#!/bin/bash

## Sequencer script is doing nothing on its own. It is included by a squence script
## which uses the sequencer.sh to provide sequencial operations with or without
## user interaction (see seqTemplate.sh)

## Version information

VERSION_REV=3
VERSION_MAJOR=0
VERSION_MINOR=0

## Start of generic script part

QUIET=0
DRY=0
VERBOSE=0
ERNO=0
MAX_STEP=255
ALIAS=
TEMPLATE_NAME=seqTemplateExample.sh
MISSING_CONF=missingConf.log
VERSION_STRING="${VERSION_REV}.${VERSION_MAJOR}.${VERSION_MINOR}"

helpSequencer() {
  echo "Usage: ${0##*/} [OPTIONS] [STEP NUMBER(s) or ALIAS]" 
  echo
  echo " [OPTIONS]"
  echo "  --dry-run, -d : Only print to console what would be done"
  echo "                  ! Attention - Sequence must support this"
  echo "  --help, -h    : Display help"
  echo "  --quiet, -q   : Don't ask for permission to execute steps"
  echo "                  If called without starting step number, only this help is shown"
  echo "  --verbose, -v : Verbose output (use exe() function to call shell commands in seqs)"
  echo "                  ( e.g.: exe apt update )"
  echo "  --version     : Display version of sequencer and revision of sequence"
  echo 
  echo " [STEP NUMBER(s) 1-${MAX_STEP} or ALIAS]"
  echo "     Single STEP or ALIAS : starting point of process"
  echo "  Multiple STEPS or ALIAS : execute only given steps"
  echo "                            execute only one step with using special step 0"
  echo "                            ( e.g. only execute step 4: $0 4 0 )"
}

# endCheckEmpty [VariableName] [DESCRIPTION]
#    DESCRIPTION : Optional text for error
endCheckEmpty() {
  local errorText=$1
  eval 'local ref=$'$1

  if [ ! -z "$2" ] ; then
    errorText=$2
  fi
  if [ -z $ref ] ; then
    echo -e "[Error] $errorText must not be empty.\nAborting installation."
    exit 666
  fi 
}

existsFunction() {
  local NOTFOUND=0
  declare -F $1 &>>/dev/null || NOTFOUND=1
  return $NOTFOUND
}

saveReturn() {
  if [ $1 -ne 0 ] ; then
    ERNO=$1
  fi
}

# endReturn [-f]
#   -f : force exit with $ERNO without user input
endReturn() {
  if [[ ( $ERNO -ne 0 && $QUIET -ne 0 ) || ( $ERNO -ne 0 && ! -z $1 && $1 == "-f" ) ]] ; then
    echo
    echo -e "[Error] Return value $ERNO detected.\nAborting installation."
    exit $ERNO
  fi
  if [ $ERNO -ne 0 ] ; then
    echo
    echo "[Error] Return value $ERNO detected."
    read -p "End installation: y(default)/n? " answer
    case $answer in
      [nN])
        echo
        echo Continuing installation...
        ;;
      *)
        echo
        echo Installation aborted
        exit $ERNO; 
        ;;
    esac
  fi
}

# addConf <CONF_MODE> <CONFIGTEXT> <CONFIGFILE>
# trying to write a file
# if exists, one attempt is made to create bck file of it
# if all fails, a log file is created with the conflicts to be resolved by the user
addConf() {
  local confMode=""
  case "$1" in
    -c) # create a new file 
      confMode="-c"
      ;;
    -a) # append to existing file
      confMode="-a"
      ;;
   *) # default
      echo "Parameter 1 (-a|-c) missing for addConf()"
      exit 0;
      ;;
  esac

  echo -n "Writing $3 ... "
  if [ "$DRY" -ne 0 ] ; then
    echo "dry-run"
    return 0;
  fi

  # try writing config directly
  if [ ! -f "$3" ] ; then
    if [ $confMode == "-c" ] ; then
      echo "$2" > "$3"
    else
      echo "$2" >> "$3"
    fi
    echo "ok"
    return 0
  fi

  # try backup existing config
  if [ ! -f "$3".bck ] ; then
    cp -ar "$3" "$3".bck
    if [ $confMode == "-c" ] ; then
      echo "$2" > "$3"
    else
      echo "$2" >> "$3"
    fi
    echo "[WARN] Existing config saved to ${3}.bck"
    return 0
  fi

