import { useCallback, useEffect, useRef, useState } from 'react';
import { Check, CircleDot, Loader2, Play, Server, Square } from 'lucide-react';
import { useClient } from 'hooks/useClient';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { readableError } from './errors';
import { Block } from './Block';
import { Console } from './Console';
import { useFlash } from './useFlash';

/**
 * The two servers that serve the site, under pm2.
 *
 * ── Both under pm2, development included ──
 *
 * A `bun dev` started in a terminal dies with the terminal, and nobody can tell whether it is running
 * without finding the window it was started in. Under pm2 the two are the same kind of thing: a named
 * process with a status and an uptime, startable from here and inspectable from anywhere.
 *
 * ── Start is really a replace ──
 *
 * The port and the database come from these settings, and pm2 keeps the environment a process was
 * STARTED with. So starting removes any existing process of that name first — otherwise a port changed
 * here would be saved, shown, and not in effect, which is the kind of thing somebody debugs for an hour.
 *
 * ── The process names are shown ──
 *
 * `fofos-dev` and `fofos-prod`, in the row. Whatever this panel can do, `pm2 logs fofos-dev` does more,
 * and somebody who knows that should not have to guess the name to use it.
 */

type Server = {
  name: 'development' | 'production';
  process: string;
  port: number | null;
  status: string | null;
  uptimeMs: number | null;
  restarts: number | null;
  url: string | null;
};

const uptime = (ms: number) => {
  const minutes = Math.floor(ms / 60000);
  if (minutes < 60) return `${minutes}m`;
  const hours = Math.floor(minutes / 60);
  return hours < 24 ? `${hours}h ${minutes % 60}m` : `${Math.floor(hours / 24)}d ${hours % 24}h`;
};

export const ServersPanel = () => {
  const client = useClient();
  const clientRef = useRef(client);
  clientRef.current = client;

  const [servers, setServers] = useState<Server[] | null>(null);
  const [dev, setDev] = useState('');
  const [prod, setProd] = useState('');
  const [busy, setBusy] = useState<string | null>(null);
  const [error, setError] = useState<string | null>(null);
  const [output, setOutput] = useState<string | null>(null);
  const [failed, setFailed] = useState(false);
  const [flashing, flash] = useFlash();

  const load = useCallback(async () => {
    try {
      const current = await clientRef.current.get<Server[]>('/fofos-admin/_config/servers');
      setServers(current);
      setDev((typed) => typed || String(current.find((s) => s.name === 'development')?.port ?? ''));
      setProd((typed) => typed || String(current.find((s) => s.name === 'production')?.port ?? ''));
    } catch {
      setServers(null);
    }
  }, []);

  useEffect(() => {
    void load();
  }, [load]);

  const savePorts = async () => {
    setBusy('ports');
    setError(null);
    try {
      setServers(
        await clientRef.current.put<Server[]>('/fofos-admin/_config/servers', {
          development: Number(dev),
          production: Number(prod),
        }),
      );
      flash();
    } catch (failure) {
      setError(readableError(failure));
    } finally {
      setBusy(null);
    }
  };

  const act = async (which: string, action: 'start' | 'stop') => {
    setBusy(`${which}:${action}`);
    setError(null);
    setFailed(false);
    setOutput(null);
    try {
      const result = await clientRef.current.post<{ ok: boolean; output: string; servers: Server[] }>(
        `/fofos-admin/_config/servers/${which}/${action}`,
        {},
      );
      setServers(result.servers);
      setOutput(result.output);
      setFailed(!result.ok);
    } catch (failure) {
      setOutput(readableError(failure));
      setFailed(true);
      void load();
    } finally {
      setBusy(null);
    }
  };

  const dirty =
    dev !== String(servers?.find((s) => s.name === 'development')?.port ?? '') ||
    prod !== String(servers?.find((s) => s.name === 'production')?.port ?? '');

  const row = (server: Server, value: string, onChange: (next: string) => void) => {
    const online = server.status === 'online';
    const label = server.name === 'development' ? 'Development' : 'Production';

    return (
      <div key={server.name} className="flex flex-wrap items-center gap-3 border-t border-border pt-3 first:border-0 first:pt-0">
        <div className="min-w-0 flex-1">
          <p className="flex items-center gap-1.5 text-xs">
            {/* pm2's own word, not an interpretation of it. `errored` and `stopped` mean different
                things to whoever has to fix it. */}
            <CircleDot className={`size-3 ${online ? 'text-success' : server.status ? 'text-destructive' : 'text-muted-foreground/40'}`} />
            {label}
            <span className="text-muted-foreground/70">
              {server.status ?? 'not started'}
              {online && server.uptimeMs !== null ? ` · up ${uptime(server.uptimeMs)}` : ''}
              {server.restarts ? ` · ${server.restarts} restarts` : ''}
            </span>
          </p>
          <p className="font-mono text-xs text-muted-foreground/60">
            {server.process}
            {online && server.url ? ` · ${server.url}` : ''}
          </p>
        </div>

        <Input
          value={value}
          onChange={(event) => onChange(event.target.value.replace(/[^0-9]/g, ''))}
          placeholder="3010"
          className="w-24 shrink-0 font-mono text-xs"
          inputMode="numeric"
          autoComplete="off"
        />

        <div className="flex shrink-0 gap-2">
          <Button
            variant="outline"
            size="sm"
            onClick={() => void act(server.name, 'start')}
            // Dirty ports are not in effect until saved, and starting with the old one silently would
            // be the confusing outcome.
            disabled={busy !== null || dirty || !value}
            title={dirty ? 'Save the ports first' : online ? 'Restart with the current settings' : undefined}
          >
            {busy === `${server.name}:start` ? <Loader2 className="size-3.5 animate-spin" /> : <Play className="size-3.5" />}
            {online ? 'Restart' : 'Start'}
          </Button>
          <Button
            variant="outline"
            size="sm"
            onClick={() => void act(server.name, 'stop')}
            disabled={busy !== null || !server.status}
          >
            {busy === `${server.name}:stop` ? <Loader2 className="size-3.5 animate-spin" /> : <Square className="size-3.5" />}
            Stop
          </Button>
        </div>
      </div>
    );
  };

  return (
    <div className="flex size-full flex-col gap-4 overflow-auto p-5">
      <Block
        icon={Server}
        title="Servers"
        hint="The site's development and production processes, run under pm2."
        status={
          flashing ? (
            <span className="flex items-center gap-1 text-xs text-success">
              <Check className="size-3.5" />
              Saved
            </span>
          ) : undefined
        }
      >
        {!servers ? null : (
          <>
            {servers.map((server) =>
              server.name === 'development' ? row(server, dev, setDev) : row(server, prod, setProd),
            )}

            {error && <p className="text-xs text-destructive">{error}</p>}
            <Console output={output} failed={failed} />

            {dirty && (
              <div className="flex justify-end border-t border-border pt-3">
                <Button size="sm" onClick={() => void savePorts()} disabled={busy !== null || !dev || !prod}>
                  {busy === 'ports' ? <Loader2 className="size-3.5 animate-spin" /> : <Check className="size-3.5" />}
                  Save ports
                </Button>
              </div>
            )}
          </>
        )}
      </Block>
    </div>
  );
};