#include <string.h>
#include "fhp/fhp.h"

#define UNUSED(a) ((void) (a))

#define CASE_ALNUM_CHARS \
  case '0': \
  case '1': \
  case '2': \
  case '3': \
  case '4': \
  case '5': \
  case '6': \
  case '7': \
  case '8': \
  case '9': \
  case 'a': \
  case 'b': \
  case 'c': \
  case 'd': \
  case 'e': \
  case 'f': \
  case 'g': \
  case 'h': \
  case 'i': \
  case 'j': \
  case 'k': \
  case 'l': \
  case 'm': \
  case 'n': \
  case 'o': \
  case 'p': \
  case 'q': \
  case 'r': \
  case 's': \
  case 't': \
  case 'u': \
  case 'v': \
  case 'w': \
  case 'x': \
  case 'y': \
  case 'z': \
  case 'A': \
  case 'B': \
  case 'C': \
  case 'D': \
  case 'E': \
  case 'F': \
  case 'G': \
  case 'H': \
  case 'I': \
  case 'J': \
  case 'K': \
  case 'L': \
  case 'M': \
  case 'N': \
  case 'O': \
  case 'P': \
  case 'Q': \
  case 'R': \
  case 'S': \
  case 'T': \
  case 'U': \
  case 'V': \
  case 'W': \
  case 'X': \
  case 'Y': \
  case 'Z':

#define CASE_DIGIT_CHARS \
  case '0': \
  case '1': \
  case '2': \
  case '3': \
  case '4': \
  case '5': \
  case '6': \
  case '7': \
  case '8': \
  case '9':

#define CASE_HEX_ALPHA_CHARS \
  case 'a': \
  case 'b': \
  case 'c': \
  case 'd': \
  case 'e': \
  case 'f': \
  case 'A': \
  case 'B': \
  case 'C': \
  case 'D': \
  case 'E': \
  case 'F':

//
// rfc7230, Appendix B
// https://tools.ietf.org/html/rfc7230
//
//   tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*" / "+" / "-" / "." /
//           "^" / "_" / "`" / "|" / "~" / DIGIT / ALPHA
//   token = 1*tchar
//
#define CASE_TOKEN_CHARS \
  CASE_ALNUM_CHARS \
  case '!': \
  case '#': \
  case '$': \
  case '%': \
  case '&': \
  case '\'': \
  case '*': \
  case '+': \
  case '-': \
  case '.': \
  case '^': \
  case '_': \
  case '|': \
  case '~': \

#define CASE_URL_CHARS \
  CASE_ALNUM_CHARS \
  case '!': \
  case '"': \
  case '#': \
  case '$': \
  case '&': \
  case '\'': \
  case '(': \
  case ')': \
  case '*': \
  case '+': \
  case ',': \
  case '-': \
  case '.': \
  case '/': \
  case ':': \
  case ';': \
  case '<': \
  case '=': \
  case '>': \
  case '?': \
  case '@': \
  case '[': \
  case '\\': \
  case ']': \
  case '^': \
  case '_': \
  case '`': \
  case '{': \
  case '|': \
  case '}': \
  case '~':

#define CASE_VISUAL_CHARS \
  CASE_URL_CHARS \
  case '%':

#define CASE_VERSION_CHARS \
  CASE_TOKEN_CHARS \
  case '/':

//
// rfc7230, Appendix B
// https://tools.ietf.org/html/rfc7230
//
//   OWS = *( SP / HTAB )
//
#define CASE_OWS_CHARS \
  case ' ': \
  case '\t':

