/** @file
 *
 *  Fundamental HTTP/2 protocol definitions and parsers.
 *
 *  @section license License
 *
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#pragma once

#include "tscore/ink_defs.h"
#include "tscore/ink_memory.h"
#include "HPACK.h"
#include "MIME.h"
#include "records/P_RecDefs.h"

class HTTPHdr;

typedef unsigned Http2StreamId;

constexpr Http2StreamId HTTP2_CONNECTION_CONTROL_STRTEAM = 0;
constexpr uint8_t HTTP2_FRAME_NO_FLAG                    = 0;

// [RFC 7540] 6.9.2. Initial Flow Control Window Size
// the flow control window can be come negative so we need to track it with a signed type.
typedef int32_t Http2WindowSize;

extern const char *const HTTP2_CONNECTION_PREFACE;
const size_t HTTP2_CONNECTION_PREFACE_LEN = 24;

extern const char *HTTP2_VALUE_SCHEME;
extern const char *HTTP2_VALUE_METHOD;
extern const char *HTTP2_VALUE_AUTHORITY;
extern const char *HTTP2_VALUE_PATH;
extern const char *HTTP2_VALUE_STATUS;

extern const unsigned HTTP2_LEN_SCHEME;
extern const unsigned HTTP2_LEN_METHOD;
extern const unsigned HTTP2_LEN_AUTHORITY;
extern const unsigned HTTP2_LEN_PATH;
extern const unsigned HTTP2_LEN_STATUS;

const size_t HTTP2_FRAME_HEADER_LEN       = 9;
const size_t HTTP2_DATA_PADLEN_LEN        = 1;
const size_t HTTP2_HEADERS_PADLEN_LEN     = 1;
const size_t HTTP2_PRIORITY_LEN           = 5;
const size_t HTTP2_RST_STREAM_LEN         = 4;
const size_t HTTP2_PING_LEN               = 8;
const size_t HTTP2_GOAWAY_LEN             = 8;
const size_t HTTP2_WINDOW_UPDATE_LEN      = 4;
const size_t HTTP2_SETTINGS_PARAMETER_LEN = 6;

// SETTINGS initial values. NOTE: These should not be modified
// unless the protocol changes! Do not change this thinking you
// are changing server defaults. that is done via RecordsConfig.cc
const uint32_t HTTP2_ENABLE_PUSH            = 1;
const uint32_t HTTP2_MAX_CONCURRENT_STREAMS = UINT_MAX;
const uint32_t HTTP2_INITIAL_WINDOW_SIZE    = 65535;
const uint32_t HTTP2_MAX_FRAME_SIZE         = 16384;
const uint32_t HTTP2_HEADER_TABLE_SIZE      = 4096;
const uint32_t HTTP2_MAX_HEADER_LIST_SIZE   = UINT_MAX;
const uint32_t HTTP2_MAX_BUFFER_USAGE       = 524288;

// [RFC 7540] 5.3.5 Default Priorities
// The RFC says weight value is 1 to 256, but the value in TS is between 0 to 255
// to use uint8_t. So the default weight is 16 minus 1.
const uint32_t HTTP2_PRIORITY_DEFAULT_STREAM_DEPENDENCY = 0;
const uint8_t HTTP2_PRIORITY_DEFAULT_WEIGHT             = 15;

// Statistics
enum {
  HTTP2_STAT_CURRENT_CLIENT_SESSION_COUNT,           // Current # of HTTP2 connections
  HTTP2_STAT_CURRENT_ACTIVE_CLIENT_CONNECTION_COUNT, // Current # of active HTTP2 connections
  HTTP2_STAT_CURRENT_CLIENT_STREAM_COUNT,            // Current # of active HTTP2 streams
  HTTP2_STAT_TOTAL_CLIENT_STREAM_COUNT,
  HTTP2_STAT_TOTAL_TRANSACTIONS_TIME,       // Total stream time and streams
  HTTP2_STAT_TOTAL_CLIENT_CONNECTION_COUNT, // Total connections running http2
  HTTP2_STAT_STREAM_ERRORS_COUNT,
  HTTP2_STAT_CONNECTION_ERRORS_COUNT,
  HTTP2_STAT_SESSION_DIE_DEFAULT,
  HTTP2_STAT_SESSION_DIE_OTHER,
  HTTP2_STAT_SESSION_DIE_ACTIVE,
  HTTP2_STAT_SESSION_DIE_INACTIVE,
  HTTP2_STAT_SESSION_DIE_EOS,
  HTTP2_STAT_SESSION_DIE_ERROR,
  HTTP2_STAT_SESSION_DIE_HIGH_ERROR_RATE,
  HTTP2_STAT_MAX_SETTINGS_PER_FRAME_EXCEEDED,
  HTTP2_STAT_MAX_SETTINGS_PER_MINUTE_EXCEEDED,
  HTTP2_STAT_MAX_SETTINGS_FRAMES_PER_MINUTE_EXCEEDED,
  HTTP2_STAT_MAX_PING_FRAMES_PER_MINUTE_EXCEEDED,
  HTTP2_STAT_MAX_PRIORITY_FRAMES_PER_MINUTE_EXCEEDED,
  HTTP2_STAT_MAX_RST_STREAM_FRAMES_PER_MINUTE_EXCEEDED,
  HTTP2_STAT_MAX_CONTINUATION_FRAMES_PER_MINUTE_EXCEEDED,
  HTTP2_STAT_INSUFFICIENT_AVG_WINDOW_UPDATE,
  HTTP2_STAT_MAX_CONCURRENT_STREAMS_EXCEEDED_IN,
  HTTP2_STAT_MAX_CONCURRENT_STREAMS_EXCEEDED_OUT,

