/* Copyright (C) 2017  Curtis 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 <sys/types.h>

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <sys/event.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/un.h>
#include <sysexits.h>
#include <time.h>
#include <unistd.h>

#include "torus.h"

static struct Tile *tiles;

static void tilesMap(void) {
	int fd = open("torus.dat", O_CREAT | O_RDWR, 0644);
	if (fd < 0) err(EX_CANTCREAT, "torus.dat");

	int error = ftruncate(fd, TILES_SIZE);
	if (error) err(EX_IOERR, "ftruncate");

	tiles = mmap(NULL, TILES_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
	if (tiles == MAP_FAILED) err(EX_OSERR, "mmap");

	error = madvise(tiles, TILES_SIZE, MADV_RANDOM);
	if (error) err(EX_OSERR, "madvise");

#ifdef MADV_NOCORE
	error = madvise(tiles, TILES_SIZE, MADV_NOCORE);
	if (error) err(EX_OSERR, "madvise");
#endif
}

static struct Tile *tileGet(uint32_t tileX, uint32_t tileY) {
	struct Tile *tile = &tiles[tileY * TILE_ROWS + tileX];
	if (!tile->createTime) {
		memset(tile->cells, ' ', CELLS_SIZE);
		memset(tile->colors, COLOR_WHITE, CELLS_SIZE);
		tile->createTime = time(NULL);
	}
	return tile;
}

static struct Tile *tileAccess(uint32_t tileX, uint32_t tileY) {
	struct Tile *tile = tileGet(tileX, tileY);
	tile->accessTime = time(NULL);
	tile->accessCount++;
	return tile;
}

static struct Tile *tileModify(uint32_t tileX, uint32_t tileY) {
	struct Tile *tile = tileGet(tileX, tileY);
	tile->modifyTime = time(NULL);
	tile->modifyCount++;
	return tile;
}

static struct Client {
	int fd;

	uint32_t tileX;
	uint32_t tileY;
	uint8_t cellX;
	uint8_t cellY;

	struct Client *prev;
	struct Client *next;
} *clientHead;

static struct Client *clientAdd(int fd) {
	struct Client *client = malloc(sizeof(*client));
	if (!client) err(EX_OSERR, "malloc");

	client->fd = fd;
	client->tileX = TILE_VOID_X;
	client->tileY = TILE_VOID_Y;
	client->cellX = CELL_INIT_X;
	client->cellY = CELL_INIT_Y;

	client->prev = NULL;
	if (clientHead) {
		clientHead->prev = client;
		client->next = clientHead;
	} else {
		client->next = NULL;
	}
	clientHead = client;

	return client;
}

static bool clientSend(const struct Client *client, struct ServerMessage msg) {
	ssize_t size = send(client->fd, &msg, sizeof(msg), 0);
	if (size < 0) return false;

	if (msg.type == SERVER_TILE) {
		struct Tile *tile = tileAccess(client->tileX, client->tileY);
		size = send(client->fd, tile, sizeof(*tile), 0);
		if (size < 0) return false;
	}

	return true;
}

static void clientCast(const struct Client *origin, struct ServerMessage msg) {
	for (struct Client *client = clientHead; client; client = client->next) {
		if (client == origin) continue;
		if (client->tileX != origin->tileX) continue;
		if (client->tileY != origin->tileY) continue;
		clientSend(client, msg);
	}
}

static void clientRemove(struct Client *client) {
	if (client->prev) client->prev->next = client->next;
	if (client->next) client->next->prev = client->prev;
	if (clientHead == client) clientHead = client->next;

	struct ServerMessage msg = {
		.type = SERVER_CURSOR,
		.cursor = {
			.oldCellX = client->cellX, .oldCellY = client->cellY,
			.newCellX = CURSOR_NONE,   .newCellY = CURSOR_NONE,
		},
	};
	clientCast(client, msg);

	close(client->fd);
	free(client);
}

static bool clientCursors(const struct Client *client) {
	struct ServerMessage msg = {
		.type = SERVER_CURSOR,
		.cursor = { .oldCellX = CURSOR_NONE, .oldCellY = CURSOR_NONE },
	};