  # add configuration to missingConf file
  if [ "$missingDate" = "" ] ; then
    missingDate=set
    echo -n "###  " >> "$MISSING_CONF"
    date >> "$MISSING_CONF"
  fi
  echo "#--- $3 ---" >> "$MISSING_CONF"
  echo "$2" >> "$MISSING_CONF"
  echo >> "$MISSING_CONF"

  echo "[WARN] Check $(realpath "$missingConf") for configuration conflicts ($3)"
  return 1
}

# execute [-q] <Step Number>
#    -q: don't stop and don't report step functions which cannot be found 
# execute given step_<Step Number> function
execute() {
  local NOTFOUND=0
  local NOREPORT=0

  if [ $1 == "-q" ] ; then
    NOREPORT=1
    shift
  fi

  # check if step function exists
  declare -F step_$1 &>>/dev/null || NOTFOUND=1
  if [ $NOTFOUND -eq 1 ] && [ $NOREPORT -ne 1 ] ; then
    echo "Step $1 not found" 
    exit 1;
  fi

  # don't execute step functions which are not available
  if [ $NOTFOUND -eq 1 ] ; then
    return $NOTFOUND
  fi 

  echo -en "\n[STEP $1] "
  existsFunction step_${1}_info
  if [ $? -eq 0 ] ; then
    step_${1}_info $1
  fi
  if [ $QUIET -ne 1 ] ; then
    read -p "Start: y/n(default)? " answer
    case $answer in
      [yY])
        step_$1 $1
        ;;
      *)
        echo Aborting installation at step $1
        exit 1; 
        ;;
    esac
  else
    step_$1 $1
  fi
}

# checkStep <Step Number or Alias>
#  return 0 - for invalid step
# Check sanitiy of step number or
# Check if alias exists
checkStep() {
  if (( $1 < 1 ||  $1 > $MAX_STEP )) ; then
    eval 'local ref=$alias_'$1
    if [ -z $ref ] || [ "$ref" == "$1" ] ; then
      return 0 
    else
      return $ref
    fi
  else
    return $1
  fi
}

# continous <Starting Step Number>
# (max $MAX_STEP)
# execute installation continously from given starting step
continous() {
  local step=0

  checkStep $1
  step=$?
  if [[ $step == 0 ]] ; then
    return 1
  fi
  
  for ((i=$step; i<=${MAX_STEP}; i++)); do
    execute -q $i
    local res=$?
    if [ $res -ne 0 ] ; then
      break;
    fi
  done
}

# selection <Step Number List (separated by space)>
# execute given step list
# e.g.: selection -q 1 4 12
selection() {
  local step=0
  for i in $@ ; do
    checkStep $i
    step=$?
    # stop on step 0 
    if [ $step -eq 0 ] ; then
      break
    else 
      execute $step
    fi
  done
}

# Creating a minimal step definition template
createTemplate() {
  if [ -f $TEMPLATE_NAME ] ; then
    return 1
  fi
  echo "#!/bin/bash" > $TEMPLATE_NAME
  echo >> $TEMPLATE_NAME
  echo "# Step 1 is mandatory" >> $TEMPLATE_NAME
  echo "step_1_info() { echo \"My custom step \$1\"; }" >> $TEMPLATE_NAME
  echo "step_1_alias() { ALIAS=\"begin\"; }" >> $TEMPLATE_NAME
  echo "step_1() {" >> $TEMPLATE_NAME
  echo "  echo \"Doing something...\"" >> $TEMPLATE_NAME
  echo "}" >> $TEMPLATE_NAME
  echo >> $TEMPLATE_NAME
  echo "VERSION_SEQREV=${VERSION_REV}" >> $TEMPLATE_NAME
  echo ". $0" >> $TEMPLATE_NAME

  chmod +x $TEMPLATE_NAME
  return 0
}

# Parse alias functions "step_[STEP NUBER]_alias" to create 
# back reference variable of schema: 
# alias_[ALIAS]=[STEP NUMBER]
parseAlias() {
  for ((i=1; i<=${MAX_STEP}; i++)); do
    # Check for alias definition
    existsFunction step_${i}_alias
    if [ $? -ne 0 ] ; then
      continue
    fi

