#!/bin/bash
# connect to iot services
THIS_DIR=$( cd "$( dirname "${BASH_SOURCE[0]:-${(%):-%x}}" )" && pwd )
source "$THIS_DIR/../tools/common.sh"
RIOT_TRUST_CLIENT=${RIOT_TRUST_CLIENT:-${DFS_TRUST:-0}}
RIOT_TRUST_SERVER=${RIOT_TRUST_SERVER:-0}

# check if port number valid
check_port() {
    ( echo $1 | grep -qxE "[1-9][0-9]{0,4}" ) || return 1
    test $1 -lt 65536 -a $1 -gt 0 || return 1
    return 0
}

# check if username valid
check_username() {
    ( echo $1 | grep -qxE "^[-.a-z0-9_]*\$" ) || return 1
    return 0
}

# get single server setting
# may be called more than once
get_server_meta() {
    # returns:
    RET_HOSTNAME=""
    RET_TRUST_SERVER=0
    RET_PORT=""  # optional
    RET_USERNAME=""  # optional
    RET_JUMP_SERVER=""  # optional
    # body
    local remote="$1"
    # if in the form user@...
    if [[ "$remote" == *@* ]]; then
        RET_USERNAME=${remote%%@*}
        remote=${remote#*@}
        check_username $RET_USERNAME || fmt_fatal invalid username \"$RET_USERNAME\"
    fi
    # if in the form ...:22
    if [[ "$remote" == "["*"]":* || ( "$remote" != "["*"]" && "$remote" == *:* ) ]]; then
        RET_PORT=${remote##*:}
        remote=${remote%:*}
        check_port $RET_PORT || fmt_fatal invalid port number \"$RET_PORT\"
    fi
    # presets -- match domain
    local domain=${remote##*.}
    local host=${remote%.*}
    # if there's no dot
    if [[ "$host" == "$domain" && "$host" != "["*"]" ]]; then
        domain="ibd"
    fi
    case $domain in
        i|ibd )
            RET_HOSTNAME=$host.ibd.ink
            RET_PORT=${RET_PORT:-12022}
            RET_USERNAME=${RET_USERNAME:-root}
            RET_TRUST_SERVER=1
            ;;
        nasp )
            RET_HOSTNAME=$host
            RET_PORT=${RET_PORT:-12022}
            RET_USERNAME=${RET_USERNAME:-dictxiong}
            RET_JUMP_SERVER="ssh@nasp.ob.ac.cn:36022"
            RET_TRUST_SERVER=1
            ;;
        x|proxied )
            RET_HOSTNAME=proxy.beardic.cn
            local tmp=$(sha256sum <<< "$host" | tr -cd "[:digit:]")
            tmp=${tmp:0:4}
            RET_PORT=$((10#$tmp+36000))
            RET_USERNAME=root
            RET_TRUST_SERVER=1
            ;;
        * )
            test -z "$domain" || fmt_warning "unknown domain: \"$domain\". will try as host name"
            RET_HOSTNAME="$remote"
    esac
}

# remote setting, including jump servers
# will be called only once
# provides:
SERVER=""
TRUST_SERVER=1
PORT=""  # optional
USERNAME=""  # optional
SSH_OPTIONS=""  # optional
if [[ "$RIOT_TRUST_CLIENT" == "1" ]]; then
    SSH_OPTIONS='-o ControlMaster=auto -o ControlPath=/tmp/sshcm-%C -o PermitLocalCommand=yes'
fi
parse_remote() {
    local remote="$1"
    local jump_servers=""
    # loop for jump servers
    while [[ -n $remote ]]; do
        local server=${remote%%,*}
        remote=${remote#*,}
        get_server_meta "$server"
        if [[ -n "$RET_JUMP_SERVER" ]]; then
            jump_servers="$jump_servers${jump_servers:+,}$RET_JUMP_SERVER"
        fi
        # only if all servers are trusted
        TRUST_SERVER=$((TRUST_SERVER*RET_TRUST_SERVER))
        if [[ "$server" == "$remote" || -z "$remote" ]]; then
            SERVER="$RET_HOSTNAME"
            PORT="$RET_PORT"
            USERNAME="$RET_USERNAME"
            remote=""
        else
            jump_servers="$jump_servers${jump_servers:+,}$RET_USERNAME${RET_USERNAME:+@}$RET_HOSTNAME${RET_PORT:+:}$RET_PORT"
        fi
    done
    # construct cmd
    if [[ "$RIOT_TRUST_SERVER" == "1" || "$TRUST_SERVER" == "1" ]]; then
        SSH_OPTIONS="$SSH_OPTIONS -o ForwardX11=yes -o ForwardAgent=yes"
    fi
    if [[ -n "$jump_servers" ]]; then
        SSH_OPTIONS="$SSH_OPTIONS -o ProxyJump=$jump_servers"
    fi
}

