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import type { Range } from './internal.ts';
/** * A flexible range specification for numeric indices. * If a start or end is defined, a tuple can be used where the second item is a boolean * indicating whether that end is inclusive or exclusive.<br/> * An IndexRange can have one of the following forms:<br/> * <br/> * - { amount: number }<br/> * - { start: number }<br/> * - { start: number, amount: number }<br/> * - { start: number, end: number }<br/> * - { start: number, end: [number, boolean] }<br/> * - { start: [number, boolean] }<br/> * - { start: [number, boolean], amount: number }<br/> * - { start: [number, boolean], end: number }<br/> * - { start: [number, boolean], end: [number, boolean] }<br/> * - { end: number }<br/> * - { end: [number, boolean] }<br/> */export type IndexRange =  | { amount: number; start?: number | [number, boolean]; end?: undefined }  | Range<number>;
export namespace IndexRange {  /**   * Returns, given the `range` `IndexRange`, a normalized tuple containing the   * start index, and optionally an end index.   * @param range - the `IndexRange` to use   */  export function getIndexRangeIndices(    range: IndexRange  ): [number, number | undefined] {    if (undefined !== range.amount) {      if (undefined === range.start) return [0, range.amount - 1];
      if (Array.isArray(range.start)) {        const [start, includeStart] = range.start;        if (includeStart) return [start, start + range.amount - 1];        return [start + 1, start + 1 + range.amount - 1];      }      return [range.start, range.start + range.amount - 1];    }
    let start = 0;    let end: number | undefined = undefined;
    if (`start` in range) {      if (Array.isArray(range.start)) {        if (range.start[1]) start = range.start[0];        else start = range.start[0] + 1;      } else start = range.start ?? 0;    }
    if (`end` in range) {      if (Array.isArray(range.end)) {        if (range.end[1]) end = range.end[0];        else end = range.end[0] - 1;      } else end = range.end;    }
    return [start, end];  }
  /**   * Returns, given the `range` `IndexRange`, and a target maximum `length`, the actual index range.   * This can be one of three options:   * - 'empty': there are no elements within the range   * - 'all': all elements are within the range   * - [start: number, end: number]: an inclusive range of element indices within the given range   * @param range - the `IndexRange` to use   * @param length - the target maximum length   */  export function getIndicesFor(    range: IndexRange,    length: number  ): [number, number] | 'empty' | 'all' {    if (length <= 0) return 'empty';
    let start = 0;    let end = length - 1;
    if (undefined !== range.start) {      if (Array.isArray(range.start)) {        start = range.start[0];        if (!range.start[1]) start++;      } else start = range.start;
      if (start >= length || -start > length) return 'empty';      if (start < 0) start = length + start;    }
    if (undefined !== range.amount) {      if (range.amount <= 0) return 'empty';      if (undefined === range.start) {        if (range.amount >= length) return 'all';        return [0, Math.min(end, range.amount - 1)];      }
      end = start + range.amount - 1;    } else if (undefined !== range.end) {      if (Array.isArray(range.end)) {        end = range.end[0];        if (!range.end[1]) {          if (end === 0) return 'empty';          end--;        }      } else end = range.end;
      if (end < 0) end = length + end;    }
    if (end < start) return 'empty';    end = Math.min(length - 1, end);
    if (start === 0 && end === length - 1) return 'all';
    return [start, end];  }}