import { useCallback, useEffect, useRef, useState } from 'react';
import { Check, Loader2, Pencil } 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 { DirectoryPicker } from './DirectoryPicker';

/**
 * Where the fofos site is on this machine.
 *
 * ── The default is a suggestion until it is saved ──
 *
 * An unset root reports `<owner home>/fofos` and says so. It is not written to the database by being
 * looked at — a value somebody has never agreed to must not become one they appear to have chosen, and
 * a default that follows the machine is more useful than one frozen on install day.
 *
 * ── Typing and picking are the same field ──
 *
 * The picker fills the field; the field is what saves. So there is one value on screen and one Save,
 * and picking a folder never commits anything by itself — the path is visible and editable before it
 * is stored. It also means a location OUTSIDE the owner's home can still be typed, which the picker
 * cannot reach.
 *
 * ── Two states, and the actions are on their own row ──
 *
 * Reading, it is a path and one Edit. Editing, it is a field and the things you can do to it. The
 * actions sit on the block's BOTTOM row rather than beside the value, so the path gets the full width
 * — it is long, absolute and the thing somebody came here to read, and it was being truncated to make
 * room for buttons that are not needed most of the time.
 *
 * Edit is a mode rather than an always-live field because this is a setting that is looked at far more
 * often than it is changed, and a live input invites a stray keystroke into a path that everything
 * else depends on.
 */

type Settings = { rootPath: string; isSet: boolean };

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

  const [saved, setSaved] = useState<Settings | null>(null);
  const [value, setValue] = useState('');
  const [editing, setEditing] = useState(false);
  const [picking, setPicking] = useState(false);
  const [busy, setBusy] = useState(false);
  const [error, setError] = useState<string | null>(null);
  const [forbidden, setForbidden] = useState(false);

  const load = useCallback(async () => {
    try {
      const current = await clientRef.current.get<Settings>('/fofos-admin/_config/root');
      setSaved(current);
      setValue(current.rootPath);
    } catch (failure) {
      // A member looking at an owner-only setting is not a fault and needs a different sentence.
      if ((failure as { status?: number })?.status === 403) setForbidden(true);
      else setError(readableError(failure));
    }
  }, []);

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

  const save = async () => {
    setBusy(true);
    setError(null);
    try {
      const result = await clientRef.current.put<Settings>('/fofos-admin/_config/root', { path: value });
      setSaved(result);
      // From the server, not from what was typed — `~` is expanded and trailing slashes go, so the
      // field must show what was actually stored rather than what was sent.
      setValue(result.rootPath);
      setEditing(false);
      setPicking(false);
    } catch (failure) {
      setError(readableError(failure));
    } finally {
      setBusy(false);
    }
  };

  if (forbidden) {
    return <p className="text-xs text-muted-foreground">Only the owner can change where the site lives.</p>;
  }

  if (!saved) {
    return <p className="text-xs text-muted-foreground">Loading…</p>;
  }

  const dirty = value.trim() !== saved.rootPath;

  const stopEditing = () => {
    // Back to what is stored, so leaving the mode cannot leave a half-typed path on screen looking
    // like the setting.
    setValue(saved.rootPath);
    setEditing(false);
    setPicking(false);
    setError(null);
  };

  return (
    <div className="flex flex-col gap-3">
      {editing ? (
        <Input
          autoFocus
          value={value}
          onChange={(event) => setValue(event.target.value)}
          placeholder="/home/you/fofos"
          className="w-full font-mono text-xs"
          autoComplete="off"
          spellCheck={false}
        />
      ) : (
        // `break-all`, not `truncate`. An absolute path is read from BOTH ends — the machine at the
        // front and the folder at the back — so hiding either one is worse than wrapping.
        <p className="rounded-md border border-border bg-muted/30 px-3 py-2 font-mono text-xs break-all">
          {saved.rootPath}
        </p>
      )}

      {editing && picking && (
        <DirectoryPicker
          onCancel={() => setPicking(false)}
          onPick={(absolutePath) => {
            setValue(absolutePath);
            setPicking(false);
          }}
        />
      )}

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

      {/* Says which of the two states this is in. "Not set" reading identically to "set to exactly the
          default" is how somebody comes to believe they configured something they did not. */}
      <p className="text-xs text-muted-foreground/80">
        {saved.isSet ? 'Saved.' : 'Not set yet — this is the default until you save it.'}
      </p>

      {/* The block's bottom row. Everything you can DO is here, on its own line, so the path above it
          gets the full width. */}
      <div className="flex flex-wrap items-center gap-2 border-t border-border pt-3">
        {editing ? (
          <>
            <Button variant="outline" size="sm" onClick={() => setPicking((open) => !open)}>
              {picking ? 'Close browser' : 'Browse'}
            </Button>
            <Button size="sm" onClick={() => void save()} disabled={busy || !dirty || !value.trim()}>
              {busy ? <Loader2 className="size-3.5 animate-spin" /> : <Check className="size-3.5" />}
              Save
            </Button>
            <Button variant="ghost" size="sm" onClick={stopEditing} disabled={busy}>
              Cancel
            </Button>
          </>
        ) : (
          <Button variant="outline" size="sm" onClick={() => setEditing(true)}>
            <Pencil className="size-3.5" />
            Edit
          </Button>
        )}
      </div>
    </div>
  );
};