import * as React from "react"

import { useOverlayScope, useOverlayScopes } from "./scope-context"
import type { OverlayScope } from "./scope"

/** A router-owned navigation attempt that is currently blocked. */
export interface OverlayNavigationAttempt {
  cancel: () => void
  /** Continues this exact attempt without notifying the adapter again. */
  proceed: () => void
}

/** Implement this bridge with a router's blocker API. */
export interface OverlayNavigationAdapter {
  subscribe: (
    listener: (attempt: OverlayNavigationAttempt) => void
  ) => VoidFunction
}

export interface OverlayNavigationContext {
  attempt: OverlayNavigationAttempt
  scopes: readonly OverlayScope[]
}

export type OverlayNavigationInterceptor = (
  context: OverlayNavigationContext
) => void

export const dismissOverlayNavigationInterceptor: OverlayNavigationInterceptor =
  ({ attempt, scopes }) => {
    let topmostScope: OverlayScope | undefined
    let topmostOrder = -1

    for (const scope of scopes) {
      const order = scope.getTopmostLayer()?.order ?? -1
      if (order > topmostOrder) {
        topmostScope = scope
        topmostOrder = order
      }
    }

    if (topmostScope?.interceptNavigation()) attempt.cancel()
    else attempt.proceed()
  }

export interface OverlayNavigationGuardProps {
  adapter: OverlayNavigationAdapter
  interceptor?: OverlayNavigationInterceptor
  scope?: OverlayScope
  scopes?: readonly OverlayScope[]
}

export function OverlayNavigationGuard({
  adapter,
  interceptor = dismissOverlayNavigationInterceptor,
  scope,
  scopes,
}: OverlayNavigationGuardProps) {
  const contextualScope = useOverlayScope()
  const namedScopes = useOverlayScopes()
  const resolvedScopes = React.useMemo(
    () =>
      Array.from(
        new Set(
          scopes ?? [scope ?? contextualScope, ...Object.values(namedScopes)]
        )
      ),
    [contextualScope, namedScopes, scope, scopes]
  )

  React.useEffect(
    () =>
      adapter.subscribe((attempt) => {
        interceptor({ attempt, scopes: resolvedScopes })
      }),
    [adapter, interceptor, resolvedScopes]
  )

  return null
}