#!/usr/bin/env bash
:<<'__comments__'
    Name: install-python
   Usage: See show_usage()
Synopsis: If host distro is $DISTRO_TYPE and version is one of
          ${DISTRO_VERSIONS[@]} and python version $1 is not already installed,
          then: 1) retrieve the source archive for that python version from
          $SRC_URL; 2) unpack the archive to $SRC_PATH; 3) install all RPM
          package dependencies; 4) configure, make and install python
          $versionChoice rooted at $BASE_PATH. Python versions above 3.8.17
          will likely fail to build on centos|rhel 7.
   Notes: Credit to https://gist.github.com/ygorth/974a01f33dbd9bcf63b2
          and https://linuxstans.com/how-to-install-python-centos/
  Author: G. D. LaBossiere, Xview Solutions Inc. <code@XviewSolutions.com>
 Release: 4
    Date: 2024-04-23
     RCS: $Id$
 License: GNU GPL v3 <http://www.gnu.org/licenses/gpl-3.0.txt>
__comments__
#------------------------------------------------------------------------------
#  bash environment
#------------------------------------------------------------------------------
#  BASH_VERSINFO[@]
#  EXEC_NAME
#  EXEC_PID
#  FUNCNAME[@]
#------------------------------------------------------------------------------
#  constants
#------------------------------------------------------------------------------
#  local installations are rooted here
BASE_PATH="/usr/local"
#  path to local installation binaries
BIN_PATH="${BASE_PATH}/bin"
#  this script works with alma|centos|redhat|rocky distros
DISTRO_TYPE="rhel"
#  this script works with versions 7 and 8 of alma|centos|redhat|rocky
DISTRO_VERSIONS=('7' '8')
#  path to local installation libraries
LIB_PATH="${BASE_PATH}/lib"
#  building python from source needs these RPM groups; quote each array element
RPM_GRP_DEPS=('Development Tools')
#  building python from source needs these RPM packages
RPM_PKG_DEPS=(bzip2-devel db4-devel gdbm-devel libffi-devel libjpeg-devel
  libpcap-devel libxml2-devel libxslt-devel mysql-devel ncurses-devel
  openssl-devel readline-devel sqlite sqlite-devel tk-devel unixODBC-devel
  xz-devel zlib-devel)
#  path to local installation sources
SRC_PATH="${BASE_PATH}/src"
#  base url for python sources; for each version the full url is composed in
#+ get_version_choice() as: $SRC_URL/$versionChoice/Python-$versionChoice.tgz
SRC_URL="https://www.python.org/ftp/python"
#  this script requires these utils to work
TOOL_LIST=(chown curl id ls realpath sort sudo tar uniq)
#------------------------------------------------------------------------------
#  error codes
#------------------------------------------------------------------------------
ERROR_10="Requires bash 4.2+"
ERROR_15="Missing required program(s)"
ERROR_16="Missing required function(s)"
ERROR_18="Bad or missing required parameter(s)"
ERROR_20="Insufficient user privilege"
ERROR_22="Required file(s) not found"
ERROR_61="Unsupported operating system or distribution"
ERROR_62="Unsupported version"
ERROR_250="Invalid access method"
ERROR_255="Called program error or user interrupt"
#------------------------------------------------------------------------------
#  variables
#------------------------------------------------------------------------------
argList=()
errFuncName=""
exitMessage=()
pkgMgr=""
versionChoice=""
#------------------------------------------------------------------------------
:<<'__function_calls__'
main─┐
     ├─exit_handler
     ├─check_distrover
     ├─check_tools
     ├─check_user_privilege
     ├─get_user_input
     ├─check_versions_installed
     ├─get_version_choice
     ├─install_required_rpms
     ├─build_version_choice
     └─show_usage
__function_calls__
#------------------------------------------------------------------------------
#  functions
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: build_version_choice
 Synopsis: Unpack source archive; build and install python versionChoice.
    Notes: If compiling with gcc < 8.1.0 make will fail with error
           "Could not import runpy module"; workaround implemented in this
           function is to remove the config option "--enable-optimizations"
           Credit to http://tech.yipp.ca/python/import-runpy-module-traceback-recent-call-last-python-3-9-5libtyping-py-line-21-import-collections-systemerror-returned-null-without-setting-error-generate-posix-vars-f/
  Globals: BASE_PATH, FUNCNAME[@], LIB_PATH, SRC_PATH, errFuncName,
           exitMessage[@], versionChoice
 Requires: chown, id, tar
  Returns: 0 on success; errFuncName, exitMessage[@] and exit 15, 20 or 255 on
           error.
