source: node_modules/immer/src/core/scope.ts

import {
        Patch,
        PatchListener,
        Drafted,
        Immer,
        DRAFT_STATE,
        ImmerState,
        ArchType,
        getPlugin
} from "../internal"

/** Each scope represents a `produce` call. */

export interface ImmerScope {
        patches_?: Patch[]
        inversePatches_?: Patch[]
        canAutoFreeze_: boolean
        drafts_: any[]
        parent_?: ImmerScope
        patchListener_?: PatchListener
        immer_: Immer
        unfinalizedDrafts_: number
}

let currentScope: ImmerScope | undefined

export function getCurrentScope() {
        return currentScope!
}

function createScope(
        parent_: ImmerScope | undefined,
        immer_: Immer
): ImmerScope {
        return {
                drafts_: [],
                parent_,
                immer_,
                // Whenever the modified draft contains a draft from another scope, we
                // need to prevent auto-freezing so the unowned draft can be finalized.
                canAutoFreeze_: true,
                unfinalizedDrafts_: 0
        }
}

export function usePatchesInScope(
        scope: ImmerScope,
        patchListener?: PatchListener
) {
        if (patchListener) {
                getPlugin("Patches") // assert we have the plugin
                scope.patches_ = []
                scope.inversePatches_ = []
                scope.patchListener_ = patchListener
        }
}

export function revokeScope(scope: ImmerScope) {
        leaveScope(scope)
        scope.drafts_.forEach(revokeDraft)
        // @ts-ignore
        scope.drafts_ = null
}

export function leaveScope(scope: ImmerScope) {
        if (scope === currentScope) {
                currentScope = scope.parent_
        }
}

export function enterScope(immer: Immer) {
        return (currentScope = createScope(currentScope, immer))
}

function revokeDraft(draft: Drafted) {
        const state: ImmerState = draft[DRAFT_STATE]
        if (state.type_ === ArchType.Object || state.type_ === ArchType.Array)
                state.revoke_()
        else state.revoked_ = true
}