#!/bin/bash
#===============================================================================
#
# DIRECTORY:
#   ---
#
# FILE:
#   ./casualscripter_functions.sh
#
# USAGE:
#   This is a library for some scripts.
#
# OPTIONS:
#   none
#
# EXIT STATES:
#   101 = logfile not set
#   102 = dir for logfile not writable
#   103 = logfile already exists but is not writable
#   104 = a wanted binary is not installed
#
# DESCRIPTION:
#   Global configuration and functions for scripts.
#
# REQUIREMENTS:
#   which, uname, basename, ps, grep, awk, sed, dirname, tee, openssl, ...
#
# BUGS:
#   ---
#
# NOTES:
#   Tested on:
#     - Debian GNU/Linux 8.x + bash, zsh, ksh, busybox ash & dash
#     - ArchLinux + bash, zsh, ksh, busybox ash & dash
#     - Linux Mint 18 (Cinnamon) + bash, zsh, ksh, busybox ash & dash
#     - FreeBSD 11 + bash, zsh & busybox ash
#     - OS X (10.11.6) + bash (sh) and zsh
#     ! (t)csh is NOT supported !
#
# AUTHOR:
#   Patrick Neumann, patrick@neumannsland.de
#
# COMPANY:
#   (privately)
#
# VERSION:
#   1.0
#
# LINK TO THE MOST CURRENT VERSION:
#   https://vcs.neumannsland.de/casualscripter/web_site_monitor
#
# CREATED:
#   2016-10-18
#
# COPYRIGHT (C):
#   2016 - Patrick Neumann
#
# LICENSE:
#   This program is free software: you can redistribute it and/or modify
#   it under the terms of the GNU General Public License as published by
#   the Free Software Foundation, either version 3 of the License, or
#   (at your option) any later version.
#
# WARRANTY:
#   This program is distributed in the hope that it will be useful,
#   but WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#   GNU General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program. If not, see <http://www.gnu.org/licenses/>.
#
# NOTE:
#   ---
#
# TODO:
#   ---
#
# HISTORY:
#   1.0 - Patrick Neumann - Initial (for the trainers eyes only) release
#
#===============================================================================

# Relative paths are more portable but less secure.
# Absolute paths are more secure but less portable.
readonly BIN_WHICH="$( which "which" )"
readonly BIN_UNAME="$( ${BIN_WHICH} "uname" )"
readonly BIN_BASENAME="$( ${BIN_WHICH} "basename" )"
readonly BIN_PS="$( ${BIN_WHICH} "ps" )"
readonly BIN_GREP="$( ${BIN_WHICH} "grep" )"
readonly BIN_AWK="$( ${BIN_WHICH} "awk" )"
readonly BIN_SED="$( ${BIN_WHICH} "sed" )"
readonly BIN_DIRNAME="$( ${BIN_WHICH} "dirname" )"
readonly BIN_TEE="$( ${BIN_WHICH} "tee" )"
readonly BIN_OPENSSL="$( ${BIN_WHICH} "openssl" )"

# Changeable defaults:
DEFAULT_SHELL="bash"
ECHO_FUNC="display"

#-------------------------------------------------------------------------------
# Detect operating system name.
#-------------------------------------------------------------------------------
readonly OS_NAME="$( ${BIN_UNAME} -s )"
# "sed -E" on macOS is the same as "sed -r" on Linux 
if [ "${OS_NAME}" = "Darwin" -o "${OS_NAME}" = "FreeBSD" ] ; then
  readonly SED_EXT_REGEXP="-E"
  readonly DATE_DISPLAY="-j -f %s "
  readonly DARWIN_FIND_REGEXP_TYPE="-E "
else
  readonly SED_EXT_REGEXP="--regexp-extended"
  readonly DATE_DISPLAY="-d @"
  readonly LINUX_FIND_REGEXP_TYPE="-regextype posix-extended "
fi

#-------------------------------------------------------------------------------
# Detect the shell in which we are running.
#-------------------------------------------------------------------------------
readonly PROCESS="$( ${BIN_BASENAME} "$( ${BIN_PS} -axco pid,command \
                                       | ${BIN_GREP} "$$" \
                                       | ${BIN_GREP} -v "grep" \
                                       | ${BIN_AWK} '{ print $2; }' )" )"
# Why conditinal command should be prefered over test:
#   https://google-styleguide.googlecode.com/svn/trunk/shell.xml#Test,_[_and_[[
# and why you don't, if you would support "dash":
#   http://mywiki.wooledge.org/Bashism
if [ "${PROCESS}" = "$( ${BIN_BASENAME} "${0}" )" ] ; then
  readonly CURRENT_SHELL="${DEFAULT_SHELL}"
else
  readonly CURRENT_SHELL="${PROCESS}"
fi

# Linux can have alle shells and "/bin/echo" has no limitations.
# Darwin (14.5.0) has bash 3.2.57, zsh 5.0.5, ksh 93 and tcsh 6.17.00
# - kshs and tcshs builtin echo does not support "-e" and/or "-n"!
# - "/bin/echo" does not support "-e"!
# FreeBSD can have all shells, but "/bin/echo" has the same limitations!
# Solution: use printf instead!
# Worth readable Link: http://hyperpolyglot.org/unix-shells#echo-note
if [ "${CURRENT_SHELL}" = "zsh" ] ; then
  # zsh does not split a string into words separated by spaces by default!
  setopt shwordsplit
  # zshs "which" find the builtin without "-p"!
  readonly BIN_PRINTF="$( which -p printf )"
else
  readonly BIN_PRINTF="$( which printf )"
fi