__comments__
build_version_choice() {
  [[ $versionChoice ]] || return 0
  errFuncName="$FUNCNAME"
  type -p chown id tar &>/dev/null || exit 15
  local admin blddir bldlog cfglog inslog msg
  blddir="${SRC_PATH}/Python-${versionChoice}"
  bldlog="${blddir}/build.log"
  cfglog="${blddir}/config.log"
  inslog="${blddir}/install.log"
#  if I'm not root I need to be a nopasswd sudoer
  [[ $(id -u) -eq 0 ]] || admin="sudo"
  cd ${SRC_PATH}/
  printf '%s' "Attempting to unpack source archive Python-${versionChoice}.tgz"
  ${admin} tar -zxf Python-${versionChoice}.tgz || {
    exitMessage+=("  Failed!")
    exit 255
  }
  printf '%s\n' "  Success!"
#  if I'm a sudoer I need to own the unpacked archive or the build will fail
  [[ $admin ]] && {
    printf '%s' "Attempting to change owner of ${blddir} to $(id -un)..."
    ${admin} chown -R $(id -un) ${blddir} || {
      exitMessage+=("  Failed!")
      exit 20
    }
    printf '%s\n' "  Success!"
  }
  cd ${blddir}
  msg="configure Python-${versionChoice} for building."
  printf '%s %s\n' "Attempting to ${msg} This may take a while." \
    "Please wait..."
#  deleted '--enable-optimizations' as workaround to handle runpy error in make
  ./configure --prefix=${BASE_PATH} LDFLAGS="-Wl,-rpath ${LIB_PATH}" \
    --with-ensurepip=install &> ${cfglog} || {
    exitMessage+=("Failed to ${msg}")
    exitMessage+=("View ${cfglog} for more information.")
    exit 255
  }
  printf '%s\n' "Success! View ${cfglog} for more information."
  msg="build Python-${versionChoice} from source."
  printf '%s %s\n' "Attempting to ${msg} This may take a (very) long time." \
    "Please wait..."
  make &> ${bldlog} || {
    exitMessage+=("Failed to ${msg}")
    exitMessage+=("View ${bldlog} for more information.")
    exit 255
  }
  printf '%s\n' "Success! View ${bldlog} for more information."
  msg="install Python-${versionChoice} to ${BASE_PATH}"
  printf '%s\n' "Attempting to ${msg}  Please wait..."
  ${admin} make altinstall &> ${inslog} || {
    exitMessage+=("Failed to ${msg}")
    exitMessage+=("View ${inslog} for more information.")
    exit 255
  }
  printf '%s %s\n' "Success! Python-${versionChoice} is installed." \
    "View ${inslog} for more information."
  return 0
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: check_distrover
 Synopsis: Get GNU/Linux distro and version installed on this host; verify
           match with DISTRO_TYPE and one of DISTRO_VERSIONS[@].
  Globals: DISTRO_TYPE, DISTRO_VERSIONS[@], FUNCNAME[@], errFuncName,
           exitMessage[@]
    Reads: /etc/os-release
  Returns: 0 on success; errFuncName, exitMessage[@] and exit 22, 61 or 62 on
           error.
__comments__
check_distrover() {
  errFuncName="$FUNCNAME"
  [[ -f /etc/os-release ]] || exit 22
  local dist i info like msg ver
  readarray -t info < /etc/os-release
  for ((i=0;i<${#info[@]};i++)); do
    [[ ${info[$i]%%=*} =~ ^ID$ ]] && dist="${info[$i]##*=}"
    [[ ${info[$i]%%=*} =~ ^ID_LIKE$ ]] && like="${info[$i]##*=}"
    [[ ${info[$i]%%=*} =~ ^VERSION_ID$ ]] && ver="${info[$i]##*=}"
    [[ $dist && $like && $ver ]] && break 1
  done
  dist="${dist//[\"\']/}"
  like="${like//[\"\']/}"
  [[ $dist =~ $DISTRO_TYPE || $like =~ $DISTRO_TYPE ]] || {
    exitMessage+=("Host distro '${dist}' is not supported.")
    exit 61
  }
  ver="${ver//[\"\']/}"
  [[ ${DISTRO_VERSIONS[@]} =~ ${ver%%\.*} ]] || {
    msg="Host distro ${dist} is supported but version ${ver} is not supported."
    exitMessage+=("${msg}")
    exit 62
  }
  return 0
}
#------------------------------------------------------------------------------
<<'__comments__'
     Name: check_tools
 Synopsis: For each program name in TOOL_LIST[@] not in the USER's PATH or not
           installed on this host add program name to missing[@]; check for dnf
           or yum and set global pkgMgr else add 'dnf or yum' to missing[@];
           return 0 if missing[@] is empty else set exitMessage[@] and exit 15.