    # Function writes global ALIAS variable
    step_${i}_alias

    eval 'alias_'$ALIAS'='$i
  done
}

# Always display sequencer help and, if available, sequence help
displayHelp() {

  helpSequencer

  # check if step definition exists by looking for step_1()
  existsFunction step_1
  if [ $? -ne 0 ] ; then
    echo -e "\n  It seems ${0##*/} was called directly."
    echo -e "  Please create a sequence script first.\n"
    read -p "  Create a template now? y/n(default)? " answer
    case $answer in
      [yY])
        createTemplate
        if [ $? -eq 0 ] ; then
          echo -e "\n  $TEMPLATE_NAME created."
        else
          echo -e "\n  $TEMPLATE_NAME exists...Nothing to do!"
        fi
        ;;
      *)
        echo -e "\n  Nothing to do!" 
        ;;
    esac
    exit 1;
  else
    echo "  Step (= alias) documentation:"
    for ((i=1; i<=${MAX_STEP}; i++)); do

      # Display step reference in help if step function exists 
      existsFunction step_${i}
      if [ $? -ne 0 ] ; then
        continue
      fi
      printf '    Step %3s ' $i

      # Display alias if exists
      existsFunction step_${i}_alias
      if [ $? -eq 0 ] ; then
        step_${i}_alias 
        echo " = $ALIAS" 
        printf '              : '
      else
        echo -n " : "
      fi

      # Display step help only if info function exists
      existsFunction step_${i}_info
      if [ $? -eq 0 ] ; then
        step_${i}_info $i 
      else
        echo " - step_${i}_info() missing"
      fi
    done
  fi
}

# showVersion
showVersion() {
  echo    "Sequencer    ${VERSION_STRING}"
  echo -n "Seq Revision "
  if [ ! -z "${VERSION_SEQREV}" ] ; then
    echo "${VERSION_SEQREV}"
  else
    echo "-"
  fi
}

exe() {
  local arr=("$@")
  if [ $DRY -ne 0 ] ; then
    echo -e "\n-- ${arr[@]}"
  elif [ $VERBOSE -eq 1 ] ; then
    (set -x; "${arr[@]}")
  else
    "${arr[@]}"
  fi
}

# Handle dry run and verbose output for commands containing pipe and/or redirects
# exep <COMMAND TO RUN AS STRING>
exep() {
  if [ $DRY -ne 0 ] || [ $VERBOSE -eq 1 ] ; then
    echo -e "\n-- $1"
  fi
  if [ $DRY -eq 0 ] ; then 
    bash -c "$1"
  fi
}


main() {
  local START=0

  # options check
  for arg in "$@" ; do
    case "$arg" in
      --dry-run|-d) # shows what would be done
        DRY=1
        QUIET=1
        shift
        ;;
      --help|-h) # show only help
        displayHelp
        exit 0;
        ;;
      --quiet|-q) # detect if option quiet is available
        QUIET=1
        shift
        ;;
      --verbose|-v) # set verbose flag
        VERBOSE=1
        shift
        ;;
      --version) # version request
        showVersion
        exit 0;
        ;;
    esac
  done

  if [ -z $1 ] || [ "$1" == "" ] ; then
    # Empty -> show help
    displayHelp
    # Assume starting at one for interactive mode
    START=1
  fi

  # compatibility check of sequence
  if [ ! -z $VERSION_SEQREV ] && [ $VERSION_SEQREV -gt $VERSION_REV ] ; then
    echo "[ERROR] Unsupported sequence revision"
    showVersion
    exit 1
  fi
  # exclude older versions if needed
  if [ ! -z $VERSION_SEQREV ] && [ $VERSION_SEQREV -lt 3 ] ; then
    echo "[ERROR] Unsupported sequence revision (addConf)"
    showVersion
    exit 1
  fi
  if [ -z $VERSION_SEQREV ] ; then
    echo -e "[WARNING] No sequence revision found. Trying anyway...\n";
  fi

  # check for starting step  
  if [ ! -z "$1" ] ; then
    START=$1
  else
    # End here on quiet mode and no step was given
    if [ $QUIET -eq 1 ] ; then
      exit 1;
    fi
  fi
  
  if [ $DRY -ne 0 ] ; then
    echo
    echo "[WARN] Dry run active."
    echo "       Printed commands may not be accurate (e.g. quotation incorrect)"
    echo "       Sequence may ignore dry run"
    read -p "Press enter to continue or Ctrl + c to abort"
  fi

  parseAlias

  # check if more than one step is given and select execution mode
  if [ ! -z $2 ] ; then
    selection $@  
  else
    continous $START
  fi

  echo
  echo "${0##*/} finished"
}

main "$@"
exit 0;