fill-pdf/index.js

Fill out pdf forms

'use strict';

const fs  = require('fs'),
    path  = require('path'),
    spawn = require('child_process').spawn,
    async = require('async'),
    temp  = require('temp');

exports.generateFdf = function(data) {
  var header, body, footer;

  header = new Buffer('%FDF-1.2\n\u00e2\u00e3\u00cf\u00d3\n1 0 obj \n<<\n/FDF \n<<\n/Fields [\n');

  footer = new Buffer(']\n>>\n>>\nendobj \ntrailer\n\n<<\n/Root 1 0 R\n>>\n%%EOF\n');

  body = new Buffer([]);

  for(let key in data) {
    var name = escapeFdf(key);
    var value = escapeFdf(data[key]);

    body = Buffer.concat([ body, new Buffer('<<\n/T (')]);
    body = Buffer.concat([ body, name]);
    body = Buffer.concat([ body, new Buffer(')\n/V (')]);
    body = Buffer.concat([ body, value]);
    body = Buffer.concat([ body, new Buffer(')\n>>\n')]);
  }

  var fdf =  Buffer.concat([ header, body, footer ]);
  return fdf;
};

exports.generatePdf = function(data, templatePath, extendArgs, callback) {
  let tempNameResult = temp.path({suffix: '.pdf'}),
      pdfPath        = isAbsolute(templatePath) ? templatePath : path.join(__dirname, templatePath);

  let normalized = normalizeArgs(extendArgs, callback);

  extendArgs = normalized.args;
  callback   = normalized.callback;

  let processArgs = [pdfPath, 'fill_form', '-', 'output', tempNameResult].concat(extendArgs);

  let child = spawn('pdftk', processArgs);

  handlePdftkError(child, callback);
  handlePdftkExit(child, tempNameResult, callback);
  writeFdfToPdftk(child, data);
};

// Escape data and return it as a buffer
function escapeFdf(data) {
  let escaped = new Buffer([]);
  let buf;

  if(typeof data === 'string' || data instanceof Buffer) {
    buf = new Buffer(data);
  } else if(typeof data.toString === 'function') {
    buf = new Buffer(data.toString());
  } else {
    buf = new Buffer(Object.prototype.toString.call(data));
  }

  for(let i=0; i<buf.length; i++) {
    let c1 = String.fromCharCode(buf[i]);
    let c2 = String.fromCharCode(buf[i+1]);

    if(c1 === '(' || c1 === ')') {
      escaped = Buffer.concat([escaped, new Buffer('\\' + c1)]);
    } else if(c1 === '\r' && c2 === '\n') {
      escaped = Buffer.concat([escaped, new Buffer('\r')]);
    } else {
      escaped = Buffer.concat([escaped, new Buffer([buf[i]])]);
    }
  }

  return escaped;
}

function normalizeArgs(extendArgs, callback) {
  // Check if extendArgs is our callback, adds backwards compat
  if (typeof extendArgs === 'function') {
   callback = extendArgs;
   extendArgs = [];
  }
  else if (!(extendArgs instanceof Array)) {
    extendArgs = [];
  }
  return { args: extendArgs, callback: callback };
}

function writeFdfToPdftk(child, data) {
  child.stdin.write(exports.generateFdf(data));
  child.stdin.end();
}

function handlePdftkError(child, callback) {
  child.on('error', function (err) {
    callback(err);
  });

  child.stderr.on('data', function (data) {
    console.error('stderr: ' + data);
  });
}

function handlePdftkExit(child, tempNameResult, callback) {
  child.on('exit', createHandlePdftkExit(tempNameResult, callback));
}

function createHandlePdftkExit(tempNameResult, callback) {
  return function(code) {
    if ( code ) {
      return callback(new Error('Non 0 exit code from pdftk spawn: ' + code));
    }

    async.waterfall([
      (cb) => {
        fs.readFile(tempNameResult, (err, filledPdf) => cb(err, filledPdf));
      },
      (filledPdf, cb) => {
        fs.unlink(tempNameResult, (err) => cb(err, filledPdf));
      }
    ],
    function(err, result) {
      callback(err, result);
    });
  };
}

function normalizeArgs(extendArgs, callback) {
  // Check if extendArgs is our callback, adds backwards compat
  if (typeof extendArgs === 'function') {
   callback = extendArgs;
   extendArgs = [];
  }
  else if (!(extendArgs instanceof Array)) {
    extendArgs = [];
  }
  return { args: extendArgs, callback: callback };
}

function isAbsolute(Path) {
    return (path.isAbsolute && path.isAbsolute(Path)) ||
           (path.normalize(Path + '/') === path.normalize(path.resolve(Path) + '/'));
}