/*  Copyright (C) CZ.NIC, z.s.p.o. <knot-resolver@labs.nic.cz>
 *  SPDX-License-Identifier: GPL-3.0-or-later
 */

#pragma once

#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/un.h>
#include <netinet/in.h>
#include <unistd.h>

#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>

#include <libknot/libknot.h>
#include <libknot/packet/pkt.h>
#include <libknot/rrset.h>
#include <libknot/rrtype/rrsig.h>
#include <uv.h>

#include "kresconfig.h"
#include "contrib/mempattern.h"
#include "lib/defines.h"
#include "lib/generic/array.h"
#include "lib/log.h"

/** When knot_pkt is passed from cache without ->wire, this is the ->size. */
static const size_t KR_PKT_SIZE_NOWIRE = -1;

/** Maximum length (excluding null-terminator) of a presentation-form address
 * returned by `kr_straddr`. */
#define KR_STRADDR_MAXLEN 109

/** Used for reserving enough space for the `kr_sockaddr_key` function
 * output. */
struct kr_sockaddr_key_storage {
	char bytes[sizeof(struct sockaddr_storage)];
};


/*
 * Logging and debugging.
 */

/** @brief Callback for request events. */
typedef void (*trace_callback_f)(struct kr_request *request);
/**
 * @brief Callback for request logging handler.
 * @param[in] msg Log message. Pointer is not valid after handler returns. */
typedef void (*trace_log_f)(const struct kr_request *request, const char *msg);

/** Assert() but always, regardless of -DNDEBUG.  See also kr_assert(). */
#define kr_require(expression) do { if (!(expression)) { \
		kr_fail(true, #expression, __func__, __FILE__, __LINE__); \
		__builtin_unreachable(); /* aid code analysis */ \
	} } while (false)

/** Check an assertion that's recoverable. Return the true if it fails and needs handling.
 *
 * If the check fails, optionally fork()+abort() to generate coredump
 * and continue running in parent process.  Return value must be handled to
 * ensure safe recovery from error.  Use kr_require() for unrecoverable checks.
 * The errno variable is not mangled, e.g. you can: if (kr_fails_assert(...)) return errno;
 */
#define kr_fails_assert(expression) !kr_assert_func((expression), #expression, \
						   __func__, __FILE__, __LINE__)

/** Kresd assertion without a return value.
 *
 * These can be turned on or off, for mandatory unrecoverable checks, use kr_require().
 * For recoverable checks, use kr_fails_assert().
 * */
#define kr_assert(expression) (void)!kr_fails_assert((expression))

/** Whether kr_assert() and kr_fails_assert() checks should abort. */
KR_EXPORT extern bool kr_dbg_assertion_abort;

/** How often kr_assert() should fork the process before issuing abort (if configured).
 *
 * This can be useful for debugging rare edge-cases in production.
 * if (kr_debug_assertion_abort && kr_debug_assertion_fork), it is
 * possible to both obtain a coredump (from forked child) and recover from the
 * non-fatal error in the parent process.
 *
 * == 0 (false): no forking
 * > 0: minimum delay between forks
 *      (in milliseconds, each instance separately, randomized +-25%)
 * < 0: no rate-limiting (not recommended)
 */
KR_EXPORT extern int kr_dbg_assertion_fork;

/** Use kr_require(), kr_assert() or kr_fails_assert() instead of directly this function. */
KR_EXPORT KR_COLD void kr_fail(bool is_fatal, const char* expr, const char *func,
				const char *file, int line);

/** Use kr_require(), kr_assert() or kr_fails_assert() instead of directly this function. */
__attribute__ ((warn_unused_result))
static inline bool kr_assert_func(bool result, const char *expr, const char *func,
				  const char *file, int line)
{
	if (!result)
		kr_fail(false, expr, func, file, line);
	return result;
}

#define KR_DNAME_GET_STR(dname_str, dname) \
	char dname_str[KR_DNAME_STR_MAXLEN]; \
	knot_dname_to_str(dname_str, (dname), sizeof(dname_str)); \
	dname_str[sizeof(dname_str) - 1] = 0;