  Globals: FUNCNAME[@], TOOL_LIST[@], errFuncName, exitMessage[@], pkgMgr
  Returns: 0 on success; errFuncName, exitMessage[@] and exit 15 on error.
__comments__
check_tools() {
  errFuncName="$FUNCNAME"
  local i missing msg
  for ((i=0;i<${#TOOL_LIST[@]};i++)); do
    type -p ${TOOL_LIST[$i]} &>/dev/null || missing+=("${TOOL_LIST[$i]}")
  done
  pkgMgr="$(type -p dnf 2>/dev/null)"
  [[ $pkgMgr ]] || pkgMgr="$(type -p yum 2>/dev/null)"
  [[ $pkgMgr ]] || missing+=("dnf or yum")
  [[ ${missing[@]} ]] || return 0
  msg="The following required utilities were not found: ${missing[*]}"
  exitMessage+=("${msg}")
  exit 15
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: check_user_privilege
 Synopsis: If EUID is non-zero verify that user is a nopasswd sudoer.
  Globals: EXEC_NAME, FUNCNAME[@], errFuncName, exitMessage[@]
 Requires: id, sudo
  Returns: 0 on success; errFuncName and exit 15 on error; errFuncName,
           exitMessage[@] and exit 20 if user is not root or a nopasswd sudoer.
__comments__
check_user_privilege() {
  errFuncName="$FUNCNAME"
  type -p id sudo &>/dev/null || exit 15
  [[ $(id -u) -eq 0 ]] && return 0
  [[ $(sudo -l -n -U $(id -un)) =~ ALL.*NOPASSWD.*ALL$  ]] && return 0
  local msg
  msg="You must be root or a nopasswd sudoer to run ${EXEC_NAME} ${0##*/}"
  exitMessage+=("${msg}")
  exit 20
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: check_versions_installed
 Synopsis: If versionChoice is set search for python binaries installed on this
           host at /bin, /usr/bin and /usr/local/bin; if none found return 0;
           if found set exitMessage[@]; if versionChoice matches any version
           found set and print exitMessage[@] and exit 0; else return 0.
  Globals: FUNCNAME[@], errFuncName, versionChoice
 Requires: ls, realpath, sort, uniq
  Returns: 0 on success; exitMessage[@] and exit 0 if versionChoice is already
           installed; errFuncName and exit 15 on error.
__comments__
check_versions_installed() {
  [[ $versionChoice ]] || return 0
  errFuncName="$FUNCNAME"
  type -p ls realpath sort uniq &>/dev/null || exit 15
#  all done if no version of python is installed; very unlikely
  type -p python &>/dev/null || return 0
  local count i inst list msg
  ls /usr/bin/python* &>/dev/null && \
    readarray -t list <<< "$(realpath /usr/bin/python*)"
#  if /bin and /usr/bin are not symlinked
  [[ $(realpath /bin) != $(realpath /usr/bin) ]] && {
    ls /bin/python* &>/dev/null && \
      readarray -O "${#list[@]}" -t list <<< "$(realpath /bin/python*)"
  }
  ls /usr/local/bin/python* &>/dev/null && \
    readarray -O "${#list[@]}" -t list <<< "$(realpath /usr/local/bin/python*)"
  [[ ${list[@]} =~ [0-9a-zA-Z] ]] || return 0
#  get and list the version numbers of the installed binaries found
  count="${#list[@]}"
  for ((i=0;i<${count};i++)); do
    [[ -x ${list[$i]} && ${list[$i]##*\/} =~ ^python[1-9]\.[1-9][0-9]*$ ]] && {
      list[$i]="$( ${list[$i]} --version 2>&1 )"
      list[$i]="${list[$i]##*\ }"
    } || unset list[$i]
  done
#  remove duplicate entries in the list
  readarray -t inst <<< "$(printf '%s\n' "${list[@]}" | sort | uniq)"
  msg="$(printf ' %s ' "${inst[@]}")"
  exitMessage+=("Found these python versions installed: ${msg}")
  for ((i=0;i<${#inst[@]};i++)); do
    [[ ${inst[$i]} == $versionChoice ]] && \
      exitMessage+=("Version ${versionChoice} is already installed.") && \
      printf '%s\n' "${exitMessage[@]}" && exit 0
  done
  return 0
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: exit_handler
 Synopsis: If $? is non-zero print error message(s); the first statement to
           appear in main() must be: trap exit_handler EXIT
  Globals: errFuncName, exitMessage[@]
  Returns: 0 on normal exit; $? on error.
