#!/bin/bash

# Show parts of a given package file name.

DIE() {
    echo "$progname: error: $1" >&2
    Usage
    exit 0
}

Usage() {
    cat <<EOF

Usage:
  $progname -h|--help
      Shows this help.

  $progname [--real] "parts" "package-file-name"
      --real
              Give output as in real parts of the package name.
      parts
              String of upper case letters consisting of: N V R A C E.
              N = pkgname
              V = pkgver
              R = pkgrel
              A = arch
              C = compressor
              E = epoch
              These letters specify what the output will contain.
              The output values are separated by the pipe '|' character.
      package-file-name
              Name of a package file.

Examples:
  $ $progname NEVRAC foo-bar-2:22.04.23-1-any.pkg.tar.zst
  foo-bar|2|22.04.23|1|any|zst

  $ $progname --real NEVRAC foo-bar-2:22.04.23-1-any.pkg.tar.zst
  foo-bar-2:22.04.23-1-any.zst

EOF
}

SeparateParts() {
    local pkg="$1"

    local all=$(echo "$pkg" | sed -E 's/([a-zA-Z0-9@_+][a-zA-Z0-9@._+-]+)-([0-9:]*[^:/\-\ \t]+)-([0-9.]+)-([a-z0-9_]+)\.pkg\.tar\.([a-z0-9]+)$/\1 \2 \3 \4 \5/')
    #                                    name...........................   epoch..pkgver......   pkgrel.   arch......              compress.
    all=($(echo $all))

    local N=${all[0]}
    local V=${all[1]}   # may include epoch!
    local R=${all[2]}
    local A=${all[3]}
    local C=${all[4]}
    local E="0"         # default (=unspecified) epoch is 0

    local sep=""
    local result=""
    local ix item

    case "$real_out" in
        yes) sep="-" ;;   # for most components
        no)  sep="|" ;;   # for all
    esac

    if [ "${V%:*}" != "$V" ] ; then
        E="${V%:*}"
        V="${V#*:}"
    fi

    for ((ix=0; ix < ${#parts}; ix++)) ; do
        item="${parts:$ix:1}"
        case "$item" in
            N) result+="$N$sep" ;;
            V) result+="$V$sep" ;;
            R) result+="$R$sep" ;;
            A) result+="$A$sep" ;;
            C) result+="$C$sep" ;;
            E) case "$real_out" in
                   yes) [ $E -ne 0 ] && result+="$E:" ;;   # don't show epoch if it is zero
                   no)  result+="$E$sep" ;;
               esac
                ;;
            *) DIE "given parameter '$parts' includes an unsupported value '$item'." ;;
        esac
    done
    [ -n "$result" ] || DIE "no result!"

    result="${result:: -1}"
    [ -n "$result" ] || DIE "result is empty!"

    echo "$result"
}

Main() {
    local real_out=no
    local parts
    local pkg
    local progname="$(basename "$0")"

    case "$1" in
        -h | --help)
            Usage
            return 0
            ;;
        --real)
            real_out=yes
            shift
            ;;
        -*)
            Usage
            return 1
            ;;
    esac
    parts="$1"
    pkg="$2"

    if [ -n "$pkg" ] ; then
        SeparateParts "$pkg"
    else
        while read pkg ; do
            SeparateParts "$pkg"
        done
    fi
}

Main "$@"