httpserver.h

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* MIT License
* 
* Copyright (c) 2019 Jeremy Williams
* 
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
* 
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
* 
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
*
* httpserver.h (0.5.0)
*
* Description:
*
*   A single header C library for building non-blocking event driven HTTP
*   servers
*
* Usage:
*
*   Do this:
*      #define HTTPSERVER_IMPL
*   before you include this file in *one* C or C++ file to create the
*   implementation.
*
*   // i.e. it should look like this:
*   #include ...
*   #include ...
*   #include ...
*   #define HTTPSERVER_IMPL
*   #include "httpserver.h"
*
*   There are some #defines that can be configured. This must be done in the
*   same file that you define HTTPSERVER_IMPL These defines have default values
*   and will need to be #undef'd and redefined to configure them.
*
*     HTTP_REQUEST_BUF_SIZE - default 1024 - The initial size in bytes of the
*       read buffer for the request. This buffer grows automatically if it's
*       capacity is reached but it certain environments it may be optimal to
*       change this value.
*
*     HTTP_RESPONSE_BUF_SIZE - default 512 - Same as above except for the
*       response buffer.
*
*     HTTP_REQUEST_TIMEOUT - default 20 - The amount of seconds the request will
*       wait for activity on the socket before closing. This only applies mid
*       request. For the amount of time to hold onto keep-alive connections see
*       below.
*
*     HTTP_KEEP_ALIVE_TIMEOUT - default 120 - The amount of seconds to keep a
*       connection alive a keep-alive request has completed.
*
*   For more details see the documentation of the interface and the example
*   below.
*
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

#ifndef HTTPSERVER_H
#define HTTPSERVER_H

#ifdef __cplusplus
extern "C" {
#endif

// String type used to read the request details. The char pointer is NOT null
// terminated.
struct http_string_s {
  char const * buf;
  int len;
};

struct http_server_s;
struct http_request_s;
struct http_response_s;

// Returns the event loop id that the server is running on. This will be an
// epoll fd when running on Linux or a kqueue on BSD. This can be used to
// listen for activity on sockets, etc. The only caveat is that the user data
// must be set to a struct where the first member is the function pointer to
// a callback that will handle the event. i.e:
//
// For kevent:
//
//   struct foo {
//     void (*handler)(struct kevent*);
//     ...
//   }
//
//   // Set ev.udata to a foo pointer when registering the event.
//
// For epoll:
//
//   struct foo {
//     void (*handler)(struct epoll_event*);
//     ...
//   }
//
//   // Set ev.data.ptr to a foo pointer when registering the event.
int http_server_loop(struct http_server_s* server);

// Allocates and initializes the http server. Takes a port and a function
// pointer that is called to process requests.
struct http_server_s* http_server_init(int port, void (*handler)(struct http_request_s*));

// Starts the event loop and the server listening. During normal operation this
// function will not return. Return value is the error code if the server fails
// to start.
int http_server_listen(struct http_server_s* server);

// Use this listen call in place of the one above when you want to integrate
// an http server into an existing application that has a loop already and you
// want to use the polling functionality instead. This works well for
// applications like games that have a constant update loop.
int http_server_listen_poll(struct http_server_s* server);

// Call this function in your update loop. It will trigger the request handler
// once if there is a request ready. Returns 1 if a request was handled and 0
// if no requests were handled. It should be called in a loop until it returns
// 0.
int http_server_poll(struct http_server_s* server);

// Returns the request method as it was read from the HTTP request line.
struct http_string_s http_request_method(struct http_request_s* request);

// Returns the full request target (url) as it was read from the HTTP request
// line.
struct http_string_s http_request_target(struct http_request_s* request);

// Returns the request body. If no request body was sent buf and len of the
// string will be set to 0.
struct http_string_s http_request_body(struct http_request_s* request);

// Returns the request header value for the given header key. The key is case
// insensitive.
struct http_string_s http_request_header(struct http_request_s* request, char const * key);

// Procedure used to iterate over all the request headers. iter should be
// initialized to zero before calling. Each call will set key and val to the
// key and value of the next header. Returns 0 when there are no more headers.
int http_request_iterate_headers(
  struct http_request_s* request,
  struct http_string_s* key,
  struct http_string_s* val,
  int* iter
);

// Retrieve the opaque data pointer.
void* http_request_userdata(struct http_request_s* request);

// Stores a pointer for future retrieval. This is not used by the library in
// any way and is strictly for you, the application programmer to make use
// of.
void http_request_set_userdata(struct http_request_s* request, void* data);

#define HTTP_KEEP_ALIVE 1
#define HTTP_CLOSE 0

// By default the server will inspect the Connection header and the HTTP
// version to determine whether the connection should be kept alive or not.
// Use this function to override that behaviour to force the connection to
// keep-alive or close by passing in the HTTP_KEEP_ALIVE or HTTP_CLOSE
// directives respectively. This may provide a minor performance improvement
// in cases where you control client and server and want to always close or
// keep the connection alive.
void http_request_connection(struct http_request_s* request, int directive);

// When reading in the HTTP request the server allocates a buffer to store
// the request details such as the headers, method, body, etc. By default this
// memory will be freed when http_respond is called. This function lets you
// free that memory before the http_respond call. This can be useful if you
// have requests that take a long time to complete and you don't require the
// request data. Accessing any http_string_s's will be invalid after this call.
void http_request_free_buffer(struct http_request_s* request);

