/** @file

  A brief file description

  @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_assert.h"
#include "tscore/ink_platform.h"
#include "P_HostDB.h"
#include "P_Net.h"
#include "HttpConfig.h"
#include "HTTP.h"
#include "HttpTransactCache.h"
#include "ControlMatcher.h"
#include "CacheControl.h"
#include "ParentSelection.h"
#include "ProxyConfig.h"
#include "Transform.h"
#include "Milestones.h"
#include "ts/remap.h"
#include "ts/parentselectdefs.h"
#include "RemapPluginInfo.h"
#include "UrlMapping.h"
#include "records/I_RecHttp.h"
#include "ProxySession.h"
#include "MgmtDefs.h"

#define HTTP_RELEASE_ASSERT(X) ink_release_assert(X)

#define DUMP_HEADER(T, H, I, S)                                 \
  {                                                             \
    if (diags->on(T)) {                                         \
      fprintf(stderr, "+++++++++ %s +++++++++\n", S);           \
      fprintf(stderr, "-- State Machine Id: %" PRId64 "\n", I); \
      char b[4096];                                             \
      int used, tmp, offset;                                    \
      int done;                                                 \
      offset = 0;                                               \
      if ((H)->valid()) {                                       \
        do {                                                    \
          used = 0;                                             \
          tmp  = offset;                                        \
          done = (H)->print(b, 4095, &used, &tmp);              \
          offset += used;                                       \
          b[used] = '\0';                                       \
          fprintf(stderr, "%s", b);                             \
        } while (!done);                                        \
      }                                                         \
    }                                                           \
  }

typedef time_t ink_time_t;

struct HttpConfigParams;
class HttpSM;

#include "tscore/InkErrno.h"
#include "HttpConnectionCount.h"

#define UNKNOWN_INTERNAL_ERROR (INK_START_ERRNO - 1)

enum ViaStringIndex_t {
  //
  // General information
  VIA_CLIENT = 0,
  VIA_CLIENT_REQUEST,
  VIA_CACHE,
  VIA_CACHE_RESULT,
  VIA_SERVER,
  VIA_SERVER_RESULT,
  VIA_CACHE_FILL,
  VIA_CACHE_FILL_ACTION,
  VIA_PROXY,
  VIA_PROXY_RESULT,
  VIA_ERROR,
  VIA_ERROR_TYPE,
  //
  // State Machine specific details
  VIA_DETAIL_SEPARATOR,
  VIA_DETAIL_TUNNEL_DESCRIPTOR,
  VIA_DETAIL_TUNNEL,
  VIA_DETAIL_CACHE_DESCRIPTOR,
  VIA_DETAIL_CACHE_TYPE,
  VIA_DETAIL_CACHE_LOOKUP,
  VIA_DETAIL_PP_DESCRIPTOR,
  VIA_DETAIL_PP_CONNECT,
  VIA_DETAIL_SERVER_DESCRIPTOR,
  VIA_DETAIL_SERVER_CONNECT,
  //
  // Total
  MAX_VIA_INDICES
};

enum ViaString_t {
  // client stuff
  VIA_CLIENT_STRING   = 'u',
  VIA_CLIENT_ERROR    = 'E',
  VIA_CLIENT_IMS      = 'I',
  VIA_CLIENT_NO_CACHE = 'N',
  VIA_CLIENT_COOKIE   = 'C',
  VIA_CLIENT_SIMPLE   = 'S',
  // cache lookup stuff
  VIA_CACHE_STRING            = 'c',
  VIA_CACHE_MISS              = 'M',
  VIA_IN_CACHE_NOT_ACCEPTABLE = 'A',
  VIA_IN_CACHE_STALE          = 'S',
  VIA_IN_CACHE_FRESH          = 'H',
  VIA_IN_RAM_CACHE_FRESH      = 'R',
  VIA_IN_CACHE_RWW_HIT        = 'W',
  // server stuff
  VIA_SERVER_STRING       = 's',
  VIA_SERVER_ERROR        = 'E',
  VIA_SERVER_NOT_MODIFIED = 'N',
  VIA_SERVER_SERVED       = 'S',
  // cache fill stuff
  VIA_CACHE_FILL_STRING = 'f',
  VIA_CACHE_DELETED     = 'D',
  VIA_CACHE_WRITTEN     = 'W',
  VIA_CACHE_UPDATED     = 'U',
  // proxy stuff
  VIA_PROXY_STRING             = 'p',
  VIA_PROXY_NOT_MODIFIED       = 'N',
  VIA_PROXY_SERVED             = 'S',
  VIA_PROXY_SERVER_REVALIDATED = 'R',
  // errors
  VIA_ERROR_STRING            = 'e',
  VIA_ERROR_NO_ERROR          = 'N',
  VIA_ERROR_AUTHORIZATION     = 'A',
  VIA_ERROR_CONNECTION        = 'C',
  VIA_ERROR_DNS_FAILURE       = 'D',
  VIA_ERROR_FORBIDDEN         = 'F',
  VIA_ERROR_HEADER_SYNTAX     = 'H',
  VIA_ERROR_SERVER            = 'S',
  VIA_ERROR_TIMEOUT           = 'T',
  VIA_ERROR_CACHE_READ        = 'R',
  VIA_ERROR_MOVED_TEMPORARILY = 'M',
  VIA_ERROR_LOOP_DETECTED     = 'L',
  VIA_ERROR_UNKNOWN           = ' ',
  //
  // Now the detailed stuff
  //
  VIA_DETAIL_SEPARATOR_STRING = ':',
  // tunnelling
  VIA_DETAIL_TUNNEL_DESCRIPTOR_STRING = 't',
  VIA_DETAIL_TUNNEL_HEADER_FIELD      = 'F',
  VIA_DETAIL_TUNNEL_METHOD            = 'M',
  VIA_DETAIL_TUNNEL_CACHE_OFF         = 'O',
  VIA_DETAIL_TUNNEL_URL               = 'U',
  VIA_DETAIL_TUNNEL_NO_FORWARD        = 'N',
  VIA_DETAIL_TUNNEL_AUTHORIZATION     = 'A',
  // cache type
  VIA_DETAIL_CACHE_DESCRIPTOR_STRING = 'c',
  VIA_DETAIL_CACHE                   = 'C',
  VIA_DETAIL_PARENT                  = 'P',
  VIA_DETAIL_SERVER                  = 'S',
  // result of cache lookup
  VIA_DETAIL_HIT_CONDITIONAL  = 'N',
  VIA_DETAIL_HIT_SERVED       = 'H',
  VIA_DETAIL_MISS_CONDITIONAL = 'I',
  VIA_DETAIL_MISS_NOT_CACHED  = 'M',
  VIA_DETAIL_MISS_EXPIRED     = 'S',
  VIA_DETAIL_MISS_CONFIG      = 'C',
  VIA_DETAIL_MISS_CLIENT      = 'U',
  VIA_DETAIL_MISS_METHOD      = 'D',
  VIA_DETAIL_MISS_COOKIE      = 'K',
  // result of pp suggested host lookup
  VIA_DETAIL_PP_DESCRIPTOR_STRING = 'p',
  VIA_DETAIL_PP_SUCCESS           = 'S',
  VIA_DETAIL_PP_FAILURE           = 'F',
  // result of server suggested host lookup
  VIA_DETAIL_SERVER_DESCRIPTOR_STRING = 's',
  VIA_DETAIL_SERVER_SUCCESS           = 'S',
  VIA_DETAIL_SERVER_FAILURE           = 'F'
};

