import { useEffect, useRef, useState } from 'react';
import { Input } from '@/components/ui/input';

/**
 * A colour, chosen without leaving the panel.
 *
 * ── Why not `<input type="color">` ──
 *
 * It was one, and the browser's own picker is a window-level popup positioned by the browser. In a
 * panel near the right edge it opened off the side of the window and was simply unreachable — nothing
 * in CSS can move it, because it is not in the document.
 *
 * ── What replaces it ──
 *
 * Swatches and a hex field, in a panel anchored to the RIGHT of its trigger so it grows inward. Text
 * over a photograph is white or black almost every time; the field is there for the times it is not.
 *
 * Deliberately not a gradient area and a hue strip. That is what the native control already does well,
 * and rebuilding it badly to fix a positioning problem would be a worse control than the one being
 * replaced.
 */

/** Enough to cover a photograph, and short enough to read as choices rather than as a palette. */
const PRESETS = [
  '#ffffff',
  '#f5f5f5',
  '#cccccc',
  '#888888',
  '#333333',
  '#000000',
  '#f0c808',
  '#e05a3a',
];

export const ColorField = ({ value, onChange }: { value: string; onChange: (color: string) => void }) => {
  const [open, setOpen] = useState(false);
  const [draft, setDraft] = useState(value);
  const wrapper = useRef<HTMLDivElement | null>(null);

  // Follows the value when it changes elsewhere — a different block being selected, or a load.
  useEffect(() => setDraft(value), [value]);

  /*
    Close on a press anywhere else.

    `pointerdown` rather than `click`, so it closes on the way down and a press meant for something
    behind the panel does not land twice. Capture, because a control inside a panel below may stop
    propagation for its own reasons.
  */
  useEffect(() => {
    if (!open) return;
    const onDown = (event: PointerEvent) => {
      if (!wrapper.current?.contains(event.target as Node)) setOpen(false);
    };
    document.addEventListener('pointerdown', onDown, true);
    return () => document.removeEventListener('pointerdown', onDown, true);
  }, [open]);

  const commit = (next: string) => {
    const trimmed = next.trim();
    const full = /^#?[0-9a-fA-F]{6}$/.test(trimmed) ? `#${trimmed.replace('#', '')}`.toLowerCase() : null;
    if (full) onChange(full);
  };

  return (
    <div ref={wrapper} className="relative shrink-0">
      <button
        type="button"
        onClick={() => setOpen((was) => !was)}
        className="size-8 rounded border border-input p-0.5"
        title="Colour"
      >
        {/* The swatch is the whole control's state. A checkered backdrop is not needed — these are
            always opaque, because text with an alpha over a photograph is unreadable by definition. */}
        <span className="block size-full rounded-sm" style={{ backgroundColor: value }} />
      </button>

      {open && (
        <div className="absolute top-9 right-0 z-50 w-52 rounded-md border border-border bg-background p-2 shadow-lg">
          <div className="grid grid-cols-8 gap-1">
            {PRESETS.map((preset) => (
              <button
                key={preset}
                type="button"
                onClick={() => {
                  onChange(preset);
                  setOpen(false);
                }}
                className={`size-5 rounded border ${
                  value.toLowerCase() === preset ? 'border-primary ring-1 ring-primary' : 'border-border'
                }`}
                style={{ backgroundColor: preset }}
                title={preset}
              />
            ))}
          </div>

          <Input
            value={draft}
            onChange={(event) => setDraft(event.currentTarget.value)}
            onBlur={() => commit(draft)}
            onKeyDown={(event) => {
              if (event.key === 'Enter') {
                commit(draft);
                setOpen(false);
              }
            }}
            placeholder="#ffffff"
            className="mt-2 h-7 font-mono text-xs"
          />
        </div>
      )}
    </div>
  );
};