import * as Cesium from 'cesium'

// id generator
export function uid(prefix) {
  const p = prefix || 'id'
  return p + ':' + Date.now().toString(36) + '_' + Math.random().toString(36).slice(2, 7)
}

// angle helpers
export const toRad = Cesium.Math.toRadians

// color normalization
export function toCesiumColor(input, alpha) {
  const a = typeof alpha === 'number' ? alpha : 1
  if (!input) return Cesium.Color.WHITE.withAlpha(a)
  if (input instanceof Cesium.Color) return input.withAlpha(a)
  if (typeof input === 'string') return Cesium.Color.fromCssColorString(input).withAlpha(a)
  if (Array.isArray(input)) {
    const r = input[0] || 1,
      g = input[1] || 1,
      b = input[2] || 1,
      al = input[3] || a
    return new Cesium.Color(r, g, b, al)
  }
  return Cesium.Color.WHITE.withAlpha(a)
}

// coordinate conversions
export function degToCartesian(arr) {
  return Cesium.Cartesian3.fromDegrees(arr[0], arr[1], arr[2] || 0)
}
export function degsToCartesians(positions) {
  return (positions || []).map(degToCartesian)
}
export function cartesianToDegrees(cartesian) {
  const c = Cesium.Cartographic.fromCartesian(cartesian)
  return {
    lon: Cesium.Math.toDegrees(c.longitude),
    lat: Cesium.Math.toDegrees(c.latitude),
    height: c.height || 0,
  }
}

// simple zoom-height heuristic
const EARTH = 40075016.68557849
const TILE = 256
export function heightToZoom(height, lat) {
  const la = typeof lat === 'number' ? lat : 0
  const z = Math.log2((EARTH * Math.cos(toRad(la))) / (TILE * Math.max(height || 1, 1))) + 8
  return Math.max(0, z)
}
export function zoomToHeight(zoom, lat) {
  const la = typeof lat === 'number' ? lat : 0
  const h = (EARTH * Math.cos(toRad(la))) / (TILE * Math.pow(2, Math.max((zoom || 0) - 8, 0)))
  return Math.max(1, h)
}

export const DEFAULT_VECTOR_LAYER_ID = 'vector:default'