feature: new immediate-style API to replace Promise/events

Replace the mix of promises and events in the old API by a simpler API
that returns a SignalK Delta object, null if there was no valid data
(invalid gps fix, unsupported sentence or partial AIS message for
example) and throws exception when something goes wrong (invalid
checksum, invalid data fields, etc).

Not using promises makes it easier for callers to use the library and
should result in less memory usage and slightly improve performance.

Author: sarfata

README.md

@@ -6,8 +6,7 @@
 
 > A node.js/javascript parser of NMEA0183 sentences. Sentences are parsed to [Signal K delta](http://signalk.org/specification/master/data_model.html#delta-format) format.
 
-
-### Supported sentences
+## Supported sentences
 
 - [ALK - Seatalk](https://en.wikipedia.org/wiki/Seatalk)
 - [APB - Autopilot Sentence "B"](http://www.catb.org/gpsd/NMEA.html#_apb_autopilot_sentence_b)
@@ -36,37 +35,34 @@
 - [VWR - Relative Wind Speed and Angle](http://www.catb.org/gpsd/NMEA.html#_vwr_relative_wind_speed_and_angle)
 - [ZDA - UTC day, month, and year, and local time zone offset](http://www.trimble.com/oem_receiverhelp/v4.44/en/NMEA-0183messages_ZDA.html)
 
+## Usage
 
-### Usage
+### JavaScript API
 
 ```javascript
 const Parser = require('@signalk/nmea0183-signalk')
 const parser = new Parser()
 
-parser.on('error', error => {
-  console.error(`[error] ${error.message}`)
-})
-
-parser.on('warning', warning => {
-  console.warn(`[warning] ${warning.message}`)
-})
-
-parser.on('signalk:delta', delta => {
-  console.log(`[delta] ${JSON.stringify(delta, null, 2)}`)
-})
-
-// Parse sentence
-parser.parse('$SDDBT,17.0,f,5.1,M,2.8,F*3E')
+try {
+  const delta = parser.parse('$SDDBT,17.0,f,5.1,M,2.8,F*3E')
+  if (delta !== null) {
+    console.log(`[delta] ${JSON.stringify(delta, null, 2)}`)
+  }
+}
+catch (e) {
+  console.error(`[error] ${e.message}`)
+}
 ```
 
+### Command line
+
 In addition to usage in your code, the parser can be used on the command-line if installed globally (`npm install --global`). This allows you to pipe data from one program into the parser directly, without using a Signal K server. The parser holds no Signal K tree in memory (a big change vs. 1.x), so the output will be stringified [Signal K delta](http://signalk.org/specification/master/data_model.html#delta-format) messages.
 
 ```bash
 $ echo '$SDDBT,17.0,f,5.1,M,2.8,F*3E' | nmea0183-signalk
 ```
 
-
-### NMEA0183v4 tag blocks
+## NMEA0183v4 tag blocks
 
 This parser has (limited) support of [NMEA0183v4 tag blocks](http://www.nmea.org/Assets/may%2009%20rtcm%200183_v400.pdf) (e.g. `\s:airmar dst800,c:1438489697*13\$SDDBT,17.0,f,5.1,M,2.8,F*3E`).
 Keep in mind that, since NMEA uses the backslash `\` as the start and end character of the tag block, you need to escape these characters *before* parsing them.
@@ -78,25 +74,42 @@ Example:
 const Parser = require('@signalk/nmea0183-signalk')
 const parser = new Parser()
 
-parser.on('error', error => {
-  console.error(`[error] ${error.message}`)
-})
-
-parser.on('warning', warning => {
-  console.warn(`[warning] ${warning.message}`)
-})
-
-parser.on('signalk:delta', delta => {
-  console.log(`[delta] ${JSON.stringify(delta, null, 2)}`)
-})
+try {
+  const delta = parser.parse('\\s:airmar dst800,c:1438489697*13\\$SDDBT,17.0,f,5.1,M,2.8,F*3E')
+  if (delta !== null) {
+    console.log(`[delta] ${JSON.stringify(delta, null, 2)}`)
+  }
+}
+catch (e) {
+  console.error(`[error] ${e.message}`)
+}
+```
 