// Allocates an http response. This memory will be freed when http_respond is
// called.
struct http_response_s* http_response_init();

// Set the response status. Accepts values between 100 and 599 inclusive. Any
// other value will map to 500.
void http_response_status(struct http_response_s* response, int status);

// Set a response header. Takes two null terminated strings.
void http_response_header(struct http_response_s* response, char const * key, char const * value);

// Set the response body. The caller is responsible for freeing any memory that
// may have been allocated for the body. It is safe to free this memory AFTER
// http_respond has been called.
void http_response_body(struct http_response_s* response, char const * body, int length);

// Starts writing the response to the client. Any memory allocated for the
// response body or response headers is safe to free after this call.
void http_respond(struct http_request_s* request, struct http_response_s* response);

// Writes a chunk to the client. The notify_done callback will be called when
// the write is complete. This call consumes the response so a new response
// will need to be initialized for each chunk. The response status of the
// request will be the response status that is set when http_respond_chunk is
// called the first time. Any headers set for the first call will be sent as
// the response headers. Headers set for subsequent calls will be ignored.
void http_respond_chunk(
  struct http_request_s* request,
  struct http_response_s* response,
  void (*notify_done)(struct http_request_s*)
);

// Ends the chunked response. Any headers set before this call will be included
// as what the HTTP spec refers to as 'trailers' which are essentially more
// response headers.
void http_respond_chunk_end(struct http_request_s* request, struct http_response_s* response);

#ifdef __cplusplus
}
#endif

// Minimal example usage.
#ifdef HTTPSERVER_EXAMPLE

#define RESPONSE "Hello, World!"

void handle_request(struct http_request_s* request) {
  struct http_response_s* response = http_response_init();
  http_response_status(response, 200);
  http_response_header(response, "Content-Type", "text/plain");
  http_response_body(response, RESPONSE, sizeof(RESPONSE) - 1);
  http_respond(request, response);
}

int main() {
  struct http_server_s* server = http_server_init(8080, handle_request);
  http_server_listen(server);
}

#endif

#endif

#ifdef HTTPSERVER_IMPL
#ifndef HTTPSERVER_IMPL_ONCE
#define HTTPSERVER_IMPL_ONCE

#ifdef __linux__
#define EPOLL
#define _POSIX_C_SOURCE 199309L
#else
#define KQUEUE
#endif

#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <netdb.h>
#include <unistd.h>
#include <string.h>
#include <stdarg.h>
#include <signal.h>
#include <limits.h>
#include <assert.h>

#ifdef KQUEUE
#include <sys/event.h>

void http_server_listen_cb(struct kevent* ev);
void http_session_io_cb(struct kevent* ev);
#else
#include <sys/epoll.h>
#include <sys/timerfd.h>

typedef void (*epoll_cb_t)(struct epoll_event*);

void http_server_listen_cb(struct epoll_event* ev);
void http_session_io_cb(struct epoll_event* ev);
void http_server_timer_cb(struct epoll_event* ev);
void http_request_timer_cb(struct epoll_event* ev);

#endif

/******************************************************************************
 *
 * HTTP Parser
 *
 *****************************************************************************/

#define HTTP_METHOD 0
#define HTTP_TARGET 1
#define HTTP_VERSION 2
#define HTTP_HEADER_KEY 3
#define HTTP_HEADER_VALUE 4
#define HTTP_NONE 6
#define HTTP_BODY 7

typedef struct {
  int index;
  int len;
  int type;
} http_token_t;

typedef struct {
  int content_length;
  int len;
  int token_start_index;
  int start;
  int content_length_i;
  char in_content_length;
  char state;
  char sub_state;
} http_parser_t;

#define HTTP_LWS 2
#define HTTP_CR 3
#define HTTP_CRLF 4

#define HTTP_HEADER_END 5

#define CONTENT_LENGTH_LOW "content-length"
#define CONTENT_LENGTH_UP "CONTENT-LENGTH"
#define PAYLOAD_TOO_LARGE -1

