declare module 'v8' {
    import { Readable } from 'stream';

    interface HeapSpaceInfo {
        space_name: string;
        space_size: number;
        space_used_size: number;
        space_available_size: number;
        physical_space_size: number;
    }

    // ** Signifies if the --zap_code_space option is enabled or not.  1 == enabled, 0 == disabled. */
    type DoesZapCodeSpaceFlag = 0 | 1;

    interface HeapInfo {
        total_heap_size: number;
        total_heap_size_executable: number;
        total_physical_size: number;
        total_available_size: number;
        used_heap_size: number;
        heap_size_limit: number;
        malloced_memory: number;
        peak_malloced_memory: number;
        does_zap_garbage: DoesZapCodeSpaceFlag;
        number_of_native_contexts: number;
        number_of_detached_contexts: number;
    }

    interface HeapCodeStatistics {
        code_and_metadata_size: number;
        bytecode_and_metadata_size: number;
        external_script_source_size: number;
    }

    /**
     * Returns an integer representing a "version tag" derived from the V8 version, command line flags and detected CPU features.
     * This is useful for determining whether a vm.Script cachedData buffer is compatible with this instance of V8.
     */
    function cachedDataVersionTag(): number;

    function getHeapStatistics(): HeapInfo;
    function getHeapSpaceStatistics(): HeapSpaceInfo[];
    function setFlagsFromString(flags: string): void;
    /**
     * Generates a snapshot of the current V8 heap and returns a Readable
     * Stream that may be used to read the JSON serialized representation.
     * This conversation was marked as resolved by joyeecheung
     * This JSON stream format is intended to be used with tools such as
     * Chrome DevTools. The JSON schema is undocumented and specific to the
     * V8 engine, and may change from one version of V8 to the next.
     */
    function getHeapSnapshot(): Readable;

    /**
     *
     * @param fileName The file path where the V8 heap snapshot is to be
     * saved. If not specified, a file name with the pattern
     * `'Heap-${yyyymmdd}-${hhmmss}-${pid}-${thread_id}.heapsnapshot'` will be
     * generated, where `{pid}` will be the PID of the Node.js process,
     * `{thread_id}` will be `0` when `writeHeapSnapshot()` is called from
     * the main Node.js thread or the id of a worker thread.
     */
    function writeHeapSnapshot(fileName?: string): string;

    function getHeapCodeStatistics(): HeapCodeStatistics;

    class Serializer {
        /**
         * Writes out a header, which includes the serialization format version.
         */
        writeHeader(): void;

        /**
         * Serializes a JavaScript value and adds the serialized representation to the internal buffer.
         * This throws an error if value cannot be serialized.
         */
        writeValue(val: any): boolean;

        /**
         * Returns the stored internal buffer.
         * This serializer should not be used once the buffer is released.
         * Calling this method results in undefined behavior if a previous write has failed.
         */
        releaseBuffer(): Buffer;

        /**
         * Marks an ArrayBuffer as having its contents transferred out of band.\
         * Pass the corresponding ArrayBuffer in the deserializing context to deserializer.transferArrayBuffer().
         */
        transferArrayBuffer(id: number, arrayBuffer: ArrayBuffer): void;

        /**
         * Write a raw 32-bit unsigned integer.
         */
        writeUint32(value: number): void;

        /**
         * Write a raw 64-bit unsigned integer, split into high and low 32-bit parts.
         */
        writeUint64(hi: number, lo: number): void;

        /**
         * Write a JS number value.
         */
        writeDouble(value: number): void;

        /**
         * Write raw bytes into the serializer’s internal buffer.
         * The deserializer will require a way to compute the length of the buffer.
         */
        writeRawBytes(buffer: NodeJS.TypedArray): void;
    }

    /**
     * A subclass of `Serializer` that serializes `TypedArray` (in particular `Buffer`) and `DataView` objects as host objects,
     * and only stores the part of their underlying `ArrayBuffers` that they are referring to.
     */
    class DefaultSerializer extends Serializer {
    }

    class Deserializer {
        constructor(data: NodeJS.TypedArray);
        /**
         * Reads and validates a header (including the format version).
         * May, for example, reject an invalid or unsupported wire format.
         * In that case, an Error is thrown.
         */
        readHeader(): boolean;

        /**
         * Deserializes a JavaScript value from the buffer and returns it.
         */
        readValue(): any;

        /**
         * Marks an ArrayBuffer as having its contents transferred out of band.
         * Pass the corresponding `ArrayBuffer` in the serializing context to serializer.transferArrayBuffer()
         * (or return the id from serializer._getSharedArrayBufferId() in the case of SharedArrayBuffers).
         */
        transferArrayBuffer(id: number, arrayBuffer: ArrayBuffer): void;

        /**
         * Reads the underlying wire format version.
         * Likely mostly to be useful to legacy code reading old wire format versions.
         * May not be called before .readHeader().
         */
        getWireFormatVersion(): number;

        /**
         * Read a raw 32-bit unsigned integer and return it.
         */
        readUint32(): number;

        /**
         * Read a raw 64-bit unsigned integer and return it as an array [hi, lo] with two 32-bit unsigned integer entries.
         */
        readUint64(): [number, number];

        /**
         * Read a JS number value.
         */
        readDouble(): number;

        /**
         * Read raw bytes from the deserializer’s internal buffer.
         * The length parameter must correspond to the length of the buffer that was passed to serializer.writeRawBytes().
         */
        readRawBytes(length: number): Buffer;
    }

    /**
     * A subclass of `Serializer` that serializes `TypedArray` (in particular `Buffer`) and `DataView` objects as host objects,
     * and only stores the part of their underlying `ArrayBuffers` that they are referring to.
     */
    class DefaultDeserializer extends Deserializer {
    }

    /**
     * Uses a `DefaultSerializer` to serialize value into a buffer.
     */
    function serialize(value: any): Buffer;

    /**
     * Uses a `DefaultDeserializer` with default options to read a JS value from a buffer.
     */
    function deserialize(data: NodeJS.TypedArray): any;

    /**
     * Begins writing coverage report based on the `NODE_V8_COVERAGE` env var.
     * Noop is the env var is not set.
     */
    function takeCoverage(): void;

    /**
     * Stops writing coverage report.
     */
    function stopCoverage(): void;
}
