/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import type VirtualizedList from '../VirtualizedList'

import * as React from 'react'
import { useContext, useMemo } from 'react'

const __DEV__ = process.env.NODE_ENV !== 'production'

type ScrollMetrics = {
  contentLength: number
  dOffset: number
  dt: number
  offset: number
  timestamp: number
  velocity: number
  visibleLength: number
  zoomScale: number
}

type Context = Readonly<{
  cellKey: string | null
  getScrollMetrics: () => ScrollMetrics
  horizontal: boolean | null
  getOutermostParentListRef: () => React.ElementRef<typeof VirtualizedList>
  registerAsNestedChild: (params: {
    cellKey: string
    ref: React.ElementRef<typeof VirtualizedList>
  }) => void
  unregisterAsNestedChild: (params: {
    ref: React.ElementRef<typeof VirtualizedList>
  }) => void
}>

export const VirtualizedListContext = React.createContext<Context | null>(null)
if (__DEV__) {
  VirtualizedListContext.displayName = 'VirtualizedListContext'
}

/**
 * Resets the context. Intended for use by portal-like components (e.g. Modal).
 */
export function VirtualizedListContextResetter({
  children,
}: {
  children: React.ReactNode
}): React.ReactNode {
  return (
    <VirtualizedListContext.Provider value={null}>
      {children}
    </VirtualizedListContext.Provider>
  )
}

/**
 * Sets the context with memoization. Intended to be used by `VirtualizedList`.
 */
export function VirtualizedListContextProvider({
  children,
  value,
}: {
  children: React.ReactNode
  value: Context
}): React.ReactNode {
  // Avoid setting a newly created context object if the values are identical.
  const context = useMemo(
    () => ({
      cellKey: null,
      getScrollMetrics: value.getScrollMetrics,
      horizontal: value.horizontal,
      getOutermostParentListRef: value.getOutermostParentListRef,
      registerAsNestedChild: value.registerAsNestedChild,
      unregisterAsNestedChild: value.unregisterAsNestedChild,
    }),
    [
      value.getScrollMetrics,
      value.horizontal,
      value.getOutermostParentListRef,
      value.registerAsNestedChild,
      value.unregisterAsNestedChild,
    ]
  )
  return (
    <VirtualizedListContext.Provider value={context}>
      {children}
    </VirtualizedListContext.Provider>
  )
}

/**
 * Sets the `cellKey`. Intended to be used by `VirtualizedList` for each cell.
 */
export function VirtualizedListCellContextProvider({
  cellKey,
  children,
}: {
  cellKey: string
  children: React.ReactNode
}): React.ReactNode {
  // Avoid setting a newly created context object if the values are identical.
  const currContext = useContext(VirtualizedListContext)
  const context = useMemo(
    () => (currContext == null ? null : { ...currContext, cellKey }),
    [currContext, cellKey]
  )
  return (
    <VirtualizedListContext.Provider value={context}>
      {children}
    </VirtualizedListContext.Provider>
  )
}