/*  Copyright (C) 2020 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

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

#include <libknot/descriptor.h>
#include <libknot/dname.h>

#include "load_queries.h"

#define ERR_PREFIX "failed loading queries "

uint16_t global_edns_size = 1232;

enum qflags {
	QFLAG_EDNS = 1,
	QFLAG_DO = 2,
};

struct pkt_payload *global_payloads = NULL;

void free_global_payloads()
{
	struct pkt_payload *g_payloads_p = global_payloads, *tmp;
	while (g_payloads_p != NULL) {
		tmp = g_payloads_p;
		g_payloads_p = tmp->next;
		free(tmp);
	}
}

bool load_queries(const char *filename)
{
	FILE *f = fopen(filename, "r");
	if (f == NULL) {
		printf(ERR_PREFIX "file '%s' (%s)\n", filename, strerror(errno));
		return false;
	}
	struct pkt_payload *g_payloads_top = NULL;

	struct {
		char line[KNOT_DNAME_TXT_MAXLEN + 256];
		char dname_txt[KNOT_DNAME_TXT_MAXLEN + 1];
		uint8_t dname[KNOT_DNAME_MAXLEN];
		char type_txt[128];
		char flags_txt[128];
	} *bufs;
	bufs = malloc(sizeof(*bufs)); // avoiding too much stuff on stack
	if (bufs == NULL) {
		printf(ERR_PREFIX "(out of memory)\n");
		goto fail;
	}

	while (fgets(bufs->line, sizeof(bufs->line), f) != NULL) {
		bufs->flags_txt[0] = '\0';
		int ret = sscanf(bufs->line, "%s%s%s", bufs->dname_txt, bufs->type_txt, bufs->flags_txt);
		if (ret < 2) {
			printf(ERR_PREFIX "(faulty line): '%.*s'\n",
			       (int)strcspn(bufs->line, "\n"), bufs->line);
			goto fail;
		}

		void *pret = knot_dname_from_str(bufs->dname, bufs->dname_txt, sizeof(bufs->dname));
		if (pret == NULL) {
			printf(ERR_PREFIX "(faulty dname): '%s'\n", bufs->dname_txt);
			goto fail;
		}

		uint16_t type;
		ret = knot_rrtype_from_string(bufs->type_txt, &type);
		if (ret < 0) {
			printf(ERR_PREFIX "(faulty type): '%s'\n", bufs->type_txt);
		}

		enum qflags flags = 0;
		switch (bufs->flags_txt[0]) {
		case '\0':
			break;
		case 'e':
		case 'E':
			flags |= QFLAG_EDNS;
			break;
		case 'd':
		case 'D':
			flags |= QFLAG_EDNS | QFLAG_DO;
			break;
		default:
			printf(ERR_PREFIX "(faulty flag): '%s'\n", bufs->flags_txt);
			goto fail;
		}

		size_t dname_len = knot_dname_size(bufs->dname);
		size_t pkt_len = 16 + dname_len;
		if (flags & QFLAG_EDNS) {
			pkt_len += 11;
		}

		struct pkt_payload *pkt = calloc(1, sizeof(void *) + sizeof(size_t) + pkt_len);
		if (pkt == NULL) {
			printf(ERR_PREFIX "(out of memory)\n");
			goto fail;
		}
		pkt->len = pkt_len;
		pkt->payload[2] = 0x01; // QR bit
		pkt->payload[5] = 0x01; // 1 question
		pkt->payload[11] = (flags & QFLAG_EDNS) ? 0x01 : 0x00;
		memcpy(pkt->payload + 12, bufs->dname, dname_len);
		pkt->payload[dname_len + 12] = type >> 8;
		pkt->payload[dname_len + 13] = type & 0xff;
		pkt->payload[dname_len + 15] = 0x01; // class IN
		if (flags & QFLAG_EDNS) {
			pkt->payload[dname_len + 18] = 41; // OPT RRtype
			pkt->payload[dname_len + 19] = global_edns_size >> 8;
			pkt->payload[dname_len + 20] = global_edns_size & 0xff;
			pkt->payload[dname_len + 23] = (flags & QFLAG_DO) ? 0x80 : 0x00;
		}

		// add pkt to list global_payloads
		if (g_payloads_top == NULL) {
			global_payloads = pkt;
			g_payloads_top = pkt;
		} else {
			g_payloads_top->next = pkt;
			g_payloads_top = pkt;
		}
	}

	if (global_payloads == NULL) {
		printf(ERR_PREFIX "(no queries in file)\n");
		goto fail;
	}

	free(bufs);
	fclose(f);
	return true;

fail:
	free_global_payloads();
	free(bufs);
	fclose(f);
	return false;
}