//
// hash functions (djb2)
// (see http://aras-p.info/blog/2016/08/02/Hash-Functions-all-the-way-down/)
//

uint32_t
fhp_hash_init(void) {
  return 5381;
}

uint32_t
fhp_hash_push(uint32_t hash, uint8_t * const buf, size_t len) {
  for (size_t i = 0; i < len; i++)
    hash = ((hash << 5) + hash) + buf[len];

  return hash;
}

uint32_t
fhp_hash_string(char * const str) {
  uint32_t r = fhp_hash_init();
  return fhp_hash_push(r, (uint8_t*) str, strlen(str));
}

uint32_t
fhp_lc_hash_push(
  uint32_t hash,
  uint8_t * const buf,
  size_t len
) {
  for (size_t i = 0; i < len; i++) {
    uint8_t c = buf[len];

    if (c >= 'A' && c <= 'Z')
      c = (c - 'A') + 'a';

    hash = ((hash << 5) + hash) + c;
  }

  return hash;
}

uint32_t
fhp_lc_hash_string(char * const str) {
  uint32_t r = fhp_hash_init();
  return fhp_lc_hash_push(r, (uint8_t*) str, strlen(str));
}

//
// error functions
//

static const char *
fhp_errors[] = {
  "OK",
  "callback error",
  "bad state",
  "invalid character",
  "invalid character in HTTP method",
  "invalid character in HTTP URL",
  "invalid percent-encoded character in HTTP URL",
  "invalid character in HTTP version",
  "invalid character after carriage return",
  "invalid character in HTTP header name",
  "invalid error code",
  "buffer too small",
};

fhp_err_t
fhp_strerror(
  fhp_err_t err,
  char * const buf,
  size_t len
) {
  // check error code
  if (err >= FHP_ERR_LAST)
    return FHP_ERR_INVALID_ERROR;

  // check buffer size
  size_t err_len = strlen(fhp_errors[err]) + 1;
  if (len < err_len)
    return FHP_ERR_BUFFER_TOO_SMALL;

  // copy string
  memcpy(buf, fhp_errors[err], err_len);

  // return success
  return FHP_OK;
}

//
// token functions
//

static const char *
fhp_tokens[] = {
  "METHOD_START",
  "METHOD_FRAGMENT",
  "METHOD_END",

  "METHOD_GET",
  "METHOD_POST",
  "METHOD_HEAD",
  "METHOD_PUT",
  "METHOD_DELETE",
  "METHOD_OPTIONS",
  "METHOD_OTHER",

  "URL_START",
  "URL_FRAGMENT",
  "URL_END",

  "VERSION_START",
  "VERSION_FRAGMENT",
  "VERSION_END",

  "VERSION_HTTP_10",
  "VERSION_HTTP_11",
  "VERSION_OTHER",

  "HEADER_NAME_START",
  "HEADER_NAME_FRAGMENT",
  "HEADER_NAME_END",

  "HEADER_VALUE_START",
  "HEADER_VALUE_FRAGMENT",
  "HEADER_VALUE_END",

  "LAST"
};

fhp_err_t
fhp_strtoken(
  fhp_token_t token,
  char * const buf,
  size_t len
) {
  // check token code
  if (token >= FHP_TOKEN_LAST)
    return FHP_ERR_INVALID_ERROR;

  // check buffer size
  size_t str_len = strlen(fhp_tokens[token]) + 1;
  if (len < str_len)
    return FHP_ERR_BUFFER_TOO_SMALL;

  // copy string
  memcpy(buf, fhp_tokens[token], str_len);

  // return success
  return FHP_OK;
}

//
// string functions
//

static char * const
fhp_strings[] = {
  "GET",
  "POST",
  "HEAD",
  "PUT",
  "DELETE",
  "OPTIONS",
  "HTTP/1.0",
  "HTTP/1.1",
  "content-length",
  "transfer-encoding",
  "gzip",
  "x-gzip",
  "deflate",
  "x-deflate",
  "chunked",
  NULL
};