  HTTP2_N_STATS // Terminal counter, NOT A STAT INDEX.
};

#define HTTP2_INCREMENT_THREAD_DYN_STAT(_s, _t) RecIncrRawStat(http2_rsb, _t, (int)_s, 1);
#define HTTP2_DECREMENT_THREAD_DYN_STAT(_s, _t) RecIncrRawStat(http2_rsb, _t, (int)_s, -1);
#define HTTP2_SUM_THREAD_DYN_STAT(_s, _t, _v) RecIncrRawStat(http2_rsb, _t, (int)_s, _v);
extern RecRawStatBlock *http2_rsb; // Container for statistics.

// [RFC 7540] 6.9.1. The Flow Control Window
static const Http2WindowSize HTTP2_MAX_WINDOW_SIZE = 0x7FFFFFFF;

// [RFC 7540] 5.4. Error Handling
enum class Http2ErrorClass {
  HTTP2_ERROR_CLASS_NONE,
  HTTP2_ERROR_CLASS_CONNECTION,
  HTTP2_ERROR_CLASS_STREAM,
};

// [RFC 7540] 7. Error Codes
enum class Http2ErrorCode {
  HTTP2_ERROR_NO_ERROR            = 0,
  HTTP2_ERROR_PROTOCOL_ERROR      = 1,
  HTTP2_ERROR_INTERNAL_ERROR      = 2,
  HTTP2_ERROR_FLOW_CONTROL_ERROR  = 3,
  HTTP2_ERROR_SETTINGS_TIMEOUT    = 4,
  HTTP2_ERROR_STREAM_CLOSED       = 5,
  HTTP2_ERROR_FRAME_SIZE_ERROR    = 6,
  HTTP2_ERROR_REFUSED_STREAM      = 7,
  HTTP2_ERROR_CANCEL              = 8,
  HTTP2_ERROR_COMPRESSION_ERROR   = 9,
  HTTP2_ERROR_CONNECT_ERROR       = 10,
  HTTP2_ERROR_ENHANCE_YOUR_CALM   = 11,
  HTTP2_ERROR_INADEQUATE_SECURITY = 12,
  HTTP2_ERROR_HTTP_1_1_REQUIRED   = 13,

  HTTP2_ERROR_MAX,
};

// [RFC 7540] 5.1. Stream States
enum class Http2StreamState {
  HTTP2_STREAM_STATE_IDLE,
  HTTP2_STREAM_STATE_RESERVED_LOCAL,
  HTTP2_STREAM_STATE_RESERVED_REMOTE,
  HTTP2_STREAM_STATE_OPEN,
  HTTP2_STREAM_STATE_HALF_CLOSED_LOCAL,
  HTTP2_STREAM_STATE_HALF_CLOSED_REMOTE,
  HTTP2_STREAM_STATE_CLOSED
};

enum Http2FrameType {
  HTTP2_FRAME_TYPE_DATA          = 0,
  HTTP2_FRAME_TYPE_HEADERS       = 1,
  HTTP2_FRAME_TYPE_PRIORITY      = 2,
  HTTP2_FRAME_TYPE_RST_STREAM    = 3,
  HTTP2_FRAME_TYPE_SETTINGS      = 4,
  HTTP2_FRAME_TYPE_PUSH_PROMISE  = 5,
  HTTP2_FRAME_TYPE_PING          = 6,
  HTTP2_FRAME_TYPE_GOAWAY        = 7,
  HTTP2_FRAME_TYPE_WINDOW_UPDATE = 8,
  HTTP2_FRAME_TYPE_CONTINUATION  = 9,