struct HttpApiInfo {
  char *parent_proxy_name       = nullptr;
  int parent_proxy_port         = -1;
  bool cache_untransformed      = false;
  bool cache_transformed        = true;
  bool logging_enabled          = true;
  bool retry_intercept_failures = false;

  HttpApiInfo() {}
};

const int32_t HTTP_UNDEFINED_CL = -1;

//////////////////////////////////////////////////////////////////////////////
//
//  HttpTransact
//
//  The HttpTransact class is purely used for scoping and should
//  not be instantiated.
//
//////////////////////////////////////////////////////////////////////////////
#define SET_VIA_STRING(I, S) s->via_string[I] = S;
#define GET_VIA_STRING(I) (s->via_string[I])

class HttpTransact
{
public:
  enum AbortState_t {
    ABORT_UNDEFINED = 0,
    DIDNOT_ABORT,
    ABORTED,
  };

  enum Authentication_t {
    AUTHENTICATION_SUCCESS = 0,
    AUTHENTICATION_MUST_REVALIDATE,
    AUTHENTICATION_MUST_PROXY,
    AUTHENTICATION_CACHE_AUTH
  };

  enum CacheAction_t {
    CACHE_DO_UNDEFINED = 0,
    CACHE_DO_NO_ACTION,
    CACHE_DO_DELETE,
    CACHE_DO_LOOKUP,
    CACHE_DO_REPLACE,
    CACHE_DO_SERVE,
    CACHE_DO_SERVE_AND_DELETE,
    CACHE_DO_SERVE_AND_UPDATE,
    CACHE_DO_UPDATE,
    CACHE_DO_WRITE,
    CACHE_PREPARE_TO_DELETE,
    CACHE_PREPARE_TO_UPDATE,
    CACHE_PREPARE_TO_WRITE,
    TOTAL_CACHE_ACTION_TYPES
  };

  enum CacheWriteLock_t {
    CACHE_WL_INIT,
    CACHE_WL_SUCCESS,
    CACHE_WL_FAIL,
    CACHE_WL_READ_RETRY,
  };

  enum ClientTransactionResult_t {
    CLIENT_TRANSACTION_RESULT_UNDEFINED,
    CLIENT_TRANSACTION_RESULT_HIT_FRESH,
    CLIENT_TRANSACTION_RESULT_HIT_REVALIDATED,
    CLIENT_TRANSACTION_RESULT_MISS_COLD,
    CLIENT_TRANSACTION_RESULT_MISS_CHANGED,
    CLIENT_TRANSACTION_RESULT_MISS_CLIENT_NO_CACHE,
    CLIENT_TRANSACTION_RESULT_MISS_UNCACHABLE,
    CLIENT_TRANSACTION_RESULT_ERROR_ABORT,
    CLIENT_TRANSACTION_RESULT_ERROR_POSSIBLE_ABORT,
    CLIENT_TRANSACTION_RESULT_ERROR_CONNECT_FAIL,
    CLIENT_TRANSACTION_RESULT_ERROR_OTHER
  };

  enum Freshness_t {
    FRESHNESS_FRESH = 0, // Fresh enough, serve it
    FRESHNESS_WARNING,   // Stale, but client says OK
    FRESHNESS_STALE      // Stale, don't use
  };

  enum HttpTransactMagic_t {
    HTTP_TRANSACT_MAGIC_ALIVE     = 0x00001234,
    HTTP_TRANSACT_MAGIC_DEAD      = 0xDEAD1234,
    HTTP_TRANSACT_MAGIC_SEPARATOR = 0x12345678
  };

  enum LookingUp_t {
    ORIGIN_SERVER,
    UNDEFINED_LOOKUP,
    PARENT_PROXY,
    INCOMING_ROUTER,
    HOST_NONE,
  };

  enum ProxyMode_t {
    UNDEFINED_MODE,
    GENERIC_PROXY,
    TUNNELLING_PROXY,
  };

