#!/bin/bash
# Desc: Append [processed] file to tar

yell() { echo "$0: $*" >&2; } # Yell, Die, Try Three-Fingered Claw technique; # Ref/Attrib: https://stackoverflow.com/a/25515370
die() { yell "$*"; exit 111; }
try() { "$@" || die "cannot $*"; }
appendFileTar(){
    # Desc: Appends [processed] file to tar
    # Usage: appendFileTar [file path] [name of file to be inserted] [tar path] [temp dir] ([process cmd])
    # Version: 2.0.1
    # Input: arg1: path of file to be (processed and) written
    #        arg2: name to use for file inserted into tar
    #        arg3: tar archive path (must exist first)
    #        arg4: temporary working dir
    #        arg5: (optional) command string to process file (ex: "gpsbabel -i nmea -f - -o kml -F - ")
    # Output: file written to disk
    # Example: decrypt multiple large files in parallel
    #          appendFileTar /tmp/largefile1.gpg "largefile1" $HOME/archive.tar /tmp "gpg --decrypt" &
    #          appendFileTar /tmp/largefile2.gpg "largefile2" $HOME/archive.tar /tmp "gpg --decrypt" &
    #          appendFileTar /tmp/largefile3.gpg "largefile3" $HOME/archive.tar /tmp "gpg --decrypt" &
    # Depends: bash 5.0.3, tar 1.30, cat 8.30, yell()
    local fn fileName tarPath tmpDir

    # Save function name
    fn="${FUNCNAME[0]}";
    #yell "DEBUG:STATUS:$fn:Started appendFileTar()."
    
    # Set file name
    if ! [ -z "$2" ]; then fileName="$2"; else yell "ERROR:$fn:Not enough arguments."; exit 1; fi
    # Check tar path is a file
    if [ -f "$3" ]; then tarPath="$3"; else yell "ERROR:$fn:Tar archive arg not a file:$3"; exit 1; fi
    # Check temp dir arg
    if ! [ -z "$4" ]; then tmpDir="$4"; else yell "ERROR:$fn:No temporary working dir set."; exit 1; fi
    # Set command strings
    if ! [ -z "$5" ]; then cmd1="$5"; else cmd1="cat "; fi # command string

    # Input command string
    cmd0="cat \"\$1\"";
    
    # Write to temporary working dir
    eval "$cmd0 | $cmd1" > "$tmpDir"/"$fileName";

    # Append to tar
    try tar --append --directory="$tmpDir" --file="$tarPath" "$fileName";
    #yell "DEBUG:STATUS:$fn:Finished appendFileTar()."
} # Append [processed] file to Tar archive

#==BEGIN sample code==
myTar="/tmp/$(date +%s).tar";
myTmpDir="/dev/shm";
try tar --create --file="$myTar" --files-from=/dev/null ;
myFile="/tmp/$(date +%s)..original";
echo "how are you doing?" > "$myFile";
appendFileTar "$myFile" "$(date +%s)..LOUD_insidetar" "$myTar" "$myTmpDir" "tee /tmp/$(date +%s)..outsidetar | tr '[:lower:]' '[:upper:]'" && \
    echo "Inserted a processed version of $myFile into $myTar using temp dir $myTmpDir ";
#==END sample code==

# Author: Steven Baltakatei Sandoval
# License: GPLv3+