import { useCallback, useEffect, useRef, useState } from 'react';
import { CircleDot, Gauge, Globe, Loader2, Lock, Plus, ShieldCheck } 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';

/**
 * The domains that reach the site, through Nginx Proxy Manager.
 *
 * ── This talks to the proxy-manager PLUGIN, from the browser ──
 *
 * Not to NPM, and not from this plugin's server. NPM's credential belongs to proxy-manager and to
 * nothing else; its skill is explicit that the sanctioned path is its own pass-through route and that
 * going around it is unauthorised. Calling it from here, in the browser, with the user's own session,
 * means this plugin never holds that credential and there is no server-to-server coupling between two
 * plugins that would each then need to know when the other was installed.
 *
 * ── `forward_host` is copied from what already works ──
 *
 * NPM runs in a container, so `127.0.0.1` there is NPM itself, not this machine — a host pointed at it
 * resolves, returns nothing, and looks like the site being down. The right value is the Docker
 * gateway, which is a fact about this machine's networking that neither this plugin nor a person
 * should have to know.
 *
 * So the default is taken from the hosts NPM ALREADY serves: whatever address they forward to is, by
 * construction, one that works here. It is shown in a field, because a guess made from other people's
 * configuration should be visible before it is used.
 *
 * ── Creating is offered; deleting is not ──
 *
 * The skill draws that line and it is the right one. A new host is additive and reversible. Removing or
 * repointing one is a live domain changing where it goes, which belongs in the Proxy Manager screen
 * where the full picture is — this panel would be offering a destructive action with a fraction of the
 * context.
 */

type Host = {
  id: number;
  domain_names: string[];
  forward_scheme: string;
  forward_host: string;
  forward_port: number;
  enabled: boolean;
  ssl_forced: boolean;
  certificate_id: number;
  http2_support: boolean;
  meta?: { nginx_online?: boolean };
};

type Server = { name: 'development' | 'production'; port: number | null };

/** NPM rejects a partial body — these are its own defaults, stated rather than omitted. */
const NEW_HOST = {
  block_exploits: true,
  allow_websocket_upgrade: true,
  caching_enabled: false,
  access_list_id: 0,
  certificate_id: 0,
  ssl_forced: false,
  /*
    HTTP/2. Only takes effect once a certificate is attached, which is why it is set here AND in
    `attach` — a host created before it was secured would otherwise keep HTTP/1.1 forever, and
    nothing in the panel would say so.

    On HTTP/1.1 a browser opens six connections and queues everything else behind them, which on this
    site meant the gallery images waited on each other. Lighthouse put it at 900 ms.
  */
  http2_support: true,
  hsts_enabled: false,
  hsts_subdomains: false,
  advanced_config: '',
  locations: [],
  meta: {},
};

export const ProxiesBlock = ({ servers }: { servers: Server[] }) => {
  const client = useClient();
  const clientRef = useRef(client);
  clientRef.current = client;

  const [hosts, setHosts] = useState<Host[] | null>(null);
  /*
    Production is not a port on this machine.

    It is a container on the same docker network as NPM, so the forward target is a NAME — `fofos-web:80`
    — and the gateway address that reaches a host process would reach nothing. Read here rather than
    passed down, because the shape of production's target is this block's business.
  */
  const [staticTarget, setStaticTarget] = useState<{ host: string; port: number } | null>(null);
  const [unavailable, setUnavailable] = useState(false);
  const [domains, setDomains] = useState<Record<string, string>>({});
  const [forwardHost, setForwardHost] = useState('');
  const [busy, setBusy] = useState<string | null>(null);
  const [output, setOutput] = useState<string | null>(null);
  const [failed, setFailed] = useState(false);

  const load = useCallback(async () => {
    try {
      const found = await clientRef.current.get<Host[]>('/proxy-manager/hosts');
      setHosts(found);
      // The address NPM already uses to reach this machine, taken by majority from its own hosts.
      const counts = new Map<string, number>();
      for (const host of found) counts.set(host.forward_host, (counts.get(host.forward_host) ?? 0) + 1);
      const common = [...counts.entries()].sort((a, b) => b[1] - a[1])[0]?.[0];
      if (common) setForwardHost((typed) => typed || common);

      const web = await clientRef.current
        .get<{ container: { name: string } }>('/fofos-admin/_config/static')
        .catch(() => null);
      if (web?.container?.name) setStaticTarget({ host: web.container.name, port: 80 });
    } catch {
      // Not installed, not running, or not permitted. Reported as absent rather than as an error: this
      // block is an integration with another plugin, and its absence is a fact rather than a fault.
      setUnavailable(true);
    }
  }, []);