  enum RequestError_t {
    NO_REQUEST_HEADER_ERROR,
    BAD_HTTP_HEADER_SYNTAX,
    BAD_CONNECT_PORT,
    FAILED_PROXY_AUTHORIZATION,
    METHOD_NOT_SUPPORTED,
    MISSING_HOST_FIELD,
    NO_POST_CONTENT_LENGTH,
    NO_REQUEST_SCHEME,
    NON_EXISTANT_REQUEST_HEADER,
    SCHEME_NOT_SUPPORTED,
    UNACCEPTABLE_TE_REQUIRED,
    INVALID_POST_CONTENT_LENGTH,
    TOTAL_REQUEST_ERROR_TYPES
  };

  enum ResponseError_t {
    NO_RESPONSE_HEADER_ERROR,
    BOGUS_OR_NO_DATE_IN_RESPONSE,
    CONNECTION_OPEN_FAILED,
    MISSING_REASON_PHRASE,
    MISSING_STATUS_CODE,
    NON_EXISTANT_RESPONSE_HEADER,
    NOT_A_RESPONSE_HEADER,
    STATUS_CODE_SERVER_ERROR,
    TOTAL_RESPONSE_ERROR_TYPES
  };

  // Please do not forget to fix TSServerState (ts/apidefs.h.in)
  // in case of any modifications in ServerState_t
  enum ServerState_t {
    STATE_UNDEFINED = 0,
    ACTIVE_TIMEOUT,
    BAD_INCOMING_RESPONSE,
    CONNECTION_ALIVE,
    CONNECTION_CLOSED,
    CONNECTION_ERROR,
    INACTIVE_TIMEOUT,
    OPEN_RAW_ERROR,
    PARSE_ERROR,
    TRANSACTION_COMPLETE,
    PARENT_RETRY,
    OUTBOUND_CONGESTION
  };

  enum CacheWriteStatus_t {
    NO_CACHE_WRITE = 0,
    CACHE_WRITE_LOCK_MISS,
    CACHE_WRITE_IN_PROGRESS,
    CACHE_WRITE_ERROR,
    CACHE_WRITE_COMPLETE
  };

  enum HttpRequestFlavor_t {
    REQ_FLAVOR_INTERCEPTED      = 0,
    REQ_FLAVOR_REVPROXY         = 1,
    REQ_FLAVOR_FWDPROXY         = 2,
    REQ_FLAVOR_SCHEDULED_UPDATE = 3
  };

  ////////////
  // source //
  ////////////
  enum Source_t {
    SOURCE_NONE = 0,
    SOURCE_HTTP_ORIGIN_SERVER,
    SOURCE_RAW_ORIGIN_SERVER,
    SOURCE_CACHE,
    SOURCE_TRANSFORM,
    SOURCE_INTERNAL // generated from text buffer
  };

  ////////////////////////////////////////////////
  // HttpTransact fills a StateMachineAction_t  //
  // to tell the state machine what to do next. //
  ////////////////////////////////////////////////
  enum StateMachineAction_t {
    SM_ACTION_UNDEFINED = 0,

    // SM_ACTION_AUTH_LOOKUP,
    SM_ACTION_DNS_LOOKUP,
    SM_ACTION_DNS_REVERSE_LOOKUP,

    SM_ACTION_CACHE_LOOKUP,
    SM_ACTION_CACHE_ISSUE_WRITE,
    SM_ACTION_CACHE_ISSUE_WRITE_TRANSFORM,
    SM_ACTION_CACHE_PREPARE_UPDATE,
    SM_ACTION_CACHE_ISSUE_UPDATE,

    SM_ACTION_ORIGIN_SERVER_OPEN,
    SM_ACTION_ORIGIN_SERVER_RAW_OPEN,
    SM_ACTION_ORIGIN_SERVER_RR_MARK_DOWN,

    SM_ACTION_READ_PUSH_HDR,
    SM_ACTION_STORE_PUSH_BODY,

    SM_ACTION_INTERNAL_CACHE_DELETE,
    SM_ACTION_INTERNAL_CACHE_NOOP,
    SM_ACTION_INTERNAL_CACHE_UPDATE_HEADERS,
    SM_ACTION_INTERNAL_CACHE_WRITE,
    SM_ACTION_INTERNAL_100_RESPONSE,
    SM_ACTION_INTERNAL_REQUEST,
    SM_ACTION_SEND_ERROR_CACHE_NOOP,

    SM_ACTION_WAIT_FOR_FULL_BODY,
    SM_ACTION_REQUEST_BUFFER_READ_COMPLETE,
    SM_ACTION_SERVE_FROM_CACHE,
    SM_ACTION_SERVER_READ,
    SM_ACTION_SERVER_PARSE_NEXT_HDR,
    SM_ACTION_TRANSFORM_READ,
    SM_ACTION_SSL_TUNNEL,
    SM_ACTION_CONTINUE,

    SM_ACTION_API_SM_START,
    SM_ACTION_API_READ_REQUEST_HDR,
    SM_ACTION_API_PRE_REMAP,
    SM_ACTION_API_POST_REMAP,
    SM_ACTION_API_OS_DNS,
    SM_ACTION_API_SEND_REQUEST_HDR,
    SM_ACTION_API_READ_CACHE_HDR,
    SM_ACTION_API_CACHE_LOOKUP_COMPLETE,
    SM_ACTION_API_READ_RESPONSE_HDR,
    SM_ACTION_API_SEND_RESPONSE_HDR,
    SM_ACTION_API_SM_SHUTDOWN,