__comments__
exit_handler() {
  local errNum="$?"
  [[ $errNum -eq 0 ]] && return 0
  local errMsg errTxt
  errTxt="ERROR_${errNum}"
  errMsg="Error ${errNum}: No description available"
  [[ ${!errTxt} ]] && errMsg="Error ${errNum}: ${!errTxt}"
  [[ ${errFuncName} ]] && errMsg="${errFuncName}: ${errMsg}"
  errMsg="${0##*/}: ${errMsg}"
  [[ ${exitMessage[@]} ]] && printf '%s\n' "${exitMessage[@]}"
  printf '%s\n' "${errMsg}"
  return $errNum
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: get_user_input
 Synopsis: If argList[0] is: missing, return 0; appears to be a valid python
           version number, set versionChoice and return 0; an invalid version
           number, append a message to exitMessage[@] and exit 18; is any other
           value, return 0.
  Globals: FUNCNAME[@], argList[@], errFuncName, exitMessage[@], versionChoice
  Returns: 0 on success; errFuncName, exitMessage[@] and exit 18 on error.
__comments__
get_user_input() {
  [[ ${argList[@]} ]] || return 0
  errFuncName="$FUNCNAME"
  [[ ${argList[0]} =~ ^[2-9]{1}\.[0-9]{1,2}\.[0-9]{1,2}$ ]] && \
    versionChoice="${argList[0]}" && return 0
  [[ ${argList[0]} =~ ^[0-9]{1,}.*$ ]] && \
    exitMessage+=("${argList[0]} is not a valid python version number.") && \
    exit 18
  printf '%s\n' "Searching for Python version ${versionChoice}"
  return 0
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: get_version_choice
 Synopsis: Retrieve python versionChoice source archive from SRC_URL and save
           to SRC_PATH
  Globals: FUNCNAME[@], SRC_PATH, SRC_URL, errFuncName, exitMessage[@],
           versionChoice
 Requires: curl, id
  Returns: 0 on success; errFuncName, exitMessage[@] and exit 15, 22 or 255 on
           error.
__comments__
get_version_choice() {
  [[ $versionChoice ]] || return 0
  errFuncName="$FUNCNAME"
  type -p curl id &>/dev/null || exit 15
  local admin msg retVal src
  src="${SRC_URL}/${versionChoice}/Python-${versionChoice}.tgz"
  msg="Checking for a source archive at ${SRC_URL}/${versionChoice}/"
  printf '%s\n' "${msg}"
  exitMessage+=("${msg}")
#  curl returns size and last mod time of $src or error if $src is not found
  curl -f -I -k -s -o /dev/null ${src} || {
    exitMessage+=("No file named Python-${versionChoice}.tgz was found.")
    exitMessage+=("Python version ${versionChoice} does not appear to exist.")
    exit 22
  }
  msg="File named Python-${versionChoice}.tgz was found."
  printf '%s\n' "${msg}"
  exitMessage+=("${msg}")
  [[ $(id -u) -eq 0 ]] || admin="sudo"
  ${admin} curl -k -s -o ${SRC_PATH}/Python-${versionChoice}.tgz ${src} || {
    retVal="$?"
    msg="curl failed to retrieve the file and returned exit value ${retVal}."
    exitMessage+=("${msg}")
    exit 255
  }
  return 0
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: install_required_rpms
 Synopsis: Install any RPM groups in RPM_GRP_DEPS[@] and RPM packages in
           RPM_PKG_DEPS[@] not already installed.
  Globals: FUNCNAME[@], RPM_GRP_DEPS[@], RPM_PKG_DEPS{@], errFuncName,
           exitMessage[@], pkgMgr, versionChoice
 Requires: id
  Returns: 0 on success; errFuncName, exitMessage[@] and exit 15 or 255 on
           error.
