start

#!/usr/bin/env bash

# ensure third party tools are installed
requirements_check() {
  local which_bin="jq python"
  local ret=0

  which ${which_bin} &>/dev/null
  ret=$?

  if [ $ret -ne 0 ]; then
    echo >&2 "binaries missing in [${which_bin}]"
  else
    # ensure python modules are installed
    python -c 'import sys, yaml, json' 2>/dev/null
    ret=$?
    if [ $ret -ne 0 ]; then
      echo >&2 "python modules missing in [yaml, json]"
    fi
  fi

  return $ret

}

show_usage() {
  echo "Usage: "$0" [get <jq_filter> | set <jq_filter> <new_value>]"
  echo ""
  exit 1
}

y2j() {
  python -c 'import sys, yaml, json; json.dump(yaml.load(sys.stdin), sys.stdout, indent=4)'
}

j2y() {
  python -c 'import sys, yaml, json; yaml.safe_dump(json.load(sys.stdin), sys.stdout, indent=2, default_flow_style=False)'
}

yq() {
  local jq_response=$(y2j | jq "$@")
  if is_json "$jq_response"; then
    echo "$jq_response" | j2y
  else
    echo "$jq_response"
  fi
}

is_json() {
  echo "$1" | jq -e 'if type=="array" or type=="object" then true else false end' &>/dev/null
}

set_value() {
  [ $# -ne 3 ] && show_usage

  if is_json $1; then
    echo "$1" | jq "$2 |= $3"
  else
    echo "$1" | y2j | jq "$2 |= $3" | j2y
  fi
}

read_value() {
  [ $# -lt 2 ] && show_usage

  local input="$1"
  shift

  if is_json "$input"; then
    echo "$input" | jq "$@"
  else
    echo "$input" | yq "$@"
  fi
}

main() {

  # on demand requirements check
  if [ "$1" == "req" ]; then
    requirements_check; exit $?
  fi
  # ensure requirements are completed at each run
  requirements_check || exit $?

  [ $# -ge 1 -a -f "$1"  ] && input="$(cat $1)" && shift || input="$(cat)"
	case "$1" in
    set)            shift; set_value "$input" "$@";;
    get)            shift; read_value "$input" "$@";;
    *)              show_usage;;
	esac
}

main "$@"