    SM_ACTION_REMAP_REQUEST,
    SM_ACTION_POST_REMAP_SKIP,
    SM_ACTION_REDIRECT_READ
  };

  enum TransferEncoding_t {
    NO_TRANSFER_ENCODING = 0,
    CHUNKED_ENCODING,
    DEFLATE_ENCODING,
  };

  enum Variability_t {
    VARIABILITY_NONE = 0,
    VARIABILITY_SOME,
    VARIABILITY_ALL,
  };

  enum CacheLookupResult_t {
    CACHE_LOOKUP_NONE,
    CACHE_LOOKUP_MISS,
    CACHE_LOOKUP_DOC_BUSY,
    CACHE_LOOKUP_HIT_STALE,
    CACHE_LOOKUP_HIT_WARNING,
    CACHE_LOOKUP_HIT_FRESH,
    CACHE_LOOKUP_SKIPPED
  };

  enum UpdateCachedObject_t {
    UPDATE_CACHED_OBJECT_NONE,
    UPDATE_CACHED_OBJECT_PREPARE,
    UPDATE_CACHED_OBJECT_CONTINUE,
    UPDATE_CACHED_OBJECT_ERROR,
    UPDATE_CACHED_OBJECT_SUCCEED,
    UPDATE_CACHED_OBJECT_FAIL
  };

  enum RangeSetup_t {
    RANGE_NONE = 0,
    RANGE_REQUESTED,
    RANGE_NOT_SATISFIABLE,
    RANGE_NOT_HANDLED,
    RANGE_NOT_TRANSFORM_REQUESTED,
  };

  enum CacheAuth_t {
    CACHE_AUTH_NONE = 0,
    // CACHE_AUTH_TRUE,
    CACHE_AUTH_FRESH,
    CACHE_AUTH_STALE,
    CACHE_AUTH_SERVE
  };

  struct State;
  typedef void (*TransactFunc_t)(HttpTransact::State *);

  typedef struct _CacheDirectives {
    bool does_client_permit_lookup      = true;
    bool does_client_permit_storing     = true;
    bool does_client_permit_dns_storing = true;
    bool does_config_permit_lookup      = true;
    bool does_config_permit_storing     = true;
    bool does_server_permit_lookup      = true;
    bool does_server_permit_storing     = true;

    _CacheDirectives() {}
  } CacheDirectives;

  typedef struct _CacheLookupInfo {
    HttpTransact::CacheAction_t action           = CACHE_DO_UNDEFINED;
    HttpTransact::CacheAction_t transform_action = CACHE_DO_UNDEFINED;

    HttpTransact::CacheWriteStatus_t write_status           = NO_CACHE_WRITE;
    HttpTransact::CacheWriteStatus_t transform_write_status = NO_CACHE_WRITE;

    URL *lookup_url = nullptr;
    URL lookup_url_storage;
    URL original_url;
    HTTPInfo object_store;
    HTTPInfo transform_store;
    CacheDirectives directives;
    HTTPInfo *object_read             = nullptr;
    int open_read_retries             = 0;
    int open_write_retries            = 0;
    CacheWriteLock_t write_lock_state = CACHE_WL_INIT;
    int lookup_count                  = 0;
    SquidHitMissCode hit_miss_code    = SQUID_MISS_NONE;
    URL *parent_selection_url         = nullptr;
    URL parent_selection_url_storage;

    _CacheLookupInfo() {}
  } CacheLookupInfo;

  typedef struct _RedirectInfo {
    bool redirect_in_process = false;
    URL original_url;

    _RedirectInfo() {}
  } RedirectInfo;

  struct ConnectionAttributes {
    HTTPVersion http_version;
    HTTPKeepAlive keep_alive = HTTP_KEEPALIVE_UNDEFINED;

    // The following variable is true if the client expects to
    // received a chunked response.
    bool receive_chunked_response = false;
    bool proxy_connect_hdr        = false;
    /// @c errno from the most recent attempt to connect.
    /// zero means no failure (not attempted, succeeded).
    int connect_result                   = 0;
    char *name                           = nullptr;
    TransferEncoding_t transfer_encoding = NO_TRANSFER_ENCODING;

    /** This is the source address of the connection from the point of view of the transaction.
        It is the address of the source of the request.
    */
    IpEndpoint src_addr;
    /** This is the destination address of the connection from the point of view of the transaction.
        It is the address of the target of the request.
    */
    IpEndpoint dst_addr;

    ServerState_t state                         = STATE_UNDEFINED;
    AbortState_t abort                          = ABORT_UNDEFINED;
    HttpProxyPort::TransportType port_attribute = HttpProxyPort::TRANSPORT_DEFAULT;

    /// @c true if the connection is transparent.
    bool is_transparent = false;
    ProxyError rx_error_code;
    ProxyError tx_error_code;

    bool
    had_connect_fail() const
    {
      return 0 != connect_result;
    }
    void
    clear_connect_fail()
    {
      connect_result = 0;
    }
    ConnectionAttributes() { clear(); }

    void
    clear()
    {
      ink_zero(src_addr);
      ink_zero(dst_addr);
      connect_result = 0;
    }
  };

  typedef struct _CurrentInfo {
    ProxyMode_t mode                           = UNDEFINED_MODE;
    LookingUp_t request_to                     = UNDEFINED_LOOKUP;
    ConnectionAttributes *server               = nullptr;
    ink_time_t now                             = 0;
    ServerState_t state                        = STATE_UNDEFINED;
    unsigned attempts                          = 0;
    unsigned simple_retry_attempts             = 0;
    unsigned unavailable_server_retry_attempts = 0;
    ParentRetry_t retry_type                   = PARENT_RETRY_NONE;

    _CurrentInfo() {}
  } CurrentInfo;

  typedef struct _DNSLookupInfo {
    /** Origin server address source selection.

