defmodule Mix.Tasks.Firmware.Gen.Script do
  use Mix.Task

  @script_name "upload.sh"

  @shortdoc "Generates a shell script for pushing firmware updates"

  @moduledoc """
  Creates a shell script for invoking ssh to upgrade devices with ssh_subsystem_fwup.

  This script may be used on its own or used as a base for more complicated
  device software upgrade deployments.

  It saves the script to #{@script_name}.
  """

  @script """
  #!/bin/sh

  #
  # Upload new firmware to a device running ssh_subsystem_fwup
  #
  # Usage:
  #   upload.sh [destination IP] [Path to .fw file]
  #
  # If unspecified, the destination is nerves.local and the .fw file is naively
  # guessed
  #
  # You may want to add the following to your `~/.ssh/config` to avoid recording
  # the IP addresses of the target:
  #
  # Host nerves.local
  #   UserKnownHostsFile /dev/null
  #   StrictHostKeyChecking no
  #
  # The firmware update protocol is:
  #
  # 1. Connect to the ssh_subsystem_fwup service running on port 22
  # 2. Send the firmware file
  # 3. The response from the device is a progress bar from fwup that can either
  #    be ignored or shown to the user.
  # 4. The ssh connection is closed with an exit code to indicate success or
  #    failure
  #
  # Feel free to copy this script wherever is convenient. The template is at
  # https://github.com/nerves-project/ssh_subsystem_fwup/blob/main/priv/templates/script.upload.eex
  #

  set -e

  DESTINATION=$1
  FILENAME="$2"

  help() {
    echo
    echo "upload.sh [destination IP] [Path to .fw file]"
    echo
    echo "Default destination IP is 'nerves.local'"
    echo "Default firmware bundle is the first .fw file in '_build/\\${MIX_TARGET}_\\${MIX_ENV}/nerves/images'"
    echo
    echo "MIX_TARGET=$MIX_TARGET"
    echo "MIX_ENV=$MIX_ENV"
    exit 1
  }

  [ -n "$DESTINATION" ] || DESTINATION=nerves.local
  if [ -z "$FILENAME" ]; then
    [ -n "$MIX_TARGET" ] || MIX_TARGET=rpi0
    [ -n "$MIX_ENV" ] || MIX_ENV=dev
    FIRMWARE_PATH="./_build/${MIX_TARGET}_${MIX_ENV}/nerves/images"
    if [ ! -d "$FIRMWARE_PATH" ]; then
        echo "Can't find the build products."
        echo
        echo "Nerves environment"
        echo "MIX_TARGET:    ${MIX_TARGET}"
        echo "MIX_ENV:       ${MIX_ENV}"
        echo
        echo "Make sure your Nerves environment is correct."
        echo
        echo "If the Nerves environment is correct make sure you have built the firmware"
        echo "using 'mix firmware'."
        echo
        echo "If you are uploading a .fw file from a custom path you can specify the"
        echo "path like so:"
        echo
        echo "  $0 <device hostname or IP address> </path/to/my/firmware.fw>"
        echo
        exit 1
    fi

    FILENAME=$(ls "$FIRMWARE_PATH/"*.fw 2> /dev/null | head -n 1)
    [ -n "$FILENAME" ] || (echo "Error: error determining firmware bundle."; help)
  fi

  [ -f "$FILENAME" ] || (echo "Error: can't find '$FILENAME'"; help)

  FIRMWARE_METADATA=$(fwup -m -i "$FILENAME" || echo "meta-product=Error reading metadata!")
  FIRMWARE_PRODUCT=$(echo "$FIRMWARE_METADATA" | grep -E "^meta-product=" -m 1 2>/dev/null | cut -d '=' -f 2- | tr -d '"')
  FIRMWARE_VERSION=$(echo "$FIRMWARE_METADATA" | grep -E "^meta-version=" -m 1 2>/dev/null | cut -d '=' -f 2- | tr -d '"')
  FIRMWARE_PLATFORM=$(echo "$FIRMWARE_METADATA" | grep -E "^meta-platform=" -m 1 2>/dev/null | cut -d '=' -f 2- | tr -d '"')
  FIRMWARE_UUID=$(echo "$FIRMWARE_METADATA" | grep -E "^meta-uuid=" -m 1 2>/dev/null | cut -d '=' -f 2- | tr -d '"')

  echo "Path: $FILENAME"
  echo "Product: $FIRMWARE_PRODUCT $FIRMWARE_VERSION"
  echo "UUID: $FIRMWARE_UUID"
  echo "Platform: $FIRMWARE_PLATFORM"
  echo
  echo "Uploading to $DESTINATION..."

  cat "$FILENAME" | ssh -s $SSH_OPTIONS $DESTINATION fwup
  """

  @spec run(keyword()) :: :ok
  def run(_args) do
    if File.exists?(@script_name) do
      Mix.shell().yes?("OK to overwrite #{@script_name}?") || Mix.raise("Aborted")
    end

    Mix.shell().info("""
    Writing #{@script_name}...
    """)

    File.write!(@script_name, @script)
    File.chmod!(@script_name, 0o755)
  end
end