#define KR_RRTYPE_GET_STR(rrtype_str, rrtype) \
	char rrtype_str[KR_RRTYPE_STR_MAXLEN]; \
	knot_rrtype_to_string((rrtype), rrtype_str, sizeof(rrtype_str)); \
	rrtype_str[sizeof(rrtype_str) - 1] = 0;

// Use this for allocations with mm.
// Use mm_alloc for allocations into mempool

/** A strcmp() variant directly usable for qsort() on an array of strings. */
static inline int strcmp_p(const void *p1, const void *p2)
{
	return strcmp(*(char * const *)p1, *(char * const *)p2);
}

/** Get current working directory with fallback value. */
static inline void get_workdir(char *out, size_t len) {
	if(getcwd(out, len) == NULL) {
		static const char errprefix[] = "<invalid working directory>";
		strncpy(out, errprefix, len);
	}
}

/** @cond internal Array types */
struct kr_context;

struct ranked_rr_array_entry {
	uint32_t qry_uid;
	uint8_t rank; /**< enum kr_rank */
	uint8_t revalidation_cnt;
	bool cached : 1;  /**< Set to true if the entry was written into cache */
	bool yielded : 1;
	bool to_wire : 1; /**< whether to be put into the answer */
	bool expiring : 1; /**< low remaining TTL; see is_expiring; only used in cache ATM */
	bool in_progress : 1; /**< build of RRset in progress, i.e. different format of RR data */
	bool dont_cache : 1; /**< avoid caching; useful e.g. for generated data */
	knot_rrset_t *rr;
};
typedef struct ranked_rr_array_entry ranked_rr_array_entry_t;

/** Array of RRsets coming from multiple queries; for struct kr_request.
 *
 * Notes:
 *  - RRSIGs are only considered to form an RRset when the types covered match;
 *    cache-related code relies on that!
 *  - RRsets from the same packet (qry_uid) get merged.
 */
typedef array_t(ranked_rr_array_entry_t *) ranked_rr_array_t;
/* @endcond */

typedef struct kr_http_header_array_entry {
	char* name;
	char* value;
} kr_http_header_array_entry_t;

/** Array of HTTP headers for DoH. */
typedef array_t(kr_http_header_array_entry_t) kr_http_header_array_t;

/** Concatenate N strings. */
KR_EXPORT
char* kr_strcatdup(unsigned n, ...);

/** Construct absolute file path, without resolving symlinks.
 * \return malloc-ed string or NULL (+errno in that case) */
KR_EXPORT
char * kr_absolutize_path(const char *dirname, const char *fname);

/** You probably want kr_rand_* convenience functions instead.
 * This is a buffered version of gnutls_rnd(GNUTLS_RND_NONCE, ..) */
KR_EXPORT
void kr_rnd_buffered(void *data, unsigned int size);

/** Return a few random bytes. */
KR_EXPORT inline
uint64_t kr_rand_bytes(unsigned int size)
{
	uint64_t result;
	if (size <= 0 || size > sizeof(result)) {
		kr_log_error(SYSTEM, "kr_rand_bytes(): EINVAL\n");
		abort();
	}
	uint8_t data[sizeof(result)];
	kr_rnd_buffered(data, size);
	/* I would have liked to dump the random data into a size_t directly,
	 * but that would work well only on little-endian machines,
	 * so instead I hope that the compiler will optimize this out.
	 * (Tested via reading assembly from usual gcc -O2 setup.)
	 * Alternatively we could waste more rnd bytes, but that seemed worse. */
	result = 0;
	for (unsigned int i = 0; i < size; ++ i) {
		result |= ((uint64_t)data[i]) << (i * 8);
	}
	return result;
}

/** Throw a pseudo-random coin, succeeding approximately with probability nomin/denomin.
 * - low precision, only one byte of randomness (or none with extreme parameters)
 * - tip: use !kr_rand_coin() to get the complementary probability
 */
static inline bool kr_rand_coin(unsigned int nomin, unsigned int denomin)
{
	/* This function might be called with non-constant values
	 * so we try to handle odd corner cases instead of crash. */
	if (nomin >= denomin)
		return true;
	else if (nomin <= 0)
		return false;

	/* threshold = how many parts from 256 are a success */
	unsigned int threshold = (nomin * 256 + /*rounding*/ denomin / 2) / denomin;
	if (threshold == 0) threshold = 1;
	if (threshold == 256) threshold = 255;
	return (kr_rand_bytes(1) < threshold);
}

