#!/bin/bash

# Convert the exit code of certain apps to human friendly text.
# The man page of the app is used for the conversion.
# Find the supported apps by using option --help.
# See also the man pages of the supported apps.

echo2() { echo -e "$@" >&2; }
Exit()  { echo2 "$1"; exit "$2"; }

Help() {
    cat <<EOF
Usage:           $progname exit-code [app-name]
                 $progname {--help | -h}
Parameters:      exit-code     The exit code of the app.
                 app-name      (Optional) The name of the app. Default: $defapp.
Supported apps:  $supported_apps
Example:         $progname 4 wget
EOF
    [ "$1" ] && exit "$1"
}

IsNum() { [ "$1" ] && [ -z "${1//[0-9]/}" ] ; }

ExitCodeToString() {
    local -r progname=${0##*/}
    local -r supported_apps='curl wget makepkg'
    local -r defapp=curl
    local app="$defapp"               # optional, defaults to 'curl'
    local exitcode=""
    local -r paraerr=126              # exit code: parameter error by user

    # check parameters
    [ "$1" ] || Help $paraerr
    while [ "$1" ] ; do
        case "$1" in
            [0-9]*)
                IsNum "$1" && exitcode="$1" || Help $paraerr ;;
            -h | --help)
                Help 0 ;;
            *)
                local item
                for item in $supported_apps ; do
                    if [ "$1" = "$item" ] ; then
                        app="$1"
                        break
                    fi
                done
                [ "$1" = "$item" ] || Help $paraerr
                ;;
        esac
        shift
    done

    # convert number to string in the man page
    case "$app" in
        curl | wget)
            # code and text on the same line
            LANG=C MANWIDTH=300 man $app 2>/dev/null | grep -E "^[ ]+$exitcode[ ]+" | sed -E "s|^[ ]+$exitcode[ ]+||"
            ;;
        makepkg)
            # code and text on different, adjacent lines
            LANG=C MANWIDTH=300 man $app 2>/dev/null | grep -A2 -E "^[ ]+$exitcode$" | grep -v "^$" | tail -n +2 | sed -E "s|^[ ]+(.+\.)$|\1|"
            ;;
    esac
}

ExitCodeToString "$@"