import { box, sideLength } from './constants'
import type { Vec } from './types'

/** bilinearly interpolate between two points */
export function bilerp(p1: Vec<2>, p2: Vec<2>, t: number): Vec<2> {
  return [p1[0] + t * (p2[0] - p1[0]), p1[1] + t * (p2[1] - p1[1])]
}

/** reflect a path of points across the origin */
export function flip<T extends Vec<2>[]>(path: T) {
  return path.map(reflect) as T
}

/** calculate hexagon vertices around a given point */
export function hexagon(origin: Vec<2>): Vec<6, Vec<2>> {
  return [
    pivot(origin, -300, sideLength),
    pivot(origin, 0, sideLength),
    pivot(origin, -60, sideLength),
    pivot(origin, -120, sideLength),
    pivot(origin, -180, sideLength),
    pivot(origin, -240, sideLength),
  ]
}

/** pivot counter-clockwise around a point */
export function pivot(point: Vec<2>, deg: number, distance: number): Vec<2> {
  const rad = radians(deg)

  return [
    distance * Math.cos(rad) + point[0],
    distance * Math.sin(rad) + point[1],
  ]
}

/** convert degrees to radians */
export function radians(deg: number) {
  return deg * (Math.PI / 180)
}

/** reflect a point across the origin */
export function reflect(v: Vec<2>): Vec<2> {
  return [-v[0], -v[1]]
}

/** sum two vectors */
export function sum(v1: Vec<2>, v2: Vec<2>): Vec<2> {
  return [v1[0] + v2[0], v1[1] + v2[1]]
}

/** convert cartesian X value to SVG coordinate */
export function x(n: number) {
  return box / 2 + n
}

/** convert cartesian Y value to SVG coordinate */
export function y(n: number) {
  return box / 2 - n
}