#!/bin/bash
# I keep forgetting how to extract the boot.img from an Android OTA update
# for patching by Magisk.
set -e

while [[ $# -gt 0 ]]; do
  case $1 in
    --payload-dumper)
      # Specify the path to the payload_dumper binary
      PAYLOAD_DUMPER=$2
      shift
      shift
      ;;
    --diff)
      PAYLOAD_DUMPER_EXTRA_ARGS="${PAYLOAD_DUMPER_EXTRA_ARGS} --diff"
      shift
      ;;
    *)
      # The last argument is the file
      UPDATE_FILE=$1
      shift
      ;;
  esac
done

if [[ ! -f "$UPDATE_FILE" ]]; then
  echo "Android update file $UPDATE_FILE does not exist"
  exit 1
fi

out_dir=./payload-dumper-output
if [[ -d "$out_dir" ]]; then
  echo "Output path $out_dir already exists. Refusing to work!"
  exit 1
fi
mkdir "$out_dir"

# Print some basic info
PAYLOAD_DUMPER=${PAYLOAD_DUMPER:-payload_dumper}
echo "INFO: payload_dumper: $PAYLOAD_DUMPER"
echo

# Extract only the payload.bin file
echo "Extracting payload..."
unzip -q -C "$UPDATE_FILE" -d "$out_dir" payload.bin

# Use payload_dumper to get to the boot.img
echo "Dumping data from payload..."
${PAYLOAD_DUMPER} ${PAYLOAD_DUMPER_EXTRA_ARGS} --out "$out_dir" "${out_dir}/payload.bin"