import type { DirectiveResult } from 'lit/directive.js';
import { styleMap, type StyleMapDirective } from 'lit/directives/style-map.js';

import type { SelectionRect } from './doc-remote-selection.js';

export function selectionStyle(
  rect: SelectionRect,
  color: string
): DirectiveResult<typeof StyleMapDirective> {
  return styleMap({
    position: 'absolute',
    width: `${rect.width}px`,
    height: `${rect.height}px`,
    top: `${rect.top}px`,
    left: `${rect.left}px`,
    backgroundColor: color,
    pointerEvent: 'none',
    opacity: '20%',
    borderRadius: '3px',
  });
}

export function cursorStyle(
  rect: SelectionRect,
  color: string
): DirectiveResult<typeof StyleMapDirective> {
  return styleMap({
    position: 'absolute',
    width: `${rect.width}px`,
    height: `${rect.height}px`,
    top: `${rect.top}px`,
    left: `${rect.left}px`,
    backgroundColor: color,
    pointerEvent: 'none',
  });
}

function covers(rect1: SelectionRect, rect2: SelectionRect): boolean {
  return (
    rect1.left <= rect2.left &&
    rect1.top <= rect2.top &&
    rect1.left + rect1.width >= rect2.left + rect2.width &&
    rect1.top + rect1.height >= rect2.top + rect2.height
  );
}

function intersects(rect1: SelectionRect, rect2: SelectionRect): boolean {
  return (
    rect1.left <= rect2.left + rect2.width &&
    rect1.left + rect1.width >= rect2.left &&
    rect1.top <= rect2.top + rect2.height &&
    rect1.top + rect1.height >= rect2.top
  );
}

function merge(rect1: SelectionRect, rect2: SelectionRect): SelectionRect {
  const left = Math.min(rect1.left, rect2.left);
  const top = Math.min(rect1.top, rect2.top);
  const right = Math.max(rect1.left + rect1.width, rect2.left + rect2.width);
  const bottom = Math.max(rect1.top + rect1.height, rect2.top + rect2.height);

  return {
    left: left,
    top: top,
    width: right - left,
    height: bottom - top,
  };
}

export function filterCoveringRects(rects: SelectionRect[]): SelectionRect[] {
  let mergedRects: SelectionRect[] = [];
  let hasChanges: boolean;

  do {
    hasChanges = false;
    const newMergedRects: SelectionRect[] = [...mergedRects];

    for (const rect of rects) {
      let merged = false;

      for (let i = 0; i < newMergedRects.length; i++) {
        if (covers(newMergedRects[i], rect)) {
          merged = true;
          break;
        } else if (intersects(newMergedRects[i], rect)) {
          newMergedRects[i] = merge(newMergedRects[i], rect);
          merged = true;
          hasChanges = true;
          break;
        }
      }

      if (!merged) {
        newMergedRects.push(rect);
      }
    }

    if (!hasChanges) {
      for (let i = 0; i < newMergedRects.length; i++) {
        for (let j = i + 1; j < newMergedRects.length; j++) {
          if (intersects(newMergedRects[i], newMergedRects[j])) {
            newMergedRects[i] = merge(newMergedRects[i], newMergedRects[j]);
            newMergedRects.splice(j, 1);
            hasChanges = true;
            break;
          }
        }
      }
    }

    mergedRects = newMergedRects;
  } while (hasChanges);

  return mergedRects;
}