/** Memory reservation routine for knot_mm_t */
KR_EXPORT
int kr_memreserve(void *baton, void **mem, size_t elm_size, size_t want, size_t *have);

/** @internal Fast packet reset. */
KR_EXPORT
int kr_pkt_recycle(knot_pkt_t *pkt);

/** @internal Clear packet payload. */
KR_EXPORT
int kr_pkt_clear_payload(knot_pkt_t *pkt);

/** Construct and put record to packet. */
KR_EXPORT
int kr_pkt_put(knot_pkt_t *pkt, const knot_dname_t *name, uint32_t ttl,
               uint16_t rclass, uint16_t rtype, const uint8_t *rdata, uint16_t rdlen);

/** Set packet header suitable for authoritative answer. (for policy module) */
KR_EXPORT
void kr_pkt_make_auth_header(knot_pkt_t *pkt);

/** Get pointer to the in-header QNAME.
 *
 * That's normally not lower-cased.  However, when receiving packets from upstream
 * we xor-apply the secret during packet-parsing, so it would get lower-cased
 * after that point if the case was right.
 */
static inline knot_dname_t * kr_pkt_qname_raw(const knot_pkt_t *pkt)
{
	if (pkt == NULL || pkt->qname_size == 0) {
		return NULL;
	}
	return pkt->wire + KNOT_WIRE_HEADER_SIZE;
}

/** Simple storage for IPx address and their ports or AF_UNSPEC. */
union kr_sockaddr {
	struct sockaddr ip;
	struct sockaddr_in ip4;
	struct sockaddr_in6 ip6;
};

/** Simple storage for IPx addresses. */
union kr_in_addr {
	struct in_addr ip4;
	struct in6_addr ip6;
};

/* TODO: rename kr_inaddr functions to kr_sockaddr */
/** Address bytes for given family. */
KR_EXPORT KR_PURE
const char *kr_inaddr(const struct sockaddr *addr);
/** Address family. */
KR_EXPORT KR_PURE
int kr_inaddr_family(const struct sockaddr *addr);
/** Address length for given family, i.e. sizeof(struct in*_addr). */
KR_EXPORT KR_PURE
int kr_inaddr_len(const struct sockaddr *addr);
/** Sockaddr length for given family, i.e. sizeof(struct sockaddr_in*). */
KR_EXPORT KR_PURE
int kr_sockaddr_len(const struct sockaddr *addr);

/** Creates a packed structure from the specified `addr`, safe for use as a key
 * in containers like `trie_t`, and writes it into `dst`. On success, returns
 * the actual length of the key.
 *
 * Returns `kr_error(EAFNOSUPPORT)` if the family of `addr` is unsupported. */
KR_EXPORT
ssize_t kr_sockaddr_key(struct kr_sockaddr_key_storage *dst,
                        const struct sockaddr *addr);

/** Creates a `struct sockaddr` from the specified `key` created using the
 * `kr_sockaddr_key()` function. */
KR_EXPORT
struct sockaddr *kr_sockaddr_from_key(struct sockaddr_storage *dst,
                                      const char *key);

/** Checks whether the two keys represent the same address;
 * does NOT compare the ports. */
KR_EXPORT
bool kr_sockaddr_key_same_addr(const char *key_a, const char *key_b);

/** Compare two given sockaddr.
 * return 0 - addresses are equal, error code otherwise.
 */
KR_EXPORT KR_PURE
int kr_sockaddr_cmp(const struct sockaddr *left, const struct sockaddr *right);
/** Port. */
KR_EXPORT KR_PURE
uint16_t kr_inaddr_port(const struct sockaddr *addr);
/** Set port. */
KR_EXPORT
void kr_inaddr_set_port(struct sockaddr *addr, uint16_t port);

/** Write string representation for given address as "<addr>#<port>".
 * \param[in]     addr   the raw address
 * \param[out]    buf    the buffer for output string
 * \param[in,out] buflen the available(in) and utilized(out) length, including \0 */
KR_EXPORT
int kr_inaddr_str(const struct sockaddr *addr, char *buf, size_t *buflen);

