/*
 * Copyright (c)2013-2020 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2026-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */

#ifndef ZT_N_CAMOPATTERN_HPP
#define ZT_N_CAMOPATTERN_HPP

#include <stdint.h>
#include <array>
#include <unordered_map>
#include <mutex>
#include <random>
#include <bitset>

#include "Address.hpp"
#include "Buffer.hpp"
#include "RuntimeEnvironment.hpp"

#define BYTES_IN_WORD (sizeof(uint32_t) / sizeof(uint8_t))
#define ID_SIZE (BYTES_IN_WORD * 2)

/**
 * Camo functions debug trace macro
 * Enables debug output when CAMO_TRACE is defined
 */
#ifdef CAMO_TRACE
    #define CT(...) do { \
        printf("%s:%d %s: ", __FILE__, __LINE__, __PRETTY_FUNCTION__); \
        printf(__VA_ARGS__); \
        printf("\n"); \
    } while(0)
#else
    #define CT(...) ((void)0)
#endif

namespace ZeroTier {

/**
 * Camouflage class enum
 */
enum CamoClass {
    NODE,
    CONTROLLER,
    MOON,
    AUTO_APPLY_COUNT,
    ALWAYS = AUTO_APPLY_COUNT,
    NEVER
};
typedef std::bitset<CamoClass::AUTO_APPLY_COUNT> CamoAutoApplyBits;
typedef std::array<uint8_t, BYTES_IN_WORD> CamoPatternBytes;
typedef std::unordered_map<Address, CamoClass> KnownHostsMap;

}

/**
 * Hash function for the KnownHostsMap
*/
namespace std {
    template<>
    struct hash<ZeroTier::Address> {
        size_t operator()(const ZeroTier::Address& address) const {
            return std::hash<uint64_t>{}(address.toInt());
        }
    };
}

namespace ZeroTier {

enum class CamoRelayRule {
    LEAVE,
    KNOWNHOSTS,
    STRIP,
    APPLY
};

/**
 * Helper class for packet camouflage operations
 */
class CamoPattern
{
    /**
     * Check if the buffer has camo
     *
     * @param buffer Buffer to check
     * @return True if the buffer has camo
     */
    template<unsigned int C>
    static bool hasCamo(const Buffer<C> &buffer)
    {
        bool result = false;
        if (buffer.size() > (ID_SIZE * 2))
        {
            size_t a = 0;
            size_t b = BYTES_IN_WORD;
            size_t x = buffer.size() - ID_SIZE;
            size_t y = buffer.size() - BYTES_IN_WORD;
            result = true;
            for (size_t i = 0; i < BYTES_IN_WORD; i++)
            {
                if ((buffer[a + i] ^ buffer[b + i]) != (buffer[x + i] ^ buffer [y + i]))
                {
                    result = false;
                    break;
                }
            }
        }
        CT("PACKET HAS CAMO: %b", result);
        return result;
    }

    /**
     * Check the host camo class
     *
     * @param host Destination address
     * @param RR RuntimeEnvironment pointer
     * @return Camo class for this host
     */
    static CamoClass getCamoClass(const Address host, const RuntimeEnvironment * const RR);

public:
    /**
     * Determine if camouflage is required for a specific host
     *
     * @param host Destination address
     * @param RR RuntimeEnvironment pointer
     * @param hadCamo Whether the packet previously had camouflage applied
     * @param isRelay Whether this is a relay operation
     * @return True if host requires camouflage
     */
    static bool isCamoRequired(const Address host, const RuntimeEnvironment * const RR, const bool hadCamo = false, const bool isRelay = false);

    /**
     * Apply camouflage to buffer
     *
     * This increases buffer length by adding ID to the end
     *
     * @param buffer Buffer to apply camouflage to
     */
    template<unsigned int C>
    static void applyCamo(Buffer<C> &buffer)
    {
        CT("APPLYING CAMO");
        if (isInitialized && !hasCamo(buffer))
        {
            // load random number into an array
            uint32_t camo = rng();
            CamoPatternBytes camoBytes;
            for (size_t i = 0; i < BYTES_IN_WORD; i++)
            {
                camoBytes[i] = camo >> 24;
                CT("CAMO BYTE %u: %02x", i, camoBytes[i]);
                camo <<= 8;
            }

            //camouflage all the data
            uint8_t * const data = reinterpret_cast<uint8_t * const>(buffer.unsafeData());
            for (size_t i = ID_SIZE; i < buffer.size(); i++)
            {
                data[i] ^= camoBytes[i % BYTES_IN_WORD];
            }

            // expand the buffer
            size_t originalSize = buffer.size();
            buffer.setSize(originalSize + ID_SIZE);
            //copy the id
            for (size_t i = 0; i < ID_SIZE; i++)
            {
                data[i + originalSize] = data[i] ^ camoBytes[i % BYTES_IN_WORD];
            }

            CT("DONE");
        }
    }

    /**
     * Remove camouflage from buffer
     *
     * This decreases buffer length by removing stored ID from the end
     *
     * @param buffer Buffer to remove camouflage from
     * @return True if buffer had camouflage and it was stripped
     */
    template<unsigned int C>
    static bool stripCamo(Buffer<C> &buffer)
    {
        bool result = false;
        if (isInitialized && hasCamo(buffer)) {
            //retrieve the camo bytes
            uint8_t * a = &buffer[0];
            uint8_t * x = &buffer[buffer.size() - ID_SIZE];
            CamoPatternBytes camoBytes;
            for (size_t i = 0; i < BYTES_IN_WORD; i++)
            {
                camoBytes[i] = a[i] ^ x[i];
                CT("CAMO BYTE %u: %02x", i, camoBytes[i]);
            }

            //remove the duplicated id
            buffer.setSize(buffer.size() - ID_SIZE);

            //strip camo
            uint8_t * const data = reinterpret_cast<uint8_t * const>(buffer.unsafeData());
            for (size_t i = ID_SIZE; i < buffer.size(); i++)
            {
                data[i] ^= camoBytes[i % BYTES_IN_WORD];
            }
            result = true;
        }
        CT("CAMO STRIPPED: %d", result);
        return result;
    }

    /**
     * Initialize the camo system
     *
     * @param autoApply Bits controlling automatic application to different host classes
     * @param hosts knownHosts preloading
     * @param relayRule Packet relay rule
     */
    static void init(CamoAutoApplyBits autoApply, KnownHostsMap hosts, CamoRelayRule rule);

private:
    static bool isInitialized;
    static CamoAutoApplyBits camoAutoApply;
    static CamoRelayRule relayRule;
    static std::mutex camoMutex;
    static KnownHostsMap knownHosts;
    static std::mt19937 rng;
};

} // namespace ZeroTier

// Implementation of Buffer::dump() method
template<unsigned int C>
void ZeroTier::Buffer<C>::dump() const
{
#ifdef CAMO_TRACE
    const unsigned char *bytes = reinterpret_cast<const unsigned char *>(data());
    const unsigned int size = this->size();

    for (unsigned int i = 0; i < size; i++) {
        printf("%02x", bytes[i]);

        if ((i + 1) % 16 == 0) {
            printf("\n");
        } else if (i < size - 1) {
            printf(" ");
        }
    }

    // Add newline if last line wasn't complete
    if (size % 16 != 0) {
        printf("\n");
    }
#endif
}

#endif // ZT_CAMOPATTERN_HPP