http_token_t http_parse(http_parser_t* parser, char* input, int n) {
  for (int i = parser->start; i < n; ++i, parser->start = i + 1, parser->len++) {
    char c = input[i];
    switch (parser->state) {
      case HTTP_METHOD:
        if (c == ' ') {
          http_token_t token;
          token.index = parser->token_start_index;
          token.type = parser->state;
          token.len = parser->len;
          parser->state = HTTP_TARGET;
          parser->len = 0;
          parser->token_start_index = i + 1;
          return token;
        }
        break;
      case HTTP_TARGET:
        if (c == ' ') {
          http_token_t token;
          token.index = parser->token_start_index;
          token.type = parser->state;
          token.len = parser->len;
          parser->state = HTTP_VERSION;
          parser->token_start_index = i + 1;
          parser->len = 0;
          return token;
        }
        break;
      case HTTP_VERSION:
        if (c == '\r') {
          parser->sub_state = HTTP_CR;
          http_token_t token;
          token.index = parser->token_start_index;
          token.type = HTTP_VERSION;
          token.len = parser->len;
          return token;
        } else if (parser->sub_state == HTTP_CR && c == '\n') {
          parser->sub_state = 0;
          parser->len = 0;
          parser->token_start_index = i + 1;
          parser->state = HTTP_HEADER_KEY;
        }
        break;
      case HTTP_HEADER_KEY:
        if (c == ':') {
          parser->state = HTTP_HEADER_VALUE;
          parser->sub_state = HTTP_LWS;
          if (parser->len == parser->content_length_i + 1) parser->in_content_length = 1;
          parser->content_length_i = 0;
          http_token_t token;
          token.index = parser->token_start_index;
          token.type = HTTP_HEADER_KEY;
          token.len = parser->len - 1;
          return token;
        } else if (
          (c == CONTENT_LENGTH_UP[parser->content_length_i] ||
            c == CONTENT_LENGTH_LOW[parser->content_length_i]) &&
          parser->content_length_i < (int)sizeof(CONTENT_LENGTH_LOW) - 1
        ) {
          parser->content_length_i++;
        }
        break;
      case HTTP_HEADER_VALUE:
        if (parser->sub_state == HTTP_LWS && (c == ' ' || c == '\t' || c == '\r' || c == '\n')) {
          continue;
        } else if (parser->sub_state == HTTP_LWS) {
          parser->sub_state = 0;
          parser->len = 0;
          parser->token_start_index = i;
          if (parser->in_content_length) {
            parser->content_length *= 10;
            parser->content_length += c - '0';
          }
        } else if (parser->sub_state != HTTP_LWS && c == '\r') {
          parser->sub_state = HTTP_CR;
          parser->state = HTTP_HEADER_END;
          parser->in_content_length = 0;
          http_token_t token;
          token.index = parser->token_start_index;
          token.type = HTTP_HEADER_VALUE;
          token.len = parser->len;
          return token;
        } else if (parser->in_content_length && parser->content_length != PAYLOAD_TOO_LARGE) {
          int64_t new_content_length = parser->content_length * 10l;
          new_content_length += c - '0';
          if (new_content_length > INT_MAX) {
            parser->content_length = PAYLOAD_TOO_LARGE;
          } else {
            parser->content_length = (int)new_content_length;
          }
        }
        break;
      case HTTP_HEADER_END:
        if (parser->sub_state == 0 && c == '\r') {
          parser->sub_state = HTTP_CR;
        } else if (parser->sub_state == HTTP_CR && c == '\n') {
          parser->sub_state = HTTP_CRLF;
        } else if (parser->sub_state == HTTP_CRLF && c == '\r') {
          parser->sub_state = 0;
          parser->state = HTTP_BODY;
          http_token_t token;
          token.index = i + 2;
          token.type = HTTP_BODY;
          token.len = parser->content_length;
          return token;
        } else if (parser->sub_state == HTTP_CRLF && c != '\r') {
          parser->sub_state = 0;
          parser->len = 0;
          parser->token_start_index = i;
          i--;
          parser->state = HTTP_HEADER_KEY;
        }
        break;
    }
  }
  http_token_t token = { 0, 0, 0 };
  token.type = HTTP_NONE;
  return token;
}

/******************************************************************************
 *
 * HTTP Server
 *
 *****************************************************************************/

#define HTTP_READY 0x2
#define HTTP_RESPONSE_READY 0x4
#define HTTP_AUTOMATIC 0x8
#define HTTP_RESPONSE_PAUSED 0x10
#define HTTP_CHUNKED 0x20

#define HTTP_FLAG_SET(var, flag) var |= flag
#define HTTP_FLAG_CLEAR(var, flag) var &= ~flag
#define HTTP_FLAG_CHECK(var, flag) (var & flag)

#define HTTP_REQUEST_TIMEOUT 20
#define HTTP_KEEP_ALIVE_TIMEOUT 120

typedef struct {
  http_token_t* buf;
  int capacity;
  int size;
} http_token_dyn_t;

typedef struct http_ev_cb_s {
#ifdef KQUEUE
  void (*handler)(struct kevent* ev);
#else
  epoll_cb_t handler;
#endif
} ev_cb_t;

typedef struct http_request_s {
#ifdef KQUEUE
  void (*handler)(struct kevent* ev);
#else
  epoll_cb_t handler;
  epoll_cb_t timer_handler;
  int timerfd;
#endif
  void (*chunk_cb)(struct http_request_s*);
  void* data;
  http_parser_t parser;
  int state;
  int socket;
  char* buf;
  int bytes;
  int capacity;
  int timeout;
  struct http_server_s* server;
  http_token_t token;
  http_token_dyn_t tokens;
  char flags;
} http_request_t;

typedef struct http_server_s {
#ifdef KQUEUE
  void (*handler)(struct kevent* ev);
#else
  epoll_cb_t handler;
  epoll_cb_t timer_handler;
#endif
  int socket;
  int port;
  int loop;
  int timerfd;
  socklen_t len;
  void (*request_handler)(http_request_t*);
  struct sockaddr_in addr;
  char* date;
} http_server_t;

void http_token_dyn_push(http_token_dyn_t* dyn, http_token_t a) {
  if (dyn->size == dyn->capacity) {
    dyn->capacity *= 2;
    dyn->buf = (http_token_t*)realloc(dyn->buf, dyn->capacity * sizeof(http_token_t));
    assert(dyn->buf != NULL);
  }
  dyn->buf[dyn->size] = a;
  dyn->size++;
}

void http_token_dyn_init(http_token_dyn_t* dyn, int capacity) {
  dyn->buf = (http_token_t*)malloc(sizeof(http_token_t) * capacity);
  assert(dyn->buf != NULL);
  dyn->size = 0;
  dyn->capacity = capacity;
}