eval_or_echo() {
    if [[ "$DFS_DRY_RUN" == "1" ]]; then
        echo $@
    else
        eval $@
    fi
}

# ssh series
prepare_ssh_cmd() {
    local ssh_bin="${1:-ssh}"
    if [[ "$ssh_bin" == "scp" || "$ssh_bin" == "sftp" ]]; then
        local port_param='-P'
    else
        local port_param='-p'
    fi
    echo "$ssh_bin ${PORT:+$port_param} $PORT $SSH_OPTIONS $SCP_SRC $USERNAME${USERNAME:+@}$SERVER $SCP_DST"
}

# ssh
run_ssh()
{
    local cmd="$(prepare_ssh_cmd $1)"
    fmt_note "-->" $cmd
    eval_or_echo $cmd
}

# sshl
run_sshl()
{
    local arg="$1"
    if [[ "$arg" != *":"* ]]; then
        # treat as a port number
        arg=localhost:$arg
    fi
    while
        local port=$(shuf -n 1 -i 49152-65535)
        netstat -atun | grep -q "$port"
    do
        continue
    done

    SSH_OPTIONS="$SSH_OPTIONS -NC -L $port:$arg"
    local cmd="$(prepare_ssh_cmd ssh)"
    fmt_note "-->" $cmd
    fmt_note "  > please access localhost:$port"
    eval_or_echo $cmd
}

# scp
run_scp() {
    local src="$1"
    local dst="$2"
    local dst_is_remote=1
    # whoever is ./*, it can't be the remote; whoever not exists on local, it's possible the remote.
    # it is suggested to use ./* for local files.
    if [[ "$src" != "./"* && ( "$dst" == "./"* || ( ! -e "$src" && -e "$dst" ) ) ]]; then
        dst_is_remote=0
    fi
    if [[ "$dst_is_remote" == "1" ]]; then
        SCP_SRC=\""$src"\"
        SERVER="$SERVER":\""$dst"\"
    else
        SERVER="$SERVER":\""$src"\"
        SCP_DST=\""$dst"\"
    fi
    SSH_OPTIONS="$SSH_OPTIONS -r"
    local cmd="$(prepare_ssh_cmd scp)"
    fmt_note "-->" $cmd
    eval_or_echo $cmd
}

# main
print_help()
{
    fmt_info "usage: $0 <service> [command] [options]"
    echo "available commands: ssh (default), sshl (ssh -L), zssh, sftp"
}

router() {
    if [[ -z "$1" || "$1" == "-h" || "$1" == "--help" ]]; then
        print_help
        exit
    fi
    parse_remote "$1"
    case $2 in
        -h|--help)
            print_help
            exit
            ;;
        ssh|"" )
            run_ssh
            ;;
        zssh )
            run_ssh zssh
            ;;
        sftp )
            run_ssh sftp
            ;;
        sshl )
            test -n "$3" || fmt_fatal "no target address provided"
            run_sshl "$3"
            ;;
        scp )
            test -n "$3" || fmt_fatal "no source path specified"
            test -n "$4" || fmt_fatal "no destination path specified"
            run_scp "$3" "$4"
            ;;
        * )
            print_help
            fmt_fatal "unknown command: $2"
            ;;
    esac
}

router "${GOT_OPTS[@]}"