// SPDX-FileCopyrightText: 2024 Lizzy Fleckenstein <lizzy@vlhl.dev>
//
// SPDX-License-Identifier: AGPL-3.0-or-later

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>
#include <endian.h>
#include <unistd.h>
#include <inttypes.h>
#include <errno.h>
#include <poll.h>
#include <png.h>
#include <perlin.h>
#include <math.h>
#include "array.h"
#include "content.h"
#include "net.h"
#include "str.h"
#include "ser.h"
#include "sig.h"
#include "chunk.h"

#define MAYBE(T) \
	typedef struct { bool present; T value; } maybe_##T; \
	maybe_##T some_##T(T value) { return (maybe_##T) { true, value }; } \
	maybe_##T none_##T = { 0 };

typedef enum {
	MAP_VALLEY,
	MAP_ISLAND,
	MAP_MOUNTAIN,
	MAP_CAVE,
	MAP_NUM,
} map_type;

typedef struct {
	entity base;
	int8_t z;
} srv_entity;

typedef struct {
	vec2 xy;
	int8_t z;
} pos;

MAYBE(pos)

typedef struct {
	const char *filename;
	str name;
	map_type type;
	int8_t z; // caves: -1
	chunk chunk;
} map;

typedef struct {
	bool auth;
	str name;
	entity_id id;
	peer conn;
} player;

typedef struct {
	int accept_fd;
	str motd;
	str passphrase;
	array(map) maps;
	arraybuf(player) players;
	arraybuf(srv_entity) entities;
	entity_id next_entity;
} game;

player *player_from_id(game *g, entity_id id)
{
	ARR_ITER(g->players, p) if (p->id == id) return p;
	return NULL;
}

player *player_from_name(game *g, str name)
{
	ARR_ITER(g->players, p) if (p->auth && str_eq(p->name, name)) return p;
	return NULL;
}

srv_entity *entity_from_id(game *g, entity_id id)
{
	ARR_ITER(g->entities, e) if (e->base.id == id) return e;
	return NULL;
}

pos entity_pos(srv_entity *e)
{
	return (pos) { e->base.pos, e->z };
}

box2 player_sight(vec2 center)
{
	return box2_around(center, SIGHT_RANGE);
}

void ser_entity_update(strbuf *w, srv_entity *e, entity_cmd cmd)
{
	ser_entity_id(w, e->base.id);
	ser_entity_cmd(w, cmd);

	switch (cmd) {
		case ENTITY_ADD:
			ser_entity_type(w, e->base.type);
			ser_vec2(w, e->base.pos);
			switch (e->base.type) {
				case ENTITY_FLOWER:
					ser_flower_type(w, e->base.flower);
					break;
				default: break;
			}
			break;
		case ENTITY_MOVE:
			ser_vec2(w, e->base.pos);
			break;
		case ENTITY_REMOVE:
			break;
		case ENTITY_CMD_COUNT:
			break; // unreachable
	}
}

static maybe_pos moved_get_pos(srv_entity *e, srv_entity *moved, maybe_pos p_moved)
{
	return (e == moved) ? p_moved : some_pos(entity_pos(e));
}

static bool moved_can_see(srv_entity *a, srv_entity *b, srv_entity *moved, maybe_pos p_moved)
{
	maybe_pos p_a = moved_get_pos(a, moved, p_moved);
	maybe_pos p_b = moved_get_pos(b, moved, p_moved);
	return p_a.present
		&& p_b.present
		&& p_a.value.z == p_b.value.z
		&& box2_contains(player_sight(p_a.value.xy), p_b.value.xy);
}

static entity_cmd moved_check_update(srv_entity *observer, srv_entity *target, srv_entity *moved, maybe_pos before, maybe_pos after)
{
	bool see_before = moved_can_see(observer, target, moved, before);
	bool see_after = moved_can_see(observer, target, moved, after);

	if (see_before && !see_after)
		return ENTITY_REMOVE;
	else if (!see_before && see_after)
		return ENTITY_ADD;
	else if (see_before && see_after && target == moved)
		return ENTITY_MOVE;
	else
		return ENTITY_CMD_COUNT;
}

void moved_entity(game *g, srv_entity *moved, maybe_pos before, maybe_pos after)
{
	ARR_ITER(g->players, p) if (p->auth) {
		srv_entity *observer = entity_from_id(g, p->id);

