#ifndef FHP_H_
#define FHP_H

#include <stdint.h> // for uint8_t
#include <stddef.h> // for size_t
#include <stdbool.h> // for size_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);
uint32_t fhp_hash_push(uint32_t, uint8_t * const, size_t);
uint32_t fhp_hash_string(char * const);
uint32_t fhp_lc_hash_push(uint32_t, uint8_t * const, size_t);
uint32_t fhp_lc_hash_string(char * const);

//
// error functions
//

typedef enum {
  FHP_OK,
  FHP_ERR_CB,
  FHP_ERR_BAD_STATE,
  FHP_ERR_INVALID_CHAR,
  FHP_ERR_INVALID_CHAR_IN_METHOD,
  FHP_ERR_INVALID_CHAR_IN_URL,
  FHP_ERR_INVALID_CHAR_IN_URL_PERCENT,
  FHP_ERR_INVALID_CHAR_IN_VERSION,
  FHP_ERR_INVALID_CHAR_AFTER_CR,
  FHP_ERR_INVALID_CHAR_IN_HEADER_NAME,
  FHP_ERR_INVALID_ERROR,
  FHP_ERR_BUFFER_TOO_SMALL,
  FHP_ERR_INVALID_BODY_TYPE,
  FHP_ERR_TOO_MANY_TES,
  FHP_ERR_INVALID_CHAR_IN_TE_NAME,
  FHP_ERR_INVALID_CHAR_IN_TE,
  FHP_ERR_BAD_TE_STATE,
  FHP_ERR_TE_PARSER_DONE,
  FHP_ERR_NULL_TE_BUF,
  FHP_ERR_SMALL_TE_BUF,
  FHP_ERR_LAST
} fhp_err_t;

fhp_err_t
fhp_strerror(fhp_err_t, char * const, size_t);

//
// token functions
//

typedef enum {
  FHP_TOKEN_METHOD_START,
  FHP_TOKEN_METHOD_FRAGMENT,
  FHP_TOKEN_METHOD_END,

  FHP_TOKEN_METHOD_GET,
  FHP_TOKEN_METHOD_POST,
  FHP_TOKEN_METHOD_HEAD,
  FHP_TOKEN_METHOD_PUT,
  FHP_TOKEN_METHOD_DELETE,
  FHP_TOKEN_METHOD_OPTIONS,
  FHP_TOKEN_METHOD_OTHER,

  FHP_TOKEN_URL_START,
  FHP_TOKEN_URL_FRAGMENT,
  FHP_TOKEN_URL_END,

  FHP_TOKEN_VERSION_START,
  FHP_TOKEN_VERSION_FRAGMENT,
  FHP_TOKEN_VERSION_END,

  FHP_TOKEN_VERSION_HTTP_10,
  FHP_TOKEN_VERSION_HTTP_11,
  FHP_TOKEN_VERSION_OTHER,

  FHP_TOKEN_HEADER_NAME_START,
  FHP_TOKEN_HEADER_NAME_FRAGMENT,
  FHP_TOKEN_HEADER_NAME_END,

  FHP_TOKEN_HEADER_VALUE_START,
  FHP_TOKEN_HEADER_VALUE_FRAGMENT,
  FHP_TOKEN_HEADER_VALUE_END,

  FHP_TOKEN_HEADER_TRANSFER_ENCODING,
  FHP_TOKEN_HEADER_CONTENT_LENGTH,

  FHP_TOKEN_LAST
} fhp_token_t;

fhp_err_t
fhp_strtoken(fhp_token_t, char * const, size_t);

typedef enum {
  FHP_BODY_TYPE_NONE,
  FHP_BODY_TYPE_CONTENT_LENGTH,
  FHP_BODY_TYPE_TRANSFER_ENCODING,
  FHP_BODY_TYPE_LAST
} fhp_body_type_t;

//
// env functions
//

#define FHP_ENV_NUM_HASHES 6

typedef struct {
  uint32_t hashes[FHP_ENV_NUM_HASHES];
} fhp_env_t;

void fhp_env_init(fhp_env_t * const env);
fhp_env_t *fhp_get_default_env(void);