__comments__
install_required_rpms() {
  [[ $versionChoice && $pkgMgr ]] || return 0
  errFuncName="$FUNCNAME"
  type -p id &>/dev/null || exit 15
  local admin i msg
  [[ $(id -u) -eq 0 ]] || admin="sudo"
  [[ ${RPM_GRP_DEPS[@]} ]] && {
    for ((i=0;i<${#RPM_GRP_DEPS[@]};i++)); do
      msg="Attempting to install or update RPM group '${RPM_GRP_DEPS[$i]}'"
      exitMessage+=("${msg}")
      msg="${msg}  This may take a while. Please wait..."
      printf '%s\n' "${msg}"
      ${admin} ${pkgMgr} -y -q groupinstall --setopt tsflags=test \
        "${RPM_GRP_DEPS[$i]}" && {
        ${admin} ${pkgMgr} -y -q groupinstall "${RPM_GRP_DEPS[$i]}"
        printf '%s\n' "Success! RPM group '${RPM_GRP_DEPS[$i]}' is installed."
      } || {
        msg="Failed to install or update RPM group '${RPM_GRP_DEPS[$i]}'"
        msg="${msg}  Cannot continue."
        exitMessage+=("${msg}")
        exit 255
      }
    done
  }
  [[ ${RPM_PKG_DEPS[@]} ]] && {
    for ((i=0;i<${#RPM_PKG_DEPS[@]};i++)); do
      msg="Attempting to install or update RPM package '${RPM_PKG_DEPS[$i]}'"
      exitMessage+=("${msg}")
      msg="${msg}  Please wait..."
      printf '%s\n' "${msg}"
      ${admin} ${pkgMgr} -y -q install --setopt tsflags=test \
        "${RPM_PKG_DEPS[$i]}" && {
        ${admin} ${pkgMgr} -y -q install "${RPM_PKG_DEPS[$i]}"
        printf '%s\n' "Success! RPM package '${RPM_PKG_DEPS[$i]}' is installed."
      } || {
        msg="Failed to install or update RPM package '${RPM_PKG_DEPS[$i]}'"
        msg="${msg}  Cannot continue."
        exitMessage+=("${msg}")
        exit 255
      }
    done
  }
  return 0
}
#------------------------------------------------------------------------------
:<<'__comments__'
     Name: show_usage
 Synopsis: If versionChoice is not set display script usage.
  Globals: BASE_PATH, EXEC_NAME, FUNCNAME[@], SRC_PATH, SRC_URL, errFuncName,
           versionChoice
  Returns: 0 in all cases.
__comments__
show_usage() {
  [[ $versionChoice ]] && return 0
  errFuncName="$FUNCNAME"
  printf '%b' "
-------------------------------------------------------------------------------

  Usage: ${EXEC_NAME} ${0##*/} VERSION

         VERSION must be a valid Python version number (e.g. 3.8.4) otherwise
         this message will be displayed. This script will retrieve the source
         archive for Python VERSION from ${SRC_URL}
         and save it to ${SRC_PATH} then build and install Python VERSION
         at ${BASE_PATH}

         Attempts to build Python versions above 3.8.17 on RHEL|CentOS 7 will
         likely fail.

-------------------------------------------------------------------------------

"
  return 0
}
#------------------------------------------------------------------------------
#  main
#------------------------------------------------------------------------------
main() {
  trap exit_handler EXIT
  argList=("$@")
  errFuncName="$FUNCNAME"
  [[ ${BASH_VERSINFO[0]} -eq 4 && ${BASH_VERSINFO[1]} -ge 2 ]] || \
    [[ ${BASH_VERSINFO[0]} -gt 4 ]] || exit 10
  [[ $EXEC_NAME && $EXEC_PID -eq $$ ]] || \
    exitMessage+=("${0##*/} may not be executed directly.")
  [[ -t 1 ]] || exitMessage+=("Script must run interactively (in a terminal).")
  [[ ${exitMessage[@]} ]] && exit 250
  declare -F build_version_choice check_distrover check_tools \
    check_user_privilege check_versions_installed exit_handler get_user_input \
    get_version_choice install_required_rpms show_usage &>/dev/null || exit 16
  check_distrover
  check_tools
  check_user_privilege
  get_user_input
  check_versions_installed
  get_version_choice
  install_required_rpms
  build_version_choice
  show_usage
  exit 0
}
#------------------------------------------------------------------------------
#  run program
#------------------------------------------------------------------------------
main "$@"