#!/usr/bin/env bash

# constants

MIAOU_BASH_ERROR=$(mktemp -t "$(basename "$0").XXXXXXXX" --tmpdir="/run/user/$(id -u)")
MIAOU_DEBUG=${MIAOU_DEBUG:-false}
readonly MIAOU_BASH_ERROR MIAOU_DEBUG

## functions

function is_true {
  [[ "${1:-}" == 'true' ]]
}

# FIXME: define an alias to bypass ARG evaluation when unnecessary!
# example:
#   alias toto="bash -c \"[[ \\\$MIAOU_DEBUG == 'true' ]] && echo yes \\\$* || echo nope\""
function miaou_debug {
  is_true "${MIAOU_DEBUG}" && >/dev/tty builtin echo -e "\e[90mDEBUG <==> \e[33m$*\e[0m" || true
}

function tty_ansi {
  fg="${1:-}"
  [[ -n $fg ]] && >/dev/tty echo -ne "\e[${fg}m" || true
}

function on_error {
  local code
  code="${1:-100}"
  >/dev/tty printf '\r' # force carriage return explicitly

  miaou_debug "on_error: $code ($$ -- $BASHPID)"

  if [[ $$ == "$BASHPID" ]]; then
    >&2 echo "${BASH_SOURCE[1]}: line ${BASH_LINENO[0]}: command_error: ${code}"
    failure_type="COMMAND_ERROR"
    error_source=("${BASH_SOURCE[@]}")
    error_lineno=("${BASH_LINENO[@]}")
    error_funcname=("${FUNCNAME[@]}")
    unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
    unset 'error_source[0]' 'error_lineno[-1]' 'error_funcname[0]'
    error_funcname[-1]='<main>'
    error_source=("${error_source[@]}")
    error_lineno=("${error_lineno[@]}")
    error_funcname=("${error_funcname[@]}")

    exit "$code"
  else
    >&2 echo "${BASH_SOURCE[1]}: line ${BASH_LINENO[0]}: subshell_error: ${code}"
    kill -PIPE $$
  fi
}

function dump_stderr {
  miaou_debug --stderr--
  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
  tty_ansi 94
  for i in "${tmp_error[@]}"; do echo "$i"; done
  tty_ansi 0
  miaou_debug --end of stderr--
}

function dump_failure {
  miaou_debug --error box--
  tty_ansi 94
  echo -n "FAILURE TYPE = "
  tty_ansi 95
  echo "$failure_type"
  tty_ansi 0
  miaou_debug --end of error box--
}

function dump_stacktrace {
  miaou_debug --stacktrace ${#error_source[@]}--
  tty_ansi 94
  local i source lineno funcname
  for i in "${!error_source[@]}"; do
    source="${error_source[$i]}"
    lineno="${error_lineno[$i]}"
    funcname="${error_funcname[$i]}"
    printf "%40s:%.4s \t%s\n" "$source" "$lineno" "$funcname"
  done
  tty_ansi 0
  miaou_debug --end of stacktrace--
}

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

  2>&3 >&3 dump_stderr
  if [[ -v failure_type ]]; then
    2>&3 >&3 dump_failure
    2>&3 >&3 dump_stacktrace
  fi

  miaou_debug "on_exit $code"
}

function on_pipe {
  local code tmp_error regex

  error_source=("${BASH_SOURCE[@]}")
  error_lineno=("${BASH_LINENO[@]}")
  error_funcname=("${FUNCNAME[@]}")
  unset 'error_source[0]' 'error_lineno[0]' 'error_funcname[0]'
  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'
  unset 'error_source[-1]' 'error_lineno[-1]' 'error_funcname[-1]'

  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
  last_error="${tmp_error[-1]}"
  regex='(.*): line ([0-9]+): subshell_error: ([0-9]+)'
  if [[ $last_error =~ $regex ]]; then
    source=${BASH_REMATCH[1]}
    lineno=${BASH_REMATCH[2]}
    code=${BASH_REMATCH[3]}
    failure_type="SUBSHELL_ERROR"
    error_source=("$source" "${error_source[@]}")
    error_lineno=("$lineno" "${error_lineno[@]}")
    error_funcname=("${error_funcname[@]}" '<main>')
  else
    code=141
    failure_type="PIPE_ERROR"
  fi

  # miaou_debug on_pipe: "${code}"
  exit "$code"
}

## main

set -euo pipefail
set -E # HALT on subshell error
# set -T # DEBUG RETURN

[[ $# -lt 1 ]] && >&2 echo 'ERROR: script expected!' && builtin exit 1
BASH_ARGV0="$1" && shift # to pretend script runs by itself

trap 'on_error $?' ERR
trap 'on_exit $?' EXIT
trap 'on_pipe' PIPE

miaou_debug "--source from ${BASHPID}"
exec 3>/dev/stderr
# shellcheck source=/dev/null
2>"$MIAOU_BASH_ERROR" source "$BASH_ARGV0"
exec 3>-
miaou_debug '--source success'