-parser.parse('\\s:airmar dst800,c:1438489697*13\\$SDDBT,17.0,f,5.1,M,2.8,F*3E')
+Output:
+```json
+[delta] {
+  "updates": [
+    {
+      "source": {
+        "sentence": "DBT",
+        "talker": "airmar dst800",
+        "type": "NMEA0183"
+      },
+      "timestamp": "2015-08-02T04:28:17.000Z",
+      "values": [
+        {
+          "path": "environment.depth.belowTransducer",
+          "value": 5.1
+        }
+      ]
+    }
+  ]
+}
 ```
 
 **Note:** *at this time, the checksum of the tag block (`c:1438489697*13`) is not validated.*
 
-
-### License
+## License
 
 ```
 Copyright 2016/2017 Signal K and Fabian Tollenaar <fabian@signalk.org>.

bin/nmea0183-signalk

@@ -11,17 +11,15 @@ process.stdin.pipe(require('split')()).on('data', data => {
     return
   }
 
-  data = data.trim()
-  parser
-    .parse(data)
-    .then(result => {
-      if (result != null) {
-        console.log(JSON.stringify(result.delta))
-      }
-    })
-    .catch(e => {
+  try {
+    const delta = parser.parse(data.trim())
+    if (delta !== null) {
+      console.log(JSON.stringify(delta))
+    }
+  }
+  catch(e) {
       console.error('Encountered an error:', e.message)
-    })
+  }
 })
 
 process.stdin.on('error', err => {

lib/index.js

@@ -16,14 +16,18 @@
  * limitations under the License.
  */
 
-const EventEmitter = require('events')
-const parseSentence = require('./parse')
+const getTagBlock = require('./getTagBlock')
+const transformSource = require('./transformSource')
+const utils = require('@signalk/nmea0183-utilities')
+const hooks = require('../hooks')
 const pkg = require('../package.json')
 
-class Parser extends EventEmitter {
+class Parser {
   constructor (opts) {
-    super()
     this.options = (typeof opts === 'object' && opts !== null) ? opts : {}
+    if (!Object.keys(this.options).includes('validateChecksum')) {
+      this.options.validateChecksum = true
+    }
     this.session = {}
 
     this.name = pkg.name
@@ -32,28 +36,54 @@ class Parser extends EventEmitter {
     this.license = pkg.license
   }
 
-  parse (sentence) {
-    if (typeof sentence === 'string' && sentence.trim().length > 0) {
-      this.emit('nmea0183', sentence.trim())
+  parse(sentence) {
+    let tags = getTagBlock(sentence)
+    if (tags !== false) {
+      sentence = tags.sentence
+      tags = tags.tags
+    } else {
+      tags = {}
+    }
+
+    if (typeof tags.timestamp === 'undefined') {
+      tags.timestamp = new Date().toISOString()
+    }
+
+    let valid = utils.valid(sentence, this.options.validateChecksum)
+    if (valid === false) {
+      throw new Error(`Sentence "${sentence.trim()}" is invalid`)
+    }
+
+    if (sentence.charCodeAt(sentence.length-1) == 10 ) {
+      //in case there's a newline
+      sentence = sentence.substr(0, sentence.length-1)
+    }
+
+    const data = sentence.split('*')[0]
+    const dataParts = data.split(',')
+    const id = dataParts[0].substr(3, 3).toUpperCase()
+    const talker = dataParts[0].substr(1, 2)
+    const split = dataParts.slice(1, dataParts.length)
+
+    if (typeof tags.source === 'undefined') {
+      tags.source = ':'
+    } else {
+      tags.source = `${tags.source}:${id}`
     }
 
-    try {
-      var result = parseSentence(this, sentence, this.options)
-      if (typeof result === 'object' && result !== null) {
-        this.emit('signalk:delta', result || {})
-      }
-      // Return value kept for backwards compatibility.
-      if (result !== null) {
-        return Promise.resolve({ delta: result })
-      }
-      else {
-        return Promise.resolve(null)
-      }
+    if (typeof hooks[id] === 'function') {
+      const result = hooks[id]({
+        id,
+        sentence,
+        parts: split,
+        tags
+      }, this.session)
+      return transformSource(result, id, talker)
     }
-    catch(e) {
-      return Promise.reject(e)
+    else {
+      return null
     }
   }
 }
 
-module.exports = Parser
+module.exports = Parser