#define HTTP_REQUEST_BUF_SIZE 1024

void bind_localhost(int s, struct sockaddr_in* addr, int port) {
  addr->sin_family = AF_INET;
  addr->sin_addr.s_addr = INADDR_ANY;
  addr->sin_port = htons(port);
  int rc = bind(s, (struct sockaddr *)addr, sizeof(struct sockaddr_in));;
  if (rc < 0) {
    exit(1);
  }
}

int read_client_socket(http_request_t* session) {
  if (!session->buf) {
    session->buf = (char*)calloc(1, HTTP_REQUEST_BUF_SIZE);
    assert(session->buf != NULL);
    session->capacity = HTTP_REQUEST_BUF_SIZE;
    http_token_dyn_init(&session->tokens, 32);
  }
  int bytes;
  do {
    bytes = read(
      session->socket,
      session->buf + session->bytes,
      session->capacity - session->bytes
    );
    if (bytes > 0) {
      session->bytes += bytes;
      HTTP_FLAG_SET(session->flags, HTTP_READY);
    }
    if (session->bytes == session->capacity) {
      session->capacity *= 2;
      session->buf = (char*)realloc(session->buf, session->capacity);
      assert(session->buf != NULL);
    }
  } while (bytes > 0);
  return bytes == 0 ? 0 : 1;
}

int write_client_socket(http_request_t* session) {
  int bytes = write(
    session->socket,
    session->buf + session->bytes,
    session->capacity - session->bytes
  );
  if (bytes > 0) session->bytes += bytes;
  return errno == EPIPE ? 0 : 1;
}

void free_buffer(http_request_t* session) {
  if (session->buf) {
    free(session->buf);
    session->buf = NULL;
    free(session->tokens.buf);
    session->tokens.buf = NULL;
  }
}

void parse_tokens(http_request_t* session) {
  http_token_t token;
  do {
    token = http_parse(&session->parser, session->buf, session->bytes);
    if (token.type != HTTP_NONE) {
      session->token = token;
      http_token_dyn_push(&session->tokens, token);
    }
  } while (token.type != HTTP_NONE);
  HTTP_FLAG_CLEAR(session->flags, HTTP_READY);
}

void init_session(http_request_t* session) {
  session->flags |= HTTP_AUTOMATIC;
  session->parser = (http_parser_t){ };
  session->bytes = 0;
  session->buf = NULL;
  session->token.len = 0;
  session->token.index = 0;
  session->token.type = HTTP_NONE;
}

int parsing_headers(http_request_t* request) {
  return request->token.type != HTTP_BODY;
}

int reading_body(http_request_t* request) {
  if (request->token.type != HTTP_BODY || request->token.len == 0) return 0;
  int size = request->token.index + request->token.len;
  return request->bytes < size;
}

void end_session(http_request_t* session) {
#ifdef KQUEUE
  struct kevent ev_set;
  EV_SET(&ev_set, session->socket, EVFILT_TIMER, EV_DELETE, 0, 0, session);
  kevent(session->server->loop, &ev_set, 1, NULL, 0, NULL);
#else
  epoll_ctl(session->server->loop, EPOLL_CTL_DEL, session->socket, NULL);
  epoll_ctl(session->server->loop, EPOLL_CTL_DEL, session->timerfd, NULL);
  close(session->timerfd);
#endif

  close(session->socket);
  free_buffer(session);
  free(session);
}

#define HTTP_SESSION_INIT 0
#define HTTP_SESSION_READ_HEADERS 1
#define HTTP_SESSION_READ_BODY 2
#define HTTP_SESSION_WRITE 3

void reset_timeout(http_request_t* request, int time) {
  request->timeout = time;
}

void exec_response_handler(http_request_t* request, void (*handler)(http_request_t*));

void write_response(http_request_t* request) {
  if (!write_client_socket(request)) { return end_session(request); }
  if (request->bytes != request->capacity) {
#ifdef KQUEUE
    struct kevent ev_set[2];
    EV_SET(&ev_set[0], request->socket, EVFILT_READ, EV_DELETE, 0, 0, NULL);
    EV_SET(&ev_set[1], request->socket, EVFILT_WRITE, EV_ADD, 0, 0, request);
    kevent(request->server->loop, ev_set, 2, NULL, 0, NULL);
#else
    struct epoll_event ev;
    ev.events = EPOLLOUT | EPOLLET;
    ev.data.ptr = request;
    epoll_ctl(request->server->loop, EPOLL_CTL_MOD, request->socket, &ev);
#endif

    request->state = HTTP_SESSION_WRITE;
    reset_timeout(request, HTTP_REQUEST_TIMEOUT);
  } else if (HTTP_FLAG_CHECK(request->flags, HTTP_CHUNKED)) {
    request->state = HTTP_SESSION_WRITE;
    reset_timeout(request, HTTP_REQUEST_TIMEOUT);
    free_buffer(request);
    HTTP_FLAG_CLEAR(request->flags, HTTP_RESPONSE_READY);
    exec_response_handler(request, request->chunk_cb);
  } else if (HTTP_FLAG_CHECK(request->flags, HTTP_KEEP_ALIVE)) {
    request->state = HTTP_SESSION_INIT;
    free_buffer(request);
    reset_timeout(request, HTTP_KEEP_ALIVE_TIMEOUT);
  } else {
    return end_session(request);
  }
}

