#!/bin/bash

function helpexit() {
    echo 'Create or append md5sum list of files
Usage: md5sum-update [-r] [-f list_name] [[files to check]]
  -r recursive
  -f list_name is md5sums.txt by default
  If files to check omitted, list files in current folder

  Check files with "md5sum -c md5sums.txt"
  To update hashes, simply delete the md5sums file.
    '
    exit
}

recursive=0
list_name="md5sums.txt"
paths=()
for ((i=1; i<=${#@}; i++)) {
    j=$(( i + 1 ))
    [[ "${!i}" = "-h" ]] && helpexit
    [[ "${!i}" = "--help" ]] && helpexit
    [[ "${!i}" = "-r" ]] && { recursive=1; continue; }
    [[ "${!i}" = "-f" ]] && { list_name="${!j}"; i=$(( $i + 1 )); continue; }
    paths+=("${!i}")
}
if [[ ${#paths[@]} -eq 0 ]]; then
    paths+=(".")
fi
which pv &>/dev/null && PVBIN=$( which pv )
set -e
echo "Updating: $list_name"
test -f "$list_name" || touch "$list_name"
updates_done=0
_update() {
    if [ "$1" = "$list_name" ]; then
        return
    fi
    if [[ -L "$1" ]]; then
        echo "$1 is a symlink"
        return
    fi
    if test -d "$1"; then
        echo "$1 is a directory"
        return
    fi
    if test -f "$1"; then
        if awk '{ print substr($0,35) }' "$list_name" | grep -qFx "$1"; then
            echo "Exists: $1"
        else
            echo "New:    $1"
            size=$( stat -c %s "$1" )
            if [[ $size -gt 100000000 ]] && [[ -n "$PVBIN" ]]; then
                # Use pv is size > 100MB
                sum=$( $PVBIN "$1" | md5sum | awk '{ print $1 }' )
                printf "%s  %s\n" "$sum" "$1" >> "$list_name"
            else
                md5sum "$1" >> "$list_name"
            fi
            updates_done=1
        fi
    fi
}
shopt -s globstar
shopt -s nullglob
for ((i=0; i<=${#paths[@]}; i++)) {
    if [[ -d "${paths[$i]}" ]]; then
        pathname="${paths[$i]}"
        pathname="${pathname%%/}"
        if [[ "$recursive" -eq 1 ]]; then
            for file in "${pathname}"/**; do
                file="${file#./}"
                _update "$file"
            done
        else
            for file in "${pathname}"/*; do
                file="${file#./}"
                _update "$file"
            done
        fi
    fi
    if [[ -f "${paths[$i]}" ]]; then
        file="${paths[$i]}"
        file="${file#./}"
        _update "$file"
    fi
}

if [[ $updates_done -eq 1 ]]; then
    sort -k 2 -o "$list_name" "$list_name"
fi