/*
 * Copyright (c) 2023, Matthew Olsson <mattco@serenityos.org>
 * Copyright (c) 2025, Shannon Booth <shannon@serenityos.org>
 *
 * SPDX-License-Identifier: BSD-2-Clause
 */

#pragma once

#include <AK/Optional.h>
#include <AK/SinglyLinkedList.h>
#include <LibWeb/Bindings/PlatformObject.h>
#include <LibWeb/Streams/Algorithms.h>

namespace Web::Streams {

enum class ReaderType {
    Default,
    Byob,
    None,
};

// https://streams.spec.whatwg.org/#pull-into-descriptor
struct PullIntoDescriptor : public GC::Cell {
    GC_CELL(PullIntoDescriptor, GC::Cell);
    GC_DECLARE_ALLOCATOR(PullIntoDescriptor);

    // https://streams.spec.whatwg.org/#pull-into-descriptor-buffer
    // An ArrayBuffer
    GC::Ref<JS::ArrayBuffer> buffer;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-buffer-byte-length
    // A positive integer representing the initial byte length of buffer
    u64 buffer_byte_length;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-byte-offset
    // A nonnegative integer byte offset into the buffer where the underlying byte source will start writing
    u64 byte_offset;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-byte-length
    // A positive integer number of bytes which can be written into the buffer
    u64 byte_length;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-bytes-filled
    // A nonnegative integer number of bytes that have been written into the buffer so far
    u64 bytes_filled;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-minimum-fill
    // A positive integer representing the minimum number of bytes that must be written into the buffer before the associated read() request may be fulfilled. By default, this equals the element size.
    u64 minimum_fill;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-element-size
    // A positive integer representing the number of bytes that can be written into the buffer at a time, using views of the type described by the view constructor
    u64 element_size;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-view-constructor
    // A typed array constructor or %DataView%, which will be used for constructing a view with which to write into the buffer
    GC::Ref<JS::NativeFunction> view_constructor;

    // https://streams.spec.whatwg.org/#pull-into-descriptor-reader-type
    // Either "default" or "byob", indicating what type of readable stream reader initiated this request, or "none" if the initiating reader was released
    ReaderType reader_type;

protected:
    virtual void visit_edges(Cell::Visitor& visitor) override;

private:
    PullIntoDescriptor(GC::Ref<JS::ArrayBuffer> buffer, u64 buffer_byte_length, u64 byte_offset, u64 byte_length, u64 bytes_filled,
        u64 minimum_fill, u64 element_size, GC::Ref<JS::NativeFunction> view_constructor, ReaderType reader_type)
        : buffer(buffer)
        , buffer_byte_length(buffer_byte_length)
        , byte_offset(byte_offset)
        , byte_length(byte_length)
        , bytes_filled(bytes_filled)
        , minimum_fill(minimum_fill)
        , element_size(element_size)
        , view_constructor(view_constructor)
        , reader_type(reader_type)
    {
    }
};

// https://streams.spec.whatwg.org/#readable-byte-stream-queue-entry
struct ReadableByteStreamQueueEntry {
    // https://streams.spec.whatwg.org/#readable-byte-stream-queue-entry-buffer
    // An ArrayBuffer, which will be a transferred version of the one originally supplied by the underlying byte source
    GC::Ref<JS::ArrayBuffer> buffer;

    // https://streams.spec.whatwg.org/#readable-byte-stream-queue-entry-byte-offset
    // A nonnegative integer number giving the byte offset derived from the view originally supplied by the underlying byte source
    u64 byte_offset;

    // https://streams.spec.whatwg.org/#readable-byte-stream-queue-entry-byte-length
    // A nonnegative integer number giving the byte length derived from the view originally supplied by the underlying byte source
    u64 byte_length;
};

// https://streams.spec.whatwg.org/#readablebytestreamcontroller
class ReadableByteStreamController : public Bindings::PlatformObject {
    WEB_PLATFORM_OBJECT(ReadableByteStreamController, Bindings::PlatformObject);
    GC_DECLARE_ALLOCATOR(ReadableByteStreamController);

public:
    virtual ~ReadableByteStreamController() override = default;

    // IDL getter, returns current [[byobRequest]] (if any), and otherwise the [[byobRequest]] for the next pending pull into request
    GC::Ptr<ReadableStreamBYOBRequest> byob_request();

    void set_byob_request(GC::Ptr<ReadableStreamBYOBRequest> request) { m_byob_request = request; }

    // Raw [[byobRequest]] slot
    GC::Ptr<ReadableStreamBYOBRequest const> raw_byob_request() const { return m_byob_request; }
    GC::Ptr<ReadableStreamBYOBRequest> raw_byob_request() { return m_byob_request; }

    Optional<double> desired_size() const;
    WebIDL::ExceptionOr<void> close();
    void error(JS::Value error);
    WebIDL::ExceptionOr<void> enqueue(GC::Root<WebIDL::ArrayBufferView>&);

