const fs = require('fs');
const pdfMerge = require('pdf-merge');
const async = require('async');
const path = require('path');

fs.readFile('./config.json', 'utf8', function(err, config) {
  if (err) {
    throw new Error('Eror while loading config file');
  }

  config = JSON.parse(config.replace(/\\/g, '/'));

  if (config.TRANSFLO_DIR[config.TRANSFLO_DIR.length - 1] !== '/' && config.TRANSFLO_DIR) {
    config.TRANSFLO_DIR += '/';
  }

  if (config.INVOICES_DIR[config.INVOICES_DIR.length - 1] !== '/' && config.INVOICES_DIR) {
    config.INVOICES_DIR += '/';
  }

  if (config.RATE_CONFIRMATION_DIR[config.RATE_CONFIRMATION_DIR.length - 1] !== '/' && config.RATE_CONFIRMATION_DIR) {
    config.RATE_CONFIRMATION_DIR += '/';
  }

  const TRANSFLO_DIR = config.TRANSFLO_DIR || './files/TRANSFLO/';
  const INVOICES_DIR = config.INVOICES_DIR || './files/INVOICES/';
  const RATE_DIR = config.RATE_CONFIRMATION_DIR || './files/RATE CONFIRMATIONS/';

  async.parallel([
    function(done) {
      fs.readdir(TRANSFLO_DIR, function(err, files) {
        if (err) {
          throw new Error('Can\'t find TRANSFLO directory');
        }

        done(null, files);
      });
    },
    function(done) {
      fs.readdir(INVOICES_DIR, function(err, files) {
        if (err) {
          throw new Error('Can\'t find INVOICES directory');
        }

        done(null, files);
      });
    },
    function(done) {
      fs.readdir(RATE_DIR, function(err, files) {
        if (err) {
          throw new Error('Can\'t find RATE CONFIRMATIONS directory');
        }

        done(null, files);
      });
    }
    ], function(err, results) {
      if (err) {
        throw new Error('An unknown error has occurred');
      }

      const pairs = [];

      results[0].forEach(function(factor) {
        const match = { factor: TRANSFLO_DIR + factor };

        factor = factor.substr(0, factor.length - 4);

        results[1].forEach(function(invoice) {
          if (invoice.indexOf(factor) !== -1) {
            match.invoice = INVOICES_DIR + invoice;
          }
        });

        results[2].forEach(function(rate) {
          if (rate.indexOf(factor) !== -1) {
            match.rate = RATE_DIR + rate;
          }
        });

        if (match.factor && match.invoice && match.rate) {
          match.label = factor;
          pairs.push(match);
        }
      });

      async.each(pairs, function(pair, done) {
        const paths = [ normalize(pair.invoice), normalize(pair.rate), normalize(pair.factor) ];
        const pdf = new pdfMerge(paths);

        pdf.merge(function(err, result) {
          if (err) {
            throw new Error('An error has occurred while merging the PDF');
          }

          fs.writeFile('./output/' + pair.label + '.pdf', result, function(err) {
            if (err) {
              throw new Error('An error has occurred while saving the PDF');
            }

            done();
          });
        });
      }, function() {
        console.log('All PDFs has been merged successfuly.');
        process.exit();
      });
    }
  );
})

const normalize = function(string) {
  return '"' + string + '"';
}