From 14f29f88d3ce83c5c91b2684fc4b5b3beff71a8f Mon Sep 17 00:00:00 2001
From: Kyle Isom <kyle@imap.cc>
Date: Tue, 19 Dec 2023 10:14:00 -0800
Subject: [PATCH] initial import

---
 go.mod  |  9 ++++++
 go.sum  |  6 ++++
 main.go | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 104 insertions(+)
 create mode 100644 go.mod
 create mode 100644 go.sum
 create mode 100644 main.go

diff --git a/go.mod b/go.mod
new file mode 100644
index 0000000..3c0c1ad
--- /dev/null
+++ b/go.mod
@@ -0,0 +1,9 @@
+module git.wntrmute.dev/kyle/gridsq
+
+go 1.21.3
+
+require (
+	git.wntrmute.dev/kyle/goutils v1.7.4 // indirect
+	github.com/logocomune/maidenhead v1.0.1 // indirect
+	gopkg.in/billups/golang-geo.v2 v2.0.0-20170124000346-c2931833be19 // indirect
+)
diff --git a/go.sum b/go.sum
new file mode 100644
index 0000000..0124620
--- /dev/null
+++ b/go.sum
@@ -0,0 +1,6 @@
+git.wntrmute.dev/kyle/goutils v1.7.4 h1:kbvUoxRwAEemz4jL52AUKaOipuCX8F8PGTQHS5V3lRY=
+git.wntrmute.dev/kyle/goutils v1.7.4/go.mod h1:1PGn83Ac98KWyI6yfpCVyP1Ji61PX6lFpROxY+IoTJg=
+github.com/logocomune/maidenhead v1.0.1 h1:WnBpC/LIhc81QnwDdxEPKHwSAspMCWwsYMuM9vQMFgA=
+github.com/logocomune/maidenhead v1.0.1/go.mod h1:FLkUKuGyo4uKESNlXG8jgQgaTSApyR2ZZfq7m2Btmjs=
+gopkg.in/billups/golang-geo.v2 v2.0.0-20170124000346-c2931833be19 h1:vu0Y9rNRRTFG70fnQ/W/CG4N629vz9uaqaY7R7fXnVo=
+gopkg.in/billups/golang-geo.v2 v2.0.0-20170124000346-c2931833be19/go.mod h1:Wo/E84lJTIKl9WdTGYGLAG+q9zRxnl9RnCZenHqASWk=
diff --git a/main.go b/main.go
new file mode 100644
index 0000000..ebc748f
--- /dev/null
+++ b/main.go
@@ -0,0 +1,89 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+
+	"git.wntrmute.dev/kyle/goutils/die"
+	"github.com/logocomune/maidenhead"
+	geo "gopkg.in/billups/golang-geo.v2"
+)
+
+var qths = map[int]string{
+	4:  "CM97",
+	6:  "CM97cq",
+	8:  "CM97cq53",
+	10: "CM97cq53CI",
+}
+
+var kmToMile = 0.621371
+
+func cToP(c maidenhead.Coordinate) *geo.Point {
+	return geo.NewPoint(c.Lat, c.Lng)
+}
+
+func distBearing(qth, qsl string) (err error) {
+	var cqth, cqsl maidenhead.Coordinate
+	cqth.Lat, cqth.Lng, err = maidenhead.GridCenter(qth)
+	if err != nil {
+		return err
+	}
+
+	cqsl.Lat, cqsl.Lng, err = maidenhead.GridCenter(qsl)
+	if err != nil {
+		return err
+	}
+
+	pqth := cToP(cqth)
+	pqsl := cToP(cqsl)
+	dist := pqth.GreatCircleDistance(pqsl)
+	bearing := pqth.BearingTo(pqsl)
+	fmt.Printf("%s => %s: distance %0.2f miles, bearing %0.1f°\n",
+		qth, qsl, dist*kmToMile, bearing)
+	return nil
+}
+
+func main() {
+	var lat, lon float64
+	var precision int64
+
+	flag.Float64Var(&lat, "lat", 0.0, "latitude of grid")
+	flag.Float64Var(&lon, "lon", 0.0, "longitude of grid")
+	flag.Int64Var(&precision, "d", 6, "number of digits")
+	flag.Parse()
+
+	if flag.NArg() == 0 {
+		fmt.Println("nothing")
+		return
+	}
+
+	cmd := flag.Arg(0)
+	switch cmd {
+	case "geo":
+		grid, err := maidenhead.Locator(lat, lon, int(precision))
+		die.If(err)
+
+		fmt.Printf("%0.6f %0.6f: ", lat, lon)
+		fmt.Println(grid)
+	case "qth":
+		grid, ok := qths[int(precision)]
+		if !ok {
+			fmt.Println(qths[6])
+		} else {
+			fmt.Println(grid)
+		}
+	case "db":
+		var qth, qsl string
+		if flag.NArg() == 2 {
+			qsl = flag.Arg(1)
+			qth = qths[len(qsl)]
+		} else {
+			qsl = flag.Arg(2)
+			qth = flag.Arg(1)
+		}
+
+		err := distBearing(qth, qsl)
+		die.If(err)
+	}
+
+}