#ifndef WEBSOCKETPROTOCOL_UWS_H
#define WEBSOCKETPROTOCOL_UWS_H

#include <uv.h>
#include <cstring>
#ifdef __APPLE__
#include <libkern/OSByteOrder.h>
#define htobe64(x) OSSwapHostToBigInt64(x)
#define be64toh(x) OSSwapBigToHostInt64(x)
#endif

namespace eioWS {
    enum OpCode : unsigned char {
        NONE = 0,
        TEXT = 1,
        BINARY = 2,
        CLOSE = 8,
        PING = 9,
        PONG = 10
    };

    // 24 bytes perfectly
    struct WebSocketState {
        public:
            static const unsigned int SHORT_MESSAGE_HEADER = 6;
            static const unsigned int MEDIUM_MESSAGE_HEADER = 8;
            static const unsigned int LONG_MESSAGE_HEADER = 14;

            // 16 bytes
            struct State {
                unsigned int wantsHead : 1;
                unsigned int spillLength : 4;
                int opStack : 2; // -1, 0, 1
                unsigned int lastFin : 1;

                // 15 bytes
                unsigned char spill[LONG_MESSAGE_HEADER - 1] = { 0 };
                OpCode opCode[2] = { NONE };

                State() {
                    wantsHead = true;
                    spillLength = 0;
                    opStack = -1;
                    lastFin = true;
                }

            } state;

            // 8 bytes
            unsigned int remainingBytes = 0;
            char mask[4];
    };

    template <class Impl>
        class WebSocketProtocol {
            public:
                static const unsigned int SHORT_MESSAGE_HEADER = 6;
                static const unsigned int MEDIUM_MESSAGE_HEADER = 8;
                static const unsigned int LONG_MESSAGE_HEADER = 14;

            protected:
                static inline bool isFin(char *frame) {return *((unsigned char *) frame) & 128;}
                static inline unsigned char getOpCode(char *frame) {return *((unsigned char *) frame) & 15;}
                static inline unsigned char payloadLength(char *frame) {return ((unsigned char *) frame)[1] & 127;}
                static inline bool rsv23(char *frame) {return *((unsigned char *) frame) & 48;}
                static inline bool rsv1(char *frame) {return *((unsigned char *) frame) & 64;}

                static inline void unmaskImprecise(char *dst, char *src, char *mask, unsigned int length) {
                    for (unsigned int n = (length >> 2) + 1; n; n--) {
                        *(dst++) = *(src++) ^ mask[0];
                        *(dst++) = *(src++) ^ mask[1];
                        *(dst++) = *(src++) ^ mask[2];
                        *(dst++) = *(src++) ^ mask[3];
                    }
                }

                static inline void unmaskImpreciseCopyMask(char *dst, char *src, char *maskPtr, unsigned int length) {
                    char mask[4] = {maskPtr[0], maskPtr[1], maskPtr[2], maskPtr[3]};
                    unmaskImprecise(dst, src, mask, length);
                }

                static inline void rotateMask(unsigned int offset, char *mask) {
                    char originalMask[4] = {mask[0], mask[1], mask[2], mask[3]};
                    mask[(0 + offset) & 3] = originalMask[0];
                    mask[(1 + offset) & 3] = originalMask[1];
                    mask[(2 + offset) & 3] = originalMask[2];
                    mask[(3 + offset) & 3] = originalMask[3];
                }

                static inline void unmaskInplace(char *data, char *stop, char *mask) {
                    while (data < stop) {
                        *(data++) ^= mask[0];
                        *(data++) ^= mask[1];
                        *(data++) ^= mask[2];
                        *(data++) ^= mask[3];
                    }
                }

                enum {
                    SND_COMPRESSED = 64
                };

                template <unsigned int MESSAGE_HEADER, typename T>
                    static inline bool consumeMessage(T payLength, char *&src, unsigned int &length, WebSocketState *wState) {
                        if (getOpCode(src)) {
                            if (wState->state.opStack == 1 || (!wState->state.lastFin && getOpCode(src) < 2)) {
                                Impl::forceClose(wState);
                                return true;
                            }
                            wState->state.opCode[++wState->state.opStack] = (OpCode) getOpCode(src);
                        } else if (wState->state.opStack == -1) {
                            Impl::forceClose(wState);
                            return true;
                        }
                        wState->state.lastFin = isFin(src);

                        if (Impl::refusePayloadLength(payLength, wState)) {
                            Impl::forceClose(wState);
                            return true;
                        }

