/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <assert.h>
#include <err.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>

#include "bounce.h"

static struct {
	char *origin;
	char *welcome;
	char *yourHost;
	char *created;
	char *myInfo[4];
} intro;

static struct {
	char *nick;
	char *origin;
} self;

static void set(char **field, const char *value) {
	if (*field) free(*field);
	*field = strdup(value);
	if (!*field) err(EX_OSERR, "strdup");
}

struct Channel {
	char *name;
	char *topic;
};

static struct {
	struct Channel *ptr;
	size_t cap, len;
} chans;

static void chanAdd(const char *name) {
	if (chans.len == chans.cap) {
		chans.cap = (chans.cap ? chans.cap * 2 : 8);
		chans.ptr = realloc(chans.ptr, sizeof(*chans.ptr) * chans.cap);
		if (!chans.ptr) err(EX_OSERR, "realloc");
	}
	struct Channel *chan = &chans.ptr[chans.len++];
	chan->name = strdup(name);
	if (!chan->name) err(EX_OSERR, "strdup");
	chan->topic = NULL;
}

static void chanTopic(const char *name, const char *topic) {
	for (size_t i = 0; i < chans.len; ++i) {
		if (strcmp(chans.ptr[i].name, name)) continue;
		free(chans.ptr[i].topic);
		chans.ptr[i].topic = strdup(topic);
		if (!chans.ptr[i].topic) err(EX_OSERR, "strdup");
		break;
	}
}

static void chanRemove(const char *name) {
	for (size_t i = 0; i < chans.len; ++i) {
		if (strcmp(chans.ptr[i].name, name)) continue;
		free(chans.ptr[i].name);
		free(chans.ptr[i].topic);
		chans.ptr[i] = chans.ptr[--chans.len];
		break;
	}
}

static struct {
	char **tokens;
	size_t cap, len;
} support;

static void supportAdd(const char *token) {
	if (support.len == support.cap) {
		support.cap = (support.cap ? support.cap * 2 : 8);
		support.tokens = realloc(support.tokens, sizeof(char *) * support.cap);
		if (!support.tokens) err(EX_OSERR, "realloc");
	}
	support.tokens[support.len] = strdup(token);
	if (!support.tokens[support.len]) err(EX_OSERR, "strdup");
	support.len++;
}

bool stateReady(void) {
	return self.nick
		&& intro.origin
		&& intro.welcome
		&& intro.yourHost
		&& intro.created
		&& intro.myInfo[0];
}

const char *stateSelf(void) {
	if (self.origin) return self.origin;
	if (self.nick) return self.nick;
	return "*";
}

typedef void Handler(struct Message *msg);

static void handleCap(struct Message *msg) {
	bool ack = msg->params[1] && !strcmp(msg->params[1], "ACK");
	bool sasl = msg->params[2] && !strncmp(msg->params[2], "sasl", 4);
	if (!ack || !sasl) errx(EX_CONFIG, "server does not support SASL");
	serverFormat("AUTHENTICATE PLAIN\r\n");
}

static void handleAuthenticate(struct Message *msg) {
	(void)msg;
	serverAuth();
}

static void handleReplyWelcome(struct Message *msg) {
	if (!msg->params[1]) errx(EX_PROTOCOL, "RPL_WELCOME without message");
	set(&intro.origin, msg->origin);
	set(&self.nick, msg->params[0]);
	set(&intro.welcome, msg->params[1]);
}

static void handleReplyYourHost(struct Message *msg) {
	if (!msg->params[1]) errx(EX_PROTOCOL, "RPL_YOURHOST without message");
	set(&intro.yourHost, msg->params[1]);
}

static void handleReplyCreated(struct Message *msg) {
	if (!msg->params[1]) errx(EX_PROTOCOL, "RPL_CREATED without message");
	set(&intro.created, msg->params[1]);
}

static void handleReplyMyInfo(struct Message *msg) {
	if (!msg->params[4]) errx(EX_PROTOCOL, "RPL_MYINFO without 4 parameters");
	set(&intro.myInfo[0], msg->params[1]);
	set(&intro.myInfo[1], msg->params[2]);
	set(&intro.myInfo[2], msg->params[3]);
	set(&intro.myInfo[3], msg->params[4]);
}

static void handleReplyISupport(struct Message *msg) {
	for (size_t i = 1; i < ParamCap; ++i) {
		if (!msg->params[i] || strchr(msg->params[i], ' ')) break;
		supportAdd(msg->params[i]);
	}
}

static void handleErrorNicknameInUse(struct Message *msg) {
	if (self.nick) return;
	if (!msg->params[1]) errx(EX_PROTOCOL, "ERR_NICKNAMEINUSE without nick");
	serverFormat("NICK %s_\r\n", msg->params[1]);
}

static bool fromSelf(const struct Message *msg) {
	if (!self.nick) return false;
	size_t len = strlen(self.nick);
	if (strlen(msg->origin) < len) return false;
	if (strncmp(msg->origin, self.nick, len)) return false;
	if (msg->origin[len] != '!') return false;
	if (!self.origin || strcmp(self.origin, msg->origin)) {
		set(&self.origin, msg->origin);
	}
	return true;
}

