/*
 * nghttp2 - HTTP/2 C Library
 *
 * Copyright (c) 2015 Tatsuhiro Tsujikawa
 *
 * 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.
 */
#include "nghttp2_http.h"

#include <string.h>
#include <assert.h>
#include <stdio.h>

static int memeq(const void *a, const void *b, size_t n) {
  return memcmp(a, b, n) == 0;
}

#define streq(A, B, N) ((sizeof((A)) - 1) == (N) && memeq((A), (B), (N)))

static char downcase(char c) {
  return 'A' <= c && c <= 'Z' ? (c - 'A' + 'a') : c;
}

static int memieq(const void *a, const void *b, size_t n) {
  size_t i;
  const uint8_t *aa = a, *bb = b;

  for (i = 0; i < n; ++i) {
    if (downcase(aa[i]) != downcase(bb[i])) {
      return 0;
    }
  }
  return 1;
}

#define strieq(A, B, N) ((sizeof((A)) - 1) == (N) && memieq((A), (B), (N)))

typedef enum {
  NGHTTP2_TOKEN__AUTHORITY,
  NGHTTP2_TOKEN__METHOD,
  NGHTTP2_TOKEN__PATH,
  NGHTTP2_TOKEN__SCHEME,
  NGHTTP2_TOKEN__STATUS,
  NGHTTP2_TOKEN_CONNECTION,
  NGHTTP2_TOKEN_CONTENT_LENGTH,
  NGHTTP2_TOKEN_HOST,
  NGHTTP2_TOKEN_KEEP_ALIVE,
  NGHTTP2_TOKEN_PROXY_CONNECTION,
  NGHTTP2_TOKEN_TE,
  NGHTTP2_TOKEN_TRANSFER_ENCODING,
  NGHTTP2_TOKEN_UPGRADE,
  NGHTTP2_TOKEN_MAXIDX,
} nghttp2_token;

/*
 * This function was generated by genlibtokenlookup.py.  Inspired by
 * h2o header lookup.  https://github.com/h2o/h2o
 */
static int lookup_token(const uint8_t *name, size_t namelen) {
  switch (namelen) {
  case 2:
    switch (name[namelen - 1]) {
    case 'e':
      if (streq("t", name, 1)) {
        return NGHTTP2_TOKEN_TE;
      }
      break;
    }
    break;
  case 4:
    switch (name[namelen - 1]) {
    case 't':
      if (streq("hos", name, 3)) {
        return NGHTTP2_TOKEN_HOST;
      }
      break;
    }
    break;
  case 5:
    switch (name[namelen - 1]) {
    case 'h':
      if (streq(":pat", name, 4)) {
        return NGHTTP2_TOKEN__PATH;
      }
      break;
    }
    break;
  case 7:
    switch (name[namelen - 1]) {
    case 'd':
      if (streq(":metho", name, 6)) {
        return NGHTTP2_TOKEN__METHOD;
      }
      break;
    case 'e':
      if (streq(":schem", name, 6)) {
        return NGHTTP2_TOKEN__SCHEME;
      }
      if (streq("upgrad", name, 6)) {
        return NGHTTP2_TOKEN_UPGRADE;
      }
      break;
    case 's':
      if (streq(":statu", name, 6)) {
        return NGHTTP2_TOKEN__STATUS;
      }
      break;
    }
    break;
  case 10:
    switch (name[namelen - 1]) {
    case 'e':
      if (streq("keep-aliv", name, 9)) {
        return NGHTTP2_TOKEN_KEEP_ALIVE;
      }
      break;
    case 'n':
      if (streq("connectio", name, 9)) {
        return NGHTTP2_TOKEN_CONNECTION;
      }
      break;
    case 'y':
      if (streq(":authorit", name, 9)) {
        return NGHTTP2_TOKEN__AUTHORITY;
      }
      break;
    }
    break;
  case 14:
    switch (name[namelen - 1]) {
    case 'h':
      if (streq("content-lengt", name, 13)) {
        return NGHTTP2_TOKEN_CONTENT_LENGTH;
      }
      break;
    }
    break;
  case 16:
    switch (name[namelen - 1]) {
    case 'n':
      if (streq("proxy-connectio", name, 15)) {
        return NGHTTP2_TOKEN_PROXY_CONNECTION;
      }
      break;
    }
    break;
  case 17:
    switch (name[namelen - 1]) {
    case 'g':
      if (streq("transfer-encodin", name, 16)) {
        return NGHTTP2_TOKEN_TRANSFER_ENCODING;
      }
      break;
    }
    break;
  }
  return -1;
}

