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import type { Constructor, TypedArrayConstructors } from "./utility-types.ts";
/** * Creates a SymmetricGrid class extending a given Array-like class. */export function SymmetricGridMixin<  ItemType = number,  U extends Constructor<Array<ItemType>> | TypedArrayConstructors = Constructor<    Array<ItemType>  >,>(Base: U) {  /**   * Implements a grid to handle symmetric or triangular matrices using half the space required for a normal grid.   */  return class SymmetricGrid extends Base {    [key: number]: ItemType
    size = 0;
    static get [Symbol.species]() {      return Base;    }
    /**     * Number of columns in the grid.     */    get columns() {      return this.size;    }
    /**     * Specifies the number of columns of the grid.     */    set columns(columns) {      this.size = columns;    }
    /**     * Number of rows in the grid.     */    get rows() {      return this.size;    }
    /**     * Creates a grid of specified dimensions.     *     * @param rows the amount of rows     * @param columns the amount of columns     * @return a new grid     */    static create<T extends typeof SymmetricGrid>(      this: T,      columns: number,    ): InstanceType<T> {      const length = this.getLength(columns);      const grid = new this(length);      grid.size = columns;      return grid as InstanceType<T>;    }
    /**     * Creates a grid from an array of arrays.     *     * @param arrays the array of arrays     * @return a new grid     */    static fromArrays<T extends typeof SymmetricGrid>(      this: T,      arrays: Array<Array<ItemType>>,    ): InstanceType<T> {      const rows = arrays.length;      const grid = this.create(rows);      let k = 0;      for (let i = 0; i < rows; i++) {        for (let j = 0; j <= i; j++) {          grid[k] = arrays[i][j];          k++;        }      }      return grid;    }
    /**     * Returns the length of the underlying Array required to hold the grid of specified dimensions.     *     * @param rows the amount of rows     * @param columns the amount of columns     * @return the required length     */    static getLength(rows: number): number {      return ((rows + 1) * rows) >> 1;    }
    getCoordinates(index: number): [row: number, column: number] {      const row = (Math.sqrt((index << 3) + 1) - 1) >> 1;      const column = index - ((row * (row + 1)) >> 1);      return [row, column];    }
    /**     * Returns the index of an element at given coordinates.     *     * @param rows the row index     * @param columns the column index     * @return the element index     */    getIndex(row: number, column: number): number {      const [x, y] = row >= column ? [column, row] : [row, column];      return x + (((y + 1) * y) >> 1);    }
    /**     * Returns the element at given coordinates.     *     * @param rows the row index     * @param columns the column index     * @return the element     */    getValue(row: number, column: number): ItemType {      return this[this.getIndex(row, column)];    }
    /**     * Sets the element at given coordinates.     *     * @param rows the row index     * @param columns the column index     * @param value the element     * @return the grid     */    setValue(row: number, column: number, value: ItemType): this {      this[this.getIndex(row, column)] = value;      return this;    }
    /**     * Creates an array of arrays representing rows of the grid.     *     * @return an array of arrays     */    toArrays(): Array<Array<ItemType>> {      const { rows } = this;      const arrays: Array<Array<ItemType>> = new Array(rows)        .fill(0)        .map(() => []);      let k = 0;      for (let i = 0; i < rows; i++) {        for (let j = 0; j <= i; j++) {          arrays[i][j] = this[k];          arrays[j][i] = this[k];          k++;        }      }      return arrays;    }  };}