#!/usr/bin/env bash
# compat: +ash +bash +dash -hush +ksh +mksh +oksh +osh +posh +yash +zsh

burl() ( ### @-
    ### turn bash into a makeshift HTTP client.
    ### inspired by [hackshell.sh.](https://thc.org/hs)
    ### also works in most other shells thanks to netcat.
    ###
    ### minimal/minified version: https://eaguru.guru/t/burl.sh (469 bytes)
    ###
    ### ```
    ### $ burl httpbin.org/get
    ###
    ### HTTP/1.1 200 OK
    ### Date: Tue, 01 Jul 2024 00:00:00 GMT
    ### Content-Type: application/json
    ### Content-Length: 192
    ### Connection: close
    ### Server: gunicorn/19.9.0
    ### Access-Control-Allow-Origin: *
    ### Access-Control-Allow-Credentials: true
    ###
    ### {
    ###   "args": {},
    ###   "headers": {
    ###     "Host": "httpbin.org",
    ###     "X-Amzn-Trace-Id": "Root=1-12345678-deadfadefeedfacebeefcafe"
    ###   },
    ###   "origin": "0.0.0.0",
    ###   "url": "http://httpbin.org/get"
    ### }
    ### ```

    # shells with /dev/tcp and /dev/udp support: bash, ksh, yash.

    ! (set -o pipefail) 2>&- || set -o pipefail
    (: </dev/udp/localhost/0) 2>&- && net=y || net=
    [ $'' ] && r=$(printf \\r) || r=$'\r'

    # nc.traditional needs the -- or else it waits for input.
    if /usr/bin/env nc --; [ $? = 1 ] # needs absolute path to env thanks to busybox
    then wrapped() { process /usr/bin/env nc -- "$@" ;}
    elif netcat; [ $? = 1 ]
    then wrapped() { process netcat -- "$@" ;}
    elif ncat; [ $? = 1 ]
    then wrapped() { process ncat -- "$@" ;}
    elif busybox nc; [ $? = 1 ]
    then wrapped() { process busybox nc -- "$@" ;}
    elif socat /dev/null /dev/null
    then wrapped() { process socat - "TCP:$1:$2" ;}
    elif websocat; [ $? = 1 ]
    then wrapped() { websocat --binary - "tcp:$1:$2" ;}
    elif curl; [ $? = 2 ]
    then wrapped() { process curl "telnet://$1:$2" ;}
    else return 127
    fi 2>&-

    request() { printf 'GET /%s HTTP/1.0\r\nHost: %s\r\n\r\n' "${query#/}" "$dom" ;}
    receive() { while IFS=$r read -r l _; [ "$l" ]; do printf %s\\n "$l"; done; echo ;} >&2
    process() { request | "$@" | { receive && cat ;} ;}

    for url; do
        proto="${url%%:*}" proto="${proto##*[!a-z0-9-]*}"
        [ "$proto" ] && url="${url#$proto://}" || url="${url#//}"
        host="${url%%/*}" query="${url#"$host"}" dom="${host%:*}"
        [ "$host" = "${dom:?}" ] && PORT="${PORT:-80}" || PORT="${host##*:}"
        if [ "$net" ]; then
            exec 3<>"/dev/tcp/$dom/$PORT" &&
            request >&3 && receive <&3 && cat <&3 || continue
            exec 3>&-
        else
            wrapped "$dom" "$PORT" || return
        fi
    done
)

[ -n "${preload+-}" ] || burl "$@"