        If config says to use CTA (client target addr) state is
        OS_ADDR_TRY_CLIENT, otherwise it remains the default. If the
        connect fails then we switch to a USE. We go to USE_HOSTDB if
        (1) the HostDB lookup is successful and (2) some address other
        than the CTA is available to try. Otherwise we keep retrying
        on the CTA (USE_CLIENT) up to the max retry value.  In essence
        we try to treat the CTA as if it were another RR value in the
        HostDB record.
     */
    enum class OS_Addr {
      OS_ADDR_TRY_DEFAULT, ///< Initial state, use what config says.
      OS_ADDR_TRY_HOSTDB,  ///< Try HostDB data.
      OS_ADDR_TRY_CLIENT,  ///< Try client target addr.
      OS_ADDR_USE_HOSTDB,  ///< Force use of HostDB target address.
      OS_ADDR_USE_CLIENT   ///< Use client target addr, no fallback.
    };

    OS_Addr os_addr_style = OS_Addr::OS_ADDR_TRY_DEFAULT;

    bool lookup_success         = false;
    char *lookup_name           = nullptr;
    char srv_hostname[MAXDNAME] = {0};
    LookingUp_t looking_up      = UNDEFINED_LOOKUP;
    bool srv_lookup_success     = false;
    short srv_port              = 0;
    HostDBApplicationInfo srv_app;

    /*** Set to true by default.  If use_client_target_address is set
     * to 1, this value will be set to false if the client address is
     * not in the DNS pool */
    bool lookup_validated = true;

    _DNSLookupInfo() {}
  } DNSLookupInfo;

  // Conversion handling for DNS host resolution type.
  static const MgmtConverter HOST_RES_CONV;

  typedef struct _HeaderInfo {
    HTTPHdr client_request;
    HTTPHdr client_response;
    HTTPHdr server_request;
    HTTPHdr server_response;
    HTTPHdr transform_response;
    HTTPHdr cache_request;
    HTTPHdr cache_response;
    int64_t request_content_length  = HTTP_UNDEFINED_CL;
    int64_t response_content_length = HTTP_UNDEFINED_CL;
    int64_t transform_request_cl    = HTTP_UNDEFINED_CL;
    int64_t transform_response_cl   = HTTP_UNDEFINED_CL;
    bool client_req_is_server_style = false;
    bool trust_response_cl          = false;
    ResponseError_t response_error  = NO_RESPONSE_HEADER_ERROR;
    bool extension_method           = false;

    _HeaderInfo() {}
  } HeaderInfo;

  typedef struct _SquidLogInfo {
    SquidLogCode log_code          = SQUID_LOG_ERR_UNKNOWN;
    SquidSubcode subcode           = SQUID_SUBCODE_EMPTY;
    SquidHierarchyCode hier_code   = SQUID_HIER_EMPTY;
    SquidHitMissCode hit_miss_code = SQUID_MISS_NONE;

    _SquidLogInfo() {}
  } SquidLogInfo;

  typedef struct _ResponseAction {
    bool handled = false;
    TSResponseAction action;

    _ResponseAction() {}
  } ResponseAction;

  struct State {
    HttpTransactMagic_t m_magic = HTTP_TRANSACT_MAGIC_ALIVE;

    HttpSM *state_machine = nullptr;

    Arena arena;

    HttpConfigParams *http_config_param = nullptr;
    CacheLookupInfo cache_info;
    DNSLookupInfo dns_info;
    RedirectInfo redirect_info;
    OutboundConnTrack::TxnState outbound_conn_track_state;
    HTTPVersion updated_server_version    = HTTP_INVALID;
    bool force_dns                        = false;
    MgmtByte cache_open_write_fail_action = 0;
    ConnectionAttributes client_info;
    ConnectionAttributes parent_info;
    ConnectionAttributes server_info;

    Source_t source                = SOURCE_NONE;
    Source_t pre_transform_source  = SOURCE_NONE;
    HttpRequestFlavor_t req_flavor = REQ_FLAVOR_FWDPROXY;

    CurrentInfo current;
    HeaderInfo hdr_info;
    SquidLogInfo squid_codes;
    HttpApiInfo api_info;
    // To handle parent proxy case, we need to be
    //  able to defer some work in building the request
    TransactFunc_t pending_work = nullptr;

    HttpRequestData request_data;
    ParentConfigParams *parent_params                           = nullptr;
    std::shared_ptr<NextHopSelectionStrategy> next_hop_strategy = nullptr;
    ParentResult parent_result;
    CacheControlResult cache_control;
    CacheLookupResult_t cache_lookup_result = CACHE_LOOKUP_NONE;

    StateMachineAction_t next_action                      = SM_ACTION_UNDEFINED; // out
    StateMachineAction_t api_next_action                  = SM_ACTION_UNDEFINED; // out
    void (*transact_return_point)(HttpTransact::State *s) = nullptr;             // out

    // We keep this so we can jump back to the upgrade handler after remap is complete
    void (*post_remap_upgrade_return_point)(HttpTransact::State *s) = nullptr; // out
    const char *upgrade_token_wks                                   = nullptr;
    bool is_upgrade_request                                         = false;

    // Some WebSocket state
    bool is_websocket        = false;
    bool did_upgrade_succeed = false;

    char *internal_msg_buffer                       = nullptr; // out
    char *internal_msg_buffer_type                  = nullptr; // out
    int64_t internal_msg_buffer_size                = 0;       // out
    int64_t internal_msg_buffer_fast_allocator_size = -1;

    int scheme               = -1;     // out
    int next_hop_scheme      = scheme; // out
    int orig_scheme          = scheme; // pre-mapped scheme
    int method               = 0;
    int cause_of_death_errno = -UNKNOWN_INTERNAL_ERROR; // in
    Ptr<HostDBInfo> hostdb_entry;                       // Pointer to the entry we are referencing in hostdb-- to keep our ref
    HostDBInfo host_db_info;                            // in

    ink_time_t client_request_time    = UNDEFINED_TIME; // internal
    ink_time_t request_sent_time      = UNDEFINED_TIME; // internal
    ink_time_t response_received_time = UNDEFINED_TIME; // internal
    ink_time_t plugin_set_expire_time = UNDEFINED_TIME;

    char via_string[MAX_VIA_INDICES + 1];

    int64_t state_machine_id = 0;

    // new ACL filtering result (calculated immediately after remap)
    bool client_connection_enabled = true;
    bool acl_filtering_performed   = false;

