#!/usr/bin/env -S -- bash
#!/usr/bin/env -S -- bash -x

# constants

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

declare -A ANSI
ANSI[RESET]=0

ANSI[STYLE_ITALIC]=3
ANSI[STYLE_BOLD]=1
ANSI[STYLE_UNDERLINE]=4
ANSI[STYLE_STRIKETHROUGH]=9

ANSI[FG_BLACK]=30
ANSI[FG_RED]=31
ANSI[FG_GREEN]=32
ANSI[FG_YELLOW]=33
ANSI[FG_BLUE]=34
ANSI[FG_PURPLE]=35
ANSI[FG_CYAN]=36
ANSI[FG_WHITE]=37
ANSI[FG_GRAY]=90
ANSI[FG_LIGHTBLUE]=94
ANSI[FG_MAGENTA]=95

ANSI[BG_BLACK]=40
ANSI[BG_RED]=41
ANSI[BG_GREEN]=42
ANSI[BG_YELLOW]=43
ANSI[BG_BLUE]=44
ANSI[BG_PURPLE]=45
ANSI[BG_CYAN]=46
ANSI[BG_WHITE]=47
ANSI[BG_GRAY]=90
ANSI[BG_MAGENTA]=95

readonly MIAOU_BASH_ERROR MIAOU_DEBUG ANSI

## functions

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

# HINT: define an alias to bypass ARG evaluation when unnecessary!
# example: alias toto="bash -c \"[[ \\\$MIAOU_DEBUG == 'true' ]] && echo yes \\\$* || echo nope\""
function miaou_debug {
  if is_true "${MIAOU_DEBUG}"; then
    local compute_hierarchy=true
    [[ ! -v miaou_debug_hierarchy ]] && miaou_debug_hierarchy=0
    local i message="$*" padding=''
    regex='^</' # starts with </
    [[ $miaou_debug_hierarchy -gt 0 ]] &&
      [[ "${message}" =~ $regex ]] &&
      ((--miaou_debug_hierarchy)) &&
      compute_hierarchy=false
    for ((i = 0; i < miaou_debug_hierarchy; i++)); do padding+='  '; done
    >&4 builtin echo -e "\e[90m <== DEBUG ==> ${padding}\e[33m${message}\e[0m"
    regex='[^/]>$' # does NOT end with />
    is_true $compute_hierarchy &&
      [[ "${message}" =~ $regex ]] &&
      ((++miaou_debug_hierarchy)) ||
      true
  fi
}

function on_return {
  local regex='return ([0-9]+)'
  if [[ "$BASH_COMMAND" =~ $regex ]] && [[ "${BASH_REMATCH[1]}" -gt 0 ]]; then
    failure_code="${BASH_REMATCH[1]}"
    failure_type="RETURN"
    failure_payload="${FUNCNAME[0]}"
    print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
    miaou_debug "<on_return code=$failure_code payload=$failure_payload/>"
  fi
  true
}

# overridden function which permits backtracing of the original `exit` statement
function exit {
  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[@]}")

  failure_code=${1:-0}
  failure_type="EXIT"
  failure_payload="${error_funcname[0]}"

  miaou_debug "<exit code=$failure_code overridden/>"
  print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
  builtin exit "$failure_code"
}

function tty_ansi {
  local code
  for code in "$@"; do
    if [[ -v ANSI[$code] ]]; then
      >&4 echo -ne "\e[${ANSI[$code]}m"
    else
      >&2 echo "unknown ansi key: <$code>"
      break
    fi
  done
}

function print_miaou_error {
  local source="$1" line="$2" code="$3" type="$4" payload="${5:-}"
  local message
  message="${source}: line ${line}: miaou_error: ${type} ${code}"
  [[ -n "$payload" ]] && message+=" payload: ${payload}"
  [[ -v tmp_error ]] && miaou_debug "tmp_error=${#tmp_error[@]}" && tmp_error+=("$message") || >&2 echo "$message"
}

function on_error {
  trap - RETURN
  failure_code="${1:-200}"
  >&4 printf '\r' # TODO: force carriage return explicitly, is it really useful?

  miaou_debug "<on_error code=${failure_code} command={${BASH_COMMAND}}>"

  if [[ $$ == "$BASHPID" ]]; then
    if [[ ! -v failure_type ]]; then
      if [[ ${BASH_COMMAND} == 'false' ]]; then
        failure_type="FALSE"
      else
        failure_type="COMMAND_ERROR"
        failure_payload="${BASH_COMMAND}"
      fi
      print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}"
    fi

    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[@]}")

    if [[ -v failure_payload ]]; then
      miaou_debug "</on_error exit=$failure_code type=${failure_type} payload={${failure_payload}}>"
    else
      miaou_debug "</on_error exit=$failure_code type=${failure_type}>"
    fi

    builtin exit "$failure_code"
  else
    miaou_debug "</on_error pipe=$failure_code sub_pid=$BASHPID pid=$$ command={${BASH_COMMAND}}>"
    print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" 'SUBSHELL_ERROR' "${BASH_COMMAND}"
    kill -PIPE $$
  fi
}

function on_pipe {
  trap - RETURN
  local tmp_error regex source lineno
  miaou_debug "<on_pipe sub_pid=$BASHPID pid=$$>"

