VDM.js

'use strict'

/**
 * Copyright 2016 Signal K and Fabian Tollenaar <fabian@signalk.org>.
 *
 * Licensed under the Apache License, Version 2.0 (the 'License');
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an 'AS IS' BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const debug = require('debug')('signalk-parser-nmea0183/VDM')
const utils = require('@signalk/nmea0183-utilities')
const Decoder = require('ggencoder').AisDecode
const schema = require('@signalk/signalk-schema')

const stateMapping = {
  0: 'motoring',
  1: 'anchored',
  2: 'not under command',
  3: 'restricted manouverability',
  4: 'constrained by draft',
  5: 'moored',
  6: 'aground',
  7: 'fishing',
  8: 'sailing',
  9: 'hazardous material high speed',
  10: 'hazardous material wing in ground',
  14: 'ais-sart'
};

const msgTypeToPrefix = {
  1: "vessels.",
  2: "vessels.",
  3: "vessels.",
  5: "vessels.",
  9: "aircraft.",
  18: "vessels.",
  19: "vessels.",
  21: "atons.",
  24: "vessels."
}

module.exports = function (input, session) {
  const { id, sentence, parts, tags } = input
  const data = new Decoder(sentence, session)
  const values = []

  if (data.valid === false) {
    return null
  }

  if (data.mmsi) {
    values.push({
      path: '',
      value: {
        mmsi: data.mmsi
      }
    })
  }

  if (data.shipname) {
    values.push({
      path: '',
      value: {
        name: data.shipname
      }
    })
  }

  if (typeof data.sog != 'undefined') {
    values.push({
      path: 'navigation.speedOverGround',
      value: utils.transform(data.sog, 'knots', 'ms')
    })
  }

  if (typeof data.cog != 'undefined') {
    values.push({
      path: 'navigation.courseOverGroundTrue',
      value: utils.transform(data.cog, 'deg', 'rad')
    })
  }

  if (typeof data.hdg != 'undefined') {
    values.push({
      path: 'navigation.headingTrue',
      value: utils.transform(data.hdg, 'deg', 'rad')
    })
  }

  if (data.lon && data.lat) {
    values.push({
      path: 'navigation.position',
      value: {
        longitude: data.lon,
        latitude: data.lat
      }
    })
  }

  if ( data.length ) {
    values.push({
      path: 'design.length',
      value: {overall: data.length}
    })
  }

  if ( data.width ) {
    values.push({
      path: 'design.beam',
      value: data.width
    })
  }

  if ( data.draught ) {
    values.push({
      path: 'design.draft',
      value: {current: data.draught}
    })
  }

  if ( data.dimA ) {
    values.push({
      path: 'sensors.ais.fromBow',
      value: data.dimA
    })
  }

  if ( data.dimD && data.width ) {
    var fromCenter;
    if (data.dimD > data.width / 2) {
      fromCenter = (data.dimD - data.width / 2) * -1
    } else {
      fromCenter =  data.width / 2 - data.dimD
    }

    values.push({
      path: 'sensors.ais.fromCenter',
      value: fromCenter
    })
  }

  if ( data.navstatus ) {
    var state = stateMapping[data.navstatus]
    if ( typeof state !== 'undefined' ) {
      values.push({
        path: 'navigation.state',
        value: state
      })
    }
  }

  if ( data.destination ) {
    values.push({
      path: 'navigation.destination.commonName',
      value: data.destination
    })
  }

  if ( data.callsign ) {
    values.push({
      path: '',
      value: {communication:{ callsignVhf: data.callsign}}
    })
  }

  var contextPrefix =  msgTypeToPrefix[data.aistype] || "vessels."

  if ( data.aidtype ) {
    contextPrefix = "atons."
    var atonType = schema.getAtonTypeName(data.aidtype)
    if ( typeof atonType !== 'undefined' ) {
      values.push({
        path: 'atonType',
        value: { "id": data.aidtype, "name": atonType }
      })
    }
  }

  if ( data.cargo )
  {
    var typeName = schema.getAISShipTypeName(data.cargo)
    if ( typeof typeName !== 'undefined' ) {
      values.push({
        path: 'design.aisShipType',
        value: { "id": data.cargo, "name": typeName }
      })
    }
  }

  if (values.length === 0) {
    return null
  }

  const delta = {
    context: contextPrefix + `urn:mrn:imo:mmsi:${data.mmsi}`,
    updates: [
      {
        source: tags.source,
        timestamp: tags.timestamp,
        values: values
      }
    ],
  }

  return delta
}