#!/bin/sh

# Dependencies: jq tr sed
# Tested with: busybox bourne bash zsh

# TODO:
# Add license
# Check --path is correct
# Prevent --env-name unless --key is being used
# Fix it so options and filenames can be mixed (right now input files must be last)
# Enable --key=val style params in addition to --key value
# Shell escape key names passed into jq
# Defaults environment variable / rcfile
# Fix chomped ending newlines from using $()
# Finish tests/
# Enable DockerHub automated tests?
# Create initial release tag
# Create dockerhub build from tag
# Create make target for release of tag

name="${0##*/}"

usage() {
  if [ "${1:-}" ]; then echo "$1" >&2; fi
  cat <<EOF
USAGE: $name [ OPTIONS ] [ FILENAMES ]

Kilna's swiss army knife for turning key-values in a JSON object into eval-able
shell code for setting environment variables.

Processes FILENAMES as JSON documents if provided, otherwise processes standard
input as a JSON document.

Options:

         --export : Export shell variables
               -x   (prepend each key=val with shell's export keyword)

      --path PATH : JSON sub-path in jq .path.to.the.object dot-prefix notation
          -p PATH   (e.g '.env_vars') - defaults to '.' for the root JSON
                    object. The referenced path must only be a JSON object
                    (dict/map/hash), not an array, string, etc.

  --prefix PREFIX : Prepend this string the to names of output shell variables
        -p PREFIX

          --upper : Translate JSON keys into uppercase shell environment vars
               -u

          --lower : Translate JSON keys into lowercase shell environment vars
               -l

        --key KEY : Only output this single key in the object
           -k KEY   (defaults to all keys)

  --env-name NAME : When outputting a single key with --key, force this value
          -e NAME   as the environment variable name

           --text : JSON objects and arrays become newline delimited text
               -t   rather than the default behavior of setting the shell
                    environment variable to a JSON string representation

  --kv-sep STRING : Key-value separator for text-style translation of JSON
        -K STRING   objects (defaults to space)

--list-sep STRING : Array / object record separator for text-style translation
        -L STRING   (defaults to newline)

          --array : JSON arrays are translated into POSIX shell native arrays
               -a   (overrides --text)

          --assoc : JSON objects are tranlated into bash-style native
               -a   associative arrays (overrides --text)

          --force : Output shell native for --array or --assoc even if the
               -f   current shell does not support it

         --strict : Fail on JSON keys which aren't alphanumeric + underscore
               -s   (defaults to translating keys)

  --out-file FILE : Output to a file instead of STDOUT
          -o FILE

        --compact : Output JSON strings in compact mode
               -c

           --help : Show help
               -h

This script defaults to /bin/sh, if you wish to run it under your current shell
instead, call it as such:

  \$SHELL $name

EOF
  if [ "${1:-}" != '' ]; then exit "${2:-1}"; else exit 0; fi
}

debug() { [ "$debug" ] && echo "$1" >&2; };

die() { echo "$1" >&2; [ -e "$outfile" ] && rm "$outfile"; exit "${2:-1}"; };

shell_quote() {
  if [ "$(echo "$1" | tr -c -d a-zA-Z0-9)" = "$1" ]; then
    echo "$1" # Simple shell values don't need quoting
  else
    echo "'$(echo "$1" | sed -e "s/'/'\\\\''/")'"
  fi
}

c='' # jq -c flag
case='as-is'
export debug=''
env_name=''
evaluate=''
force=''
kv_sep=' '
list_sep=$'\n'
native_array=''
native_assoc=''
outfile=''
json_path='.'
prefix=''
strict=''
text=''
only_key=''
x='' # declare -x flag

while [ $# -gt 0 ]; do case "$1" in
  -a|--array)    native_array=true;;
  -A|--assoc)    native_assoc=true;;
  -c|--compact)  c='c';;
  -d|--debug)    debug=true;;
  -e|--env-name) env_name="$2"; shift;;
  -f|--force)    force=true;;
  -h|--help)     usage;;
  -k|--key)      only_key="$2"; shift;;
  -K|--kv-sep)   kv_sep="$2"; shift;;
  -l|--lower)    case='lower';;
  -L|--list-sep) list_sep="$2"; shift;;
  -o|--out-file) outfile="$2"; shift;;
  -p|--path)     json_path="$2"; shift;;
  -P|--prefix)   prefix="$2"; shift;;
  -s|--strict)   strict=true;;
  -t|--text)     text=true;;
  -u|--upper)    case='upper';;
  -x|--export)   x='x';;
  -*)            usage "Unknown flag: $1";;
  *)             break;;
esac; shift; done