/** Write string representation for given address as "<addr>#<port>".
 * It's the same as kr_inaddr_str(), but the input address is input in native format
 * like for inet_ntop() (4 or 16 bytes) and port must be separate parameter.  */
KR_EXPORT
int kr_ntop_str(int family, const void *src, uint16_t port, char *buf, size_t *buflen);

/** @internal Create string representation addr#port.
 *  @return pointer to a *static* string, i.e. each call will overwrite it
 */
KR_EXPORT
char *kr_straddr(const struct sockaddr *addr);

/** Return address type for string. */
KR_EXPORT KR_PURE
int kr_straddr_family(const char *addr);
/** Return address length in given family (struct in*_addr). */
KR_EXPORT KR_CONST
int kr_family_len(int family);

/** Create a sockaddr* from string+port representation.
 * Also accepts IPv6 link-local and AF_UNIX starting with "/" (ignoring port) */
KR_EXPORT
struct sockaddr * kr_straddr_socket(const char *addr, int port, knot_mm_t *pool);

/** Parse address and return subnet length (bits).
  * @warning 'dst' must be at least `sizeof(struct in6_addr)` long. */
KR_EXPORT
int kr_straddr_subnet(void *dst, const char *addr);

/** Splits ip address specified as "addr@port" or "addr#port" into addr and port.
 * \param[in]  instr zero-terminated input, e.g. "192.0.2.1#12345\0"
 * \param[out] ipaddr working buffer for the port-less prefix of instr;
 *                    length >= INET6_ADDRSTRLEN + 1.
 * \param[out] port written in case it's specified in instr
 * \return error code
 * \note Typically you follow this by kr_straddr_socket().
 * \note Only internet addresses are supported, i.e. no AF_UNIX sockets.
 */
KR_EXPORT
int kr_straddr_split(const char *instr, char ipaddr[static restrict (INET6_ADDRSTRLEN + 1)],
		     uint16_t *port);

/** Formats ip address and port in "addr#port" format.
  * and performs validation.
  * @note Port always formatted as five-character string with leading zeros.
  * @return kr_error(EINVAL) - addr or buf is NULL or buflen is 0 or
  *                            addr doesn't contain a valid ip address
  *         kr_error(ENOSP)  - buflen is too small
  */
KR_EXPORT
int kr_straddr_join(const char *addr, uint16_t port, char *buf, size_t *buflen);

/** Compare memory bitwise.  The semantics is "the same" as for memcmp().
 *  The partial byte is considered with more-significant bits first,
 *  so this is e.g. suitable for comparing IP prefixes. */
KR_EXPORT KR_PURE
int kr_bitcmp(const char *a, const char *b, int bits);

/** Masks bits. The specified number of bits in `a` from the left (network order)
 * will remain their original value, while the rest will be set to zero.
 * This is useful for storing network addresses in a trie. */
KR_EXPORT
void kr_bitmask(unsigned char *a, size_t a_len, int bits);

/** Check whether `addr` points to an `AF_INET6` address and whether the address
 * is link-local. */
static inline bool kr_sockaddr_link_local(const struct sockaddr *addr)
{
	if (addr->sa_family != AF_INET6)
		return false;

	/* Link-local: https://tools.ietf.org/html/rfc4291#section-2.4 */
	const uint8_t prefix[] = { 0xFE, 0x80 };
	const struct sockaddr_in6 *ip6 = (const struct sockaddr_in6 *) addr;
	return kr_bitcmp((char *) ip6->sin6_addr.s6_addr, (char *) prefix, 10) == 0;
}

/* Stash key = {[5] class, [1-255] owner, [5] type, [5] additional, [1] \x00 } */
#define KR_RRKEY_LEN (16 + KNOT_DNAME_MAXLEN)
/** Create unique null-terminated string key for RR.
  * @param key Destination buffer for key size, MUST be KR_RRKEY_LEN or larger.
  * @param class RR class.
  * @param owner RR owner name.
  * @param type RR type.
  * @param additional flags (for instance can be used for storing covered type
  *	   when RR type is RRSIG).
  * @return key length if successful or an error
  * */
KR_EXPORT
int kr_rrkey(char *key, uint16_t class, const knot_dname_t *owner,
	     uint16_t type, uint16_t additional);