	for (struct Client *friend = clientHead; friend; friend = friend->next) {
		if (friend == client) continue;
		if (friend->tileX != client->tileX) continue;
		if (friend->tileY != client->tileY) continue;

		msg.cursor.newCellX = friend->cellX;
		msg.cursor.newCellY = friend->cellY;
		if (!clientSend(client, msg)) return false;
	}
	return true;
}

static bool clientUpdate(const struct Client *client, const struct Client *old) {
	struct ServerMessage msg = {
		.type = SERVER_MOVE,
		.move = { .cellX = client->cellX, .cellY = client->cellY },
	};
	if (!clientSend(client, msg)) return false;

	if (client->tileX != old->tileX || client->tileY != old->tileY) {
		msg.type = SERVER_TILE;
		if (!clientSend(client, msg)) return false;

		if (!clientCursors(client)) return false;

		msg = (struct ServerMessage) {
			.type = SERVER_CURSOR,
			.cursor = {
				.oldCellX = old->cellX,  .oldCellY = old->cellY,
				.newCellX = CURSOR_NONE, .newCellY = CURSOR_NONE,
			},
		};
		clientCast(old, msg);

		msg = (struct ServerMessage) {
			.type = SERVER_CURSOR,
			.cursor = {
				.oldCellX = CURSOR_NONE,   .oldCellY = CURSOR_NONE,
				.newCellX = client->cellX, .newCellY = client->cellY,
			},
		};
		clientCast(client, msg);

	} else {
		msg = (struct ServerMessage) {
			.type = SERVER_CURSOR,
			.cursor = {
				.oldCellX = old->cellX,    .oldCellY = old->cellY,
				.newCellX = client->cellX, .newCellY = client->cellY,
			},
		};
		clientCast(client, msg);
	}

	return true;
}

static bool clientSpawn(struct Client *client, uint8_t spawn) {
	if (spawn >= SPAWNS_LEN) return false;
	struct Client old = *client;
	client->tileX = SPAWNS[spawn].tileX;
	client->tileY = SPAWNS[spawn].tileY;
	client->cellX = CELL_INIT_X;
	client->cellY = CELL_INIT_Y;
	return clientUpdate(client, &old);
}

static bool clientMove(struct Client *client, int8_t dx, int8_t dy) {
	struct Client old = *client;

	if (dx > CELL_COLS - client->cellX) dx = CELL_COLS - client->cellX;
	if (dx < -client->cellX - 1)        dx = -client->cellX - 1;
	if (dy > CELL_ROWS - client->cellY) dy = CELL_ROWS - client->cellY;
	if (dy < -client->cellY - 1)        dy = -client->cellY - 1;

	client->cellX += dx;
	client->cellY += dy;

	if (client->cellX == CELL_COLS) {
		client->tileX++;
		client->cellX = 0;
	}
	if (client->cellX == UINT8_MAX) {
		client->tileX--;
		client->cellX = CELL_COLS - 1;
	}
	if (client->cellY == CELL_ROWS) {
		client->tileY++;
		client->cellY = 0;
	}
	if (client->cellY == UINT8_MAX) {
		client->tileY--;
		client->cellY = CELL_ROWS - 1;
	}

	if (client->tileX == TILE_COLS)  client->tileX = 0;
	if (client->tileX == UINT32_MAX) client->tileX = TILE_COLS - 1;
	if (client->tileY == TILE_ROWS)  client->tileY = 0;
	if (client->tileY == UINT32_MAX) client->tileY = TILE_ROWS - 1;

	assert(client->cellX < CELL_COLS);
	assert(client->cellY < CELL_ROWS);
	assert(client->tileX < TILE_COLS);
	assert(client->tileY < TILE_ROWS);

	return clientUpdate(client, &old);
}

static bool clientPut(const struct Client *client, uint8_t color, char cell) {
	struct Tile *tile = tileModify(client->tileX, client->tileY);
	tile->colors[client->cellY][client->cellX] = color;
	tile->cells[client->cellY][client->cellX] = cell;