typedef enum {
  FHP_STR_GET,
  FHP_STR_POST,
  FHP_STR_HEAD,
  FHP_STR_PUT,
  FHP_STR_DELETE,
  FHP_STR_OPTIONS,
  FHP_STR_HTTP_10,
  FHP_STR_HTTP_11,
  FHP_STR_CONTENT_LENGTH,
  FHP_STR_TRANSFER_ENCODING,
  FHP_STR_GZIP,
  FHP_STR_X_GZIP,
  FHP_STR_DEFLATE,
  FHP_STR_X_DEFLATE,
  FHP_STR_CHUNKED,
  FHP_STR_LAST
} fhp_str_t;

void
fhp_env_init(fhp_env_t * const env) {
  for (size_t i = 0; i < FHP_STR_LAST; i++)
    env->hashes[i] = fhp_lc_hash_string(fhp_strings[i]);
}

static fhp_env_t fhp_default_env;

fhp_env_t *
fhp_get_default_env(void) {
  static fhp_env_t *r = NULL;

  if (!r) {
    r = &fhp_default_env;
    fhp_env_init(r);
  }

  return r;
}

//
// context functions
//

static const fhp_t DEFAULT_CONTEXT = {
  .state = FHP_STATE_INIT,
  .user_data = NULL,
  .cb = NULL,
  .err = FHP_OK,
  .ofs = 0,
  .buf_len = 0,
  .is_hashing = false,
  .header_name_hash = 0,
};

fhp_err_t
fhp_init(
  fhp_t * const fhp,
  fhp_env_t * const env,
  fhp_cb_t cb,
  void * const user_data
) {
  *fhp = DEFAULT_CONTEXT;
  fhp->env = env ? env : fhp_get_default_env();
  fhp->user_data = user_data;
  fhp->cb = cb;

  /* return success */
  return FHP_OK;
}

static void
fhp_buf_clear(fhp_t * const fhp) {
  // clear buffer
  fhp->buf_len = 0;
}

static bool
fhp_buf_flush(
  fhp_t * const fhp,
  fhp_token_t token
) {
  if (fhp->buf_len > 0) {
    // push data
    if (!fhp->cb(fhp, token, fhp->buf, fhp->buf_len))
      return false;

    // update buffer hash
    if (fhp->is_hashing)
      fhp->buf_hash = fhp_hash_push(fhp->buf_hash, fhp->buf, fhp->buf_len);

    // clear buffer
    fhp_buf_clear(fhp);
  }

  // return success
  return true;
}

static bool
fhp_buf_push(
  fhp_t * const fhp,
  fhp_token_t token,
  uint8_t byte
) {
  // flush buffer
  if (fhp->buf_len + 1 >= FHP_BUF_SIZE) {
    if (!fhp_buf_flush(fhp, token))
      return false;
  }

  // append to buffer
  fhp->buf[fhp->buf_len] = byte;
  fhp->buf_len++;

  // return success
  return true;
}

static fhp_err_t
fhp_push_byte(
  fhp_t * const fhp,
  uint8_t byte
) {
retry:
  switch (fhp->state) {
  case FHP_STATE_INIT:
    switch (byte) {
    CASE_TOKEN_CHARS
      // send start token
      if (!fhp->cb(fhp, FHP_TOKEN_METHOD_START, 0, 0))
        return FHP_ERR_CB;

      // enable buffer hashing
      fhp->is_hashing = true;
      fhp->buf_hash = fhp_hash_init();

      // set state
      fhp->state = FHP_STATE_METHOD;
      goto retry;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_IN_METHOD;
    }

    break;
  case FHP_STATE_METHOD:
    switch (byte) {
    CASE_TOKEN_CHARS
      // add to buffer
      if (!fhp_buf_push(fhp, FHP_TOKEN_METHOD_FRAGMENT, byte))
        return FHP_ERR_CB;

      break;
    case ' ':
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_METHOD_FRAGMENT))
        return FHP_ERR_CB;

      // disable buffer hashing
      fhp->is_hashing = false;

      // send end token
      if (!fhp->cb(fhp, FHP_TOKEN_METHOD_END, 0, 0))
        return FHP_ERR_CB;

