#!/usr/bin/env bash

# constants

MIAOU_BASH_ERROR=$(mktemp -t "$(basename "$0").XXXXXXXX" --tmpdir="/run/user/$(id -u)")
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 {
  is_true "${MIAOU_DEBUG}" && >&4 builtin echo -e "\e[90m <== DEBUG ==> \e[33m$*\e[0m" || true
}

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:-}"
  >&2 echo -n "${source}: line ${line}: miaou_error: code=${code} type=${type}"
  [[ -n "$payload" ]] && >&2 echo " payload=${payload}" || >&2 echo
}

function on_error {
  failure_code="${1:-200}"
  >&4 printf '\r' # force carriage return explicitly

  if [[ $$ == "$BASHPID" ]]; then
    miaou_debug "<on_error exit=$failure_code/>"
    failure_type="COMMAND_ERROR"
    print_miaou_error "${BASH_SOURCE[1]}" "${BASH_LINENO[0]}" "${failure_code}" "${failure_type}" '...'

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

function on_pipe {
  local tmp_error regex source lineno

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

function dump_stderr {
  miaou_debug '<stderr>'
  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 in $(seq 1 $length_box); 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 in $(seq 1 4); do echo -n '═'; done
  echo -n '╦'
  for i in $(seq $((i + 2)) $length_box); 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 {
  local code
  code="${1:-0}"

  mapfile -t tmp_error <"$MIAOU_BASH_ERROR"
  2>&3 >&3 dump_stderr

  if [[ $code -gt 0 && ${#tmp_error[@]} -gt 0 ]]; then
    local last_error regex
    last_error="${tmp_error[-1]}"
    miaou_debug "<on_exit exit=$code last_error='$last_error'>"
    if [[ $code -eq 1 ]]; then
      regex='^(.*): line ([0-9]+): (.*): unbound variable$'
      if [[ "$last_error" =~ $regex ]]; then
        local source line payload
        source="${BASH_REMATCH[1]}"
        line="${BASH_REMATCH[2]}"
        payload="${BASH_REMATCH[3]}"
        miaou_debug "<unbound_variable source=${source} line=${line} payload=${payload}>"
        failure_code=$code
        failure_type='UNBOUND_VARIABLE'
        failure_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>')
      fi
    fi
    miaou_debug "</on_exit>"
  fi

  if [[ -v failure_type ]]; then
    2>&3 >&4 dump_failure
    2>&3 >&4 dump_stacktrace
  fi

  miaou_debug "</source type=failure exit=$code pid=${BASHPID}>"
}

## 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

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

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