#!/usr/bin/env bash

## rdlink [-d|--debug] <PATH>
##
## License: GNU GPL V3 or later
##  Author: Martin Winkler

# Exit on error. Append "|| true" if you expect an error.
set -o errexit
# Exit on error inside any functions or subshells.
set -o errtrace
# Do not allow use of undefined vars. Use ${VAR:-} to use an undefined VAR
set -o nounset
# Catch the error in case mysqldump fails (but gzip succeeds) in `mysqldump |gzip`
set -o pipefail

LOG_LEVEL="${LOG_LEVEL:-1}" # 7 = debug -> 0 = emergency

function rl::log () {
  local log_level="${1:-${LOG_LEVEL}}"
  shift

  # all remaining arguments are to be printed
  local log_line=""

  while IFS=$'\n' read -r log_line; do
    printf "%s [%9s] %s\n" "$(date -u +"%Y-%m-%d %H:%M:%S UTC")" "${log_level}" "${log_line}" 1>&2
  done <<< "${@:-}"
}
emergency() {                                  rl::log emergency "${@}"; exit 1; }
alarm()     { [[ "${LOG_LEVEL:-0}" -ge 1 ]] && rl::log alert "${@}"; true; }
critical()  { [[ "${LOG_LEVEL:-0}" -ge 2 ]] && rl::log critical "${@}"; true; }
error()     { [[ "${LOG_LEVEL:-0}" -ge 3 ]] && rl::log error "${@}"; true; }
warning()   { [[ "${LOG_LEVEL:-0}" -ge 4 ]] && rl::log warning "${@}"; true; }
notice()    { [[ "${LOG_LEVEL:-0}" -ge 5 ]] && rl::log notice "${@}"; true; }
info()      { [[ "${LOG_LEVEL:-0}" -ge 6 ]] && rl::log info "${@}"; true; }
debug()     { [[ "${LOG_LEVEL:-0}" -ge 7 ]] && rl::log debug "${@}"; true; }
msg()       {                                  echo "$@"; true; }

### Script
rl::rdlink() {
  local subject=

  subject="${1:-}"
  while [[ "${subject:-}" = *"//"* ]]; do subject="${subject/\/\///}"; done
  while subject="$(rl::quicklink "${subject}")" ; do : ; done
  [ -L "${subject}" ] && printf "\n" && return 1
  subject="$(rl::canon "${subject}")" || { printf "\n"; return 1; }
  printf "%s\n" "${subject}"
}

rl::quicklink() {
  local subject=
  local work=

  subject=$(readlink -- "${1:-}") || { printf -- "%s\n" "${1:-}"; return 1; }
  if [[ "${subject}" != "/"* ]]; then
    work="$(rl::canon "$(dirname -- "${1:-}")")"
    subject="${work}/${subject}"
  fi
  printf "%s\n" "${subject}"
}

rl::canon() {
  local subject=
  local work=
  local bname=
  local run=1
  local start=
  local retval=0

  start="${1:-}"
  while (( run )) ; do
    if work="$(cd "${start}" >/dev/null 2>&1 && pwd -P)" ; then
      subject="$(rl::normalize "${work}")"; run=0
    elif work="$(cd "$(dirname -- "${start}")" >/dev/null 2>&1 && pwd -P)" ; then
      bname="$(basename -- "${start}")"
      [[ "${work}" == "/" ]] && work=
      subject="${work}${bname:+"/${bname}"}"
      (( retval )) && [ -e "${subject}" ] && retval=0; run=0
    else
      work="$(rl::normalize "${start}")"
      [[ "${work}" != "${start}" ]] && start="${work}" && retval=1 && continue
      subject="${work}"; run=0 && retval=1
    fi
  done
  printf -- "%s\n" "${subject}"; return ${retval}
}

rl::normalize() {
  local work=
  work="${1:-}"

  while [[ "${work}" =~ [^/][^/]*/\.\./* ]] ; do work="${work/"${BASH_REMATCH[0]}"/}"; done
  while [[ "$work" =~ /\.(/|$) ]]; do work="${work/${BASH_REMATCH[0]}/${BASH_REMATCH[1]/$//}}"; done
  work="${work#./*}"
  [[ "${work}" =~ (.*[^/])/$ ]] && work="${BASH_REMATCH[1]}"
  printf -- "%s\n" "${work}"
}

rl::main() {
  local file=
  local arg=

  for arg in "$@"; do
    case "$arg" in
      --) shift; break ;;
      -d|--debug) shift; LOG_LEVEL=7 ;;
      -dd) shift; set -o xtrace ;;
      -*) shift ;;
    esac
  done

  for file in "$@"; do rl::rdlink "$file"; done
}

# Provide as function to be called when sourced
rdlink() { rl::main "$@"; }

### Check if script is _sourced
### https://stackoverflow.com/a/28776166
_sourced=0
if [ -n "${ZSH_EVAL_CONTEXT:-}" ]; then
  case ${ZSH_EVAL_CONTEXT:-} in *:file) _sourced=1;; esac
elif [ -n "${KSH_VERSION:-}" ]; then
  [ "$(cd "$(dirname -- "$0")" && pwd -P)/$(basename -- "$0")" \
    != "$(cd "$(dirname -- "${.sh.file}")" && pwd -P)/$(basename -- "${.sh.file}")" ] && _sourced=1
elif [ -n "${BASH_VERSION:-}" ]; then
  (return 0 2>/dev/null) && _sourced=1
else # All other shells: examine $0 for known shell binary filenames
  # Detects `sh` and `dash`; add additional shell filenames as needed.
  case ${0##*/} in sh|dash) _sourced=1;; esac
fi
###

(( ! _sourced )) && rl::main "$@"

### Script EOF