  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]'

  miaou_debug '<load_tmp_error/>' && mapfile -t tmp_error <"$MIAOU_BASH_ERROR"

  last_error="${tmp_error[-1]}"
  regex='^(.*): line ([0-9]+): miaou_error: SUBSHELL_ERROR ([0-9]+) payload: (.*)$'
  if [[ $last_error =~ $regex ]]; then
    source=${BASH_REMATCH[1]}
    lineno=${BASH_REMATCH[2]}
    failure_code=${BASH_REMATCH[3]}
    failure_payload=${BASH_REMATCH[4]}
    failure_type="SUBSHELL_ERROR"
    error_source=("$source" "${error_source[@]}")
    error_lineno=("$lineno" "${error_lineno[@]}")
    error_funcname=("${error_funcname[@]}" '<main>')
  else
    failure_code=141
    failure_type="PIPE_ERROR"
  fi
  miaou_debug "</on_pipe/>"
  builtin exit "$failure_code"
}

function dump_stderr {
  miaou_debug "<stderr count=${#tmp_error[@]}>"
  tty_ansi FG_LIGHTBLUE
  for i in "${tmp_error[@]}"; do echo "$i"; done
  tty_ansi RESET
  miaou_debug '</stderr>'
}

function dump_failure {
  local i
  miaou_debug '<error_box>'
  tty_ansi FG_MAGENTA
  length_box=$((${#failure_type} + ${#failure_code} + (2 * 2) + 2))
  [[ -v failure_payload ]] && length_box=$((length_box + ${#failure_payload} + (2 * 2) + 1))
  echo -n '╔'
  for ((i = 0; i < length_box; i++)); do echo -n '═'; done
  echo '╗'
  echo -n "║ $failure_type "
  [[ -v failure_payload ]] && echo -n ' ' && tty_ansi BG_WHITE FG_BLACK && echo -n "  $failure_payload  " && tty_ansi RESET
  tty_ansi FG_YELLOW
  printf "%5s" "  $failure_code  "
  tty_ansi FG_MAGENTA
  echo "║"
  echo -n '╚'
  for ((i = 0; i < 4; i++)); do echo -n '═'; done
  echo -n '╦'
  for ((i = 5; i < length_box; i++)); do echo -n '═'; done
  echo '╝'
  echo "     ║"
  tty_ansi RESET
  miaou_debug '</error_box>'
}

function dump_stacktrace {
  miaou_debug "<stacktrace count=${#error_source[@]}>"
  local i source lineno funcname
  for i in "${!error_source[@]}"; do
    tty_ansi FG_MAGENTA
    echo -n "     ╟──▷"
    [[ $i -gt 0 ]] && tty_ansi FG_GRAY
    tty_ansi STYLE_ITALIC
    source="${error_source[$i]}"
    lineno="${error_lineno[$i]}"
    funcname="${error_funcname[$i]}"
    printf "%40s:%.4s" "$source" "$lineno"
    tty_ansi RESET
    printf " \t%s" "$funcname"
    echo
  done
  miaou_debug '</stacktrace>'
}

function on_exit {
  trap - RETURN
  local code="${1:-0}" last_error regex

  miaou_debug "<on_exit code=$code>"

  [[ ! -v tmp_error ]] &&
    miaou_debug '<load_tmp_error/>' &&
    mapfile -t tmp_error <"$MIAOU_BASH_ERROR"

  if [[ -v failure_type && "$failure_type" == 'RETURN' ]]; then
    last_error="${tmp_error[-1]}"
    regex='^(.*): line ([0-9]+): miaou_error: RETURN [0-9]+'
    if [[ "$last_error" =~ $regex ]]; then
      miaou_debug "<return code=$code/>"
      local source line
      source="${BASH_REMATCH[1]}"
      line="${BASH_REMATCH[2]}"
      error_source=("$source" "${error_source[@]}")
      error_lineno=("$line" "${error_lineno[@]}")
      error_funcname=("$failure_payload" "${error_funcname[@]}")
    else
      miaou_debug "<return type=unexpected/>"
    fi

  else
    if [[ $code -gt 0 && ${#tmp_error[@]} -gt 0 ]]; then
      last_error="${tmp_error[-1]}"
      miaou_debug "<investigate_tmp_error last={$last_error}>"

      regex='^(.*): line ([0-9]+): (.*): unbound variable$'
      if [[ $code -eq 1 ]] && [[ "$last_error" =~ $regex ]]; then
        local source line payload

        source="${BASH_REMATCH[1]}"
        line="${BASH_REMATCH[2]}"
        payload="${BASH_REMATCH[3]}"
        error_source=("${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]'
        error_source=("$source" "${error_source[@]}")
        error_lineno=("$line" "${error_lineno[@]}")
        error_funcname=("${error_funcname[@]}" '<main>')

        failure_code=$code
        failure_type='UNBOUND_VARIABLE'
        failure_payload=$payload

        print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" "${failure_payload}"
        unset 'tmp_error[-2]' # replace previous last_error
        miaou_debug "<unbound_variable source=${source} line=${line} payload={${failure_payload}}/>"
      fi
      miaou_debug "</investigate_tmp_error>"
    fi
  fi

  2>&3 >&3 dump_stderr
  if [[ -v failure_type ]]; then
    2>&3 >&4 dump_failure
    2>&3 >&4 dump_stacktrace
  fi
  if [[ $code -gt 0 ]]; then
    miaou_debug "</on_exit exit=$code>"
  else
    miaou_debug "</on_exit success>"
  fi
}

## 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
trap 'on_return' RETURN

if [[ -e /proc/$$/fd/3 ]]; then exec 4>&3 3>&-; else exec 4>/dev/tty; fi # swap fd 3 4 when fd 3 sent off
exec 3>/dev/stderr 2>"$MIAOU_BASH_ERROR"

miaou_debug "<source from=$BASH_ARGV0 pid=${BASHPID}/>"
# shellcheck source=/dev/null
source "$BASH_ARGV0"