#=== FUNCTION ==================================================================
# NAME:        trim
# DESCRIPTION: Remove leading and trailing whitespace characters from a string.
# PARAMETER 1: string
#-------------------------------------------------------------------------------
# SOMETIMES NEEDED FOR CONFIGURATION!
#===============================================================================
# Do not use "function" if you want to support dash:
#   http://mywiki.wooledge.org/Bashism
trim () {
  var="${1}"
  var="${var#"${var%%[![:space:]]*}"}"
  var="${var%"${var##*[![:space:]]}"}"
  ${BIN_PRINTF} "${var}"
}

#=== FUNCTION ==================================================================
# NAME: logfile_checks
# DESCRIPTION: Checks if a logfile is set and can be created.
# PARAMETERS: none (a global var will be used.)
#===============================================================================
logfile_checks () {
  if [ -z "${LOG_FILE}" ] ; then
    ${BIN_PRINTF} "\033[01;31;40mERROR: logfile not set... EXIT!!!\033[00m\n"
    exit 101
  fi
  if ! [ -w "$( ${BIN_DIRNAME} "${LOG_FILE}" )" ] ; then
    ${BIN_PRINTF} "\033[01;31;40mERROR: dir for logfile not writable... EXIT!!!\033[00m\n"
    exit 102
  fi
  if [ -e "${LOG_FILE}" ] ; then
    if ! [ -w "${LOG_FILE}" ] ; then
      ${BIN_PRINTF} "\033[01;31;40mERROR: logfile already exists but is not writable... EXIT!!!\033[00m\n"
      exit 103
    fi
  fi
}

#=== FUNCTION ==================================================================
# NAME: overwrite
# DESCRIPTION: Check if the custom file already exists and ask for overwriting
#   or exit.
# PARAMETER 1: custom file
# PARAMETER 2: file type
#===============================================================================
overwrite() {
  if [ -e "${1}" ] ; then
    ${BIN_PRINTF} "\n${2} does already exist, overwrite? \
(type YES in UPPER letters and hit return!) : "
    read -r answer
    if [ "${answer}" != "YES" ] ; then
      ${BIN_PRINTF} "\033[01;34;40mHINT: move the old ${2} to a save place and try again... EXIT!!!\033[00m\n"
      exit 0
    fi
    # clear logfile
    ${BIN_PRINTF} "" > "${LOG_FILE}"
  fi
}

#=== FUNCTION ==================================================================
# NAME: display
# DESCRIPTION: Wrapper for "echo -n -e".
# PARAMETER 1: message (string)
#===============================================================================
display () {
  ${BIN_PRINTF} "${1}"
}

#=== FUNCTION ==================================================================
# NAME: log
# DESCRIPTION: Wrapper for "echo -n -e" incl. redirection into logfile.
# PARAMETER 1: message (string)
#===============================================================================
log () {
  logfile_checks
  ${BIN_PRINTF} "${1}" >> "${LOG_FILE}"
}

#=== FUNCTION ==================================================================
# NAME: display_and_log
# DESCRIPTION: Wrapper for "echo -n -e" incl. output to stdout AND redirection
#                into logfile.
# PARAMETER 1: message (string)
#===============================================================================
display_and_log () {
  logfile_checks
  ${BIN_PRINTF} "${1}" | ${BIN_TEE} -a "${LOG_FILE}"
}

#=== FUNCTION ==================================================================
# NAME: quiet
# DESCRIPTION: Wrapper for "echo -n -e" incl. redirection into "nirvana".
# PARAMETER 1: message (string)
#===============================================================================
quiet () {
  ${BIN_PRINTF} "${1}" > /dev/null
}

#=== FUNCTION ==================================================================
# NAME: error
# DESCRIPTION: Display red error messages starting with "ERROR:".
# PARAMETER 1: message (string)
#===============================================================================
error () {
  # TODO: stderr!?
  "${ECHO_FUNC}" "\033[01;31;40mERROR: ${1}!!!\033[00m\n"
}

#=== FUNCTION ==================================================================
# NAME: hint
# DESCRIPTION: Display blue hint messages starting with "HINT:".
# PARAMETER 1: message (string)
#===============================================================================
hint () {
  "${ECHO_FUNC}" "\033[01;34;40mHINT: ${1}!\033[00m\n"
}

#=== FUNCTION ==================================================================
# NAME: success
# DESCRIPTION: Display green success messages starting with "SUCCESS:".
# PARAMETER 1: message (string)
#===============================================================================
success () {
  "${ECHO_FUNC}" "\033[01;32;40mSUCCESS: ${1}!\033[00m\n"
}

#=== FUNCTION ==================================================================
# NAME:        assign_binary
# DESCRIPTION: ...
# PARAMETER 1: string
#===============================================================================
assign_binary () {
  if [ ${1:0:1} = "/" ] ; then
    # Absolute paths are more secure but less portable.
    if ! [ -e "${1}" ] ; then
      error "${1} not installed"
      exit 104
    fi
    local var="BIN_$( ${BIN_PRINTF} "$( ${BIN_BASENAME} "${1}" )" | tr [:lower:] [:upper:] )"
    eval "readonly $var=\${1}"
  else
    # Relative paths are more portable but less secure.
    local var="BIN_$( ${BIN_PRINTF} "${1}" | tr [:lower:] [:upper:] )"
    eval "readonly $var=\$( ${BIN_WHICH} "${1}" )"
    if [ -z "$( eval "${BIN_PRINTF} \$$var" )" ] ; then
      error "${1} not installed"
      exit 104
    fi
  fi
}

# Do not use "exit" at the end of a library!