const vec2 = require('../vec2')
const direction = require('./direction')
const origin = require('./origin')
/**
* Determine the closest point on the given line to the given point.
*
* @param {line2} line - line of reference
* @param {vec2} point - point of reference
* @returns {vec2} closest point
* @alias module:modeling/maths/line2.closestPoint
*/
const closestPoint = (line, point) => {
// linear function of AB
const a = origin(line)
const b = direction(line)
const m1 = (b[1] - a[1]) / (b[0] - a[0])
const t1 = a[1] - m1 * a[0]
// linear function of PC
const m2 = -1 / m1 // perpendicular
const t2 = point[1] - m2 * point[0]
// c.x * m1 + t1 === c.x * m2 + t2
const x = (t2 - t1) / (m1 - m2)
const y = m1 * x + t1
const closest = vec2.fromValues(x, y)
return closest
}
module.exports = closestPoint