  HTTP2_FRAME_TYPE_MAX,
};

// [RFC 7540] 6.1. Data
enum Http2FrameFlagsData {
  HTTP2_FLAGS_DATA_END_STREAM = 0x01,
  HTTP2_FLAGS_DATA_PADDED     = 0x08,

  HTTP2_FLAGS_DATA_MASK = 0x09,
};

// [RFC 7540] 6.2. Headers
enum Http2FrameFlagsHeaders {
  HTTP2_FLAGS_HEADERS_END_STREAM  = 0x01,
  HTTP2_FLAGS_HEADERS_END_HEADERS = 0x04,
  HTTP2_FLAGS_HEADERS_PADDED      = 0x08,
  HTTP2_FLAGS_HEADERS_PRIORITY    = 0x20,

  HTTP2_FLAGS_HEADERS_MASK = 0x2D,
};

// [RFC 7540] 6.3. Priority
enum Http2FrameFlagsPriority {
  HTTP2_FLAGS_PRIORITY_MASK = 0x00,
};

// [RFC 7540] 6.4. Rst Stream
enum Http2FrameFlagsRstStream {
  HTTP2_FLAGS_RST_STREAM_MASK = 0x00,
};

// [RFC 7540] 6.5. Settings
enum Http2FrameFlagsSettings {
  HTTP2_FLAGS_SETTINGS_ACK = 0x01,

  HTTP2_FLAGS_SETTINGS_MASK = 0x01
};

// [RFC 7540] 6.6. Push Promise
enum Http2FrameFlagsPushPromise {
  HTTP2_FLAGS_PUSH_PROMISE_END_HEADERS = 0x04,
  HTTP2_FLAGS_PUSH_PROMISE_PADDED      = 0x08,

  HTTP2_FLAGS_PUSH_PROMISE_MASK = 0x0C,
};

// [RFC 7540] 6.7. Ping
enum Http2FrameFlagsPing {
  HTTP2_FLAGS_PING_ACK = 0x01,

  HTTP2_FLAGS_PING_MASK = 0x01
};

// [RFC 7540] 6.8. Goaway
enum Http2FrameFlagsGoaway {
  HTTP2_FLAGS_GOAWAY_MASK = 0x00,
};

// [RFC 7540] 6.9. Window Update
enum Http2FrameFlagsWindowUpdate {
  HTTP2_FLAGS_WINDOW_UPDATE_MASK = 0x00,
};

// [RFC 7540] 6.10. Continuation
enum Http2FrameFlagsContinuation {
  HTTP2_FLAGS_CONTINUATION_END_HEADERS = 0x04,

  HTTP2_FLAGS_CONTINUATION_MASK = 0x04,
};

// [RFC 7540] 6.5.2. Defined SETTINGS Parameters
enum Http2SettingsIdentifier {
  HTTP2_SETTINGS_HEADER_TABLE_SIZE      = 1,
  HTTP2_SETTINGS_ENABLE_PUSH            = 2,
  HTTP2_SETTINGS_MAX_CONCURRENT_STREAMS = 3,
  HTTP2_SETTINGS_INITIAL_WINDOW_SIZE    = 4,
  HTTP2_SETTINGS_MAX_FRAME_SIZE         = 5,
  HTTP2_SETTINGS_MAX_HEADER_LIST_SIZE   = 6,

  HTTP2_SETTINGS_MAX
};

// [RFC 7540] 4.1. Frame Format
struct Http2FrameHeader {
  uint32_t length;
  uint8_t type;
  uint8_t flags;
  Http2StreamId streamid;
};

// [RFC 7540] 5.4. Error Handling
struct Http2Error {
  Http2Error(const Http2ErrorClass error_class = Http2ErrorClass::HTTP2_ERROR_CLASS_NONE,
             const Http2ErrorCode error_code = Http2ErrorCode::HTTP2_ERROR_NO_ERROR, const char *err_msg = "")
  {
    cls  = error_class;
    code = error_code;
    msg  = err_msg;
  };

  Http2ErrorClass cls;
  Http2ErrorCode code;
  const char *msg;
};

// [RFC 7540] 6.5.1. SETTINGS Format
struct Http2SettingsParameter {
  uint16_t id;
  uint32_t value;
};

// [RFC 7540] 6.3 PRIORITY Format
struct Http2Priority {
  Http2Priority() : weight(HTTP2_PRIORITY_DEFAULT_WEIGHT), stream_dependency(HTTP2_PRIORITY_DEFAULT_STREAM_DEPENDENCY) {}

  bool exclusive_flag = false;
  uint8_t weight;
  uint32_t stream_dependency;
};

