export interface GeoJsonBounds {
  minX: number
  minY: number
  maxX: number
  maxY: number
}

function extendBounds(bounds: GeoJsonBounds | null, x: number, y: number): GeoJsonBounds {
  if (!bounds) {
    return { minX: x, minY: y, maxX: x, maxY: y }
  }
  bounds.minX = Math.min(bounds.minX, x)
  bounds.minY = Math.min(bounds.minY, y)
  bounds.maxX = Math.max(bounds.maxX, x)
  bounds.maxY = Math.max(bounds.maxY, y)
  return bounds
}

function scanCoordinates(coordinates: unknown, initial: GeoJsonBounds | null): GeoJsonBounds | null {
  let bounds = initial
  const stack: unknown[] = [coordinates]
  while (stack.length > 0) {
    const value = stack.pop()
    if (!Array.isArray(value)) {
      continue
    }
    if (value.length >= 2 && typeof value[0] === 'number' && typeof value[1] === 'number') {
      if (Number.isFinite(value[0]) && Number.isFinite(value[1])) {
        bounds = extendBounds(bounds, value[0], value[1])
      }
      continue
    }
    for (const child of value) {
      stack.push(child)
    }
  }
  return bounds
}

export function geometryBounds(geometry: GeoJSON.Geometry | null | undefined): GeoJsonBounds | null {
  if (!geometry) {
    return null
  }
  if (geometry.type === 'GeometryCollection') {
    return geometry.geometries.reduce<GeoJsonBounds | null>(
      (bounds, child) => mergeBounds(bounds, geometryBounds(child)),
      null,
    )
  }
  return scanCoordinates(geometry.coordinates, null)
}

export function mergeBounds(left: GeoJsonBounds | null, right: GeoJsonBounds | null): GeoJsonBounds | null {
  if (!left) {
    return right ? { ...right } : null
  }
  if (!right) {
    return left
  }
  left.minX = Math.min(left.minX, right.minX)
  left.minY = Math.min(left.minY, right.minY)
  left.maxX = Math.max(left.maxX, right.maxX)
  left.maxY = Math.max(left.maxY, right.maxY)
  return left
}

export function featureCollectionBounds(collection: GeoJSON.FeatureCollection | null | undefined): GeoJsonBounds | null {
  if (!collection) {
    return null
  }
  return collection.features.reduce<GeoJsonBounds | null>(
    (bounds, feature) => mergeBounds(bounds, geometryBounds(feature.geometry)),
    null,
  )
}