#!/bin/bash
function help() {
    echo "Flatten the directory structure from the current folder downwards"
    echo "Files in subfolders will be renamed / -> _"
    echo "Empty folders are removed"
    echo "   -f  to force action "
    echo "   -n  to move files as is, i.e. not include path names in new name "
    echo "   -H  include hidden files/folders "
    echo "   -p C Replace path separator / with character C "
}

function helpexit() {
    help
    exit
}

function finder() {
    if [[ "$FILTER" -eq 0 ]]; then
      find .  -mindepth 2 -type f -path '*.*' -printf %P'\n'
      return $?
    fi
    if [[ "$FILTER" -eq 1 ]]; then
      find .  -mindepth 2 -not -path '*/\.*' -type f -printf %P'\n'
      return $?
    fi
}

function preview() {
  echo ""
  for f in $( finder | head ); do
    [[ "$NO_PATH" = "1" ]] && {
      echo "$f => " .
    } || {
      echo "$f =>" "${f//\//$SEP}"
    }
  done
  echo "..."
}

function flat() {
  [[ "$FORCE" = "0" ]] && INTERACT="-i"
  for f in $( finder ); do
    [[ "$NO_PATH" = "1" ]] && {
      mv -v $INTERACT "$f" .
    } || {
      mv -v $INTERACT "$f" "${f//\//$SEP}"
    }
  done
  find . -depth -type d -empty -delete
}

SEP="_"
FORCE=0
FILTER=1
while getopts fhHnp: opt
do  case "$opt" in
    f)
        FORCE=1
    ;;
    h)
        helpexit
    ;;
    H)
        FILTER=0
    ;;
    n)
        NO_PATH=1
    ;;
    p)
        SEP=$OPTARG
    ;;
    esac
done
IFS=$'\n'
[[ "$FORCE" = "0" ]] && {
    help
    preview
    echo "Are you sure? Break with ctrl-c"
    read i
}
flat