'use client'

import { useEffect, useRef } from 'react'

/**
 * Closes an overlay when the user presses the browser/Android Back button,
 * without changing the visible URL.
 *
 * How it works
 * - On open: `history.pushState` (same path/search) so Back targets this overlay.
 * - On Back (`popstate`): call `onRequestClose` (do not `history.back` again).
 * - On programmatic close: `history.back()` once and ignore that `popstate`.
 * - Nested overlays share a module stack; Back always dismisses the topmost entry.
 * - When `allowClose` is false, Back is trapped by re-pushing the history entry.
 */

const HISTORY_STATE_KEY = 'consumerModalHistory'

interface HistoryBackEntry {
  id: number
  onBack: () => void
  canClose: () => boolean
}

let nextId = 1
const stack: HistoryBackEntry[] = []
let ignorePopCount = 0
let listenerAttached = false

function onPopState() {
  if (ignorePopCount > 0) {
    ignorePopCount -= 1

    return
  }

  const top = stack[stack.length - 1]

  if (!top) return

  if (!top.canClose()) {
    // Browser already consumed the entry — restore so the overlay keeps Back trapped.
    window.history.pushState({ [HISTORY_STATE_KEY]: top.id }, '')

    return
  }

  stack.pop()
  top.onBack()
}

function ensureListener() {
  if (listenerAttached || typeof window === 'undefined') return
  window.addEventListener('popstate', onPopState)
  listenerAttached = true
}

function register(entry: HistoryBackEntry) {
  ensureListener()
  stack.push(entry)
  window.history.pushState({ [HISTORY_STATE_KEY]: entry.id }, '')
}

function unregister(entry: HistoryBackEntry) {
  const idx = stack.indexOf(entry)

  if (idx === -1) {
    // Already removed by user Back
    return
  }

  // Parent closed while nested children still registered — drop this entry and above.
  const removeCount = stack.length - idx

  stack.splice(idx, removeCount)

  if (typeof window === 'undefined' || removeCount === 0) return

  ignorePopCount += removeCount
  for (let i = 0; i < removeCount; i += 1) {
    window.history.back()
  }
}

/** Clears module stack between tests (jsdom shares the page history). */
export function resetCloseOnHistoryBackForTests() {
  stack.length = 0
  ignorePopCount = 0
  nextId = 1
}

export interface UseCloseOnHistoryBackOptions {
  isOpen: boolean
  /** When false, no history entry is pushed. Default true. */
  enabled?: boolean
  /**
   * When false while open, Back does not close — the history entry is re-pushed.
   * Use for `!isDismissable` / busy submit states.
   */
  allowClose?: boolean
  onRequestClose: () => void
}

/**
 * Syncs overlay open state with the session history so Back dismisses the overlay.
 */
export function useCloseOnHistoryBack({ isOpen, enabled = true, allowClose = true, onRequestClose }: UseCloseOnHistoryBackOptions) {
  const onRequestCloseRef = useRef(onRequestClose)
  const allowCloseRef = useRef(allowClose)

  useEffect(() => {
    onRequestCloseRef.current = onRequestClose
    allowCloseRef.current = allowClose
  }, [allowClose, onRequestClose])

  useEffect(() => {
    if (!isOpen || !enabled || typeof window === 'undefined') return

    const entry: HistoryBackEntry = {
      id: nextId++,
      onBack: () => {
        onRequestCloseRef.current()
      },
      canClose: () => allowCloseRef.current,
    }

    register(entry)

    return () => {
      unregister(entry)
    }
  }, [enabled, isOpen])
}