import {
  Point,
  Vector2,
} from '../anvil'

export class Geo2Util {

  // linear
  // negative  = \
  // positive  = /
  // 0         = horizontal
  // undefined = vertical
  public static getSlopeOfLine(ls: Point, le: Point): boolean | number {
    if (le.x === ls.x) {
      return false
    } else {
      let rise: number = le.y - ls.y
      let run: number = le.x - ls.x
      return rise / run
    }
  }

  public static checkIfTwoLineSegmentsAreParallel(ls1: Point, le1: Point, ls2: Point, le2: Point): boolean {
    let s1 = Geo2Util.getSlopeOfLine(ls1, le1)
    let s2 = Geo2Util.getSlopeOfLine(ls2, le2)
    return s1 === s2 ? true : false
  }

  // Two lines will always intersect unless they are parallel.
  // Check if two line segments intersect each other
  public static checkIfTwoLineSegmentsIntersect(ls1: Point, le1: Point, ls2: Point, le2: Point): boolean {
    let pi = Geo2Util.getPointOfIntersectionBetweenTwoLineSegments(ls1, le1, ls2, le2)
    if (pi === false) {
      return false
    }
    pi = <Vector2>pi
    if (
      pi.x > Math.max(ls1.x, le1.x) ||
      pi.x < Math.min(ls1.x, le1.x) ||
      pi.x > Math.max(ls2.x, le2.x) ||
      pi.x < Math.min(ls2.x, le2.x) ||
      pi.y > Math.max(ls1.y, le1.y) ||
      pi.y < Math.min(ls1.y, le1.y) ||
      pi.y > Math.max(ls2.y, le2.y) ||
      pi.y < Math.min(ls2.y, le2.y)
    ) {
      return false
    } else {
      return true
    }
  }

  public static getPointOfIntersectionBetweenTwoLineSegments(ls1: Point, le1: Point, ls2: Point, le2: Point): boolean | Vector2 {
    if (Geo2Util.checkIfTwoLineSegmentsAreParallel(ls1, le1, ls2, le2) === true) {
      return false
    }
    let ix: number = 0
    let iy: number = 0
    // Get slope.
    let m1 = Geo2Util.getSlopeOfLine(ls1, le1)
    let m2 = Geo2Util.getSlopeOfLine(ls2, le2)
    let yi1: number
    let yi2: number
    if (
      m1 === false &&
      typeof m2 === 'number'
    ) {
      ix = ls1.x
      yi2 = -1 * m2 * ls2.x + ls2.y
      iy = m2 * ix + yi2
    } else if (
      m2 === false &&
      typeof m1 === 'number'
    ) {
      ix = ls2.x
      yi1 = -1 * m1 * ls1.x + ls1.y
      iy = m1 * ix + yi1
    } else if (
      typeof m1 === 'number' &&
      typeof m2 === 'number'
    ) {
      // Get y-intercept
      // b = -m * x + y
      yi1 = -1 * m1 * ls1.x + ls1.y
      yi2 = -1 * m2 * ls2.x + ls2.y
      // Complete line equations
      ix = (yi1 - yi2) / (m2 - m1)
      iy = m1 * ix + yi1
    }
    return new Vector2(ix, iy)
  }

}