    Optional<u64> const& auto_allocate_chunk_size() { return m_auto_allocate_chunk_size; }
    void set_auto_allocate_chunk_size(Optional<u64> value) { m_auto_allocate_chunk_size = value; }

    GC::Ptr<CancelAlgorithm> cancel_algorithm() { return m_cancel_algorithm; }
    void set_cancel_algorithm(GC::Ptr<CancelAlgorithm> value) { m_cancel_algorithm = value; }

    bool close_requested() const { return m_close_requested; }
    void set_close_requested(bool value) { m_close_requested = value; }

    bool pull_again() const { return m_pull_again; }
    void set_pull_again(bool value) { m_pull_again = value; }

    GC::Ptr<PullAlgorithm> pull_algorithm() { return m_pull_algorithm; }
    void set_pull_algorithm(GC::Ptr<PullAlgorithm> value) { m_pull_algorithm = value; }

    bool pulling() const { return m_pulling; }
    void set_pulling(bool value) { m_pulling = value; }

    SinglyLinkedList<GC::Ref<PullIntoDescriptor>>& pending_pull_intos() { return m_pending_pull_intos; }
    SinglyLinkedList<GC::Ref<PullIntoDescriptor>> const& pending_pull_intos() const { return m_pending_pull_intos; }

    SinglyLinkedList<ReadableByteStreamQueueEntry>& queue() { return m_queue; }

    double queue_total_size() const { return m_queue_total_size; }
    void set_queue_total_size(double size) { m_queue_total_size = size; }

    bool started() const { return m_started; }
    void set_started(bool value) { m_started = value; }

    double strategy_hwm() const { return m_strategy_hwm; }
    void set_strategy_hwm(double value) { m_strategy_hwm = value; }

    GC::Ptr<ReadableStream const> stream() const { return m_stream; }
    GC::Ptr<ReadableStream> stream() { return m_stream; }
    void set_stream(GC::Ptr<ReadableStream> stream) { m_stream = stream; }

    GC::Ref<WebIDL::Promise> cancel_steps(JS::Value reason);
    void pull_steps(GC::Ref<ReadRequest>);
    void release_steps();

private:
    explicit ReadableByteStreamController(JS::Realm&);

    virtual void visit_edges(Cell::Visitor&) override;

    virtual void initialize(JS::Realm&) override;

    // https://streams.spec.whatwg.org/#readablebytestreamcontroller-autoallocatechunksize
    // A positive integer, when the automatic buffer allocation feature is enabled. In that case, this value specifies the size of buffer to allocate. It is undefined otherwise.
    Optional<u64> m_auto_allocate_chunk_size;

    // https://streams.spec.whatwg.org/#readablebytestreamcontroller-byobrequest
    // A ReadableStreamBYOBRequest instance representing the current BYOB pull request, or null if there are no pending requests
    GC::Ptr<ReadableStreamBYOBRequest> m_byob_request;

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-cancelalgorithm
    // A promise-returning algorithm, taking one argument (the cancel reason), which communicates a requested cancelation to the underlying source
    GC::Ptr<CancelAlgorithm> m_cancel_algorithm;

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-closerequested
    // A boolean flag indicating whether the stream has been closed by its underlying source, but still has chunks in its internal queue that have not yet been read
    bool m_close_requested { false };

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-pullagain
    // A boolean flag set to true if the stream’s mechanisms requested a call to the underlying source's pull algorithm to pull more data, but the pull could not yet be done since a previous call is still executing
    bool m_pull_again { false };

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-pullalgorithm
    // A promise-returning algorithm that pulls data from the underlying source
    GC::Ptr<PullAlgorithm> m_pull_algorithm;

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-pulling
    // A boolean flag set to true while the underlying source's pull algorithm is executing and the returned promise has not yet fulfilled, used to prevent reentrant calls
    bool m_pulling { false };

    // https://streams.spec.whatwg.org/#readablebytestreamcontroller-pendingpullintos
    // A list of pull-into descriptors
    SinglyLinkedList<GC::Ref<PullIntoDescriptor>> m_pending_pull_intos;

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-queue
    // A list representing the stream’s internal queue of chunks
    SinglyLinkedList<ReadableByteStreamQueueEntry> m_queue;

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-queuetotalsize
    // The total size of all the chunks stored in [[queue]]
    double m_queue_total_size { 0 };

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-started
    // A boolean flag indicating whether the underlying source has finished starting
    bool m_started { false };

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-strategyhwm
    // A number supplied to the constructor as part of the stream’s queuing strategy, indicating the point at which the stream will apply backpressure to its underlying source
    double m_strategy_hwm { 0 };

    // https://streams.spec.whatwg.org/#readablestreamdefaultcontroller-stream
    // The ReadableStream instance controlled
    GC::Ptr<ReadableStream> m_stream;
};

}
