Add minimum battery level to adb_wait_for_device

platform_tools/android/bin/adb_wait_for_device

 #!/bin/bash
 #
-# Wait for the device to be both attached and booted.
+# Wait for the device to be ready to run tests.
 
 SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 source $SCRIPT_DIR/android_setup.sh
 source $SCRIPT_DIR/utils/setup_adb.sh
 
+BATTERY_LEVEL=0

[rmistry, 2015/12/14 13:35:05]

Remove.

[borenet, 2015/12/14 13:42:09]

Done.

+
+function get_battery_level {
+  STATS="$($ADB $DEVICE_SERIAL shell dumpsys batteryproperties)"
+  SPLIT=( $STATS )
+  for i in "${!SPLIT[@]}"; do
+    if [ "${SPLIT[$i]}" = "level:" ]; then
+      BATTERY_LEVEL="${SPLIT[$i+1]}"
+      return
+    fi
+  done
+  echo "No battery level found!"
+}
+
 set -e
-set -x
 
+# Wait for the device to be connected and fully booted.
 while [ "$($ADB $DEVICE_SERIAL shell getprop sys.boot_completed | tr -d '\r')" != "1" ]; do
+  echo "Waiting for the device to be connected and ready."
   sleep 5
 done
+
+# Wait for battery charge.
+DESIRED_BATTERY_LEVEL=30
+get_battery_level

[rmistry, 2015/12/14 13:11:27]

Working on the global BATTERY_LEVEL is confusing. Why not have get_battery level
return the battery level? i.e.

current_battery_level = get_battery_level

[borenet, 2015/12/14 13:26:56]

I'm not aware of a way to do that in a bash script.  Changed to have the
function echo its "return" value and the caller to read that.

[rmistry, 2015/12/14 13:35:05]

Yes that is how you return values from bash functions.
Are the quotes here and below needed?

[borenet, 2015/12/14 13:42:09]

No, but they don't hurt anything, and my bash paranoia requires me to always use
them.

+while [ "$BATTERY_LEVEL" -lt "$DESIRED_BATTERY_LEVEL" ]; do
+  echo "Battery level is ${BATTERY_LEVEL}; waiting to charge to ${DESIRED_BATTERY_LEVEL}"
+  sleep 5

[rmistry, 2015/12/14 13:11:27]

5 seconds seems like a very short time to wait for battery level to rise by any
amount. Should this instead be 30seconds? or 1min? or more?

[borenet, 2015/12/14 13:26:56]

The work we're doing every 5 seconds is cheap, and running more often prevents
us from wasting time when we could have already started the next build. IMO
there's no reason to wait longer between checks.

[rmistry, 2015/12/14 13:35:05]

Sounds good since the calls are cheap. Can always revisit later by looking at
the logs to see how long these actually end up waiting.

+  get_battery_level
+done
+
+echo "Ready!"