import Projection from './projection.js'

/**
 * This is a projection file, that grants access to the
 * MERCATOR projection.
 *
 * Regulary only few Projections will be used in one
 * project, therefore only required one's should be
 * loaded.
 */

export default class Mercator extends Projection {
    forward(coords) {
        let lat = coords.x
        let lng = coords.y

        const PI_180 = Math.PI / 180.0
        const PI_4 = Math.PI * 4

        const sinLatitude = Math.sin(lat * PI_180)
        let y = 0.5 - Math.log((1 + sinLatitude) / (1 - sinLatitude)) / PI_4
        let x = (lng + 180) / 360

        y = y < 0 ? 0 : y > 1 ? 1 : y

        return new PIXI.Point(x, y)
    }

    backward(point) {
        let lng = point.x * 360 - 180
        let lat = (Math.asin(-2 / (Math.exp(4 * Math.PI * (0.5 - point.y)) + 1) + 1) * 180) / Math.PI

        return new PIXI.Point(lat, lng)
    }

    toString() {
        return 'Mercator Projection'
    }

    get maxViewport() {
        return { min: new PIXI.Point(-85, -180), max: new PIXI.Point(85, 180) }
    }
}