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

  const create = async (server: Server) => {
    const domain = (domains[server.name] ?? '').trim();
    if (!domain || !server.port) return;

    setBusy(`${server.name}:create`);
    setFailed(false);
    setOutput(null);
    try {
      // Production goes to the container by name; development to the host, at its port.
      const target =
        server.name === 'production' && staticTarget
          ? { host: staticTarget.host, port: staticTarget.port }
          : { host: forwardHost.trim(), port: server.port! };

      await clientRef.current.post('/proxy-manager/npm/nginx/proxy-hosts', {
        ...NEW_HOST,
        domain_names: [domain],
        forward_scheme: 'http',
        forward_host: target.host,
        forward_port: target.port,
      });
      setOutput(`${domain} → ${target.host}:${target.port}`);
      setDomains((current) => ({ ...current, [server.name]: '' }));
      await load();
    } catch (failure) {
      setOutput(readableError(failure));
      setFailed(true);
    } finally {
      setBusy(null);
    }
  };

  /**
   * Give a host a certificate: find one, or ask for one, then attach it.
   *
   * ── The request outlives the browser, and this has to cope ──
   *
   * Issuing waits for a DNS record to propagate — two minutes by default, before certbot even looks.
   * The proxy in front of Officer gives up at sixty seconds and answers 504, while certbot carries on
   * and succeeds. So the failure everybody sees is a timeout, and underneath it the certificate exists
   * and is simply not attached to anything: exactly what happened to dev.fofosfluffybastards.com.
   *
   * So a timeout is not treated as a failure. Afterwards — whether the call returned, failed, or timed
   * out — this looks for a certificate covering these names and attaches the one it finds.
   *
   * ── It never issues a second certificate for a name that already has one ──
   *
   * Checked FIRST, before asking for anything. A retry after a timeout would otherwise burn a Let's
   * Encrypt rate limit to obtain a duplicate of a certificate already sitting on the disk, and rate
   * limits are per-week: the cost of getting that wrong is not being able to fix it today.
   */
  const findCertificate = async (names: string[]): Promise<number | null> => {
    const all = await clientRef.current
      .get<Array<{ id: number; domain_names: string[] }>>('/proxy-manager/npm/nginx/certificates')
      .catch(() => [] as Array<{ id: number; domain_names: string[] }>);
    // Covers every name this host serves. A certificate for one of two domains is not this host's.
    const match = all.find((cert) => names.every((name) => cert.domain_names?.includes(name)));
    return match?.id ?? null;
  };

  const attach = async (host: Host, certificateId: number) => {
    await clientRef.current.put(`/proxy-manager/npm/nginx/proxy-hosts/${host.id}`, {
      certificate_id: certificateId,
      ssl_forced: true,
      // The moment HTTP/2 becomes possible at all, so this is where it is turned on for a host that
      // predates the default above.
      http2_support: true,
    });
  };

  /**
   * Turn HTTP/2 on for a host that predates it being the default.
   *
   * Offered rather than done on load, even though it is one field and always the right answer: a
   * panel that silently rewrites the proxy while you are reading it is not something to build, and
   * the change momentarily reloads nginx for every site behind it.
   *
   * Only shown for a host that HAS a certificate — HTTP/2 is negotiated during the TLS handshake, so
   * on a plain host the setting is stored and never used, and offering it there would be offering a
   * button that does nothing visible.
   */
  const upgrade = async (host: Host) => {
    setBusy(`http2:${host.id}`);
    setFailed(false);
    setOutput(null);
    try {
      await clientRef.current.put(`/proxy-manager/npm/nginx/proxy-hosts/${host.id}`, { http2_support: true });
      setOutput(`${host.domain_names.join(', ')} → HTTP/2`);
      await load();
    } catch (failure) {
      setOutput(readableError(failure));
      setFailed(true);
    } finally {
      setBusy(null);
    }
  };

  const secure = async (host: Host) => {
    const names = host.domain_names;
    setBusy(`cert:${host.id}`);
    setFailed(false);

    try {
      // Already issued — from an earlier attempt that timed out, or done by hand in Proxy Manager.
      const existing = await findCertificate(names);
      if (existing) {
        setOutput(`A certificate for ${names.join(', ')} already exists. Attaching it.`);
        await attach(host, existing);
        setOutput(`${names.join(', ')} now uses its certificate, and http redirects to https.`);
        await load();
        return;
      }

      setOutput(
        `Asking for a certificate for ${names.join(', ')}.\n` +
          'This waits for DNS to propagate and takes a few minutes. A timeout here is expected and is not a failure.',
      );

