#!/usr/bin/env bash
#
# embs.sh - connect to the York CS Linux server with the Vivado / Vitis GUI
#           forwarded to the XQuartz X server running on this Mac.
#
# Vivado and Vitis have no macOS build, so they run on csteach0.york.ac.uk and
# their windows are drawn here by XQuartz over an X11-forwarded SSH connection.
#
# Usage:
#   ./embs.sh                      interactive shell, X11 forwarded (normal use)
#   ./embs.sh --check              verify the local X server and show what would run
#   ./embs.sh 'vivado -version'    run one remote command, then disconnect
#
# The remote host can be overridden, e.g.  EMBS_HOST=csteach1.york.ac.uk ./embs.sh
#
# Note: this script only prepares the local X server and starts ssh. The hop
# through the SSH gateway, and any 2FA prompt it raises, are handled by the
# ProxyCommand already configured in ~/.ssh/config.

set -e

HOST="${EMBS_HOST:-csteach0.york.ac.uk}"
XDPYINFO=/opt/X11/bin/xdpyinfo

# Return the first local X display we can actually reach, or nothing.
working_display() {
    local d
    for d in "${DISPLAY:-}" ":0"; do
        [ -n "$d" ] || continue
        if [ -x "$XDPYINFO" ] && "$XDPYINFO" -display "$d" >/dev/null 2>&1; then
            printf '%s' "$d"
            return 0
        fi
    done
    return 1
}

start_xquartz() {
    if [ ! -d /Applications/Utilities/XQuartz.app ]; then
        echo "error: XQuartz is not installed." >&2
        echo "       Install it with:  brew install --cask xquartz" >&2
        return 1
    fi
    echo "Starting XQuartz..."
    open -a XQuartz || return 1
    local i
    for i in $(seq 1 30); do
        if "$XDPYINFO" -display :0 >/dev/null 2>&1; then
            return 0
        fi
        sleep 0.5
    done
    return 1
}

CHECK_ONLY=no
if [ "${1:-}" = "--check" ]; then
    CHECK_ONLY=yes
    shift
fi

# --- 1. Make sure there is a usable local X server ---------------------------
DISP="$(working_display || true)"
if [ -z "$DISP" ] && [ "$CHECK_ONLY" = no ]; then
    if start_xquartz; then
        DISP=":0"
    fi
fi

if [ -z "$DISP" ]; then
    echo "warning: no X server reachable on this Mac." >&2
    echo "         XQuartz is installed but may not be running, or DISPLAY is not exported." >&2
    echo "         Try:  open -a XQuartz   (then log out and back in once)" >&2
    echo "         Vivado / Vitis windows will NOT appear until this is fixed." >&2
else
    export DISPLAY="$DISP"
fi

# --- 2. Report and connect ---------------------------------------------------
if [ "$CHECK_ONLY" = yes ]; then
    echo "XQuartz installed : yes"
    echo "X server reachable: ${DISP:-no}"
    echo "DISPLAY would be  : ${DISP:-<unset>}"
    echo "Would run         : ssh -Y -C -o ServerAliveInterval=60 $HOST"
    if [ "$#" -gt 0 ]; then
        echo "Remote command    : $*"
    fi
    exit 0
fi

echo "Connecting to $HOST with DISPLAY=${DISPLAY:-<unset>} ..."
echo "If the gateway asks for a password or Duo approval, that is the university's 2FA."
echo

if [ "$#" -gt 0 ]; then
    exec ssh -Y -C -o ServerAliveInterval=60 "$HOST" "$@"
else
    exec ssh -Y -C -o ServerAliveInterval=60 "$HOST"
fi