static int64_t parse_uint(const uint8_t *s, size_t len) {
  int64_t n = 0;
  size_t i;
  if (len == 0) {
    return -1;
  }
  for (i = 0; i < len; ++i) {
    if ('0' <= s[i] && s[i] <= '9') {
      if (n > INT64_MAX / 10) {
        return -1;
      }
      n *= 10;
      if (n > INT64_MAX - (s[i] - '0')) {
        return -1;
      }
      n += s[i] - '0';
      continue;
    }
    return -1;
  }
  return n;
}

static int lws(const uint8_t *s, size_t n) {
  size_t i;
  for (i = 0; i < n; ++i) {
    if (s[i] != ' ' && s[i] != '\t') {
      return 0;
    }
  }
  return 1;
}

static int check_pseudo_header(nghttp2_stream *stream, const nghttp2_nv *nv,
                               int flag) {
  if (stream->http_flags & flag) {
    return 0;
  }
  if (lws(nv->value, nv->valuelen)) {
    return 0;
  }
  stream->http_flags |= flag;
  return 1;
}

static int expect_response_body(nghttp2_stream *stream) {
  return (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_HEAD) == 0 &&
         stream->status_code / 100 != 1 && stream->status_code != 304 &&
         stream->status_code != 204;
}

static int http_request_on_header(nghttp2_stream *stream, nghttp2_nv *nv,
                                  int trailer) {
  int token;

  if (nv->name[0] == ':') {
    if (trailer ||
        (stream->http_flags & NGHTTP2_HTTP_FLAG_PSEUDO_HEADER_DISALLOWED)) {
      return -1;
    }
  }

  token = lookup_token(nv->name, nv->namelen);

  switch (token) {
  case NGHTTP2_TOKEN__AUTHORITY:
    if (!check_pseudo_header(stream, nv, NGHTTP2_HTTP_FLAG__AUTHORITY)) {
      return -1;
    }
    break;
  case NGHTTP2_TOKEN__METHOD:
    if (!check_pseudo_header(stream, nv, NGHTTP2_HTTP_FLAG__METHOD)) {
      return -1;
    }
    if (streq("HEAD", nv->value, nv->valuelen)) {
      stream->http_flags |= NGHTTP2_HTTP_FLAG_METH_HEAD;
    } else if (streq("CONNECT", nv->value, nv->valuelen)) {
      if (stream->stream_id % 2 == 0) {
        /* we won't allow CONNECT for push */
        return -1;
      }
      stream->http_flags |= NGHTTP2_HTTP_FLAG_METH_CONNECT;
      if (stream->http_flags &
          (NGHTTP2_HTTP_FLAG__PATH | NGHTTP2_HTTP_FLAG__SCHEME)) {
        return -1;
      }
    }
    break;
  case NGHTTP2_TOKEN__PATH:
    if (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_CONNECT) {
      return -1;
    }
    if (!check_pseudo_header(stream, nv, NGHTTP2_HTTP_FLAG__PATH)) {
      return -1;
    }
    break;
  case NGHTTP2_TOKEN__SCHEME:
    if (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_CONNECT) {
      return -1;
    }
    if (!check_pseudo_header(stream, nv, NGHTTP2_HTTP_FLAG__SCHEME)) {
      return -1;
    }
    break;
  case NGHTTP2_TOKEN_HOST:
    if (!check_pseudo_header(stream, nv, NGHTTP2_HTTP_FLAG_HOST)) {
      return -1;
    }
    break;
  case NGHTTP2_TOKEN_CONTENT_LENGTH: {
    if (stream->content_length != -1) {
      return -1;
    }
    stream->content_length = parse_uint(nv->value, nv->valuelen);
    if (stream->content_length == -1) {
      return -1;
    }
    break;
  }
  /* disallowed header fields */
  case NGHTTP2_TOKEN_CONNECTION:
  case NGHTTP2_TOKEN_KEEP_ALIVE:
  case NGHTTP2_TOKEN_PROXY_CONNECTION:
  case NGHTTP2_TOKEN_TRANSFER_ENCODING:
  case NGHTTP2_TOKEN_UPGRADE:
    return -1;
  case NGHTTP2_TOKEN_TE:
    if (!strieq("trailers", nv->value, nv->valuelen)) {
      return -1;
    }
    break;
  default:
    if (nv->name[0] == ':') {
      return -1;
    }
  }

