import { useCallback } from 'react';
import { Link } from 'react-router';
import { Loader2, TerminalSquare } from 'lucide-react';
import { offscaleSectionPath } from './shared';
import { useOffscaleServers } from './useOffscaleServers';
import { TerminalView } from 'officerdev';
import { Button } from './Cards';

// A shell on the machine behind the active Headscale server — the escape hatch for everything the API cannot
// answer (why headscale won't start, what the logs say, whether the disk is full).
//
// It is deliberately the SAME terminal every other panel uses, driven by nothing more than `ssh <host>` typed
// into a login shell. Officer holds no key, no password and no port: whatever `ssh` on this box can already
// reach, this can reach, and nothing more. If the connection needs a jump host or an odd port, that belongs in
// `~/.ssh/config` as a Host alias — which this field accepts by name.
//
// The session id is derived from the server id rather than minted per panel, so re-opening the Console lands
// back in the shell that is already running and mid-command, and switching servers is a different shell rather
// than the same one re-purposed. TerminalView suppresses its initial input when the sidecar replays a buffer,
// which is what stops a re-attach from typing a second `ssh` inside the first.

const consoleSessionId = (serverId: number) => `headscale-console-${serverId}`;

const Centred = ({ children }: { children: React.ReactNode }) => (
  <div className="flex h-full flex-col items-center justify-center gap-3 p-6 text-center">
    <div className="flex h-14 w-14 items-center justify-center rounded-2xl bg-white/5 text-zinc-400">
      <TerminalSquare className="h-6 w-6" />
    </div>
    {children}
  </div>
);

export const ConsoleView = () => {
  const { active, isLoading } = useOffscaleServers();

  // The terminal reports its connection state; nothing in this section acts on it yet, but TerminalView wants
  // a stable callback and an inline arrow would remount its effect on every render.
  const onConnectionChange = useCallback(() => {}, []);

  if (isLoading) {
    return (
      <div className="flex h-full items-center justify-center text-sm text-zinc-500">
        <Loader2 className="mr-2 h-4 w-4 animate-spin" />
        Loading servers…
      </div>
    );
  }

  if (!active) {
    return (
      <Centred>
        <div>
          <div className="text-base font-semibold text-zinc-100">No server selected</div>
          <p className="mt-1 text-sm text-zinc-500">Pick one in the Servers section to open its console.</p>
        </div>
      </Centred>
    );
  }

  if (!active.sshHost) {
    return (
      <Centred>
        <div>
          <div className="text-base font-semibold text-zinc-100">No SSH address for {active.name}</div>
          <p className="mt-1 max-w-sm text-sm text-zinc-500">
            Add one on the server to open a shell on the machine behind it. Use the machine's own address rather than
            the Headscale hostname — the console is most useful exactly when that name has stopped answering.
          </p>
        </div>
        <Link to={offscaleSectionPath('servers')}>
          <Button variant="primary">Go to Servers</Button>
        </Link>
      </Centred>
    );
  }

  return (
    <div className="flex h-full flex-col">
      <div className="flex shrink-0 items-center gap-2 border-b border-white/10 px-3 py-2 text-[11px] text-zinc-500">
        <TerminalSquare className="h-3.5 w-3.5" />
        <span className="truncate">
          ssh <span className="font-mono text-zinc-300">{active.sshHost}</span> · {active.name}
        </span>
      </div>
      <TerminalView
        // Remount on a server switch: the session id is a mount-time argument, so without this the panel would
        // keep showing the previous server's shell under the new server's name.
        key={active.id}
        className="min-h-0 flex-1 p-2"
        sessionId={consoleSessionId(active.id)}
        initialInput={`ssh ${active.sshHost}`}
        onConnectionChange={onConnectionChange}
      />
    </div>
  );
};