void exec_response_handler(http_request_t* request, void (*handler)(http_request_t*)) {
  handler(request);
  if (HTTP_FLAG_CHECK(request->flags, HTTP_RESPONSE_READY)) {
    write_response(request);
  } else {
    request->state = HTTP_SESSION_WRITE;
    HTTP_FLAG_SET(request->flags, HTTP_RESPONSE_PAUSED);
  }
}

void error_response(http_request_t* request, int code, char const * message) {
  struct http_response_s* response = http_response_init();
  http_response_status(response, code);
  http_response_header(response, "Content-Type", "text/plain");
  http_response_body(response, message, strlen(message));
  http_respond(request, response);
  write_response(request);
}

void http_session(http_request_t* request) {
  switch (request->state) {
    case HTTP_SESSION_INIT:
      init_session(request);
      request->state = HTTP_SESSION_READ_HEADERS;
      // fallthrough
    case HTTP_SESSION_READ_HEADERS:
      if (!read_client_socket(request)) { return end_session(request); }
      parse_tokens(request);
      if (!parsing_headers(request) && request->parser.content_length == PAYLOAD_TOO_LARGE) {
        return error_response(request, 413, "Payload Too Large");
      } else if (reading_body(request)) {
        request->state = HTTP_SESSION_READ_BODY;
      } else if (!parsing_headers(request)) {
        return exec_response_handler(request, request->server->request_handler);
      }
      reset_timeout(request, HTTP_REQUEST_TIMEOUT);
      break;
    case HTTP_SESSION_READ_BODY:
      if (!read_client_socket(request)) { return end_session(request); }
      if (!reading_body(request)) {
        return exec_response_handler(request, request->server->request_handler);
      }
      reset_timeout(request, 20);
      break;
    case HTTP_SESSION_WRITE:
      write_response(request);
      break;
  }
}

void accept_connections(http_server_t* server) {
  int sock = 0;
  do {
    sock = accept(server->socket, (struct sockaddr *)&server->addr, &server->len);
    if (sock > 0) {
      http_request_t* session = (http_request_t*)calloc(1, sizeof(http_request_t));
      assert(session != NULL);
      session->socket = sock;
      session->server = server;
      session->timeout = HTTP_REQUEST_TIMEOUT;
      session->handler = http_session_io_cb;
      int flags = fcntl(sock, F_GETFL, 0);
      fcntl(sock, F_SETFL, flags | O_NONBLOCK);

#ifdef KQUEUE
      struct kevent ev_set[2];
      EV_SET(&ev_set[0], sock, EVFILT_READ, EV_ADD, 0, 0, session);
      EV_SET(&ev_set[1], sock, EVFILT_TIMER, EV_ADD | EV_ENABLE, NOTE_SECONDS, 1, session);
      kevent(server->loop, ev_set, 2, NULL, 0, NULL);
#else
      session->timer_handler = http_request_timer_cb;
      struct epoll_event ev;
      ev.events = EPOLLIN | EPOLLET;
      ev.data.ptr = session;
      epoll_ctl(server->loop, EPOLL_CTL_ADD, sock, &ev);

      int tfd = timerfd_create(CLOCK_MONOTONIC, 0);
      struct itimerspec ts = {};
      ts.it_value.tv_sec = 1;
      ts.it_interval.tv_sec = 1;
      timerfd_settime(tfd, 0, &ts, NULL);

      ev.events = EPOLLIN | EPOLLET;
      ev.data.ptr = &session->timer_handler;
      epoll_ctl(server->loop, EPOLL_CTL_ADD, tfd, &ev);
      session->timerfd = tfd;
#endif

      http_session(session);
    }
  } while (sock > 0);
}

void generate_date_time(char** datetime) {
  time_t rawtime;
  struct tm * timeinfo;
  time(&rawtime);
  timeinfo = localtime(&rawtime);
  *datetime = asctime(timeinfo);
}

#ifdef KQUEUE
void http_server_listen_cb(struct kevent* ev) {
  http_server_t* server = (http_server_t*)ev->udata;
  if (ev->filter == EVFILT_TIMER) {
    generate_date_time(&server->date);
  } else {
    accept_connections(server);
  }
}

void http_session_io_cb(struct kevent* ev) {
  http_request_t* request = (http_request_t*)ev->udata;
  if (ev->filter == EVFILT_TIMER) {
    request->timeout -= 1;
    if (request->timeout == 0) end_session(request);
  } else {
    http_session(request);
  }
}