/** Add RRSet copy to a ranked RR array.
 *
 * To convert to standard RRs inside, you need to call _finalize() afterwards,
 * and the memory of rr->rrs.rdata has to remain until then.
 *
 * \return array index (>= 0) or error code (< 0)
 */
KR_EXPORT
int kr_ranked_rrarray_add(ranked_rr_array_t *array, const knot_rrset_t *rr,
			  uint8_t rank, bool to_wire, uint32_t qry_uid, knot_mm_t *pool);
/** Finalize in_progress sets - all with matching qry_uid. */
KR_EXPORT
int kr_ranked_rrarray_finalize(ranked_rr_array_t *array, uint32_t qry_uid, knot_mm_t *pool);

/** @internal Mark the RRSets from particular query as
 * "have (not) to be recorded in the final answer".
 * @param array RRSet array.
 * @param to_wire Records must be\must not be recorded in final answer.
 * @param qry_uid Query uid.
 * @param check_dups When to_wire is true, try to avoid duplicate RRSets.
 * @param extraCheck optional function checking whether to consider the record
 * @return 0 or an error
 */
int kr_ranked_rrarray_set_wire(ranked_rr_array_t *array, bool to_wire,
			       uint32_t qry_uid, bool check_dups,
			       bool (*extraCheck)(const ranked_rr_array_entry_t *));


/** Style used by the kr_*_text() functions. */
KR_EXPORT extern
const knot_dump_style_t KR_DUMP_STYLE_DEFAULT;

/**
 * @return Newly allocated string representation of packet.
 * Caller has to free() returned string.
 */
KR_EXPORT
char *kr_pkt_text(const knot_pkt_t *pkt);

KR_PURE
char *kr_rrset_text(const knot_rrset_t *rr);

KR_PURE
static inline char *kr_dname_text(const knot_dname_t *name) {
	return knot_dname_to_str_alloc(name);
}

KR_CONST
static inline char *kr_rrtype_text(const uint16_t rrtype) {
	char type_str[32] = {0};
	knot_rrtype_to_string(rrtype, type_str, sizeof(type_str));
	return strdup(type_str);
}

/**
 * Call module property.
 */
KR_EXPORT
char *kr_module_call(struct kr_context *ctx, const char *module, const char *prop, const char *input);

/** Swap two places.  Note: the parameters need to be without side effects. */
#define SWAP(x, y) do { /* http://stackoverflow.com/a/3982430/587396 */ \
	unsigned char swap_temp[sizeof(x) == sizeof(y) ? (ssize_t)sizeof(x) : -1]; \
	memcpy(swap_temp, &y, sizeof(x)); \
	memcpy(&y,        &x, sizeof(x)); \
	memcpy(&x, swap_temp, sizeof(x)); \
	} while(0)

/** Return the (covered) type of an nonempty RRset. */
static inline uint16_t kr_rrset_type_maysig(const knot_rrset_t *rr)
{
	kr_require(rr && rr->rrs.count && rr->rrs.rdata);
	uint16_t type = rr->type;
	if (type == KNOT_RRTYPE_RRSIG)
		type = knot_rrsig_type_covered(rr->rrs.rdata);
	return type;
}

/** The current time in monotonic milliseconds.
 *
 * \note it may be outdated in case of long callbacks; see uv_now().
 */
KR_EXPORT
uint64_t kr_now(void);

/** Call free(handle->data); it's useful e.g. as a callback in uv_close(). */
KR_EXPORT void kr_uv_free_cb(uv_handle_t* handle);

/** Convert name from lookup format to wire.  See knot_dname_lf
 *
 * \note len bytes are read and len+1 are written with *normal* LF,
 * 	 but it's also allowed that the final zero byte is omitted in LF.
 * \return the number of bytes written (>0) or error code (<0)
 */
int knot_dname_lf2wire(knot_dname_t *dst, uint8_t len, const uint8_t *lf);

