Add error handling

mic_over_mumble

@@ -1,4 +1,5 @@
 #!/bin/bash
+# https://github.com/pzmarzly/mic_over_mumble
 set -euo pipefail
 # To debug, uncomment the following line:
 # set -x
@@ -7,7 +8,6 @@ set -euo pipefail
 # ID = PID / process ID
 
 main () {
-    prepare_env
     set_up
     echo "Press Return to shut down..."
     read -n1 -s -r
@@ -38,6 +38,7 @@ run_mumble_client_wizard () {
 }
 
 set_up () {
+    prepare_env
     start_mumble_server
     start_mumble_client
     change_pa_config
@@ -52,12 +53,16 @@ shut_down () {
 }
 
 start_mumble_client () {
-    echo "Starting Mumble client..."
+    echo "Starting Mumble client (a window should appear in a moment)..."
     mumble "mumble://localhost" >/dev/null 2>&1 &
     MUMBLE_CLIENT_ID=$!
+    # FIXME: I don't remember why I thought this
+    # was necessary.
     disown
     # Mumble is slow to launch, and the
     # user may need to click on OK button.
+    # FIXME: probe PulseAudio server to see if
+    # Mumble has connected.
     sleep 15
 }
 
@@ -136,28 +141,56 @@ set_default_source () {
 # Data fetching & parsing.
 
 get_mumble_client_paid () {
-    pacmd list-sink-inputs |
+    result=$(pacmd list-sink-inputs |
         grep -F -e "index: " -e "media.name = " |
         cut_every_second_newline |
         grep -F -e "Mumble" |
-        print_second_column
+        take_second_column)
+
+    if [ -z "$result" ]; then
+        echo "Error: Mumble client did not connect to PulseAudio (yet?)." 2>&1
+        print_how_to_restart 2>&1
+        exit 1
+    fi
+
+    if [ "$(echo "$result" | wc -l)" != "1" ]; then
+        echo "Error: Multiple Mumble instances found." 2>&1
+        print_how_to_restart 2>&1
+        exit 1
+    fi
+
+    echo "$result"
 }
 
 get_sink_paid () {
-    pacmd list-sinks |
+    result=$(pacmd list-sinks |
         grep -F -e "index: " -e "name: " |
         cut_every_second_newline |
         grep -F -e "Loopback" |
         cut_active_device_indicator |
-        print_second_column
+        take_second_column)
+
+     if [ -z "$result" ]; then
+        echo "Error: Failed to find the device the script should have added." 2>&1
+        print_how_to_restart 2>&1
+        exit 1
+    fi
+
+    if [ "$(echo "$result" | wc -l)" != "1" ]; then
+        echo "Error: Multiple virtual devices found." 2>&1
+        print_how_to_restart 2>&1
+        exit 1
+    fi
+
+    echo "$result"
 }
 
 # https://serverfault.com/a/375098/449626
 cut_every_second_newline () {
     awk 'ORS=NR%2?" ":"\n"'
 }
 
-print_second_column () {
+take_second_column () {
     awk '{print $2}'
 }
 
@@ -168,4 +201,13 @@ cut_active_device_indicator () {
     cut -c 5-
 }
 
+# Errors
+
+print_how_to_restart () {
+    echo "Please find the reason why this happened, try fixing it"
+    echo "(\`pacmd list-sink-inputs\` and \`pacmd list-sinks\` may be"
+    echo "useful), then kill mumble and murmurd, restart PulseAudio via"
+    echo "\`pulseaudio -k\`, and finally, restart the script."
+}
+
 main