import type { XYPosition } from "@xyflow/react";

/**
 * Each bounding box is a collection of X/Y points in a graph, and we
 * need to convert them to "occupied" cells in a 2D grid representation.
 *
 * The top most position of the grid (grid[0][0]) needs to be equivalent
 * to the top most point in the graph (the graph.topLeft point).
 *
 * Since the top most point can have X/Y values different than zero,
 * and each cell in a grid represents a 10x10 pixel area in the grid (or a
 * gridRatio area), there's need to be a conversion between a point in a graph
 * to a point in the grid.
 *
 * We do this conversion by dividing a graph point X/Y values by the grid ratio,
 * and "shifting" their values up or down, depending on the values of the top
 * most point in the graph. The top most point in the graph will have the
 * smallest values for X and Y.
 *
 * We avoid setting nodes in the border of the grid (x=0 or y=0), so there's
 * always a "walkable" area around the grid.
 */
export const graphToGridPoint = (
  graphPoint: XYPosition,
  smallestX: number,
  smallestY: number,
  gridRatio: number,
): XYPosition => {
  // Affine transform: translate by top-left, scale by grid size, then offset border (1 cell)
  const posX = (graphPoint.x - smallestX) / gridRatio + 1;
  const posY = (graphPoint.y - smallestY) / gridRatio + 1;
  return { x: posX, y: posY };
};

/**
 * Converts a grid point back to a graph point, using the reverse logic of
 * graphToGridPoint.
 */
export const gridToGraphPoint = (
  gridPoint: XYPosition,
  smallestX: number,
  smallestY: number,
  gridRatio: number,
): XYPosition => {
  // Inverse affine transform: remove border, scale by grid size, then translate by top-left
  const posX = (gridPoint.x - 1) * gridRatio + smallestX;
  const posY = (gridPoint.y - 1) * gridRatio + smallestY;
  return { x: posX, y: posY };
};