/** Patched knot_dname_lf.  LF for "." has length zero instead of one, for consistency.
 * (TODO: consistency?)
 * \param add_wildcard append the wildcard label
 * \note packet is always NULL
 */
static inline int kr_dname_lf(uint8_t *dst, const knot_dname_t *src, bool add_wildcard)
{
	knot_dname_storage_t right_aligned_dst;
	uint8_t *right_aligned_dname_start = knot_dname_lf(src, right_aligned_dst);
	if (!right_aligned_dname_start) {
		return kr_error(EINVAL);
	}
	int len = right_aligned_dname_start[0];
	if (kr_fails_assert(right_aligned_dname_start + 1 + len - KNOT_DNAME_MAXLEN == right_aligned_dst))
		return kr_error(EINVAL);
	memcpy(dst + 1, right_aligned_dname_start + 1, len);
	if (add_wildcard) {
		if (len + 2 > KNOT_DNAME_MAXLEN)
			return kr_error(ENOSPC);
		dst[len + 1] = '*';
		dst[len + 2] = '\0';
		len += 2;
	}
	dst[0] = len;
	return KNOT_EOK;
}


/** Timer, i.e stop-watch. */
typedef struct timespec kr_timer_t;

/** Start, i.e. set the reference point. */
static inline void kr_timer_start(kr_timer_t *start)
{
	/* The call should be very reliable, but let's check it in _start() at least. */
	kr_require(start && clock_gettime(CLOCK_MONOTONIC, start) == 0);
}

/** Get elapsed time in floating-point seconds. */
static inline double kr_timer_elapsed(kr_timer_t *start)
{
	kr_require(start);
	kr_timer_t end = { 0 };
	(void)clock_gettime(CLOCK_MONOTONIC, &end);
	return (end.tv_sec - start->tv_sec) + (double)(end.tv_nsec - start->tv_nsec) / 1e9;
}

/** Get elapsed time in micro-seconds. */
static inline uint64_t kr_timer_elapsed_us(kr_timer_t *start)
{
	kr_require(start);
	kr_timer_t end = { 0 };
	(void)clock_gettime(CLOCK_MONOTONIC, &end);
	// avoid negative differences, because of integer division
	if (end.tv_nsec - start->tv_nsec < 0) {
		end.tv_nsec += 1000*1000*1000;
		end.tv_sec  -= 1;
	}
	return (uint64_t)(end.tv_sec - start->tv_sec) * 1000000
		// adding 500 gives us rounding
		+ (end.tv_nsec - start->tv_nsec + 500) / 1000;
}


/**
 * Difference between two calendar times specified as strings.
 * \param[in]  format format for strptime
 * \param[out] diff result from C difftime(time1, time0)
 */
KR_EXPORT
const char *kr_strptime_diff(const char *format, const char *time1_str,
		             const char *time0_str, double *diff);

/* Trivial non-inline wrappers, to be used in lua. */
KR_EXPORT void kr_rrset_init(knot_rrset_t *rrset, knot_dname_t *owner,
				uint16_t type, uint16_t rclass, uint32_t ttl);
KR_EXPORT bool kr_pkt_has_wire(const knot_pkt_t *pkt);
KR_EXPORT bool kr_pkt_has_dnssec(const knot_pkt_t *pkt);
KR_EXPORT uint16_t kr_pkt_qclass(const knot_pkt_t *pkt);
KR_EXPORT uint16_t kr_pkt_qtype(const knot_pkt_t *pkt);
KR_EXPORT uint32_t kr_rrsig_sig_inception(const knot_rdata_t *rdata);
KR_EXPORT uint32_t kr_rrsig_sig_expiration(const knot_rdata_t *rdata);
KR_EXPORT uint16_t kr_rrsig_type_covered(const knot_rdata_t *rdata);

KR_EXPORT time_t kr_file_mtime (const char* fname);
/** Return filesystem size in bytes. */
KR_EXPORT long long kr_fssize(const char *path);
/** Simply return de->dname. (useful from Lua) */
KR_EXPORT const char * kr_dirent_name(const struct dirent *de);


/* trivial libknot versions compatibility */
static inline size_t kr_dname_prefixlen(const uint8_t *name, unsigned nlabels)
{
	return knot_dname_prefixlen(name, nlabels
		#if KNOT_VERSION_HEX < 0x030400
			, NULL
		#endif
	);
}
#if KNOT_VERSION_HEX < 0x030400
static inline const  knot_dname_t * knot_dname_next_label(const knot_dname_t *dname)
{
	return knot_wire_next_label(dname, NULL);
}
#endif