      /*
        Deliberately not awaited on its own. The proxy will very likely cut this off before it returns,
        and the polling below is what actually establishes whether it worked — so a rejection here is
        recorded and then ignored in favour of asking the far side what exists.
      */
      const requested = clientRef.current
        .post<{ id: number }>('/proxy-manager/domains/certificate', { domain_names: names })
        .then((cert) => cert.id)
        .catch(() => null);

      // Up to five minutes, asking every ten seconds. Longer than the default propagation wait, because
      // a certificate that arrives at three minutes should still be attached.
      let certificateId = await requested;
      for (let attempt = 0; attempt < 30 && !certificateId; attempt++) {
        await new Promise((resolve) => setTimeout(resolve, 10_000));
        certificateId = await findCertificate(names);
      }

      if (!certificateId) {
        setOutput(
          `No certificate for ${names.join(', ')} appeared within five minutes. It may still arrive — press this again and it will attach rather than ask for another.`,
        );
        setFailed(true);
        return;
      }

      await attach(host, certificateId);
      setOutput(`Certificate issued for ${names.join(', ')}. http now redirects to https.`);
      await load();
    } catch (failure) {
      /*
        Its refusals are specific and each one is somebody's to fix, so they are translated rather than
        shown raw — "Not in the domain list" is a true sentence that tells nobody what to do next.
      */
      const message = readableError(failure);
      const apex = names[0]?.split('.').slice(-2).join('.') ?? 'the domain';
      setOutput(
        message.includes('Not in the domain list')
          ? `${apex} is not in Officer's Domains list, so it does not know whose DNS it is. Add it there first.`
          : message.includes('No API key')
            ? `${apex} is known but has no DNS API key stored. Add it in the Domains section.`
            : message.includes('two DNS providers')
              ? 'One certificate can only cover names from a single DNS provider. Ask for them separately.'
              : message,
      );
      setFailed(true);
    } finally {
      setBusy(null);
    }
  };

  if (unavailable) {
    return (
      <Block icon={Globe} title="Domains" hint="Which addresses reach the site, through Nginx Proxy Manager.">
        <p className="text-xs text-muted-foreground">
          The Proxy Manager plugin is not available here, so there is nothing to show.
        </p>
      </Block>
    );
  }

  const row = (server: Server) => {
    const label = server.name === 'development' ? 'Development' : 'Production';
    // Everything NPM already points at this server's port, whoever made it.
    /*
      What already points at this server.

      Matched on the FULL target rather than the port alone: production forwards to a container on port
      80, and every other site behind this NPM that happens to use port 80 would otherwise be listed here
      as though it belonged to fofos.
    */
    const mine = (hosts ?? []).filter((host) =>
      server.name === 'production' && staticTarget
        ? host.forward_host === staticTarget.host && host.forward_port === staticTarget.port
        : host.forward_port === server.port && server.port !== null,
    );

    return (
      <div key={server.name} className="flex flex-col gap-2 border-t border-border pt-3 first:border-0 first:pt-0">
        <p className="text-xs text-muted-foreground">
          {label}
          <span className="font-mono">
            {' · '}
            {server.name === 'production'
              ? staticTarget
                ? `${staticTarget.host}:${staticTarget.port}`
                : 'static, no server yet'
              : server.port
                ? `port ${server.port}`
                : 'no port set'}
          </span>
        </p>