    /// True if the response is cacheable because of negative caching configuration.
    ///
    /// This being true implies the following:
    ///
    /// * The response code was negative.
    /// * Negative caching is enabled.
    /// * The response is considered cacheable because of negative caching
    ///   configuration.
    bool is_cacheable_due_to_negative_caching_configuration = false;
    // for authenticated content caching
    CacheAuth_t www_auth_content = CACHE_AUTH_NONE;

    RemapPluginInst *os_response_plugin_inst = nullptr;
    HTTPStatus http_return_code              = HTTP_STATUS_NONE;

    int api_txn_active_timeout_value      = -1;
    int api_txn_connect_timeout_value     = -1;
    int api_txn_dns_timeout_value         = -1;
    int api_txn_no_activity_timeout_value = -1;

    // Used by INKHttpTxnCachedReqGet and INKHttpTxnCachedRespGet SDK functions
    // to copy part of HdrHeap (only the writable portion) for cached response headers
    // and request headers
    // These ptrs are deallocate when transaction is over.
    HdrHeapSDKHandle *cache_req_hdr_heap_handle   = nullptr;
    HdrHeapSDKHandle *cache_resp_hdr_heap_handle  = nullptr;
    bool api_cleanup_cache_read                   = false;
    bool api_server_response_no_store             = false;
    bool api_server_response_ignore               = false;
    bool api_http_sm_shutdown                     = false;
    bool api_modifiable_cached_resp               = false;
    bool api_server_request_body_set              = false;
    bool api_req_cacheable                        = false;
    bool api_resp_cacheable                       = false;
    bool api_server_addr_set                      = false;
    UpdateCachedObject_t api_update_cached_object = UPDATE_CACHED_OBJECT_NONE;
    StateMachineAction_t saved_update_next_action = SM_ACTION_UNDEFINED;
    CacheAction_t saved_update_cache_action       = CACHE_DO_UNDEFINED;

    // Remap plugin processor support
    UrlMappingContainer url_map;
    host_hdr_info hh_info = {nullptr, 0, 0};

    int congestion_control_crat = 0; // Client retry after

    unsigned int filter_mask = 0;
    char *remap_redirect     = nullptr;
    bool reverse_proxy       = false;
    bool url_remap_success   = false;

    bool api_skip_all_remapping = false;

    bool already_downgraded = false;
    URL unmapped_url; // unmapped url is the effective url before remap

    // Http Range: related variables
    RangeSetup_t range_setup = RANGE_NONE;
    int64_t num_range_fields = 0;
    int64_t range_output_cl  = 0;
    RangeRecord *ranges      = nullptr;

    OverridableHttpConfigParams const *txn_conf = nullptr;
    OverridableHttpConfigParams &
    my_txn_conf() // Storage for plugins, to avoid malloc
    {
      auto p = reinterpret_cast<OverridableHttpConfigParams *>(_my_txn_conf);

      ink_assert(p == txn_conf);

      return *p;
    }

    bool transparent_passthrough = false;
    bool range_in_cache          = false;

    ResponseAction response_action;

    // Methods
    void
    init()
    {
      parent_params = ParentConfig::acquire();
    }

    // Constructor
    State()
    {
      int i;
      char *via_ptr = via_string;

      for (i = 0; i < MAX_VIA_INDICES; i++) {
        *via_ptr++ = ' ';
      }

      via_string[VIA_CLIENT]                   = VIA_CLIENT_STRING;
      via_string[VIA_CACHE]                    = VIA_CACHE_STRING;
      via_string[VIA_SERVER]                   = VIA_SERVER_STRING;
      via_string[VIA_CACHE_FILL]               = VIA_CACHE_FILL_STRING;
      via_string[VIA_PROXY]                    = VIA_PROXY_STRING;
      via_string[VIA_ERROR]                    = VIA_ERROR_STRING;
      via_string[VIA_ERROR_TYPE]               = VIA_ERROR_NO_ERROR;
      via_string[VIA_DETAIL_SEPARATOR]         = VIA_DETAIL_SEPARATOR_STRING;
      via_string[VIA_DETAIL_TUNNEL_DESCRIPTOR] = VIA_DETAIL_TUNNEL_DESCRIPTOR_STRING;
      via_string[VIA_DETAIL_CACHE_DESCRIPTOR]  = VIA_DETAIL_CACHE_DESCRIPTOR_STRING;
      via_string[VIA_DETAIL_PP_DESCRIPTOR]     = VIA_DETAIL_PP_DESCRIPTOR_STRING;
      via_string[VIA_DETAIL_SERVER_DESCRIPTOR] = VIA_DETAIL_SERVER_DESCRIPTOR_STRING;
      via_string[MAX_VIA_INDICES]              = '\0';

      memset((void *)&host_db_info, 0, sizeof(host_db_info));
    }

    void
    destroy()
    {
      m_magic = HTTP_TRANSACT_MAGIC_DEAD;

      free_internal_msg_buffer();
      ats_free(internal_msg_buffer_type);

      ParentConfig::release(parent_params);
      parent_params = nullptr;

      hdr_info.client_request.destroy();
      hdr_info.client_response.destroy();
      hdr_info.server_request.destroy();
      hdr_info.server_response.destroy();
      hdr_info.transform_response.destroy();
      hdr_info.cache_request.destroy();
      hdr_info.cache_response.destroy();
      cache_info.lookup_url_storage.destroy();
      cache_info.parent_selection_url_storage.destroy();
      cache_info.original_url.destroy();
      cache_info.object_store.destroy();
      cache_info.transform_store.destroy();
      redirect_info.original_url.destroy();

      url_map.clear();
      arena.reset();
      unmapped_url.clear();
      hostdb_entry.clear();
      outbound_conn_track_state.clear();

      delete[] ranges;
      ranges      = nullptr;
      range_setup = RANGE_NONE;
      return;
    }

