#!/bin/bash
# Comparission script for compression tools.
# Require bash V5+
# (C) 2020 - F-Hauri.ch
# Licensed by GNU GENERAL PUBLIC LICENSE Version 3
#     https://www.gnu.org/licenses/gpl-3.0.txt

# cmds=(	gzip	bzip2		xz		zstd	zstd\ -T4)
# decmds=(zcat:gz	bzcat:bz2	xzcat:xz	zstdcat:zst	)
cmds=(  gzip:gz   bzip2:bz2      xz:xz      zstd:zst       brotli:b)
decmds=(zcat:gz   bzcat:bz2   xzcat:xz   zstdcat:zst   brotli\ -d:b)

numtry=3

txtsize() {
    local _idx=$(( $1 > 1125899906842623 ? 5 : $1 > 1099511627775 ? 4 :
	   $1 > 1073741823 ? 3 : $1 > 1048575 ? 2 : $1 > 1023 ? 1 : 0 )) \
	       _abr=(b K M G T P)
    local _res=000$((1000*$1/(1024**_idx)))
    printf -v $2 %.2f%s ${_res::-3}.${_res: -3} ${_abr[_idx]}
}
percent() { local _pct=000$(($1*100000/$2))
    printf -v $3 %.2f%% ${_pct::-3}.${_pct: -3}
}
musec2str () { local -n _result=$2; local _elapsed=000000$1
    printf -v _elapsed "%0.4f" ${_elapsed::-6}.${_elapsed:${#_elapsed}-6}
    TZ=UTC printf -v _result "%(%Y %j %H %M %S)T" ${_elapsed%.*}
    _elapsed=.${_elapsed#*.} _elapsed=${_elapsed%%*(0)} _elapsed=${_elapsed%.}
    [ "$_elapsed" ] && printf -v _elapsed %-4s $_elapsed &&
	_elapsed=${_elapsed// /0} || unset _elapsed
    _result=($_result)
    _result=$((10#$_result-1970)) _result[1]=$((10#${_result[1]}-1))
    printf -v _result "%dy %dd %.0fh %.0f' %.0fs" ${_result[@]}
    _result=($_result)
    printf -v _result "%s" ${_result[@]#0?}
    [ "${_result#*s}" ] && {  [ "$_elapsed" ] && _result+=0
    } || {  [ "$_elapsed" ] || _result=${_result%s}\" ;}
    _result=(${_result%s}${_elapsed}${_elapsed+\"})
}

printf "%-20s %14s %8s %7s %15s %15s\n" File Size HSize Prct {C,Dec}ompression
for file;do
    output=()
    # Doing full read instead of ``stat -c %s'' to prevent cache inequity
    fsize=$(LANG=C wc -c <"$file")
    txtsize $fsize hfsize
    printf "%-20s %14u %8s 100.00%%\n" "$file" $fsize "$hfsize"
    for cmd in "${cmds[@]}";do
	IFS=: read cmd ext <<<$cmd
	sort=()
	for ((i=numtry;i--;)) ;do
	    start=${EPOCHREALTIME//.}
	    $cmd < "$file" >/dev/null
	    sort[${EPOCHREALTIME//.}-start]=
	done
	sort=(${!sort[@]})
	output+=($sort)
    done
    . <( echo -n "tee <'$file' > "
	 for((i=0;i<${#cmds[@]};i++)){
		printf ">(%s >'$file'.%s) " "${cmds[i]%:*}" ${cmds[i]#*:} ;}
       )
    wait
    for ((i=3;i--;)){ sync;((i))&&sleep .2;} # Force wait sync...
    for decmd in "${decmds[@]}";do
	IFS=: read decmd ext <<<$decmd
	musec2str $output hcomp
	output=("${output[@]:1}")
	csize=$(LANG=C wc -c <"$file".$ext)
	txtsize $csize hsize
	percent $csize $fsize prct
	sort=()
	for ((i=numtry;i--;)) ;do
	    start=${EPOCHREALTIME//.}
	    $decmd < "$file".$ext >/dev/null
	    sort[${EPOCHREALTIME//.}-start]=
	done
	elap=(${!sort[@]})
	musec2str $elap hdeco
	printf "%-20s %14u %8s %7s %15s %15s\n" "$file.$ext" \
	       $csize $hsize $prct $hcomp $hdeco
    done |
	sort -t \\0 -nk 1.21
    . <(printf rm;printf " ${file@Q}.%s" ${decmds[@]#*:};echo)
done