      // get method token
      fhp->http_method = FHP_TOKEN_METHOD_OTHER;
      if (fhp->buf_hash == fhp->env->hashes[FHP_STR_GET]) {
        fhp->http_method = FHP_TOKEN_METHOD_GET;
      } else if (fhp->buf_hash == fhp->env->hashes[FHP_STR_POST]) {
        fhp->http_method = FHP_TOKEN_METHOD_POST;
      } else if (fhp->buf_hash == fhp->env->hashes[FHP_STR_HEAD]) {
        fhp->http_method = FHP_TOKEN_METHOD_HEAD;
      } else if (fhp->buf_hash == fhp->env->hashes[FHP_STR_PUT]) {
        fhp->http_method = FHP_TOKEN_METHOD_PUT;
      } else if (fhp->buf_hash == fhp->env->hashes[FHP_STR_DELETE]) {
        fhp->http_method = FHP_TOKEN_METHOD_DELETE;
      } else if (fhp->buf_hash == fhp->env->hashes[FHP_STR_OPTIONS]) {
        fhp->http_method = FHP_TOKEN_METHOD_OPTIONS;
      }

      // send method token
      if (!fhp->cb(fhp, fhp->http_method, 0, 0))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_METHOD_END;
      goto retry;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_IN_METHOD;
    }

    break;
  case FHP_STATE_METHOD_END:
    switch (byte) {
    case ' ':
      // FIXME: do we want to allow more than one whitespace?
      // ignore
      break;
    CASE_URL_CHARS
      if (!fhp->cb(fhp, FHP_TOKEN_URL_START, 0, 0))
        return FHP_ERR_CB;

      fhp->state = FHP_STATE_URL;
      goto retry;
    default:
      return FHP_ERR_INVALID_CHAR_IN_URL;
    }

    break;
  case FHP_STATE_URL:
    switch (byte) {
    case ' ':
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_URL_FRAGMENT))
        return FHP_ERR_CB;

      // send end token
      if (!fhp->cb(fhp, FHP_TOKEN_URL_END, 0, 0))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_URL_END;
      goto retry;

      break;
    case '%':
      // set state
      fhp->state = FHP_STATE_URL_PERCENT;

      break;
    CASE_URL_CHARS
      // add to buffer
      if (!fhp_buf_push(fhp, FHP_TOKEN_URL_FRAGMENT, byte))
        return FHP_ERR_CB;
    }

    break;
  case FHP_STATE_URL_PERCENT:
    switch (byte) {
    CASE_DIGIT_CHARS
      fhp->hex = byte - '0';
      fhp->state = FHP_STATE_URL_PERCENT_LAST;

      break;
    CASE_HEX_ALPHA_CHARS
      fhp->hex = 10 + byte - ((byte >= 'a') ? 'a' : 'A');
      fhp->state = FHP_STATE_URL_PERCENT_LAST;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_IN_URL_PERCENT;
    }

    break;
  case FHP_STATE_URL_PERCENT_LAST:
    switch (byte) {
    CASE_DIGIT_CHARS
      fhp->hex = (fhp->hex << 4) + (byte - '0');
      break;
    CASE_HEX_ALPHA_CHARS
      fhp->hex = (fhp->hex << 4) + (10 + byte - ((byte >= 'a') ? 'a' : 'A'));
      break;
    default:
      return FHP_ERR_INVALID_CHAR_IN_URL_PERCENT;
    }

    // add to buffer
    if (!fhp_buf_push(fhp, FHP_TOKEN_URL_FRAGMENT, fhp->hex))
      return FHP_ERR_CB;

    // set state
    fhp->state = FHP_STATE_URL;

    break;
  case FHP_STATE_URL_END:
    switch (byte) {
    case ' ':
      // ignore
      break;
    default:
      if (!fhp->cb(fhp, FHP_TOKEN_VERSION_START, 0, 0))
        return FHP_ERR_CB;