static void handleNick(struct Message *msg) {
	if (!msg->origin) errx(EX_PROTOCOL, "NICK without origin");
	if (!msg->params[0]) errx(EX_PROTOCOL, "NICK without nick");
	if (fromSelf(msg)) set(&self.nick, msg->params[0]);
}

static void handleJoin(struct Message *msg) {
	if (!msg->origin) errx(EX_PROTOCOL, "JOIN without origin");
	if (!msg->params[0]) errx(EX_PROTOCOL, "JOIN without channel");
	if (fromSelf(msg)) chanAdd(msg->params[0]);
}

static void handlePart(struct Message *msg) {
	if (!msg->origin) errx(EX_PROTOCOL, "PART without origin");
	if (!msg->params[0]) errx(EX_PROTOCOL, "PART without channel");
	if (fromSelf(msg)) chanRemove(msg->params[0]);
}

static void handleKick(struct Message *msg) {
	if (!msg->params[0]) errx(EX_PROTOCOL, "KICK without channel");
	if (!msg->params[1]) errx(EX_PROTOCOL, "KICK without nick");
	if (self.nick && !strcmp(msg->params[1], self.nick)) {
		chanRemove(msg->params[0]);
	}
}

static void handleTopic(struct Message *msg) {
	if (!msg->params[0]) errx(EX_PROTOCOL, "TOPIC without channel");
	if (!msg->params[1]) errx(EX_PROTOCOL, "TOPIC without topic");
	chanTopic(msg->params[0], msg->params[1]);
}

static void handleReplyTopic(struct Message *msg) {
	if (!msg->params[1]) errx(EX_PROTOCOL, "RPL_TOPIC without channel");
	if (!msg->params[2]) errx(EX_PROTOCOL, "RPL_TOPIC without topic");
	chanTopic(msg->params[1], msg->params[2]);
}

static void handleError(struct Message *msg) {
	errx(EX_UNAVAILABLE, "%s", msg->params[0]);
}

static const struct {
	const char *cmd;
	Handler *fn;
} Handlers[] = {
	{ "001", handleReplyWelcome },
	{ "002", handleReplyYourHost },
	{ "003", handleReplyCreated },
	{ "004", handleReplyMyInfo },
	{ "005", handleReplyISupport },
	{ "332", handleReplyTopic },
	{ "433", handleErrorNicknameInUse },
	{ "AUTHENTICATE", handleAuthenticate },
	{ "CAP", handleCap },
	{ "ERROR", handleError },
	{ "JOIN", handleJoin },
	{ "KICK", handleKick },
	{ "NICK", handleNick },
	{ "PART", handlePart },
	{ "TOPIC", handleTopic },
};

void stateParse(char *line) {
	struct Message msg = parse(line);
	if (!msg.cmd) return;
	for (size_t i = 0; i < ARRAY_LEN(Handlers); ++i) {
		if (strcmp(msg.cmd, Handlers[i].cmd)) continue;
		Handlers[i].fn(&msg);
		break;
	}
}

void stateSync(struct Client *client) {
	assert(stateReady());

	clientFormat(
		client,
		":%s NOTICE %s :"
		"pounce is AGPLv3 fwee softwawe ^w^  code is avaiwable fwom %s\r\n",
		Origin, self.nick, SourceURL
	);

	clientFormat(
		client,
		":%s 001 %s :%s\r\n"
		":%s 002 %s :%s\r\n"
		":%s 003 %s :%s\r\n",
		intro.origin, self.nick, intro.welcome,
		intro.origin, self.nick, intro.yourHost,
		intro.origin, self.nick, intro.created
	);
	clientFormat(
		client, ":%s 004 %s %s %s %s %s\r\n",
		intro.origin, self.nick,
		intro.myInfo[0], intro.myInfo[1], intro.myInfo[2], intro.myInfo[3]
	);

	size_t i;
	for (i = 0; support.len - i >= 13; i += 13) {
		clientFormat(
			client,
			":%s 005 %s"
			" %s %s %s %s %s %s %s %s %s %s %s %s %s"
			" :are supported by this server\r\n",
			intro.origin, self.nick,
			support.tokens[i + 0], support.tokens[i + 1],
			support.tokens[i + 2], support.tokens[i + 3],
			support.tokens[i + 4], support.tokens[i + 5],
			support.tokens[i + 6], support.tokens[i + 7],
			support.tokens[i + 8], support.tokens[i + 9],
			support.tokens[i + 10], support.tokens[i + 11],
			support.tokens[i + 12]
		);
	}
	if (i < support.len) {
		clientFormat(client, ":%s 005 %s", intro.origin, self.nick);
		for (; i < support.len; ++i) {
			clientFormat(client, " %s", support.tokens[i]);
		}
		clientFormat(client, " :are supported by this server\r\n");
	}

	if (chans.len) assert(self.origin);
	for (size_t i = 0; i < chans.len; ++i) {
		const struct Channel *chan = &chans.ptr[i];
		clientFormat(client, ":%s JOIN %s\r\n", self.origin, chan->name);
		if (chan->topic) {
			clientFormat(
				client, ":%s 332 %s %s :%s\r\n",
				Origin, self.nick, chan->name, chan->topic
			);
		}
		if (stateJoinNames) serverFormat("NAMES %s\r\n", chan->name);
	}
}