#ifndef _DNS_HEAD_H
#define _DNS_HEAD_H

#include <arpa/inet.h>
#include <linux/filter.h>
#include <netdb.h>
#include <stdint.h>

#define DNS_RR_A_LEN 4
#define DNS_RR_AAAA_LEN 16
#define DNS_MAX_CNAME_LEN 256
#define DNS_IN_PACKSIZE (512 * 2)
#define DNS_PACKSIZE (512 * 4)

typedef enum dns_qr {
	DNS_QR_QUERY = 0,
	DNS_QR_ANSWER = 1,
}dns_qr;

typedef enum dns_rr_type {
	DNS_RRS_QD = 0,
	DNS_RRS_AN = 1,
	DNS_RRS_NS = 2,
	DNS_RRS_NR = 3,
	DNS_RRS_END = 4,
} dns_rr_type;

typedef enum dns_class { DNS_C_IN = 1, DNS_C_ANY = 255 } dns_class_t;

typedef enum dns_type {
	DNS_T_A = 1,
	DNS_T_NS = 2,
	DNS_T_CNAME = 5,
	DNS_T_SOA = 6,
	DNS_T_PTR = 12,
	DNS_T_MX = 15,
	DNS_T_TXT = 16,
	DNS_T_AAAA = 28,
	DNS_T_SRV = 33,
	DNS_T_OPT = 41,
	DNS_T_SSHFP = 44,
	DNS_T_SPF = 99,
	DNS_T_AXFR = 252,
	DNS_T_ALL = 255
} dns_type_t;

typedef enum dns_opcode {
	DNS_OP_QUERY = 0,
	DNS_OP_IQUERY = 1,
	DNS_OP_STATUS = 2,
	DNS_OP_NOTIFY = 4,
	DNS_OP_UPDATE = 5,
} dns_opcode_t; /* dns_opcode */

typedef enum dns_rtcode {
	DNS_RC_NOERROR = 0,
	DNS_RC_FORMERR = 1,
	DNS_RC_SERVFAIL = 2,
	DNS_RC_NXDOMAIN = 3,
	DNS_RC_NOTIMP = 4,
	DNS_RC_REFUSED = 5,
	DNS_RC_YXDOMAIN = 6,
	DNS_RC_YXRRSET = 7,
	DNS_RC_NXRRSET = 8,
	DNS_RC_NOTAUTH = 9,
	DNS_RC_NOTZONE = 10,
	/* EDNS(0) extended RCODEs */
	DNS_RC_BADVERS = 16,
} dns_rtcode_t; /* dns_rcode */

struct dns_head {
	unsigned short id;      // identification number
	unsigned short qr;      /* Query/Response Flag */
	unsigned short opcode;  /* Operation Code */
	unsigned char aa;       /* Authoritative Answer Flag */
	unsigned char tc;       /* Truncation Flag */
	unsigned char rd;       /* Recursion Desired */
	unsigned char ra;       /* Recursion Available */
	unsigned short rcode;   /* Response Code */
	unsigned short qdcount; // number of question entries
	unsigned short ancount; // number of answer entries
	unsigned short nscount; // number of authority entries
	unsigned short nrcount; // number of addititional resource entries
} __attribute__((packed));

struct dns_rrs {
	unsigned short next;
	unsigned short len;
	dns_type_t type;
	unsigned char data[0];
};

struct dns_packet {
	struct dns_head head;
	unsigned short questions;
	unsigned short answers;
	unsigned short nameservers;
	unsigned short additional;
	int size;
	int len;
	unsigned char data[0];
};

struct dns_data_context {
	unsigned char *data;
	unsigned char *ptr;
	unsigned int maxsize;
};

struct dns_context {
	struct dns_packet *packet;
	unsigned char *data;
	unsigned int maxsize;
	unsigned char *ptr;
};

struct dns_rrs *dns_get_rrs_next(struct dns_packet *packet, struct dns_rrs *rrs);

struct dns_rrs *dns_get_rrs_start(struct dns_packet *packet, dns_rr_type type, int *count);

/*
 * Question
 */
int dns_add_domain(struct dns_packet *packet, char *domain, int qtype, int qclass);

int dns_get_domain(struct dns_rrs *rrs, char *domain, int maxsize, int *qtype, int *qclass);

/*
 * Answers
 */
int dns_add_CNAME(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, char *cname);

int dns_get_CNAME(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, char *cname, int cname_size);

int dns_add_A(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, unsigned char addr[DNS_RR_A_LEN]);

int dns_get_A(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, unsigned char addr[DNS_RR_A_LEN]);

int dns_add_PTR(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, char *cname);

int dns_get_PTR(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, char *cname, int cname_size);

int dns_add_AAAA(struct dns_packet *packet, dns_rr_type type, char *domain, int ttl, unsigned char addr[DNS_RR_AAAA_LEN]);

int dns_get_AAAA(struct dns_rrs *rrs, char *domain, int maxsize, int *ttl, unsigned char addr[DNS_RR_AAAA_LEN]);


/* 
 * Packet operation
 */
int dns_decode(struct dns_packet *packet, int maxsize, unsigned char *data, int size);

int dns_encode(unsigned char *data, int size, struct dns_packet *packet);

int dns_packet_init(struct dns_packet *packet, int size, struct dns_head *head);

#endif