                        if (payLength + MESSAGE_HEADER <= length) {
                            unmaskImpreciseCopyMask(src + MESSAGE_HEADER - 4, src + MESSAGE_HEADER, src + MESSAGE_HEADER - 4, (unsigned int) payLength);
                            if (Impl::handleFragment(src + MESSAGE_HEADER - 4, payLength, 0, wState->state.opCode[wState->state.opStack], isFin(src), wState)) {
                                return true;
                            }

                            if (isFin(src)) {
                                wState->state.opStack--;
                            }

                            src += payLength + MESSAGE_HEADER;
                            length -= payLength + MESSAGE_HEADER;
                            wState->state.spillLength = 0;
                            return false;
                        } else {
                            wState->state.spillLength = 0;
                            wState->state.wantsHead = false;
                            wState->remainingBytes = (unsigned int) (payLength - length + MESSAGE_HEADER);
                            bool fin = isFin(src);
                            memcpy(wState->mask, src + MESSAGE_HEADER - 4, 4);
                            unmaskImprecise(src, src + MESSAGE_HEADER, wState->mask, length - MESSAGE_HEADER);
                            rotateMask(4 - ((length - MESSAGE_HEADER) & 3), wState->mask);
                            Impl::handleFragment(src, length - MESSAGE_HEADER, wState->remainingBytes, wState->state.opCode[wState->state.opStack], fin, wState);
                            return true;
                        }
                    }

                static inline bool consumeContinuation(char *&src, unsigned int &length, WebSocketState *wState) {
                    if (wState->remainingBytes <= length) {
                        int n = wState->remainingBytes >> 2;
                        unmaskInplace(src, src + n * 4, wState->mask);
                        for (int i = 0, s = wState->remainingBytes & 3; i < s; i++) {
                            src[n * 4 + i] ^= wState->mask[i];
                        }

                        if (Impl::handleFragment(src, wState->remainingBytes, 0, wState->state.opCode[wState->state.opStack], wState->state.lastFin, wState)) {
                            return false;
                        }

                        if (wState->state.lastFin) {
                            wState->state.opStack--;
                        }

                        src += wState->remainingBytes;
                        length -= wState->remainingBytes;
                        wState->state.wantsHead = true;
                        return true;
                    } else {
                        unmaskInplace(src, src + ((length >> 2) + 1) * 4, wState->mask);

                        wState->remainingBytes -= length;
                        if (Impl::handleFragment(src, length, wState->remainingBytes, wState->state.opCode[wState->state.opStack], wState->state.lastFin, wState)) {
                            return false;
                        }

                        if (length & 3) {
                            rotateMask(4 - (length & 3), wState->mask);
                        }
                        return false;
                    }
                }

            public:
                WebSocketProtocol() {

                }

                // Based on utf8_check.c by Markus Kuhn, 2005
                // https://www.cl.cam.ac.uk/~mgk25/ucs/utf8_check.c
                // Optimized for predominantly 7-bit content by Alex Hultman, 2016
                // Licensed as Zlib, like the rest of this project
                static bool isValidUtf8(unsigned char *s, size_t length) {
                    for (unsigned char *e = s + length; s != e; ) {
                        if (s + 4 <= e && ((*reinterpret_cast<uint32_t *>(s)) & 0x80808080) == 0) {
                            s += 4;
                        } else {
                            while (!(*s & 0x80)) {
                                if (++s == e) {
                                    return true;
                                }
                            }

                            if ((s[0] & 0x60) == 0x40) {
                                if (s + 1 >= e || (s[1] & 0xc0) != 0x80 || (s[0] & 0xfe) == 0xc0) {
                                    return false;
                                }
                                s += 2;
                            } else if ((s[0] & 0xf0) == 0xe0) {
                                if (s + 2 >= e || (s[1] & 0xc0) != 0x80 || (s[2] & 0xc0) != 0x80 ||
                                        (s[0] == 0xe0 && (s[1] & 0xe0) == 0x80) || (s[0] == 0xed && (s[1] & 0xe0) == 0xa0)) {
                                    return false;
                                }
                                s += 3;
                            } else if ((s[0] & 0xf8) == 0xf0) {
                                if (s + 3 >= e || (s[1] & 0xc0) != 0x80 || (s[2] & 0xc0) != 0x80 || (s[3] & 0xc0) != 0x80 ||
                                        (s[0] == 0xf0 && (s[1] & 0xf0) == 0x80) || (s[0] == 0xf4 && s[1] > 0x8f) || s[0] > 0xf4) {
                                    return false;
                                }
                                s += 4;
                            } else {
                                return false;
                            }
                        }
                    }
                    return true;
                }

