/**
 * Internal dependencies
 */

import { isFormatEqual } from './is-format-equal';

/** @typedef {import('./types').RichTextValue} RichTextValue */

/**
 * Efficiently updates all the formats from `start` (including) until `end`
 * (excluding) with the active formats. Mutates `value`.
 *
 * @param {Object}        $1         Named paramentes.
 * @param {RichTextValue} $1.value   Value te update.
 * @param {number}        $1.start   Index to update from.
 * @param {number}        $1.end     Index to update until.
 * @param {Array}         $1.formats Replacement formats.
 *
 * @return {RichTextValue} Mutated value.
 */
export function updateFormats({
  value,
  start,
  end,
  formats
}) {
  // Start and end may be switched in case of delete.
  const min = Math.min(start, end);
  const max = Math.max(start, end);
  const formatsBefore = value.formats[min - 1] || [];
  const formatsAfter = value.formats[max] || [];

  // First, fix the references. If any format right before or after are
  // equal, the replacement format should use the same reference.
  value.activeFormats = formats.map((format, index) => {
    if (formatsBefore[index]) {
      if (isFormatEqual(format, formatsBefore[index])) {
        return formatsBefore[index];
      }
    } else if (formatsAfter[index]) {
      if (isFormatEqual(format, formatsAfter[index])) {
        return formatsAfter[index];
      }
    }
    return format;
  });
  while (--end >= start) {
    if (value.activeFormats.length > 0) {
      value.formats[end] = value.activeFormats;
    } else {
      delete value.formats[end];
    }
  }
  return value;
}
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