    // Little helper function to setup the per-transaction configuration copy
    void
    setup_per_txn_configs()
    {
      if (txn_conf != reinterpret_cast<OverridableHttpConfigParams *>(_my_txn_conf)) {
        txn_conf = reinterpret_cast<OverridableHttpConfigParams *>(_my_txn_conf);
        memcpy(_my_txn_conf, &http_config_param->oride, sizeof(_my_txn_conf));
      }
    }

    void
    free_internal_msg_buffer()
    {
      if (internal_msg_buffer) {
        if (internal_msg_buffer_fast_allocator_size >= 0) {
          ioBufAllocator[internal_msg_buffer_fast_allocator_size].free_void(internal_msg_buffer);
        } else {
          ats_free(internal_msg_buffer);
        }
        internal_msg_buffer = nullptr;
      }
      internal_msg_buffer_size = 0;
    }

    ProxyProtocol pp_info;

    void
    set_connect_fail(int e)
    {
      if (e == EIO || this->current.server->connect_result == EIO) {
        this->current.server->connect_result = e;
      }
      if (e != EIO) {
        this->cause_of_death_errno = e;
      }
    }

  private:
    // Make this a raw byte array, so it will be accessed through the my_txn_conf() member function.
    alignas(OverridableHttpConfigParams) char _my_txn_conf[sizeof(OverridableHttpConfigParams)];

  }; // End of State struct.

  static void HandleBlindTunnel(State *s);
  static void StartRemapRequest(State *s);
  static void EndRemapRequest(State *s);
  static void PerformRemap(State *s);
  static void ModifyRequest(State *s);
  static void HandleRequest(State *s);
  static void HandleRequestBufferDone(State *s);
  static bool handleIfRedirect(State *s);

  static void StartAccessControl(State *s);
  static void HandleRequestAuthorized(State *s);
  static void BadRequest(State *s);
  static void Forbidden(State *s);
  static void SelfLoop(State *s);
  static void TooEarly(State *s);
  static void OriginDead(State *s);
  static void PostActiveTimeoutResponse(State *s);
  static void PostInactiveTimeoutResponse(State *s);
  static void DecideCacheLookup(State *s);
  static void LookupSkipOpenServer(State *s);

  static void CallOSDNSLookup(State *s);
  static void OSDNSLookup(State *s);
  static void ReDNSRoundRobin(State *s);
  static void PPDNSLookup(State *s);
  static void PPDNSLookupAPICall(State *s);
  static void OriginServerRawOpen(State *s);
  static void HandleCacheOpenRead(State *s);
  static void HandleCacheOpenReadHitFreshness(State *s);
  static void HandleCacheOpenReadHit(State *s);
  static void HandleCacheOpenReadMiss(State *s);
  static void build_response_from_cache(State *s, HTTPWarningCode warning_code);
  static void handle_cache_write_lock(State *s);
  static void HandleResponse(State *s);
  static void HandleUpdateCachedObject(State *s);
  static void HandleUpdateCachedObjectContinue(State *s);
  static void HandleStatPage(State *s);
  static void handle_100_continue_response(State *s);
  static void handle_transform_ready(State *s);
  static void handle_transform_cache_write(State *s);
  static void handle_response_from_parent(State *s);
  static void handle_response_from_parent_plugin(State *s);
  static void handle_response_from_server(State *s);
  static void delete_server_rr_entry(State *s, int max_retries);
  static void retry_server_connection_not_open(State *s, ServerState_t conn_state, unsigned max_retries);
  static void error_log_connection_failure(State *s, ServerState_t conn_state);
  static void handle_server_connection_not_open(State *s);
  static void handle_forward_server_connection_open(State *s);
  static void handle_cache_operation_on_forward_server_response(State *s);
  static void handle_no_cache_operation_on_forward_server_response(State *s);
  static void merge_and_update_headers_for_cache_update(State *s);
  static void set_headers_for_cache_write(State *s, HTTPInfo *cache_info, HTTPHdr *request, HTTPHdr *response);
  static void set_header_for_transform(State *s, HTTPHdr *base_header);
  static void merge_response_header_with_cached_header(HTTPHdr *cached_header, HTTPHdr *response_header);
  static void merge_warning_header(HTTPHdr *cached_header, HTTPHdr *response_header);
  static void SetCacheFreshnessLimit(State *s);
  static void HandleApiErrorJump(State *);
  static void handle_websocket_upgrade_pre_remap(State *s);
  static void handle_websocket_upgrade_post_remap(State *s);
  static bool handle_upgrade_request(State *s);
  static void handle_websocket_connection(State *s);

  static void HandleCacheOpenReadPush(State *s, bool read_successful);
  static void HandlePushResponseHdr(State *s);
  static void HandlePushCacheWrite(State *s);
  static void HandlePushTunnelSuccess(State *s);
  static void HandlePushTunnelFailure(State *s);
  static void HandlePushError(State *s, const char *reason);
  static void HandleBadPushRespHdr(State *s);

  // Utility Methods
  static void issue_revalidate(State *s);
  static bool get_ka_info_from_config(State *s, ConnectionAttributes *server_info);
  static void get_ka_info_from_host_db(State *s, ConnectionAttributes *server_info, ConnectionAttributes *client_info,
                                       HostDBInfo *host_db_info);
  static void setup_plugin_request_intercept(State *s);
  static void add_client_ip_to_outgoing_request(State *s, HTTPHdr *request);
  static RequestError_t check_request_validity(State *s, HTTPHdr *incoming_hdr);
  static ResponseError_t check_response_validity(State *s, HTTPHdr *incoming_hdr);
  static void set_client_request_state(State *s, HTTPHdr *incoming_hdr);
  static bool delete_all_document_alternates_and_return(State *s, bool cache_hit);
  static bool does_client_request_permit_cached_response(const OverridableHttpConfigParams *p, CacheControlResult *c, HTTPHdr *h,
                                                         char *via_string);
  static bool does_client_request_permit_dns_caching(CacheControlResult *c, HTTPHdr *h);
  static bool does_client_request_permit_storing(CacheControlResult *c, HTTPHdr *h);
  static bool handle_internal_request(State *s, HTTPHdr *incoming_hdr);
  static bool handle_trace_and_options_requests(State *s, HTTPHdr *incoming_hdr);
  static void bootstrap_state_variables_from_request(State *s, HTTPHdr *incoming_request);
  static void initialize_state_variables_from_request(State *s, HTTPHdr *obsolete_incoming_request);
  static void initialize_state_variables_from_response(State *s, HTTPHdr *incoming_response);
  static bool is_server_negative_cached(State *s);
  static bool is_cache_response_returnable(State *s);
  static bool is_stale_cache_response_returnable(State *s);
  static bool need_to_revalidate(State *s);
  static bool url_looks_dynamic(URL *url);
  static bool is_request_cache_lookupable(State *s);
  static bool is_request_valid(State *s, HTTPHdr *incoming_request);
  static bool is_request_retryable(State *s);

