source: imaps-frontend/node_modules/@popperjs/core/lib/enums.js.flow

// @flow
export const top: 'top' = 'top';
export const bottom: 'bottom' = 'bottom';
export const right: 'right' = 'right';
export const left: 'left' = 'left';
export const auto: 'auto' = 'auto';
export type BasePlacement =
  | typeof top
  | typeof bottom
  | typeof right
  | typeof left;
export const basePlacements: Array<BasePlacement> = [top, bottom, right, left];

export const start: 'start' = 'start';
export const end: 'end' = 'end';
export type Variation = typeof start | typeof end;

export const clippingParents: 'clippingParents' = 'clippingParents';
export const viewport: 'viewport' = 'viewport';
export type Boundary = Element | Array<Element> | typeof clippingParents;
export type RootBoundary = typeof viewport | 'document';

export const popper: 'popper' = 'popper';
export const reference: 'reference' = 'reference';
export type Context = typeof popper | typeof reference;

export type VariationPlacement =
  | 'top-start'
  | 'top-end'
  | 'bottom-start'
  | 'bottom-end'
  | 'right-start'
  | 'right-end'
  | 'left-start'
  | 'left-end';
export type AutoPlacement = 'auto' | 'auto-start' | 'auto-end';
export type ComputedPlacement = VariationPlacement | BasePlacement;
export type Placement = AutoPlacement | BasePlacement | VariationPlacement;

export const variationPlacements: Array<VariationPlacement> = basePlacements.reduce(
  (acc: Array<VariationPlacement>, placement: BasePlacement) =>
    acc.concat([(`${placement}-${start}`: any), (`${placement}-${end}`: any)]),
  []
);
export const placements: Array<Placement> = [...basePlacements, auto].reduce(
  (
    acc: Array<Placement>,
    placement: BasePlacement | typeof auto
  ): Array<Placement> =>
    acc.concat([
      placement,
      (`${placement}-${start}`: any),
      (`${placement}-${end}`: any),
    ]),
  []
);

// modifiers that need to read the DOM
export const beforeRead: 'beforeRead' = 'beforeRead';
export const read: 'read' = 'read';
export const afterRead: 'afterRead' = 'afterRead';
// pure-logic modifiers
export const beforeMain: 'beforeMain' = 'beforeMain';
export const main: 'main' = 'main';
export const afterMain: 'afterMain' = 'afterMain';
// modifier with the purpose to write to the DOM (or write into a framework state)
export const beforeWrite: 'beforeWrite' = 'beforeWrite';
export const write: 'write' = 'write';
export const afterWrite: 'afterWrite' = 'afterWrite';
export const modifierPhases: Array<ModifierPhases> = [
  beforeRead,
  read,
  afterRead,
  beforeMain,
  main,
  afterMain,
  beforeWrite,
  write,
  afterWrite,
];

export type ModifierPhases =
  | typeof beforeRead
  | typeof read
  | typeof afterRead
  | typeof beforeMain
  | typeof main
  | typeof afterMain
  | typeof beforeWrite
  | typeof write
  | typeof afterWrite;