#!/bin/bash

function helpexit() {
    echo 'Create or append md5/sha* list of files
Usage:
    Creating hashes: hash-update [-r] [-t hash-type] [-f list_name] [[files to hash]]
    Checking hashes: hash-update -c [-f list_name]
  -r recursive
  -c check
  -t hash-type defaults to sha256. choose from md5, sha1, sha256, sha512 etc..
  -f list_name is [type]sums.txt by default
  -i individual [filename].[hash] files, instead of -f list of files.
  If files to check omitted, list files in current folder

  Check files with "sha256sum -c sha256sums.txt", or passing -c to this script.
  To update hashes, simply delete the sha256sums file.
'
    exit
}

function valid_type() {
    local valid
    for valid in b2 md5 sha1 sha224 sha256 sha384 sha512; do
      if [[ "$1" = "$valid" ]]; then
        return 0
      fi
    done
    return 1
}

recursive=0
check=0
hashtype=sha256
individual=0

paths=()
for ((i=1; i<=${#@}; i++)) {
    j=$(( i + 1 ))
    [[ "${!i}" = "-h" ]] && helpexit
    [[ "${!i}" = "--help" ]] && helpexit
    [[ "${!i}" = "-r" ]] && { recursive=1; continue; }
    [[ "${!i}" = "-c" ]] && { check=1; continue; }
    [[ "${!i}" = "-i" ]] && { individual=1; continue; }
    [[ "${!i}" = "-t" ]] && { hashtype="${!j}"; i=$(( $i + 1 )); continue; }
    [[ "${!i}" = "-f" ]] && { list_name="${!j}"; i=$(( $i + 1 )); continue; }
    paths+=("${!i}")
}
valid_type "$hashtype" || {
    echo Type "$hashtype" is not valid.
    echo Choose from b2 md5 sha1 sha224 sha256 sha384 sha512
    exit 1
}

if [[ -z "$list_name" ]]; then
  list_name="${hashtype}sums.txt"
fi
SUMBIN="${hashtype}sum"
which $SUMBIN &>/dev/null || {
    echo $SUMBIN not in PATH
    exit 1
}

if [[ $check -eq 1 ]]; then
    $SUMBIN -c "$list_name"
    exit $?
fi

if [[ ${#paths[@]} -eq 0 ]]; then
    paths+=(".")
fi
which pv &>/dev/null && PVBIN=$( which pv )
set -e
if [[ $individual = 0 ]]; then
  echo "Updating: $list_name"
  test -f "$list_name" || touch "$list_name"
fi
updates_done=0
_add_single() {
    size=$( stat -c %s "$1" )
    if [[ $size -gt 100000000 ]] && [[ -n "$PVBIN" ]]; then
        # Use pv is size > 100MB
        touch "$2"
        sum=$( $PVBIN "$1" | $SUMBIN | awk '{ print $1 }' )
        printf "%s  %s\n" "$sum" "$1" >> "$2"
    else
        $SUMBIN "$1" >> "$2"
    fi
}

_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
    # individual checksum files
    if [[ $individual = 1 ]]; then
        if [[ "$1" = *.$hashtype ]]; then
            return
        fi
        if [[ -e "$1.$hashtype" ]]; then
            return
        fi
        _add_single "$1" "$1.$hashtype"
        return
    fi
    # sum list file
    if test -f "$1"; then
        if sed 's,^[^ ]\+  ,,' "$list_name" | grep -qFx "$1"; then
            echo "Exists: $1"
        else
            echo "New:    $1"
            _add_single "$1" "$list_name"
            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