#else
void http_server_listen_cb(struct epoll_event* ev) {
  accept_connections((http_server_t*)ev->data.ptr);
}

void http_session_io_cb(struct epoll_event* ev) {
  http_session((http_request_t*)ev->data.ptr);
}

void http_server_timer_cb(struct epoll_event* ev) {
  http_server_t* server = (http_server_t*)((char*)ev->data.ptr - sizeof(epoll_cb_t));
  uint64_t res;
  int bytes = read(server->timerfd, &res, sizeof(res));
  (void)bytes; // suppress warning
  generate_date_time(&server->date);
}

void http_request_timer_cb(struct epoll_event* ev) {
  http_request_t* request = (http_request_t*)((char*)ev->data.ptr - sizeof(epoll_cb_t));
  uint64_t res;
  int bytes = read(request->timerfd, &res, sizeof(res));
  (void)bytes; // suppress warning
  request->timeout -= 1;
  if (request->timeout == 0) end_session(request);
}
#endif

http_server_t* http_server_init(int port, void (*handler)(http_request_t*)) {
  http_server_t* serv = (http_server_t*)malloc(sizeof(http_server_t));
  assert(serv != NULL);
  serv->port = port;
  serv->handler = http_server_listen_cb;

#ifdef KQUEUE
  serv->loop = kqueue();

  struct kevent ev_set;
  EV_SET(&ev_set, 1, EVFILT_TIMER, EV_ADD | EV_ENABLE, NOTE_SECONDS, 1, serv);
  kevent(serv->loop, &ev_set, 1, NULL, 0, NULL);
#else
  serv->loop = epoll_create1(0);
  serv->timer_handler = http_server_timer_cb;

  int tfd = timerfd_create(CLOCK_MONOTONIC, 0);
  struct itimerspec ts = {};
  ts.it_value.tv_sec = 1;
  ts.it_interval.tv_sec = 1;
  timerfd_settime(tfd, 0, &ts, NULL);

  struct epoll_event ev;
  ev.events = EPOLLIN | EPOLLET;
  ev.data.ptr = &serv->timer_handler;
  epoll_ctl(serv->loop, EPOLL_CTL_ADD, tfd, &ev);
  serv->timerfd = tfd;
#endif

  generate_date_time(&serv->date);
  serv->request_handler = handler;
  return serv;
}

void http_listen(http_server_t* serv) {
  signal(SIGPIPE, SIG_IGN);
  serv->socket = socket(AF_INET, SOCK_STREAM, 0);
  int flag = 1;
  setsockopt(serv->socket, SOL_SOCKET, SO_REUSEPORT, &flag, sizeof(flag));
  bind_localhost(serv->socket, &serv->addr, serv->port);
  serv->len = sizeof(serv->addr);
  int flags = fcntl(serv->socket, F_GETFL, 0);
  fcntl(serv->socket, F_SETFL, flags | O_NONBLOCK);
  listen(serv->socket, 128);

#ifdef KQUEUE
  struct kevent ev_set;
  EV_SET(&ev_set, serv->socket, EVFILT_READ, EV_ADD, 0, 0, serv);
  kevent(serv->loop, &ev_set, 1, NULL, 0, NULL);
#else
  struct epoll_event ev;
  ev.events = EPOLLIN | EPOLLET;
  ev.data.ptr = serv;
  epoll_ctl(serv->loop, EPOLL_CTL_ADD, serv->socket, &ev);
#endif
}

int http_server_listen_poll(http_server_t* serv) {
  http_listen(serv);
  return 0;
}

int http_server_poll(http_server_t* serv) {
#ifdef KQUEUE
  struct kevent ev;
  struct timespec ts;
  memset(&ts, 0, sizeof(ts));
  int nev = kevent(serv->loop, NULL, 0, &ev, 1, &ts);
  if (nev <= 0) return nev;
  ev_cb_t* ev_cb = (ev_cb_t*)ev.udata;
#else
  struct epoll_event ev;
  int nev = epoll_wait(serv->loop, &ev, 1, 0);
  if (nev <= 0) return nev;
  ev_cb_t* ev_cb = (ev_cb_t*)ev.data.ptr;
#endif
  ev_cb->handler(&ev);
  return nev;
}

int http_server_listen(http_server_t* serv) {
  http_listen(serv);

#ifdef KQUEUE
  struct kevent ev_list[1];

  while (1) {
    int nev = kevent(serv->loop, NULL, 0, ev_list, 1, NULL);
    for (int i = 0; i < nev; i++) {
      ev_cb_t* ev_cb = (ev_cb_t*)ev_list[i].udata;
      ev_cb->handler(&ev_list[i]);
    }
  }
#else
  struct epoll_event ev_list[1];

  while (1) {
    int nev = epoll_wait(serv->loop, ev_list, 1, -1);
    for (int i = 0; i < nev; i++) {
      ev_cb_t* ev_cb = (ev_cb_t*)ev_list[i].data.ptr;
      ev_cb->handler(&ev_list[i]);
    }
  }
#endif

  return 0;
}

int http_server_loop(http_server_t* server) {
  return server->loop;
}

/******************************************************************************
 *
 * HTTP Request
 *
 *****************************************************************************/

typedef struct http_string_s http_string_t;

http_string_t http_get_token_string(http_request_t* request, int token_type) {
  http_string_t str = { 0, 0 };
  for (int i = 0; i < request->tokens.size; i++) {
    http_token_t token = request->tokens.buf[i];
    if (token.type == token_type) {
      str.buf = &request->buf[token.index];
      str.len = token.len;
      return str;
    }
  }
  return str;
}

int case_insensitive_cmp(char const * a, char const * b, int len) {
  for (int i = 0; i < len; i++) {
    char c1 = a[i] >= 'A' && a[i] <= 'Z' ? a[i] + 32 : a[i];
    char c2 = b[i] >= 'A' && b[i] <= 'Z' ? b[i] + 32 : b[i];
    if (c1 != c2) return 0;
  }
  return 1;
}

