index.js

var fs = require('fs');
var path = require('path');
var invalid = require('./lib/invalid');
var mapnik = require('mapnik');
var sniffer = require('@mapbox/mapbox-file-sniff');
var queue = require('queue-async');
var Csv = require('./lib/csv');

// Register datasource plugins
mapnik.register_default_input_plugins();

var modules = [
  require('./lib/geojson'),
  require('./lib/raster'),
  require('./lib/shape'),
  require('./lib/ogr'),
  require('./lib/topojson'),
  Csv
];

// silence mapnik logs
mapnik.Logger.setSeverity(mapnik.Logger.NONE);

/**
 * Initializes the module
 * @param file (filepath)
 * @returns metadata {filesize, projection, filename, center, extent, json, minzoom, maxzoom, layers, dstype, filetype}
 */
module.exports.digest = function(file, callback) {
  sniffer.fromFile(file, function(err, fileinfo) {
    if (err && err.code === 'EINVALID') {
      try {
        new Csv(file);
        fileinfo.type = 'csv';
      }
      catch (error) { return callback(err); }
    } else if (err) return callback(err);

    getMetadata(file, fileinfo.type, function(err, metadata) {
      if (err) return callback(err);
      return callback(null, metadata);
    });
  });
};

/**
 * Validates size of file and processes the file
 * @param file (filepath)
 * @returns metadata {filesize, projection, filename, center, extent, json, minzoom, maxzoom, layers, dstype, filetype}
 */
function getMetadata(file, filetype, callback) {
  var type = modules.filter(function(module) {
    return module.validFileType.some(function(t) {
      return t === filetype;
    });
  });

  var metadata = { filename: path.basename(file, path.extname(file)) };
  var q = queue(1);
  var source;

  // Instantiate new object, based on datatype
  try {
    source = new type[0](file);
  } catch (err) {
    if (err.message.indexOf('could not parse') !== -1) {
      // Sanitize error message
      var filepath = err.message.split('could not parse')[1];
      err.message = err.message.replace(filepath, ' source');
    }

    return callback(invalid('Error creating Mapnik Datasource: ' + err.message));
  }

  // Build metadata object for source asynchronously
  metadata.filetype = '.' + filetype;
  metadata.dstype = source.dstype;

  q.defer(function(next) {
    fs.stat(file, function(err, stats) {
      if (err) return callback(invalid(err));
      metadata.filesize = stats.size;
      next();
    });
  });

  q.defer(function(next) {
    source.getCenter(function(err, center) {
      if (err) return next(err);
      metadata.center = center;
      next();
    });
  });

  q.defer(function(next) {
    source.getExtent(function(err, extent) {
      if (err) return next(err);
      metadata.extent = extent;
      next();
    });
  });

  q.defer(function(next) {
    source.getZooms(function(err, minzoom, maxzoom) {
      if (err) return next(err);
      metadata.minzoom = minzoom;
      metadata.maxzoom = maxzoom;
      next();
    });
  });

  q.defer(function(next) {
    source.getProjection(function(err, projection) {
      if (err) return next(err);
      metadata.projection = projection;
      next();
    });
  });

  q.defer(function(next) {
    source.getDetails(function(err, details) {
      if (err) return next(err);
      var detailsName = source.detailsName;
      metadata[detailsName] = details;
      next();
    });
  });

  q.defer(function(next) {
    source.getLayers(function(err, layers) {
      if (err) return next(err);
      metadata.layers = layers;
      next();
    });
  });

  q.await(function(err) {
    if (err) return callback(invalid(err));
    callback(err, metadata);
  });
}