                struct CloseFrame {
                    uint16_t code;
                    char const *message;
                    size_t length;
                };

                static inline CloseFrame parseClosePayload(char *src, size_t length) {
                    CloseFrame cf = {1005, "", 0};

                    if (length >= 2) {
                        memcpy(&cf.code, src, 2);
                        cf = {ntohs(cf.code), src + 2, length - 2};
                        if (cf.code < 1000 || cf.code > 4999 || (cf.code > 1011 && cf.code < 4000) ||
                            (cf.code >= 1004 && cf.code <= 1006) || !isValidUtf8((unsigned char *) cf.message, cf.length)) {
                            return {1006, "", 0};
                        }
                    }
                    return cf;
                }

                static inline size_t formatClosePayload(char *dst, uint16_t code, const char *message, size_t length) {
                    if (code && code != 1005 && code != 1006) {
                        code = htons(code);
                        memcpy(dst, &code, 2);
                        if (message) {
                            memcpy(dst + 2, message, length);
                        }
                        return length + 2;
                    }
                    return 0;
                }

                static inline size_t formatMessage(char *dst, const char *src, size_t length, OpCode opCode, size_t reportedLength, bool compressed) {
                    size_t messageLength;
                    size_t headerLength;
                    if (reportedLength < 126) {
                        headerLength = 2;
                        dst[1] = reportedLength;
                    } else if (reportedLength <= UINT16_MAX) {
                        headerLength = 4;
                        dst[1] = 126;
                        *(reinterpret_cast<uint16_t *>(&dst[2])) = htons(reportedLength);
                    } else {
                        headerLength = 10;
                        dst[1] = 127;
                        *(reinterpret_cast<uint64_t *>(&dst[2])) = htobe64(reportedLength);
                    }

                    dst[0] = 128 | (compressed ? SND_COMPRESSED : 0) | opCode;

                    messageLength = headerLength + length;
                    memcpy(dst + headerLength, src, length);

                    return messageLength;
                }

                static inline void consume(char *src, unsigned int length, WebSocketState *wState) {
                    if (wState->state.spillLength) {
                        src -= wState->state.spillLength;
                        length += wState->state.spillLength;
                        memcpy(src, wState->state.spill, wState->state.spillLength);
                    }
                    if (wState->state.wantsHead) {
parseNext:
                        while (length >= SHORT_MESSAGE_HEADER) {

                            // invalid reserved bits / invalid opcodes / invalid control frames / set compressed frame
                            if ((rsv1(src) && !Impl::setCompressed(wState)) || rsv23(src) || (getOpCode(src) > 2 && getOpCode(src) < 8) ||
                                    getOpCode(src) > 10 || (getOpCode(src) > 2 && (!isFin(src) || payloadLength(src) > 125))) {
                                Impl::forceClose(wState);
                                return;
                            }

                            if (payloadLength(src) < 126) {
                                if (consumeMessage<SHORT_MESSAGE_HEADER, uint8_t>(payloadLength(src), src, length, wState)) {
                                    return;
                                }
                            } else if (payloadLength(src) == 126) {
                                if (length < MEDIUM_MESSAGE_HEADER) {
                                    break;
                                } else if (consumeMessage<MEDIUM_MESSAGE_HEADER, uint16_t>(ntohs(*reinterpret_cast<uint16_t *>(&src[2])), src, length, wState)) {
                                    return;
                                }
                            } else if (length < LONG_MESSAGE_HEADER) {
                                break;
                            } else if (consumeMessage<LONG_MESSAGE_HEADER, uint64_t>(be64toh(*reinterpret_cast<uint64_t *>(&src[2])), src, length, wState)) {
                                return;
                            }
                        }
                        if (length) {
                            memcpy(wState->state.spill, src, length);
                            wState->state.spillLength = length;
                        }
                    } else if (consumeContinuation(src, length, wState)) {
                        goto parseNext;
                    }
                }

                static const int CONSUME_POST_PADDING = 4;
                static const int CONSUME_PRE_PADDING = LONG_MESSAGE_HEADER - 1;
        };
}

#endif // WEBSOCKETPROTOCOL_UWS_H