  if (nv->name[0] != ':') {
    stream->http_flags |= NGHTTP2_HTTP_FLAG_PSEUDO_HEADER_DISALLOWED;
  }

  return 0;
}

static int http_response_on_header(nghttp2_stream *stream, nghttp2_nv *nv,
                                   int trailer) {
  int token;

  if (nv->name[0] == ':') {
    if (trailer ||
        (stream->http_flags & NGHTTP2_HTTP_FLAG_PSEUDO_HEADER_DISALLOWED)) {
      return -1;
    }
  }

  token = lookup_token(nv->name, nv->namelen);

  switch (token) {
  case NGHTTP2_TOKEN__STATUS: {
    if (!check_pseudo_header(stream, nv, NGHTTP2_HTTP_FLAG__STATUS)) {
      return -1;
    }
    if (nv->valuelen != 3) {
      return -1;
    }
    stream->status_code = parse_uint(nv->value, nv->valuelen);
    if (stream->status_code == -1) {
      return -1;
    }
    break;
  }
  case NGHTTP2_TOKEN_CONTENT_LENGTH: {
    if (stream->content_length != -1) {
      return -1;
    }
    stream->content_length = parse_uint(nv->value, nv->valuelen);
    if (stream->content_length == -1) {
      return -1;
    }
    break;
  }
  /* disallowed header fields */
  case NGHTTP2_TOKEN_CONNECTION:
  case NGHTTP2_TOKEN_KEEP_ALIVE:
  case NGHTTP2_TOKEN_PROXY_CONNECTION:
  case NGHTTP2_TOKEN_TRANSFER_ENCODING:
  case NGHTTP2_TOKEN_UPGRADE:
    return -1;
  case NGHTTP2_TOKEN_TE:
    if (!strieq("trailers", nv->value, nv->valuelen)) {
      return -1;
    }
    break;
  default:
    if (nv->name[0] == ':') {
      return -1;
    }
  }

  if (nv->name[0] != ':') {
    stream->http_flags |= NGHTTP2_HTTP_FLAG_PSEUDO_HEADER_DISALLOWED;
  }

  return 0;
}

int nghttp2_http_on_header(nghttp2_session *session, nghttp2_stream *stream,
                           nghttp2_frame *frame, nghttp2_nv *nv, int trailer) {
  if (!nghttp2_check_header_name(nv->name, nv->namelen) ||
      !nghttp2_check_header_value(nv->value, nv->valuelen)) {
    return -1;
  }

  if (session->server || frame->hd.type == NGHTTP2_PUSH_PROMISE) {
    return http_request_on_header(stream, nv, trailer);
  }