        {mine.map((host) => (
          <div key={host.id} className="flex flex-wrap items-center gap-3">
            <p className="flex min-w-0 flex-1 items-center gap-1.5 text-xs">
              {/* `nginx_online` is what "is the site up" means here — not whether the row exists. */}
              <CircleDot
                className={`size-3 ${host.meta?.nginx_online ? 'text-success' : host.enabled ? 'text-destructive' : 'text-muted-foreground/40'}`}
              />
              <span className="truncate font-mono">{host.domain_names.join(', ')}</span>
              {host.certificate_id ? (
                <Lock className="size-3 shrink-0 text-success" />
              ) : (
                <span className="shrink-0 text-muted-foreground/60">no certificate</span>
              )}
            </p>

            {/*
              Only when it is both possible and missing. A host created since http2_support became the
              default never shows this, which is the point — it is a repair, not a setting.
            */}
            {host.certificate_id > 0 && !host.http2_support && (
              <Button variant="outline" size="sm" onClick={() => void upgrade(host)} disabled={busy !== null}>
                {busy === `http2:${host.id}` ? (
                  <Loader2 className="size-3.5 animate-spin" />
                ) : (
                  <Gauge className="size-3.5" />
                )}
                {busy === `http2:${host.id}` ? 'Enabling…' : 'Enable HTTP/2'}
              </Button>
            )}

            {!host.certificate_id && (
              <Button variant="outline" size="sm" onClick={() => void secure(host)} disabled={busy !== null}>
                {busy === `cert:${host.id}` ? (
                  <Loader2 className="size-3.5 animate-spin" />
                ) : (
                  <ShieldCheck className="size-3.5" />
                )}
                {busy === `cert:${host.id}` ? 'Issuing…' : 'Add certificate'}
              </Button>
            )}
          </div>
        ))}

        {/*
          Only while there is nothing here.

          A server with a domain has been set up, and the field asking for another is a form offering
          work nobody came to do — the second address for one site is the rare case, and it lives in
          Proxy Manager with the rest of the picture.

          `min-w-0` on the input: without it a flex child refuses to shrink below its content, and the
          button beside it gets pushed off the edge of the card.
        */}
        {mine.length === 0 && (
          <div className="flex gap-2">
            <Input
              value={domains[server.name] ?? ''}
              onChange={(event) => setDomains((current) => ({ ...current, [server.name]: event.target.value }))}
              placeholder={server.name === 'production' ? 'www.example.com' : 'dev.example.com'}
              className="min-w-0 flex-1 font-mono text-xs"
              autoComplete="off"
              spellCheck={false}
            />
            <Button
              variant="outline"
              size="sm"
              className="w-28 shrink-0 justify-center"
              onClick={() => void create(server)}
              disabled={busy !== null || !server.port || !forwardHost.trim() || !(domains[server.name] ?? '').trim()}
              title={server.port ? undefined : 'Set a port for this server first'}
            >
              {busy === `${server.name}:create` ? (
                <Loader2 className="size-3.5 animate-spin" />
              ) : (
                <Plus className="size-3.5" />
              )}
              Point here
            </Button>
          </div>
        )}
      </div>
    );
  };

  // Nothing left to point anywhere: every server already has a domain.
  // Development only: production's target is a container name, not the gateway address this field holds.
  const anythingToCreate = servers.some(
    (server) => server.name === 'development' && !(hosts ?? []).some((host) => host.forward_port === server.port),
  );

  return (
    <Block icon={Globe} title="Domains" hint="Which addresses reach the site, through Nginx Proxy Manager.">
      {!hosts ? null : (
        <>
          {servers.map(row)}

          <Console output={output} failed={failed} />

          {/* Shown while it is still needed, because it is a guess made from other people's configuration
              and NPM being in a container is exactly why `127.0.0.1` would fail in a way that looks like
              the site is down. Once both servers have a domain it configures nothing, so it goes. */}
          {anythingToCreate && (
          <div className="flex items-center gap-2 border-t border-border pt-3">
            <span className="text-xs text-muted-foreground/70">NPM reaches this machine at</span>
            <Input
              value={forwardHost}
              onChange={(event) => setForwardHost(event.target.value)}
              className="w-40 font-mono text-xs"
              autoComplete="off"
              spellCheck={false}
            />
          </div>
          )}

          <p className="text-xs text-muted-foreground/60">
            Certificates are proved over DNS with the key Officer holds for the domain, so a name works
            before it points here — and takes a few minutes. Removing or repointing a domain lives in
            Proxy Manager, where the whole picture is.
          </p>
        </>
      )}
    </Block>
  );
};