	struct ServerMessage msg = {
		.type = SERVER_PUT,
		.put = {
			.cellX = client->cellX,
			.cellY = client->cellY,
			.color = color,
			.cell = cell,
		},
	};
	bool success = clientSend(client, msg);
	clientCast(client, msg);
	return success;
}

static bool clientMap(const struct Client *client) {
	int32_t mapY = (int32_t)client->tileY - MAP_ROWS / 2;
	int32_t mapX = (int32_t)client->tileX - MAP_COLS / 2;

	struct Map map;
	for (int32_t y = 0; y < MAP_ROWS; ++y) {
		for (int32_t x = 0; x < MAP_COLS; ++x) {
			uint32_t tileY = ((mapY + y) % TILE_ROWS + TILE_ROWS) % TILE_ROWS;
			uint32_t tileX = ((mapX + x) % TILE_COLS + TILE_COLS) % TILE_COLS;

			const struct Tile *tile = &tiles[tileY * TILE_ROWS + tileX];
			map.tiles[y][x] = (struct MapTile) {
				.createTime = tile->createTime,
				.modifyTime = tile->modifyTime,
				.accessTime = tile->accessTime,
				.modifyCount = tile->modifyCount,
				.accessCount = tile->accessCount,
			};
		}
	}

	struct ServerMessage msg = { .type = SERVER_MAP };
	if (!clientSend(client, msg)) return false;
	if (0 > send(client->fd, &map, sizeof(map), 0)) return false;
	return true;
}

int main() {
	int error;

	tilesMap();

	int server = socket(PF_LOCAL, SOCK_STREAM, 0);
	if (server < 0) err(EX_OSERR, "socket");

	error = unlink("torus.sock");
	if (error && errno != ENOENT) err(EX_IOERR, "torus.sock");

	struct sockaddr_un addr = {
		.sun_family = AF_LOCAL,
		.sun_path = "torus.sock",
	};
	error = bind(server, (struct sockaddr *)&addr, sizeof(addr));
	if (error) err(EX_CANTCREAT, "torus.sock");

	error = listen(server, 0);
	if (error) err(EX_OSERR, "listen");

	int kq = kqueue();
	if (kq < 0) err(EX_OSERR, "kqueue");

	struct kevent event = {
		.ident = server,
		.filter = EVFILT_READ,
		.flags = EV_ADD,
	};
	int nevents = kevent(kq, &event, 1, NULL, 0, NULL);
	if (nevents < 0) err(EX_OSERR, "kevent");

	for (;;) {
		nevents = kevent(kq, NULL, 0, &event, 1, NULL);
		if (nevents < 0) err(EX_IOERR, "kevent");

		if (!event.udata) {
			int fd = accept(server, NULL, NULL);
			if (fd < 0) err(EX_IOERR, "accept");
			fcntl(fd, F_SETFL, O_NONBLOCK);

			int on = 1;
			error = setsockopt(fd, SOL_SOCKET, SO_NOSIGPIPE, &on, sizeof(on));
			if (error) err(EX_IOERR, "setsockopt");

			struct Client *client = clientAdd(fd);

			struct kevent event = {
				.ident = fd,
				.filter = EVFILT_READ,
				.flags = EV_ADD,
				.udata = client,
			};
			nevents = kevent(kq, &event, 1, NULL, 0, NULL);
			if (nevents < 0) err(EX_IOERR, "kevent");

			if (!clientSpawn(client, 0)) clientRemove(client);

			continue;
		}

		struct Client *client = event.udata;
		if (event.flags & EV_EOF) {
			clientRemove(client);
			continue;
		}

		struct ClientMessage msg;
		ssize_t size = recv(client->fd, &msg, sizeof(msg), 0);
		if (size != sizeof(msg)) {
			clientRemove(client);
			continue;
		}

		bool success = false;
		switch (msg.type) {
			break; case CLIENT_MOVE: {
				success = clientMove(client, msg.move.dx, msg.move.dy);
			}
			break; case CLIENT_PUT: {
				success = clientPut(client, msg.put.color, msg.put.cell);
			}
			break; case CLIENT_SPAWN: success = clientSpawn(client, msg.spawn);
			break; case CLIENT_MAP: success = clientMap(client);
		}
		if (!success) clientRemove(client);
	}
}