//    OpenVPN -- An application to securely tunnel IP networks
//               over a single port, with support for SSL/TLS-based
//               session authentication and key exchange,
//               packet encryption, packet authentication, and
//               packet compression.
//
//    Copyright (C) 2012- OpenVPN Inc.
//
//    SPDX-License-Identifier: MPL-2.0 OR AGPL-3.0-only WITH openvpn3-openssl-exception
//

// This code implements an OpenSSL BIO object for datagrams based on the
// MemQ buffer queue object.

#ifndef OPENVPN_OPENSSL_BIO_BIO_MEMQ_DGRAM_H
#define OPENVPN_OPENSSL_BIO_BIO_MEMQ_DGRAM_H

#include <cstring> // for std::strlen

#include <openssl/err.h>
#include <openssl/bio.h>

#include <openvpn/common/size.hpp>
#include <openvpn/common/exception.hpp>
#include <openvpn/frame/frame.hpp>
#include <openvpn/frame/memq_dgram.hpp>

namespace openvpn::bmq_dgram {

class MemQ : public MemQDgram
{
  public:
    MemQ()
    {
        mtu = 0;
        query_mtu_return = 0;
        std::memset(&next_timeout, 0, sizeof(next_timeout));
    }

    void set_mtu(long mtu)
    {
        query_mtu_return = mtu;
    }
    const struct timeval *get_next_timeout(void) const
    {
        return &next_timeout;
    }

    long ctrl(BIO *b, int cmd, long num, void *ptr)
    {
        long ret = 1;

        switch (cmd)
        {
        case BIO_CTRL_RESET:
            clear();
            break;
        case BIO_CTRL_EOF:
            ret = (long)empty();
            break;
        case BIO_C_SET_BUF_MEM_EOF_RETURN:
            return_eof_on_empty = (num == 0);
            break;
        case BIO_CTRL_GET_CLOSE:
            ret = (long)(BIO_get_shutdown(b));
            break;
        case BIO_CTRL_SET_CLOSE:
            BIO_set_shutdown(b, (int)num);
            break;
        case BIO_CTRL_WPENDING:
            ret = 0L;
            break;
        case BIO_CTRL_PENDING:
            ret = (long)pending();
            break;
        case BIO_CTRL_DUP:
        case BIO_CTRL_FLUSH:
            ret = 1;
            break;
        case BIO_CTRL_DGRAM_QUERY_MTU:
            ret = mtu = query_mtu_return;
            break;
        case BIO_CTRL_DGRAM_GET_MTU:
            ret = mtu;
            break;
        case BIO_CTRL_DGRAM_SET_MTU:
            ret = mtu = num;
            break;
        case BIO_CTRL_DGRAM_SET_NEXT_TIMEOUT:
            std::memcpy(&next_timeout, ptr, sizeof(struct timeval));
            break;
        default:
            // OPENVPN_LOG("*** MemQ-dgram unimplemented ctrl method=" << cmd);
            ret = 0;
            break;
        }
        return (ret);
    }

  private:
    long mtu;
    long query_mtu_return;
    bool return_eof_on_empty;
    struct timeval next_timeout;
};

namespace bio_memq_internal {
static int memq_method_type = 0;
static BIO_METHOD *memq_method = nullptr;

inline int memq_new(BIO *b)
{
    MemQ *bmq = new (std::nothrow) MemQ();
    if (!bmq)
        return 0;
    BIO_set_shutdown(b, 1);
    BIO_set_init(b, 1);
    b->return_eof_on_empty = false;
    BIO_set_data(b, (void *)bmq);
    return 1;
}

inline int memq_free(BIO *b)
{
    if (b == nullptr)
        return (0);
    if (BIO_get_shutdown(b))
    {
        MemQ *bmq = (MemQ *)(BIO_get_data(b));
        if (BIO_get_init(b) && (bmq != nullptr))
        {
            delete bmq;
            BIO_set_data(b, nullptr);
        }
    }
    return 1;
}

inline int memq_write(BIO *b, const char *in, int len)
{
    MemQ *bmq = (MemQ *)(BIO_get_data(b));
    if (in)
    {
        BIO_clear_retry_flags(b);
        try
        {
            if (len)
                bmq->write((const unsigned char *)in, (size_t)len);
            return len;
        }
        catch (...)
        {
            BIOerr(BIO_F_MEM_WRITE, BIO_R_INVALID_ARGUMENT);
            return -1;
        }
    }
    else
    {
        BIOerr(BIO_F_MEM_WRITE, BIO_R_NULL_PARAMETER);
        return -1;
    }
}

inline int memq_read(BIO *b, char *out, int size)
{
    MemQ *bmq = (MemQ *)(BIO_get_data(b));
    int ret = -1;
    BIO_clear_retry_flags(b);
    if (!bmq->empty())
    {
        try
        {
            ret = (int)bmq->read((unsigned char *)out, (size_t)size);
        }
        catch (...)
        {
            BIOerr(BIO_F_MEM_READ, BIO_R_INVALID_ARGUMENT);
            return -1;
        }
    }
    else
    {
        ret = b->num;
        if (ret != 0)
            BIO_set_retry_read(b);
    }
    return ret;
}

inline long memq_ctrl(BIO *b, int cmd, long arg1, void *arg2)
{
    MemQ *bmq = (MemQ *)(BIO_get_data(b));
    return bmq->ctrl(b, cmd, arg1, arg2);
}

inline int memq_puts(BIO *b, const char *str)
{
    const int len = std::strlen(str);
    const int ret = memq_write(b, str, len);
    return ret;
}

inline void create_bio_method()
{
    if (!memq_method_type)
        memq_method_type = BIO_get_new_index();

    memq_method = BIO_meth_new(memq_method_type, "datagram memory queue");
    BIO_meth_set_write(memq_method, memq_write);
    BIO_meth_set_read(memq_read);
    BIO_meth_set_puts(memq_puts);
    BIO_meth_set_create(memq_new);
    BIO_meth_set_destroy(memq_destroy);
    BIO_meth_set_gets(nullptr);
    BIO_meth_set_ctrl(memq_method, memq_ctrl);
}

inline void free_bio_method()
{
    BIO_meth_free(memq_method);
}
} // namespace bio_memq_internal

inline BIO_METHOD *BIO_s_memq(void)
{
    // TODO: call free in some cleanup
    bio_memq_internal::create_bio_method();
    return bio_memq_internal::memq_method;
}

inline MemQ *memq_from_bio(BIO *b)
{
    if (BIO_method_type(b) == bio_memq_internal::memq_method_type)
        return (MemQ *)(BIO_get_data(b));
    else
        return nullptr;
}

inline const MemQ *const_memq_from_bio(const BIO *b)
{
    if (BIO_method_type(b) == bio_memq_internal::memq_method_type)
        return (const MemQ *)(BIO_get_data(const_cast<BIO *>(b)));
    else
        return nullptr;
}

MemQ()
{
    mtu = 0;
    query_mtu_return = 0;
    std::memset(&next_timeout, 0, sizeof(next_timeout));

    bio_memq_internal::create_bio_method();
}

~MemQ()
{
    bio_memq_internal::free_bio_method();
}
} // namespace openvpn::bmq_dgram

#endif // OPENVPN_OPENSSL_BIO_BIO_MEMQ_DGRAM_H