import { useEffect, useState } from 'react';
import { Columns2, Loader2, Square } from 'lucide-react';
import { Button } from '@/components/ui/button';
import { Input } from '@/components/ui/input';
import { Dialog, DialogContent, DialogFooter, DialogHeader, DialogTitle } from '@/components/ui/dialog';

export type SectionLayout = 'one' | 'two';

/**
 * The layouts, drawn rather than named.
 *
 * "One column" and "Two columns" are words for a shape, and a shape is faster to recognise than to
 * read. The words stay underneath for anybody the picture does not reach.
 *
 * This list and the site's own are two copies of the same fact — the database has it as a check
 * constraint and PageSection.tsx has it as a branch. A layout offered here that the site cannot draw
 * would render as nothing, so adding one means all three.
 */
const LAYOUTS: { value: SectionLayout; label: string; Icon: typeof Square; columns: number }[] = [
  { value: 'one', label: 'One column', Icon: Square, columns: 1 },
  { value: 'two', label: 'Two columns', Icon: Columns2, columns: 2 },
];

/**
 * Naming a section and choosing its shape, before it exists.
 *
 * ── Why a name is asked for and not generated ──
 *
 * The name is never rendered on the site. It exists so a page of eight bands is navigable, and
 * "Section 4" tells nobody anything — which is precisely the state a generated name would leave every
 * page in. Asked once, at the only moment somebody knows what they are about to build.
 */
export const AddSectionDialog = ({
  open,
  busy,
  onCancel,
  onCreate,
}: {
  open: boolean;
  busy: boolean;
  onCancel: () => void;
  onCreate: (values: { name: string; layout: SectionLayout }) => void;
}) => {
  const [name, setName] = useState('');
  const [layout, setLayout] = useState<SectionLayout>('one');

  // Fresh every time it opens. A dialog that remembers the last thing somebody typed and abandoned is
  // a dialog that quietly suggests they meant it.
  useEffect(() => {
    if (open) {
      setName('');
      setLayout('one');
    }
  }, [open]);

  const create = () => {
    const trimmed = name.trim();
    if (!trimmed || busy) return;
    onCreate({ name: trimmed, layout });
  };

  return (
    <Dialog open={open} onOpenChange={(next) => !next && onCancel()}>
      <DialogContent className="sm:max-w-md">
        <DialogHeader>
          <DialogTitle>Add a section</DialogTitle>
        </DialogHeader>

        <div className="flex flex-col gap-4">
          <div className="flex flex-col gap-1.5">
            <label className="text-xs text-muted-foreground">Section name</label>
            <Input
              autoFocus
              value={name}
              placeholder="Intro"
              onChange={(event) => setName(event.currentTarget.value)}
              // Enter creates, because a two-field form is one somebody expects to finish from the
              // keyboard. Guarded by the same check the button uses.
              onKeyDown={(event) => event.key === 'Enter' && create()}
            />
            <span className="text-[10px] text-muted-foreground">
              For you, not for the site. It never appears on the page.
            </span>
          </div>

          <div className="flex flex-col gap-1.5">
            <label className="text-xs text-muted-foreground">Layout</label>
            <div className="grid grid-cols-2 gap-2">
              {LAYOUTS.map(({ value, label, Icon, columns }) => (
                <button
                  key={value}
                  type="button"
                  onClick={() => setLayout(value)}
                  className={`flex flex-col items-center gap-2 rounded-lg border p-4 transition-colors ${
                    layout === value ? 'border-primary bg-muted' : 'border-border hover:bg-muted/50'
                  }`}
                >
                  <Icon className="size-6 text-muted-foreground" />
                  <span className="text-xs">{label}</span>
                  <span className="sr-only">{columns} column preview</span>
                </button>
              ))}
            </div>
          </div>
        </div>

        <DialogFooter>
          <Button variant="ghost" onClick={onCancel} disabled={busy}>
            Cancel
          </Button>
          {/* Dead without a name. The server refuses an empty one, and a button that fires a request
              only to show an error is a slower way of saying what the button could have said. */}
          <Button onClick={create} disabled={!name.trim() || busy}>
            {busy && <Loader2 className="size-3.5 animate-spin" />}
            Create section
          </Button>
        </DialogFooter>
      </DialogContent>
    </Dialog>
  );
};