.0",
     "mupdf": "^1.0.0",
+    "pdf2json": "^4.0.0",
     "react": "^18",
     "typescript": "5.6.2",
     "zod": "3.24.1"

packages/lib/server-only/pdf/auto-place-fields.ts

@@ -0,0 +1,202 @@
+import { PDFDocument, rgb } from '@cantoo/pdf-lib';
+import PDFParser from 'pdf2json';
+
+import { getPageSize } from './get-page-size';
+
+type TextPosition = {
+  text: string;
+  x: number;
+  y: number;
+  w: number;
+};
+
+type CharIndexMapping = {
+  textPosIndex: number;
+};
+
+type PlaceholderInfo = {
+  placeholder: string;
+  fieldType: string;
+  recipient: string;
+  isRequired: string;
+  page: number;
+  // PDF2JSON coordinates (in page units - these are relative to page dimensions)
+  x: number;
+  y: number;
+  width: number;
+  height: number;
+  // Page dimensions from PDF2JSON (in page units)
+  pageWidth: number;
+  pageHeight: number;
+};
+
+/*
+  Questions for later:
+    - Does it handle multi-page PDFs?
+    - What happens with incorrect placeholders? E.g. those containing non-accepted properties.
+    - The placeholder data is dynamic. How to handle this parsing? Perhaps we need to do it similar to the fieldMeta parsing.
+*/
+
+export const extractPlaceholdersFromPDF = async (pdf: Buffer): Promise<PlaceholderInfo[]> => {
+  return new Promise((resolve, reject) => {
+    const parser = new PDFParser(null, true);
+
+    parser.on('pdfParser_dataError', (errData) => {
+      reject(errData);
+    });
+
+    parser.on('pdfParser_dataReady', (pdfData) => {
+      const placeholders: PlaceholderInfo[] = [];
+
+      pdfData.Pages.forEach((page, pageIndex) => {
+        /*
+          pdf2json returns the PDF page content as an array of characters.
+          We need to concatenate the characters to get the full text.
+          We also need to get the position of the text so we can place the placeholders in the correct position.
+          
+          Page dimensions from PDF2JSON are in "page units" (relative coordinates)
+        */
+        const pageWidth = page.Width;
+        const pageHeight = page.Height;
+
+        let pageText = '';
+        const textPositions: TextPosition[] = [];
+        const charIndexToTextPos: CharIndexMapping[] = [];
+
+        page.Texts.forEach((text) => {
+          /*
+            R is an array that contains objects with each character.
+            The decodedText contains only the character, without any other information.
+
+            textPositions stores each character and its position on the page.
+          */
+          const decodedText = text.R.map((run) => decodeURIComponent(run.T)).join('');
+
+          for (let i = 0; i < decodedText.length; i++) {
+            charIndexToTextPos.push({
+              textPosIndex: textPositions.length,
+            });
+          }
+
+          pageText += decodedText;
+
+          textPositions.push({
+            text: decodedText,
+            x: text.x,
+            y: text.y,
+            w: text.w || 0,
+          });
+        });
+
+        const placeholderMatches = pageText.matchAll(/{{([^}]+)}}/g);
+
+        for (const match of placeholderMatches) {
+          const placeholder = match[0];
+          const placeholderData = match[1].split(',').map((part) => part.trim());
+
+          const [fieldType, recipient, isRequired] = placeholderData;
+
+          /*
+            Find the position of where the placeholder starts in the text
+
+            Then find the position of where the placeholder ends in the text by adding the length of the placeholder to the index of the placeholder.
+          */
+          const matchIndex = match.index;
+          const placeholderLength = placeholder.length;
+          const placeholderEndIndex = matchIndex + placeholderLength;
+
+          const startCharInfo = charIndexToTextPos[matchIndex];
+          const endCharInfo = charIndexToTextPos[placeholderEndIndex - 1];
+
+          if (!startCharInfo || !endCharInfo) {
+            console.error('Could not find text position for placeholder', placeholder);
+
+            return;
+          }
+
+          const startTextPos = textPositions[startCharInfo.textPosIndex];
+          const endTextPos = textPositions[endCharInfo.textPosIndex];
+
+          /* 
+            PDF2JSON coordinates - these are in "page units" (relative coordinates)
+            Calculate width as the distance from start to end, plus a portion of the last character's width
+            Use 10% of the last character width to avoid extending too far beyond the placeholder
+          */
+          const x = startTextPos.x;
+          const y = startTextPos.y;
+          const width = endTextPos.x + endTextPos.w * 0.1 - startTextPos.x;
+
+          placeholders.push({
+            placeholder,
+            fieldType,
+            recipient,
+            isRequired,
+            page: pageIndex + 1,
+            x,
+            y,
+            width,
+            height: 1,
+            pageWidth,
+            pageHeight,
+          });
+        }
+      });
+
+      resolve(placeholders);
+    });
+
+    parser.parseBuffer(pdf);
+  });
+};
+
+export const replacePlaceholdersInPDF = async (pdf: Buffer): Promise<Buffer> => {
+  const placeholders = await extractPlaceholdersFromPDF(pdf);
+
+  const pdfDoc = await PDFDocument.load(new Uint8Array(pdf));
+  const pages = pdfDoc.getPages();
+
+  for (const placeholder of placeholders) {
+    const pageIndex = placeholder.page - 1;
+    const page = pages[pageIndex];
+
+    const { width: pdfLibPageWidth, height: pdfLibPageHeight } = getPageSize(page);
+
+    /*
+      Convert PDF2JSON coordinates to pdf-lib coordinates:
+      
+      PDF2JSON uses relative "page units":
+      - x, y, width, height are in page units
+      - Page dimensions (Width, Height) are also in page units
+      
+      pdf-lib uses absolute points (1 point = 1/72 inch):
+      - Need to convert from page units to points
+      - Y-axis in pdf-lib is bottom-up (origin at bottom-left)
+      - Y-axis in PDF2JSON is top-down (origin at top-left)
+      
+      Conversion formulas:
+      - x_points = (x / pageWidth) * pdfLibPageWidth
+      - y_points = pdfLibPageHeight - ((y / pageHeight) * pdfLibPageHeight)
+      - width_points = (width / pageWidth) * pdfLibPageWidth
+      - height_points = (height / pageHeight) * pdfLibPageHeight
+    */
+
+    const xPoints = (placeholder.x / placeholder.pageWidth) * pdfLibPageWidth;
+    const yPoints = pdfLibPageHeight - (placeholder.y / placeholder.pageHeight) * pdfLibPageHeight;
+    const widthPoints = (placeholder.width / placeholder.pageWidth) * pdfLibPageWidth;
+    const heightPoints = (placeholder.height / placeholder.pageHeight) * pdfLibPageHeight;
+
+    page.drawRectangle({
+      x: xPoints,
+      y: yPoints - heightPoints, // Adjust for height since y is at baseline
+      width: widthPoints,
+      height: heightPoints,
+      color: rgb(1, 1, 1),
+      borderColor: rgb(1, 1, 1),
+      borderWidth: 2,
+    });
+  }
+
+  const modifiedPdfBytes = await pdfDoc.save();
+
+  return Buffer.from(modifiedPdfBytes);
+};