http_string_t http_request_method(http_request_t* request) {
  return http_get_token_string(request, HTTP_METHOD);
}

http_string_t http_request_target(http_request_t* request) {
  return http_get_token_string(request, HTTP_TARGET);
}

http_string_t http_request_body(http_request_t* request) {
  return http_get_token_string(request, HTTP_BODY);
}

int assign_iteration_headers(
  http_request_t* request,
  http_string_t* key,
  http_string_t* val,
  int* iter
) {
  http_token_t token = request->tokens.buf[*iter];
  if (request->tokens.buf[*iter].type == HTTP_BODY) return 0;
  *key = (http_string_t) {
    .buf = &request->buf[token.index],
    .len = token.len
  };
  (*iter)++;
  token = request->tokens.buf[*iter];
  *val = (http_string_t) {
    .buf = &request->buf[token.index],
    .len = token.len
  };
  return 1;
}

int http_request_iterate_headers(
  http_request_t* request,
  http_string_t* key,
  http_string_t* val,
  int* iter
) {
  if (*iter == 0) {
    for ( ; *iter < request->tokens.size; (*iter)++) {
      http_token_t token = request->tokens.buf[*iter];
      if (token.type == HTTP_HEADER_KEY) {
        return assign_iteration_headers(request, key, val, iter);
      }
    }
    return 0;
  } else {
    (*iter)++;
    return assign_iteration_headers(request, key, val, iter);
  }
}

http_string_t http_request_header(http_request_t* request, char const * key) {
  int len = strlen(key);
  for (int i = 0; i < request->tokens.size; i++) {
    http_token_t token = request->tokens.buf[i];
    if (token.type == HTTP_HEADER_KEY && token.len == len) {
      if (case_insensitive_cmp(&request->buf[token.index], key, len)) {
        token = request->tokens.buf[i + 1];
        return (http_string_t) {
          .buf = &request->buf[token.index],
          .len = token.len
        };
      }
    }
  }
  return (http_string_t) { };
}

void http_request_free_buffer(http_request_t* request) {
  free_buffer(request);
}

void* http_request_userdata(http_request_t* request) {
  return request->data;
}

void http_request_set_userdata(http_request_t* request, void* data) {
  request->data = data;
}

#define HTTP_1_0 0
#define HTTP_1_1 1

void auto_detect_keep_alive(http_request_t* request) {
  http_string_t str = http_get_token_string(request, HTTP_VERSION);
  int version = str.buf[str.len - 1] == '1';
  str = http_request_header(request, "Connection");
  if (
    (str.len == 5 && case_insensitive_cmp(str.buf, "close", 5)) ||
    (str.len == 0 && version == HTTP_1_0)
  ) {
    HTTP_FLAG_CLEAR(request->flags, HTTP_KEEP_ALIVE);
  } else {
    HTTP_FLAG_SET(request->flags, HTTP_KEEP_ALIVE);
  }
}

void http_request_connection(http_request_t* request, int directive) {
  if (directive == HTTP_KEEP_ALIVE) {
    HTTP_FLAG_CLEAR(request->flags, HTTP_AUTOMATIC);
    HTTP_FLAG_SET(request->flags, HTTP_KEEP_ALIVE);
  } else if (directive == HTTP_CLOSE) {
    HTTP_FLAG_CLEAR(request->flags, HTTP_AUTOMATIC);
    HTTP_FLAG_CLEAR(request->flags, HTTP_KEEP_ALIVE);
  }
}

/******************************************************************************
 *
 * HTTP Response
 *
 *****************************************************************************/

typedef struct http_header_s {
  char const * key;
  char const * value;
  struct http_header_s* next;
} http_header_t;

typedef struct http_response_s {
  http_header_t* headers;
  char const * body;
  int content_length;
  int status;
} http_response_t;

#define HTTP_RESPONSE_BUF_SIZE 512

char const * status_text[] = {
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  
  //100s
  "Continue", "Switching Protocols", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",

  //200s
  "OK", "Created", "Accepted", "Non-Authoritative Information", "No Content",
  "Reset Content", "Partial Content", "", "", "",

  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",

  //300s
  "Multiple Choices", "Moved Permanently", "Found", "See Other", "Not Modified",
  "Use Proxy", "", "Temporary Redirect", "", "",

  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",

  //400s
  "Bad Request", "Unauthorized", "Payment Required", "Forbidden", "Not Found",
  "Method Not Allowed", "Not Acceptable", "Proxy Authentication Required",
  "Request Timeout", "Conflict",

  "Gone", "Length Required", "", "Payload Too Large", "", "", "", "", "", "",

  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",

  //500s
  "Internal Server Error", "Not Implemented", "Bad Gateway", "Service Unavailable",
  "Gateway Timeout", "", "", "", "", ""