// [RFC 7540] 6.2 HEADERS Format
struct Http2HeadersParameter {
  Http2HeadersParameter() {}
  uint8_t pad_length = 0;
  Http2Priority priority;
};

// [RFC 7540] 6.8 GOAWAY Format
struct Http2Goaway {
  Http2Goaway() {}
  Http2StreamId last_streamid = 0;
  Http2ErrorCode error_code   = Http2ErrorCode::HTTP2_ERROR_NO_ERROR;

  // NOTE: we don't (de)serialize the variable length debug data at this layer
  // because there's
  // really nothing we can do with it without some out of band agreement. Trying
  // to deal with it
  // just complicates memory management.
};

// [RFC 7540] 6.4 RST_STREAM Format
struct Http2RstStream {
  uint32_t error_code;
};

// [RFC 7540] 6.6 PUSH_PROMISE Format
struct Http2PushPromise {
  uint8_t pad_length              = 0;
  Http2StreamId promised_streamid = 0;
};

static inline bool
http2_is_client_streamid(Http2StreamId streamid)
{
  return (streamid & 0x1u) == 0x1u;
}

static inline bool
http2_is_server_streamid(Http2StreamId streamid)
{
  return (streamid & 0x1u) == 0x0u && streamid != 0x0u;
}

bool http2_parse_frame_header(IOVec, Http2FrameHeader &);

bool http2_write_frame_header(const Http2FrameHeader &, IOVec);

bool http2_write_rst_stream(uint32_t, IOVec);

bool http2_write_settings(const Http2SettingsParameter &, const IOVec &);

bool http2_write_ping(const uint8_t *, IOVec);

bool http2_write_goaway(const Http2Goaway &, IOVec);

bool http2_write_window_update(const uint32_t new_size, const IOVec &);

bool http2_write_push_promise(const Http2PushPromise &push_promise, const uint8_t *src, size_t length, const IOVec &iov);

bool http2_frame_header_is_valid(const Http2FrameHeader &, unsigned);

bool http2_settings_parameter_is_valid(const Http2SettingsParameter &);

bool http2_parse_headers_parameter(IOVec, Http2HeadersParameter &);

bool http2_parse_priority_parameter(IOVec, Http2Priority &);

bool http2_parse_rst_stream(IOVec, Http2RstStream &);

bool http2_parse_settings_parameter(IOVec, Http2SettingsParameter &);

bool http2_parse_goaway(IOVec, Http2Goaway &);

bool http2_parse_window_update(IOVec, uint32_t &);

Http2ErrorCode http2_decode_header_blocks(HTTPHdr *, const uint8_t *, const uint32_t, uint32_t *, HpackHandle &, bool &, uint32_t);

Http2ErrorCode http2_encode_header_blocks(HTTPHdr *, uint8_t *, uint32_t, uint32_t *, HpackHandle &, int32_t);

ParseResult http2_convert_header_from_2_to_1_1(HTTPHdr *);
ParseResult http2_convert_header_from_1_1_to_2(HTTPHdr *);
void http2_init_pseudo_headers(HTTPHdr &);
void http2_init();

// Not sure where else to put this, but figure this is as good of a start as
// anything else.
// Right now, only the static init() is available, which sets up some basic
// librecords
// dependencies.
class Http2
{
public:
  static uint32_t max_concurrent_streams_in;
  static uint32_t min_concurrent_streams_in;
  static uint32_t max_active_streams_in;
  static bool throttling;
  static uint32_t stream_priority_enabled;
  static uint32_t initial_window_size;
  static uint32_t max_frame_size;
  static uint32_t header_table_size;
  static uint32_t max_header_list_size;
  static uint32_t accept_no_activity_timeout;
  static uint32_t no_activity_timeout_in;
  static uint32_t active_timeout_in;
  static uint32_t push_diary_size;
  static uint32_t zombie_timeout_in;
  static float stream_error_rate_threshold;
  static uint32_t stream_error_sampling_threshold;
  static uint32_t max_settings_per_frame;
  static uint32_t max_settings_per_minute;
  static uint32_t max_settings_frames_per_minute;
  static uint32_t max_ping_frames_per_minute;
  static uint32_t max_priority_frames_per_minute;
  static uint32_t max_rst_stream_frames_per_minute;
  static uint32_t max_continuation_frames_per_minute;
  static float min_avg_window_update;
  static uint32_t con_slow_log_threshold;
  static uint32_t stream_slow_log_threshold;
  static uint32_t header_table_size_limit;
  static uint32_t write_buffer_block_size;
  static float write_size_threshold;
  static uint32_t write_time_threshold;
  static uint32_t buffer_water_mark;

  static void init();
};