AprsPacket.scala

package de.duenndns.aprsdroid

import _root_.android.location.Location

object AprsPacket {

	// position report regexes:
	val SYM_TAB_RE = """([/\\A-Z0-9])"""			// symbol table character
	val SYM_TAB_COMP_RE = """([/\\A-Za-j])"""		// symbol table character for compressed packets
	val COORD_COMP_RE = """([!-{]{4})"""
	val PATH_RE = """([A-Za-z0-9-]+)>[^:]*:"""		// header for APRS packet
	val POS_START_RE = """([^!;)`']{0,40}!|=|[/@]\d{6}[/zh])"""	// header for position report
	val OBJ_START_RE = """;([A-Za-z0-9 -_]{9})\*\d{6}[/zh]"""	// header for position report
	val COMMENT_RE = """(\d{3}/\d{3})?\s*(.*)"""
	val POSIT_RE = """(\d{4}\.\d{2}[NS])""" + SYM_TAB_RE + """(\d{5}\.\d{2}[EW])(.)\s*(.*)"""
	// #0: call  #2: latitude  #3: sym1  #4: longitude  #5: sym2  #6: comment
	val POS_REPORT_RE = PATH_RE + POS_START_RE + POSIT_RE
	// #0: call  #2: sym1comp  #3: latcom  #4: loncomp  #5: sym2  #6: csespdtype  #7: comment
	val COMP_RE = PATH_RE + POS_START_RE + SYM_TAB_COMP_RE + COORD_COMP_RE + COORD_COMP_RE + """(.)(...)\s*(.*)"""
	// #0: call  #1: object call  #2: latitude  #3: sym1  #4: longitude  #5: sym2  #6: comment
	val OBJ_REPORT_RE = PATH_RE + OBJ_START_RE + POSIT_RE
	lazy val PositionRegex = POS_REPORT_RE.r
	lazy val PositionCompRegex = COMP_RE.r
	lazy val ObjectRegex = OBJ_REPORT_RE.r
	lazy val CoordRegex = """(\d{2,3})(\d{2})\.(\d{2})([NSEW])""".r

	def passcode(callssid : String) : Int = {
		// remove ssid, uppercase, add \0 for odd-length calls
		val call = callssid.split("-")(0).toUpperCase() + "\0"
		var hash = 0x73e2
		for (i <- 0 to call.length-2 by 2) {
			hash ^= call(i) << 8
			hash ^= call(i+1)
		}
		hash & 0x7fff
	}

	def splitCoord(c : Double) : (Int, Int, Int, Int) = {
		var letter = 0
		var minDec = (c*6000).asInstanceOf[Int]
		if (minDec < 0) {
			minDec = -minDec
			letter = 1
		}
		var deg = minDec / 6000
		val min = (minDec / 100) % 60
		val minFrac = minDec % 100
		(deg, min, minFrac, letter)
	}

	def formatLat(c : Double) : String = {
		val (deg, min, minFrac, letter) = splitCoord(c)
		"%02d%02d.%02d%c".format(deg, min, minFrac, "NS"(letter))
	}
	def formatLon(c : Double) : String = {
		val (deg, min, minFrac, letter) = splitCoord(c)
		"%03d%02d.%02d%c".format(deg, min, minFrac, "EW"(letter))
	}

	def coord2microdeg(s : String) : Int = {
		val CoordRegex(captures @ _*) = s
		val Seq(deg, min, minFrac) = captures.take(3).map(_.toInt)
		val nsew = captures.last(0)
		// .d = M.m/60 = (M + (m/100))/60
		val microdeg = deg*1000000 + 10000*(min*100 + minFrac)/60
		nsew match {
		case 'N' => microdeg
		case 'E' => microdeg
		case 'S' => -microdeg
		case 'W' => -microdeg
		}
	}

	def double2microdeg(value : Double) = {
		(value*1000000).toInt
	}
	// the compressed number format is: base-91 with each character +33
	def compressed2lat(comp : String) = {
		double2microdeg(90 - comp.map(_-33).reduceLeft(_*91+_)/380926.0)
	}

	def compressed2lon(comp : String) = {
		double2microdeg(comp.map(_-33).reduceLeft(_*91+_)/190463.0 - 180)
	}

	def parseReport(report : String) : (String, Int, Int, String, String, String) = {
		report match {
		case PositionRegex(call, _, lat, sym1, lon, sym2, comment) =>
			(call, coord2microdeg(lat), coord2microdeg(lon), sym1+sym2, comment, null)
		case PositionCompRegex(call, _, sym1comp, latcomp, loncomp, sym2, _, comment) =>
		        val sym1 = if ('a' <= sym1comp(0) && sym1comp(0) <= 'j') (sym1comp(0) - 'a' + '0').toChar else sym1comp
			(call, compressed2lat(latcomp), compressed2lon(loncomp), sym1+sym2, comment, null)
		case ObjectRegex(call, objcall, lat, sym1, lon, sym2, comment) =>
			(objcall.trim(), coord2microdeg(lat), coord2microdeg(lon), sym1+sym2, comment, call)
		}
	}

	def formatCallSsid(callsign : String, ssid : String) : String = {
		if (ssid != null && ssid != "")
			return callsign + "-" + ssid
		else
			return callsign
	}

	def m2ft(meter : Double) : Int = (meter*3.2808399).asInstanceOf[Int]

	def mps2kt(mps : Double) : Int = (mps*1.94384449).asInstanceOf[Int]

	def formatAltitude(location : Location) : String = {
		if (location.hasAltitude)
			"/A=%06d".format(m2ft(location.getAltitude))
		else
			""
	}

	def formatCourseSpeed(location : Location) : String = {
		// only report speeds above 2m/s (7.2km/h)
		if (location.hasSpeed && location.hasBearing)
		   // && location.getSpeed > 2)
			"%03d/%03d".format(location.getBearing.asInstanceOf[Int],
				mps2kt(location.getSpeed))
		else
			""
	}

	def formatLoc(callssid : String, symbol : String,
			status : String, location : Location) : String = {
		callssid + ">APAND1,TCPIP*:!" + formatLat(location.getLatitude) +
			symbol(0) + formatLon(location.getLongitude) + symbol(1) +
			formatCourseSpeed(location) + formatAltitude(location) +
			" " + status
	}

	def formatLogin(callsign : String, ssid : String, passcode : String) : String = {
		"user " + formatCallSsid(callsign, ssid) + " pass " + passcode + " vers APRSdroid 0.1"
	}

	def parseHostPort(hostport : String, defaultport : Int) : (String, Int) = {
		val splits = hostport.split(":")
		if (splits.length == 2)
			return (splits(0), splits(1).toInt)
		else
			return (splits(0), defaultport)
	}
}