  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", "",
  "", "", "", "", "", "", "", "", "", ""
};

http_response_t* http_response_init() {
  http_response_t* response = (http_response_t*)calloc(1, sizeof(http_response_t));
  assert(response != NULL);
  response->status = 200;
  return response;
}

void http_response_header(http_response_t* response, char const * key, char const * value) {
  http_header_t* header = (http_header_t*)malloc(sizeof(http_header_t));
  assert(header != NULL);
  header->key = key;
  header->value = value;
  http_header_t* prev = response->headers;
  header->next = prev;
  response->headers = header;
}

void http_response_status(http_response_t* response, int status) {
  response->status = status > 599 || status < 100 ? 500 : status;
}

void http_response_body(http_response_t* response, char const * body, int length) {
  response->body = body;
  response->content_length = length;
}

typedef struct {
  char* buf;
  int capacity;
  int size;
} grwprintf_t;

void grwprintf_init(grwprintf_t* ctx, int capacity) {
  ctx->size = 0;
  ctx->buf = (char*)malloc(capacity);
  assert(ctx->buf != NULL);
  ctx->capacity = capacity;
}

void grwmemcpy(grwprintf_t* ctx, char const * src, int size) {
  if (ctx->size + size > ctx->capacity) {
    ctx->capacity = ctx->size + size;
    ctx->buf = (char*)realloc(ctx->buf, ctx->capacity);
    assert(ctx->buf != NULL);
  }
  memcpy(ctx->buf + ctx->size, src, size);
  ctx->size += size;
}

void grwprintf(grwprintf_t* ctx, char const * fmt, ...) {
  va_list args;
  va_start(args, fmt);

  int bytes = vsnprintf(ctx->buf + ctx->size, ctx->capacity - ctx->size, fmt, args);
  if (bytes + ctx->size > ctx->capacity) {
    while (bytes + ctx->size > ctx->capacity) ctx->capacity *= 2;
    ctx->buf = (char*)realloc(ctx->buf, ctx->capacity);
    assert(ctx->buf != NULL);
    bytes += vsnprintf(ctx->buf + ctx->size, ctx->capacity - ctx->size, fmt, args);
  }
  ctx->size += bytes;
 
  va_end(args);
}

void http_buffer_headers(
  http_request_t* request,
  http_response_t* response,
  grwprintf_t* printctx
) {
  http_header_t* header = response->headers;
  while (header) {
    grwprintf(printctx, "%s: %s\r\n", header->key, header->value);
    header = header->next;
  }
  if (!HTTP_FLAG_CHECK(request->flags, HTTP_CHUNKED)) {
    grwprintf(printctx, "Content-Length: %d\r\n", response->content_length);
  }
  grwprintf(printctx, "\r\n");
}

void http_respond_headers(
  http_request_t* request,
  http_response_t* response,
  grwprintf_t* printctx
) {
  if (HTTP_FLAG_CHECK(request->flags, HTTP_AUTOMATIC)) {
    auto_detect_keep_alive(request);
  }
  if (HTTP_FLAG_CHECK(request->flags, HTTP_KEEP_ALIVE)) {
    http_response_header(response, "Connection", "keep-alive");
  } else {
    http_response_header(response, "Connection", "close");
  }
  grwprintf(
    printctx, "HTTP/1.1 %d %s\r\nDate: %.24s\r\n",
    response->status, status_text[response->status], request->server->date
  );
  http_buffer_headers(request, response, printctx);
}

void http_end_response(http_request_t* request, http_response_t* response, grwprintf_t* printctx) {
  http_header_t* header = response->headers;
  while (header) {
    http_header_t* tmp = header;
    header = tmp->next;
    free(tmp);
  }
  free_buffer(request);
  free(response);
  request->buf = printctx->buf;
  request->bytes = 0;
  request->capacity = printctx->size;
  HTTP_FLAG_SET(request->flags, HTTP_RESPONSE_READY);
  if (HTTP_FLAG_CHECK(request->flags, HTTP_RESPONSE_PAUSED)) {
    HTTP_FLAG_CLEAR(request->flags, HTTP_RESPONSE_PAUSED);
    http_session(request);
  }
}

void http_respond(http_request_t* request, http_response_t* response) {
  grwprintf_t printctx;
  grwprintf_init(&printctx, HTTP_RESPONSE_BUF_SIZE);
  http_respond_headers(request, response, &printctx);
  if (response->body) {
    grwmemcpy(&printctx, response->body, response->content_length);
  }
  http_end_response(request, response, &printctx);
}

void http_respond_chunk(
  http_request_t* request,
  http_response_t* response,
  void (*cb)(http_request_t*)
) {
  grwprintf_t printctx;
  grwprintf_init(&printctx, HTTP_RESPONSE_BUF_SIZE);
  if (!HTTP_FLAG_CHECK(request->flags, HTTP_CHUNKED)) {
    HTTP_FLAG_SET(request->flags, HTTP_CHUNKED);
    http_response_header(response, "Transfer-Encoding", "chunked");
    http_respond_headers(request, response, &printctx);
  }
  request->chunk_cb = cb;
  grwprintf(&printctx, "%X\r\n", response->content_length);
  grwmemcpy(&printctx, response->body, response->content_length);
  grwprintf(&printctx, "\r\n");
  http_end_response(request, response, &printctx);
}

void http_respond_chunk_end(http_request_t* request, http_response_t* response) {
  grwprintf_t printctx;
  grwprintf_init(&printctx, HTTP_RESPONSE_BUF_SIZE);
  grwprintf(&printctx, "0\r\n");
  http_buffer_headers(request, response, &printctx);
  grwprintf(&printctx, "\r\n");
  HTTP_FLAG_CLEAR(request->flags, HTTP_CHUNKED);
  http_end_response(request, response, &printctx);
}

#endif
#endif