#!/bin/bash
# Copyright (C) 2019 Ian Kelling
# SPDX-License-Identifier: AGPL-3.0-or-later

# meant to be sourced. copy/pasted from https://iankelling.org/git/?p=errhandle;a=summary

# Commentary: Bash stack trace and error handling functions. This file
# is meant to be sourced. It loads some functions which you may want to
# call manually (see the comments at the start of each one), and then
# runs err-catch. See the README file for a slightly longer explanation.


#######################################
# Print stack trace
#
# usage: err-bash-trace [MESSAGE]
#
# This function is called by the other functions which print stack
# traces.
#
# It does not show function args unless you first run:
# shopt -s extdebug
# which err-catch & err-print do for you.
#
# MESSAGE       Message to print just before the stack trace.
#
# _frame_start  Optional variable to set before calling. The frame to
#               start printing on. default=1. Useful when printing from
#               an ERR trap function to avoid printing that function.
#######################################
err-bash-trace() {
  local -i argc_index=0 frame i start=${_frame_start:-1}
  local source
  if [[ $1 ]]; then
    printf "%s\n" "$1"
  fi
  for ((frame=0; frame < ${#FUNCNAME[@]}; frame++)); do
    argc=${BASH_ARGC[frame]}
    argc_index+=$argc
    ((frame < start)) && continue
    if (( ${#BASH_SOURCE[@]} > 1 )); then
      source="${BASH_SOURCE[frame]}:${BASH_LINENO[frame-1]}:"
    fi
    printf "  from %sin \`%s" "$source" "${FUNCNAME[frame]}"
    if shopt extdebug >/dev/null; then
      for ((i=argc_index-1; i >= argc_index-argc; i--)); do
        printf " %s" "${BASH_ARGV[i]}"
      done
    fi
    echo \'
  done
  return 0
}

#######################################
# On error print stack trace and exit
#
# Globals:
#   errcatch-cleanup  If set, this command will run just before exiting.
#######################################
err-catch() {
  set -E; shopt -s extdebug
  _err-trap() {
    err=$?
    exec >&2
    set +x
    local msg="${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
    if (( ${#FUNCNAME[@]} > 2 )); then
      local _frame_start=2
      err-bash-trace "$msg"
    else
      echo "$msg"
    fi
    set -e # err trap does not work within an error trap
    if type -t errcatch-cleanup >/dev/null; then
      errcatch-cleanup
    fi
    echo "$0: exiting with status $err"
    exit $err
  }
  trap _err-trap ERR
  set -o pipefail
}


#######################################
# For interactive shells: on error, print stack trace and return
#
# Globals:
#   err_catch_ignore  Array containing glob patterns to test against filenames to ignore
#                     errors from. Initialized to ignore bash-completion scripts on debian
#                     based systems.
#   _err_func_last  Used internally.
#   _err_catch_err  Used internally.
#   _err_catch_i    Used internally.
#   _err_catch_ignore Used internally.
#
# misc: All shellcheck disables for this function are false positives.
#######################################
# shellcheck disable=SC2120
err-catch-interactive() {
  err_catch_ignore=(
    '/etc/bash_completion.d/*'
  )
  # shellcheck disable=SC2034
  declare -i _err_func_last=0
  set -E; shopt -s extdebug
  # shellcheck disable=SC2154
  trap '_err_catch_err=$? _trap_bc="$BASH_COMMAND"
  _err_catch_ignore=false
  for _err_catch_i in "${err_catch_ignore[@]}"; do
    if [[ ${BASH_SOURCE[0]} == $_err_catch_i ]]; then
      _err_catch_ignore=true
      break
    fi
  done
  if ! $_err_catch_ignore; then
    if (( ${#FUNCNAME[@]} > _err_func_last )); then
      echo ERR: \`$_trap_bc'"\'"' returned $_err_catch_err
    fi
    _err_func_last=${#FUNCNAME[@]}
    if (( _err_func_last )); then
      printf "  from %s:%s:in \`%s" "${BASH_SOURCE[0]}" "$(declare -F "${FUNCNAME[0]}"|awk "{print \$2}")" "${FUNCNAME[0]}"
      if shopt extdebug >/dev/null; then
        for ((_err_catch_i=${BASH_ARGC[0]}-1; _err_catch_i >= 0; _err_catch_i--)); do
          printf " %s" "${BASH_ARGV[_err_catch_i]}"
        done
      fi
      echo '"\'"'
      return $_err_catch_err
    fi
  fi' ERR
  set -o pipefail
}


#######################################
# Undoes err-catch/err-catch-interactive
#######################################
err-allow() {
  shopt -u extdebug
  set +E +o pipefail
  trap ERR
}

#######################################
# On error, print stack trace
#######################################
err-print() {
  # help: on errors: print stack trace
  #
  # This function depends on err-bash-trace.

  set -E; shopt -s extdebug
  _err-trap() {
    err=$?
    exec >&2
    set +x
    echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}: \`$BASH_COMMAND' returned $err"
    err-bash-trace 2
  }
  trap _err-trap ERR
  set -o pipefail
}


#######################################
# Print stack trace and exit
#
# Use this instead of the exit command to be more informative.
#
# usage: err-exit [EXIT_CODE] [MESSAGE]
#
# EXIT_CODE  Default is 1.
# MESSAGE    Print MESSAGE to stderr. If only one of EXIT_CODE
#            and MESSAGE is given, we consider it to be an
#            exit code if it is a number.
#######################################
err-exit() {
  exec >&2
  code=1
  if [[ "$*" ]]; then
    if [[ ${1/[^0-9]/} == "$1" ]]; then
      code=$1
      if [[ $2 ]]; then
        printf '%s\n' "$2" >&2
      fi
    else
      printf '%s\n' "$0: $1" >&2
    fi
  fi
  echo "${BASH_SOURCE[1]}:${BASH_LINENO[0]}"
  err-bash-trace 2
  echo "$0: exiting with code $code"
  exit $err
}

# We want this more often than not, so run it now.
if [[ $- == *i* ]]; then
  err-catch-interactive
else
  err-catch
fi