      // enable buffer hashing
      fhp->is_hashing = true;
      fhp->buf_hash = fhp_hash_init();

      // set state
      fhp->state = FHP_STATE_VERSION;
      goto retry;
    }

    break;
  case FHP_STATE_VERSION:
    switch (byte) {
    case '\r':
    case '\n':
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_VERSION_FRAGMENT))
        return FHP_ERR_CB;

      // send end token
      if (!fhp->cb(fhp, FHP_TOKEN_VERSION_END, 0, 0))
        return FHP_ERR_CB;

      // disable buffer hashing
      fhp->is_hashing = false;

      // get version token
      fhp->http_version = FHP_TOKEN_VERSION_OTHER;
      if (fhp->buf_hash == fhp->env->hashes[FHP_STR_HTTP_10]) {
        fhp->http_version = FHP_TOKEN_VERSION_HTTP_10;
      } else if (fhp->buf_hash == fhp->env->hashes[FHP_STR_HTTP_11]) {
        fhp->http_version = FHP_TOKEN_VERSION_HTTP_11;
      }

      // send version token
      if (!fhp->cb(fhp, fhp->http_version, 0, 0))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_VERSION_END;
      goto retry;

      break;
    CASE_VERSION_CHARS
      // add to buffer
      if (!fhp_buf_push(fhp, FHP_TOKEN_VERSION_FRAGMENT, byte))
        return FHP_ERR_CB;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_IN_VERSION;
    }

    break;
  case FHP_STATE_VERSION_END:
    switch (byte) {
    case '\r':
      fhp->state = FHP_STATE_VERSION_END_CR;

      break;
    case '\n':
      fhp->state = FHP_STATE_STATUS_END;

      break;
    default:
      // invalid character
      // (should never be reached)
      return FHP_ERR_INVALID_CHAR;
    };

    break;
  case FHP_STATE_VERSION_END_CR:
    switch (byte) {
    case '\n':
      fhp->state = FHP_STATE_STATUS_END;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_AFTER_CR;
    };

    break;
  case FHP_STATE_STATUS_END:
    switch (byte) {
    CASE_TOKEN_CHARS
      // send start token
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_NAME_START, 0, 0))
        return FHP_ERR_CB;

      // enable buffer hashing
      fhp->is_hashing = true;
      fhp->buf_hash = fhp_hash_init();

      // set state
      fhp->state = FHP_STATE_HEADER_NAME;
      goto retry;

      break;
    case '\r':
      // set state
      fhp->state = FHP_STATE_STATUS_END_CR;

      break;
    case '\n':
      // set state
      fhp->state = FHP_STATE_HEADERS_END;

      break;
    }

    break;
  case FHP_STATE_STATUS_END_CR:
    switch (byte) {
    case '\n':
      // set state
      fhp->state = FHP_STATE_HEADERS_END;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_AFTER_CR;
    }

    break;
  case FHP_STATE_HEADER_NAME:
    switch (byte) {
    CASE_TOKEN_CHARS
      // add to buffer
      if (!fhp_buf_push(fhp, FHP_TOKEN_HEADER_NAME_FRAGMENT, byte))
        return FHP_ERR_CB;

      break;
    case ':':
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_HEADER_NAME_FRAGMENT))
        return FHP_ERR_CB;

      // send end token
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_NAME_END, 0, 0))
        return FHP_ERR_CB;

      // disable buffer hashing
      fhp->is_hashing = false;
      fhp->header_name_hash = fhp->buf_hash;

