create a macos launchd file, use channels to wait for BLE con

README.md

@@ -14,3 +14,7 @@ If you're on macOS, the Python pybluez Bluetooth drivers don't work (well) on th
 The script checks a folder for files (intended to be set up as a cron job), if there are any, sends them to the printer (if detected), **and deletes them**. 
 
 See `main.go`, you'll probably want to edit some variables. I hacked everything together in a day for our specific case. 
+
+## Launchd service
+
+To install as a `launchd` service (mac's "cron"), copy the binary to `/usr/local/bin` and the file `com.brainbaking.PhomemoPrinter.plist` to `~/Library/LaunchAgents`. Then, in a terminal, type `launchctl load com.brainbaking.PhomemoPrinter.plist`.

com.brainbaking.PhomemoPrinter.plist

@@ -0,0 +1,28 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+  <key>Label</key>
+  <string>com.brainbaking.phomemoprinter</string>
+
+  <key>ProgramArguments</key>
+  <array>
+    <string>/usr/local/bin/phomemoprinter</string>
+  </array>
+
+  <key>Nice</key>
+  <integer>1</integer>
+
+  <key>StartInterval</key>
+  <integer>60</integer>
+
+  <key>RunAtLoad</key>
+  <true/>
+
+  <key>StandardErrorPath</key>
+  <string>/tmp/PhomemoPrinter.err</string>
+
+  <key>StandardOutPath</key>
+  <string>/tmp/PhomemoPrinter.out</string>
+</dict>
+</plist>

main.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/exec"
 	"strconv"
+	"strings"
 	"time"
 	"tinygo.org/x/bluetooth"
 )
@@ -18,29 +19,40 @@ func main() {
 	inDir := home + phomemoFolder
 
 	files, err := os.ReadDir(inDir)
-	must(phomemoFolder, err)
+	must(phomemoFolder + " does not exist", err)
 	if len(files) == 0 {
-		log.Printf("No files to print found in %s. Quitting.\n", inDir)
+		log.Printf("No files to print found in %s, nothing to do. Quitting.\n", inDir)
 		os.Exit(0)
 	}
 
-	// Enable BLE interface.
-	must("enable BLE stack", adapter.Enable())
+	must("Enable Bluetooth stack", adapter.Enable())
 
-	// Start scanning. Use this to figure out your device's UUID. Phomemo uses a non-random one.
-	println("scanning...")
-	var phomemoAddress bluetooth.ScanResult
-	err = adapter.Scan(func(adapter *bluetooth.Adapter, device bluetooth.ScanResult) {
-		if device.LocalName() == "Mr.in_M02" {
-			phomemoAddress = device
+	log.Println("Scanning for Bluetooth devices...")
+	ch := make(chan bluetooth.ScanResult, 1)
+	timeout := make(chan bool, 1)
+	go func() {
+		time.Sleep(10 * time.Second)
+		timeout <- true
+	}()
 
-			println("found device: ", device.Address.String(), device.RSSI, device.LocalName())
-			adapter.StopScan()
-		}
-	})
-	must("start scan", err)
+	go func() {
+		err = adapter.Scan(func(adapter *bluetooth.Adapter, device bluetooth.ScanResult) {
+			if device.LocalName() == "Mr.in_M02" {
+				ch <- device
+				adapter.StopScan()
+			}
+		})
+		must("start scan", err)
+	}()
+
+	select {
+	case device := <- ch:
+		log.Println("Found device: ", device.Address.String(), device.RSSI, device.LocalName())		
+		tryToPrint(device, inDir, files)
+	case <- timeout:
+		log.Fatal("Timeout trying to locate Phomemo M02, is it on? Quitting.")
+	}
 
-	tryToPrint(phomemoAddress, inDir, files)
 }
 
 func tryToPrint(phomemoAddress bluetooth.ScanResult, dir string, files []os.DirEntry) {
@@ -66,31 +78,42 @@ func tryToPrint(phomemoAddress bluetooth.ScanResult, dir string, files []os.DirE
 	chars, err := srvc.DiscoverCharacteristics(nil)
 	must("failed to discover characteristics of service", err)
 
-	dumpFilter("phomemo-filter.py")
+	pyfilterloc := dir + "/" + "phomemo-filter.py"
+	dumpFilter(pyfilterloc)
 	defer func() {
-		os.RemoveAll("phomemo-filter.py")
+		os.RemoveAll(pyfilterloc)
 	}()
 
 	// 3 characteristics to discover 0000ff01, 0000ff02, and 0000ff03
 	for _, file := range files {
 		filePath := dir + "/" + file.Name()
-		writeData(filePath, chars[1]) // 0000ff02-...
-		readResult(chars[0])          // 0000ff01-...
-		os.RemoveAll(filePath)
+		if isPossibleToPrint(filePath) {
+			writeData(pyfilterloc, filePath, chars[1]) // 0000ff02-...
+			readResult(chars[0])          // 0000ff01-...
+			os.RemoveAll(filePath)
+		}
 	}
 
 	log.Println("-- DONE")
 }
 
+func isPossibleToPrint(filename string) bool {
+	return strings.HasSuffix(filename, ".jpg") ||
+		strings.HasSuffix(filename, ".JPG") ||
+		strings.HasSuffix(filename, ".png") ||
+		strings.HasSuffix(filename, ".PNG")
+}
+
 func dumpFilter(filename string) {
 	err := os.WriteFile(filename, phomemofilter.Pyfilter, 0666)
 	must("unable to dump python filter for use", err)
 }
 
-func writeData(path string, char bluetooth.DeviceCharacteristic) {
+func writeData(pyfilterloc string, path string, char bluetooth.DeviceCharacteristic) {
 	// first, it needs to be prepared for the printer
 	pathpho := path + ".pho"
-	argstr := []string{"-c", "python phomemo-filter.py " + path + " > " + pathpho}
+	argstr := []string{"-c", "/usr/local/bin/python " + pyfilterloc + " " + path + " > " + pathpho}
+	log.Println("args", argstr)
 	_, err := exec.Command("/bin/zsh", argstr...).Output()
 	must("something went wrong while filtering phomemo data py", err)