if [ "${#@}" -eq 0 ]; then
  if [ -t 0 ]; then
    usage "Must be piped into or a JSON filename provided on command line" 3
  else
    set -- '-'
  fi
fi

if [ "$native_array" ] && [ ! "$force" ]; then
  if ! (eval 'declare -a zzz=(a b) && [ "${zzz[1]}" = "b" ]' >/dev/null 2>&1); then
    die "$SHELL does not support arrays with --array, use --force to output anyway"
  fi
fi

if [ "$native_assoc" ] && [ ! "$force" ]; then
  if ! (eval 'declare -A zzz=([a]=b) && [ "${zzz[a]}" = "b" ]' >/dev/null 2>&1); then
    die "$SHELL does not support associative arrays with --assoc, use --force to output anyway"
  fi
fi

process_key() {

  key="$1"
  json="$(cat -)"

  debug ''
  debug "  KEY: $key"

  if [ "$env_name" ]; then varname="$env_name"; else varname="$key"; fi
  # Clean up varname to translate space and - to underscore, and
  # remove non-alphanum + underscore chars
  varname="$(echo "$varname" | tr ' -' '__' | tr -c -d a-zA-Z0-9_)"
  # If we're in strict mode, fail if the key has been changed
  if [ "$strict" ] && [ "$varname" != "$key" ]; then
    die "Invalid key '$(shell_quote "$key")'" 6
  fi
  if [ "$case" = 'lower' ]; then
    varname="$(echo "$varname" | tr A-Z a-z)"
  fi
  if [ "$case" = 'upper' ]; then
    varname="$(echo "$varname" | tr a-z A-Z)"
  fi
  varname="$prefix$varname"
  debug "  VARNAME: $varname"

  translate='raw'
  type="$(echo "$json" | jq -r "$json_path | .[\"$key\"] | type")"
  debug "  TYPE: $type"
  if [ "$type" = "array" ]; then
    [ "$text" ]         && translate=text-array
    [ "$native_array" ] && translate=native-array
  elif [ "$type" = "object" ]; then
    [ "$text" ]         && translate=text-assoc
    [ "$native_assoc" ] && translate=native-assoc
  fi
  debug "  TRANSLATE: $translate"

  case "$translate" in
    raw)
      [ "$x" ] && printf '%s' 'export ';
      val="$(echo "$json" | jq -${c}r "$json_path | .[\"$key\"]")";
      echo "$varname=$(shell_quote "$val")";
      ;;
    native-assoc)
      echo "declare -A$x $varname=(";
      echo "$json" | jq -j "$json_path | .[\"$key\"] | keys[] | (. + \"\u0000\")" | \
      while read -r -d '' objkey; do
        objval="$(echo "$json" | jq -${c}r "$json_path | .[\"$key\"] | .[\"$objkey\"]")";
        echo "  [$(shell_quote "$objkey")]=$(shell_quote "$objval")";
      done;
      echo ')';
      ;;
    native-array)
      [ "$x" ] && printf '%s' 'export ';
      echo "$varname=($(echo "$json" | jq -${c}r "$json_path | .[\"$key\"] | @sh"))";
      ;;
    text-array)
      [ "$x" ] && printf '%s' 'export ';
      val="$(
        echo "$json" | jq -j "$json_path | .[\"$key\"] | .[] | (. + \"\u0000\")" | \
        while read -r -d '' thisval; do
          printf '%s' "${thisval}${list_sep}"
        done
      )"
      echo "$varname=$(shell_quote "${val%"${list_sep}"}")";
      ;;
    text-assoc)
      [ "$x" ] && printf '%s' 'export ';
      val="$(
        echo "$json" | jq -j "$json_path | .[\"$key\"] | keys[] | (. + \"\u0000\")" | \
        while read -r -d '' thiskey; do
          thisval="$(echo "$json" | jq -${c}r "$json_path | .[\"$key\"] | .[\"$thiskey\"]")"
          printf '%s' "${thiskey}${kv_sep}${thisval}${list_sep}"
        done
      )"
      echo "$varname=$(shell_quote "${val%"${list_sep}"}")";
      ;;
  esac

}

for file in "$@"; do

  debug "FILE: $file"
  json="$(cat "$file")"
  debug "JSON:"
  debug "$json"

  out="$(
    if [ "$only_key" ]; then
      echo "$json" | process_key "$only_key"
    else
      echo "$json" | jq -j "$json_path | keys[] | (. + \"\u0000\")" | \
      while read -r -d '' key; do
        echo "$json" | process_key "$key"
      done
    fi
  )"

  if [ "$outfile" ]; then
    echo "$out" >"$outfile"
  else
    echo "$out"
  fi

done