      // set state
      fhp->state = FHP_STATE_HEADER_NAME_END;

      break;
    default:
      return FHP_ERR_INVALID_CHAR_IN_HEADER_NAME;
    }

    break;
  case FHP_STATE_HEADER_NAME_END:
    switch (byte) {
    CASE_OWS_CHARS
      // ignore leading spaces

      break;
    default:
      // send start token
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_VALUE_START, 0, 0))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_HEADER_VALUE;
      goto retry;

      break;
    }

    break;
  case FHP_STATE_HEADER_VALUE:
    switch (byte) {
    case '\r':
      fhp->state = FHP_STATE_HEADER_VALUE_END_CR;

      break;
    case '\n':
      fhp->state = FHP_STATE_HEADER_VALUE_END;
      break;
    default:
      // FIXME: need more limits on valid octets

      // add to buffer
      if (!fhp_buf_push(fhp, FHP_TOKEN_HEADER_VALUE_FRAGMENT, byte))
        return FHP_ERR_CB;

      break;
    }

    break;
  case FHP_STATE_HEADER_VALUE_END_CR:
    switch (byte) {
    case '\n':
      fhp->state = FHP_STATE_HEADER_VALUE_END;
      break;
    default:
      return FHP_ERR_INVALID_CHAR;
    }

    break;
  case FHP_STATE_HEADER_VALUE_END:
    switch (byte) {
    CASE_OWS_CHARS
      // ows-fold

      // add space to buffer
      // folding to ' ', as per RFC7230 3.2.4
      // https://tools.ietf.org/html/rfc7230#section-3.2.4
      if (!fhp_buf_push(fhp, FHP_TOKEN_HEADER_VALUE_FRAGMENT, ' '))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_HEADER_VALUE;

      break;
    CASE_TOKEN_CHARS
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_HEADER_VALUE_FRAGMENT))
        return FHP_ERR_CB;

      // end header value
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_VALUE_END, 0, 0))
        return FHP_ERR_CB;

      // send start token
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_NAME_START, 0, 0))
        return FHP_ERR_CB;

      // add to buffer
      if (!fhp_buf_push(fhp, FHP_TOKEN_HEADER_NAME_FRAGMENT, byte))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_HEADER_NAME;

      break;
    case '\r':
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_HEADER_VALUE_FRAGMENT))
        return FHP_ERR_CB;

      // end header value
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_VALUE_END, 0, 0))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_HEADERS_END_CR;

      break;
    case '\n':
      // flush buffer
      if (!fhp_buf_flush(fhp, FHP_TOKEN_HEADER_VALUE_FRAGMENT))
        return FHP_ERR_CB;

      // end header value
      if (!fhp->cb(fhp, FHP_TOKEN_HEADER_VALUE_END, 0, 0))
        return FHP_ERR_CB;

      // set state
      fhp->state = FHP_STATE_HEADERS_END;

      break;
    default:
      return FHP_ERR_INVALID_CHAR;
    }

    break;
  case FHP_STATE_HEADERS_END_CR:
    switch (byte) {
    case '\n':
      fhp->state = FHP_STATE_HEADERS_END;

      break;
    default:
      return FHP_ERR_INVALID_CHAR;
    }

    break;
  case FHP_STATE_HEADERS_END:
    // TODO

    break;
  default:
    // invalid state
    // (should never be reached)
    return FHP_ERR_BAD_STATE;
  }

  // increment byte offset
  fhp->ofs++;

  /* return success */
  return FHP_OK;
}

fhp_err_t
fhp_push(
  fhp_t * const fhp,
  uint8_t * const buf,
  size_t len
) {
  switch (fhp->state) {
  case FHP_STATE_ERROR:
    return fhp->err;

    break;
  default:
    for (size_t i = 0; i < len; i++) {
      // push byte
      fhp_err_t err = fhp_push_byte(fhp, buf[i]);

      // check result
      if (err != FHP_OK) {
        fhp->state = FHP_STATE_ERROR;
        fhp->err = err;
        return err;
      }
    }
  }

  // return success
  return FHP_OK;
}

fhp_env_t *
fhp_get_env(fhp_t * const fhp) {
  return fhp->env;
}

void *
fhp_get_user_data(fhp_t * const fhp) {
  return fhp->user_data;
}