  return http_response_on_header(stream, nv, trailer);
}

int nghttp2_http_on_request_headers(nghttp2_stream *stream,
                                    nghttp2_frame *frame) {
  if (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_CONNECT) {
    if ((stream->http_flags & NGHTTP2_HTTP_FLAG__AUTHORITY) == 0) {
      return -1;
    }
    stream->content_length = -1;
  } else if ((stream->http_flags & NGHTTP2_HTTP_FLAG_REQ_HEADERS) !=
                 NGHTTP2_HTTP_FLAG_REQ_HEADERS ||
             (stream->http_flags &
              (NGHTTP2_HTTP_FLAG__AUTHORITY | NGHTTP2_HTTP_FLAG_HOST)) == 0) {
    return -1;
  }

  if (frame->hd.type == NGHTTP2_PUSH_PROMISE) {
    /* we are going to reuse data fields for upcoming response.  Clear
       them now, except for method flags. */
    stream->http_flags &= NGHTTP2_HTTP_FLAG_METH_ALL;
    stream->content_length = -1;
  }

  return 0;
}

int nghttp2_http_on_response_headers(nghttp2_stream *stream) {
  if ((stream->http_flags & NGHTTP2_HTTP_FLAG__STATUS) == 0) {
    return -1;
  }

  if (stream->status_code / 100 == 1) {
    /* non-final response */
    stream->http_flags = (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_ALL) |
                         NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE;
    stream->content_length = -1;
    stream->status_code = -1;
    return 0;
  }

  stream->http_flags &= ~NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE;

  if (!expect_response_body(stream)) {
    stream->content_length = 0;
  } else if (stream->http_flags & NGHTTP2_HTTP_FLAG_METH_CONNECT) {
    stream->content_length = -1;
  }

  return 0;
}

int nghttp2_http_on_trailer_headers(nghttp2_stream *stream _U_,
                                    nghttp2_frame *frame) {
  if ((frame->hd.flags & NGHTTP2_FLAG_END_STREAM) == 0) {
    return -1;
  }

  return 0;
}

int nghttp2_http_on_remote_end_stream(nghttp2_stream *stream) {
  if (stream->http_flags & NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE) {
    return -1;
  }

  if (stream->content_length != -1 &&
      stream->content_length != stream->recv_content_length) {
    return -1;
  }

  return 0;
}

int nghttp2_http_on_data_chunk(nghttp2_stream *stream, size_t n) {
  stream->recv_content_length += n;

  if ((stream->http_flags & NGHTTP2_HTTP_FLAG_EXPECT_FINAL_RESPONSE) ||
      (stream->content_length != -1 &&
       stream->recv_content_length > stream->content_length)) {
    return -1;
  }

  return 0;
}

void nghttp2_http_record_request_method(nghttp2_stream *stream,
                                        nghttp2_frame *frame) {
  const nghttp2_nv *nva;
  size_t nvlen;
  size_t i;

  switch (frame->hd.type) {
  case NGHTTP2_HEADERS:
    nva = frame->headers.nva;
    nvlen = frame->headers.nvlen;
    break;
  case NGHTTP2_PUSH_PROMISE:
    nva = frame->push_promise.nva;
    nvlen = frame->push_promise.nvlen;
    break;
  default:
    return;
  }

  /* TODO we should do this strictly. */
  for (i = 0; i < nvlen; ++i) {
    const nghttp2_nv *nv = &nva[i];
    if (lookup_token(nv->name, nv->namelen) != NGHTTP2_TOKEN__METHOD) {
      continue;
    }
    if (streq("CONNECT", nv->value, nv->valuelen)) {
      stream->http_flags |= NGHTTP2_HTTP_FLAG_METH_CONNECT;
      return;
    }
    if (streq("HEAD", nv->value, nv->valuelen)) {
      stream->http_flags |= NGHTTP2_HTTP_FLAG_METH_HEAD;
      return;
    }
    return;
  }
}