//
// transfer encoding parser functions
//

typedef enum {
  FHP_TE_STATE_INIT,
  FHP_TE_STATE_NAME,
  FHP_TE_STATE_IGNORE_UNTIL_COMMA,
  FHP_TE_STATE_SPACE,
  FHP_TE_STATE_ERROR,
  FHP_TE_STATE_DONE,
  FHP_TE_STATE_LAST
} fhp_te_state_t;

#define FHP_TE_MAX_BUF_SIZE 16
#define FHP_TE_MAX_TES 4

typedef struct {
  fhp_te_state_t state;

  uint8_t buf[FHP_TE_MAX_BUF_SIZE];
  size_t len;

  uint32_t buf_hash;

  uint32_t tes[FHP_TE_MAX_TES];
  size_t num_tes;

  fhp_err_t err;
} fhp_te_parser_t;

fhp_err_t
fhp_te_parser_init(fhp_te_parser_t * const te);

fhp_err_t
fhp_te_parser_push(fhp_te_parser_t *, uint8_t * const, size_t);

fhp_err_t
fhp_te_parser_done(fhp_te_parser_t * const, size_t * const);

fhp_err_t
fhp_te_parser_get_tes(fhp_te_parser_t * const, uint32_t * const, size_t);

//
// context functions
//

typedef struct fhp_t_ fhp_t;

typedef bool (*fhp_cb_t)(
  fhp_t * const,
  fhp_token_t,
  uint8_t * const,
  size_t
);

typedef enum {
  FHP_STATE_INIT,
  FHP_STATE_ERROR,
  FHP_STATE_METHOD,
  FHP_STATE_METHOD_END,
  FHP_STATE_URL,
  FHP_STATE_URL_PERCENT,
  FHP_STATE_URL_PERCENT_LAST,
  FHP_STATE_URL_END,
  FHP_STATE_VERSION,
  FHP_STATE_VERSION_END,
  FHP_STATE_VERSION_END_CR,
  FHP_STATE_STATUS_END,
  FHP_STATE_STATUS_END_CR,
  FHP_STATE_HEADER_NAME,
  FHP_STATE_HEADER_NAME_END,
  FHP_STATE_HEADER_NAME_END_CR,
  FHP_STATE_HEADER_VALUE,
  FHP_STATE_HEADER_VALUE_END_CR,
  FHP_STATE_HEADER_VALUE_END,
  FHP_STATE_HEADERS_END,
  FHP_STATE_HEADERS_END_CR,
  FHP_STATE_LAST
} fhp_state_t;

typedef enum {
  FHP_HEADER_VALUE_PARSER_NONE,
  FHP_HEADER_VALUE_PARSER_TRANSFER_ENCODING,
  FHP_HEADER_VALUE_PARSER_CONTENT_LENGTH,
  FHP_HEADER_VALUE_PARSER_LAST
} fhp_header_value_parser_t;

#define FHP_MAX_BUF_SIZE 1024
#define FHP_MAX_TRANSFER_ENCODINGS 4

struct fhp_t_ {
  // env pointer
  fhp_env_t *env;

  // opaque user data
  void *user_data;

  // current parser state
  fhp_state_t state;

  // user callback
  fhp_cb_t cb;

  // last error
  fhp_err_t err;

  // number of bytes read
  uint64_t ofs;

  // fragment data buffer
  uint8_t buf[FHP_MAX_BUF_SIZE];
  size_t buf_len;

  // buffer hashing state
  bool is_hashing;
  uint32_t buf_hash;

  // cached http method and version
  fhp_token_t http_method, http_version;

  // hash of last header name
  uint32_t header_name_hash;

  // header value parser
  fhp_header_value_parser_t header_value_parser;

  union {
    fhp_te_parser_t te;
  } parsers;

  // request body type
  fhp_body_type_t body_type;

  // content length
  uint64_t content_length;

  // transfer encodings
  uint32_t tes[FHP_MAX_TRANSFER_ENCODINGS];
  size_t num_tes;

  // state for url hex decoder
  uint32_t hex;
};

fhp_err_t
fhp_init(fhp_t * const, fhp_env_t * const, fhp_cb_t, void * const);

fhp_err_t
fhp_push(fhp_t * const, uint8_t * const, size_t);

fhp_env_t *
fhp_get_env(fhp_t * const);

void *
fhp_get_user_data(fhp_t * const);

#endif /* FHP_H */