#!/usr/bin/env bash

# CONSTANTS
DEBUG=${BASH_BACK_DEBUG:-false}
TMP_ERROR=$(mktemp -t "$(basename $0).XXXXXXXX" --tmpdir=/run/user/$(id -u))
SCRIPT=$1

# FUNCTIONS

function on_return {
  if [[ "${BASH_COMMAND}" == 'return '* ]]; then
    code=$(echo "${BASH_COMMAND}" | cut -d' ' -f2) # regex does not work here unfortunately! thus use of basic cut
    if [[ -n "$code" ]] && [[ "$code" -ne 0 ]]; then
      trap - DEBUG
      >&2 echo "${BASH_SOURCE[2]}: line ${BASH_LINENO[0]}: return $code from ${FUNCNAME[1]}"
    fi
  fi
}

# overridden function which permits stacktracing of original `return` statement
function exit {
  code=${1:-0}
  >&2 echo "${BASH_SOURCE[2]}:${BASH_LINENO[0]} exit $@"
  # >&2 echo "${BASH_SOURCE[2]}: line ${BASH_LINENO[0]}: exit $@"
  builtin exit $code
}

function on_exit {
  code=${1:-0}

  stack_lines=("${BASH_LINENO[@]}")
  stack_functions=("${FUNCNAME[@]}")
  stack_sources=("${BASH_SOURCE[@]}")

  unset stack_lines[-1]
  unset stack_lines[-1]
  unset stack_functions[0]
  unset stack_functions[-1]
  stack_functions[-1]='<main>'
  unset stack_sources[0]
  unset stack_sources[-1]

  if [[ "${stack_functions[1]}" == exit && "${stack_sources[1]}" == "${BASH_SOURCE[0]}" ]]; then
    # the exit case scenario
    unset stack_functions[1]
    unset stack_sources[1]
    unset stack_lines[0]
  fi

  stack_lines=("${stack_lines[@]}")
  stack_functions=("${stack_functions[@]}")
  stack_sources=("${stack_sources[@]}")

  stack_summary=()

  if [[ $code -gt 0 ]]; then
    last_error=$(tail -n1 $TMP_ERROR)
    last_source=${stack_sources[0]}
    last_source=${last_source//./"\."} # replace . by \.
    regex1="^$last_source: line ([0-9]+): (.*)\$"
    regex2="^$last_source:([0-9]+) (.*)\$"
    if [[ "$last_error" =~ $regex1 || "$last_error" =~ $regex2 ]]; then
      line=${BASH_REMATCH[1]}
      message=${BASH_REMATCH[2]}
      regex=': unbound variable$'
      [[ $code == 1 ]] && [[ "$message" =~ $regex ]] && stack_lines[0]=$line

      regex="^return ([0-9]*) from (.*)\$"
      if [[ "$message" =~ $regex ]]; then
        return_code="${BASH_REMATCH[1]}"
        funcname="${BASH_REMATCH[2]}"
        # >&4 echo "RETURN DETECTED line ${stack_sources[0]} $line $funcname"
        stack_sources=("${stack_sources[0]}" "${stack_sources[@]}")
        stack_lines=("$line" "${stack_lines[@]}")
        stack_functions=("$funcname" "${stack_functions[@]}")
        stack_summary+=("ERROR $code: [return $return_code]")
      else
        stack_summary+=("ERROR $code: [$message]")
      fi
    else
      regex="^	.*:[0-9]*	.*\$"
      [[ "$last_error" =~ $regex ]] || stack_summary+=("ERROR $code: <undefined>")
    fi

    for i in "${!stack_functions[@]}"; do
      stack_detail=$(printf "\t%30s\t%s\n" "${stack_sources[$i]}:${stack_lines[$i]}" "${stack_functions[$i]}")
      stack_summary+=("$stack_detail")
    done
    >&4 dump_stderr true
    dump_summary
  else
    >&4 dump_stderr false
  fi

  cleanup
  builtin exit $code
}

function dump_summary {
  $DEBUG && >/dev/tty echo '---stacktrace---'
  for i in "${stack_summary[@]}"; do
    >&4 echo -e "$i"
  done
}

function dump_stderr {
  last_trim=${1:-false}
  mapfile -t tmp_error <$TMP_ERROR
  if $last_trim; then
    unset tmp_error[-1]
    tmp_error=("${tmp_error[@]}")
  fi
  if [[ "${#tmp_error[@]}" -gt 0 ]]; then
    $DEBUG && >/dev/tty echo '---stderr---'
    for i in "${tmp_error[@]}"; do
      echo -e "$i"
    done
  fi
}

function success {
  >&2 dump_stderr
  cleanup
}

function cleanup {
  trap - ERR TERM INT EXIT
  exec 3>&- 4>&-
  rm $TMP_ERROR
}

# MAIN

set -TEue -o pipefail
trap 'on_exit $?' ERR TERM INT EXIT
trap 'on_return' DEBUG

# magic FD
exec 3>$TMP_ERROR 4>/dev/stderr
$DEBUG && >/dev/tty echo '---stdout---'
source $SCRIPT 2>&3
success