  static bool is_response_cacheable(State *s, HTTPHdr *request, HTTPHdr *response);
  static bool is_response_valid(State *s, HTTPHdr *incoming_response);

  static void process_quick_http_filter(State *s, int method);
  static bool will_this_request_self_loop(State *s);
  static bool is_request_likely_cacheable(State *s, HTTPHdr *request);
  static bool is_cache_hit(CacheLookupResult_t r);
  static bool is_fresh_cache_hit(CacheLookupResult_t r);

  static void build_request(State *s, HTTPHdr *base_request, HTTPHdr *outgoing_request, HTTPVersion outgoing_version);
  static void build_response(State *s, HTTPHdr *base_response, HTTPHdr *outgoing_response, HTTPVersion outgoing_version,
                             HTTPStatus status_code, const char *reason_phrase = nullptr);
  static void build_response(State *s, HTTPHdr *base_response, HTTPHdr *outgoing_response, HTTPVersion outgoing_version);
  static void build_response(State *s, HTTPHdr *outgoing_response, HTTPVersion outgoing_version, HTTPStatus status_code,
                             const char *reason_phrase = nullptr);

  static void build_response_copy(State *s, HTTPHdr *base_response, HTTPHdr *outgoing_response, HTTPVersion outgoing_version);
  static void handle_content_length_header(State *s, HTTPHdr *header, HTTPHdr *base);
  static void change_response_header_because_of_range_request(State *s, HTTPHdr *header);

  static void handle_request_keep_alive_headers(State *s, HTTPVersion ver, HTTPHdr *heads);
  static void handle_response_keep_alive_headers(State *s, HTTPVersion ver, HTTPHdr *heads);
  static int get_max_age(HTTPHdr *response);
  static int calculate_document_freshness_limit(State *s, HTTPHdr *response, time_t response_date, bool *heuristic);
  static Freshness_t what_is_document_freshness(State *s, HTTPHdr *client_request, HTTPHdr *cached_obj_response);
  static Authentication_t AuthenticationNeeded(const OverridableHttpConfigParams *p, HTTPHdr *client_request,
                                               HTTPHdr *obj_response);
  static void handle_parent_died(State *s);
  static void handle_server_died(State *s);
  static void build_error_response(State *s, HTTPStatus status_code, const char *reason_phrase_or_null,
                                   const char *error_body_type);
  static void build_redirect_response(State *s);
  static const char *get_error_string(int erno);

  // the stat functions
  static void update_size_and_time_stats(State *s, ink_hrtime total_time, ink_hrtime user_agent_write_time,
                                         ink_hrtime origin_server_read_time, int user_agent_request_header_size,
                                         int64_t user_agent_request_body_size, int user_agent_response_header_size,
                                         int64_t user_agent_response_body_size, int origin_server_request_header_size,
                                         int64_t origin_server_request_body_size, int origin_server_response_header_size,
                                         int64_t origin_server_response_body_size, int pushed_response_header_size,
                                         int64_t pushed_response_body_size, const TransactionMilestones &milestones);
  static void milestone_start_api_time(State *s);
  static void milestone_update_api_time(State *s);
  static void histogram_request_document_size(State *s, int64_t size);
  static void histogram_response_document_size(State *s, int64_t size);
  static void user_agent_connection_speed(State *s, ink_hrtime transfer_time, int64_t nbytes);
  static void origin_server_connection_speed(State *s, ink_hrtime transfer_time, int64_t nbytes);
  static void client_result_stat(State *s, ink_hrtime total_time, ink_hrtime request_process_time);
  static void delete_warning_value(HTTPHdr *to_warn, HTTPWarningCode warning_code);
  static bool is_connection_collapse_checks_success(State *s); // YTS Team, yamsat
};

typedef void (*TransactEntryFunc_t)(HttpTransact::State *s);

/* The spec says about message body the following:
 *
 * All responses to the HEAD and CONNECT request method
 * MUST NOT include a message-body, even though the presence
 * of entity-header fields might lead one to believe they do.
 *
 * All 1xx (informational), 204 (no content), and 304 (not modified)
 * responses MUST NOT include a message-body.
 *
 * Refer : [https://tools.ietf.org/html/rfc7231#section-4.3.6]
 */
inline bool
is_response_body_precluded(HTTPStatus status_code)
{
  if (((status_code != HTTP_STATUS_OK) &&
       ((status_code == HTTP_STATUS_NOT_MODIFIED) || ((status_code < HTTP_STATUS_OK) && (status_code >= HTTP_STATUS_CONTINUE)) ||
        (status_code == HTTP_STATUS_NO_CONTENT)))) {
    return true;
  } else {
    return false;
  }
}

inline bool
is_response_body_precluded(HTTPStatus status_code, int method)
{
  if ((method == HTTP_WKSIDX_HEAD) || (method == HTTP_WKSIDX_CONNECT) || is_response_body_precluded(status_code)) {
    return true;
  } else {
    return false;
  }
}

extern ink_time_t ink_local_time();