#!/bin/sh
# gc -- gopher client
die() {
    echo "$*" 1>&2
    exit 1
}

[ -z "$1" ] && die "usage: gc URL"

pretty() {
    awk -F"	" "
/^[^01i\.]/ { sub(\"^.\", \"\", \$1); printf \"   ???| %s\\n\", \$1 }
/^i/ { sub(\"^i\", \"\", \$1); printf \"      | %s\\n\", \$1 }
/^0/ { sub(\"^0\", \"\", \$1); links[n++] = sprintf(\"%s/0%s\", \$3, \$2); printf \"%2d TXT| %s\\n\", n, \$1 }
/^1/ { sub(\"^1\", \"\", \$1); links[n++] = sprintf(\"%s/1%s\", \$3, \$2); printf \"%2d DIR| %s\\n\", n, \$1 }
END {
    printf \"\" > \"$LINKS\"
    for (i=0; i < length(links); i++) {
        printf \"[%d]: %s\\n\", i + 1, links[i] >>\"$LINKS\"
    }
}
"
}

parseurl() {
    bare=${URL##gopher://}
    host=${bare%%/*}
    target=${bare##$host}
}

catlike() {
    parseurl
    case "$target" in
        /0/*) echo "${target##/0}" | nc "$host" 70 ;;
        /1/*) echo "${target##/1}" | nc "$host" 70 | pretty ;;
        *) echo "$target" | nc "$host" 70 | pretty ;;  # TODO: handle other types?
    esac
}

goto() {
    printf "goto> "
    read -r URL
}

graburl() {
    N="$1"
    link=$(grep "^\[$N\]:" "$LINKS")
    URL=${link##\[*\]: }
}

ui() {
    while [ -n "$URL" ]; do
        parseurl
        case "$target" in
            /0/*) echo "${target##/0}" | nc "$host" 70 | ${PAGER:-less} ;;
            /1/*) echo "${target##/1}" | nc "$host" 70 | pretty ;;
            *) echo "$target" | nc "$host" 70 | pretty ;;  # TODO: handle other types?
        esac

        URL=""
        while true; do
            printf "> "
            read -r opt
            case $opt in
                [0-9]*) graburl "$opt" && if [ -n "$URL" ]; then break; else echo "no such link"; fi ;;
                l*) cat "$LINKS" ;;
                g*) goto ; break ;;
                h*) cat <<EOM ;;
NUM    -- go to this target
g[oto] -- specify new URL
h[elp] -- print this message
l[ist] -- list targets
q[uit] -- quit
EOM
                q*) break;;
                *) echo "no such command; 'h' for help, 'q' to quit" ;;
            esac
        done
    done
}

URL=$1
LINKS=$(mktemp)

if ! tty >/dev/null; then
    catlike
else
    ui
fi

rm -f "$LINKS"