		if (observer == moved) {
			SEND_PKT(p->conn, CPKT_ENTITY,
				ARR_ITER(g->entities, target) {
					entity_cmd cmd = moved_check_update(observer, target, moved, before, after);
					if (cmd != ENTITY_CMD_COUNT)
						ser_entity_update(&pkt, target, cmd);
				}
			)
		} else {
			entity_cmd cmd = moved_check_update(observer, moved, moved, before, after);
			if (cmd != ENTITY_CMD_COUNT)
				SEND_PKT(p->conn, CPKT_ENTITY, ser_entity_update(&pkt, moved, cmd);)
		}
	}
}

node *map_node(game *g, vec2 p, int8_t z)
{
	ARR_ITER(g->maps, m) {
		if (m->z != z)
			continue;
		node *n = chunk_index_abs(m->chunk, p);
		if (n == NULL || !n->present)
			continue;
		return n;
	}
	return NULL;
}

bool silly_noise(vec2 pos, uint32_t grid, double sillyness, int seed)
{
	int64_t x = (int64_t) pos.x+INT_MAX+1;
	int64_t y = (int64_t) pos.y+INT_MAX+1;

	if ((y/grid) % 2 == 0)
		x += grid/2;

	x += round(noise2d(x/grid, y/grid, 0, seed) * sillyness);
	y += round(noise2d(y/grid, x/grid, 0, seed) * sillyness);

	return x % grid == 0 && y % grid == 0;
}

srv_entity *spawn_entity(game *g, entity_type type, pos p)
{
	srv_entity *e = ARR_APPEND(g->entities);
	e->base.id = g->next_entity++;
	e->base.type = type;
	e->base.pos = p.xy;
	e->z = p.z;
	return e;
}

void remove_entity(game *g, srv_entity *e)
{
	moved_entity(g, e, some_pos(entity_pos(e)), none_pos);
	ARR_REMOVE(g->entities, e);
}

void map_load_node(game *g, map *m, uvec2 v, color col)
{
	uint32_t ucol = color_to_u32(col);

	pos p = { vec2_add(m->chunk.bounds.pos, CVEC2(v)), m->z };

	node *n = chunk_index(m->chunk, v);
	*n = (node) { 0 };

	n->present = ucol != 0xffffff;
	if (!n->present)
		return;

	switch (ucol) {
		case 0xff9de2:
			spawn_entity(g, ENTITY_FLOWER, p)->base.flower = rand() % FLOWER_COUNT;
			[[fallthrough]];
		case 0x00880d: n->type = N_GRASS;
			n->variant = silly_noise(p.xy, 3, 1.0, 0);
			break;
		case 0x595959: n->type = N_ROCK; n->z = 1; break;
		case 0x001b51:
			spawn_entity(g, ENTITY_FLOWER, p)->base.flower = FLOWER_DANDELION;
			[[fallthrough]];
		case 0x484848: n->type = N_ROCK; n->z = 2; break;
		case 0x00ffe8:
			spawn_entity(g, ENTITY_FLOWER, p)->base.flower = FLOWER_DANDELION;
			[[fallthrough]];
		case 0x373737: n->type = N_ROCK; n->z = 3; break;
		case 0xa09700: n->type = N_PATH; break;
		case 0x015100: n->type = N_NEEDLE_TREE; break;
		case 0x00c6ff: n->type = N_WATER;
			n->variant = silly_noise(p.xy, 3, 0.7, 1);
			n->z = -1;
			break;
		case 0x5c3b12: n->type = N_PLANK; break;
		case 0x016300: n->type = N_BIG_TREE; break;
		case 0xfce84e: n->type = N_SAND;
			n->variant = silly_noise(p.xy, 4, 1.0, 1);
			break;
		default:
			fprintf(stderr, "invalid color in map %.*s at %"PRIu32" %"PRIu32": %06x\n",
				PSTR(m->name), v.x, v.y, ucol);
			n->present = false;
			break;
	}
}

bool map_load(game *g, map *m)
{
#define TRY(expr, ...) if (!(expr)) { \
	fprintf(stderr, __VA_ARGS__); \
	if (file != NULL) fclose(file); \
	png_destroy_read_struct(&png, &info, NULL); \
	return false; }

	FILE *file = NULL;
	png_structp png = NULL;
	png_infop info = NULL;

	TRY((file = fopen(m->filename, "r")) != NULL, "failed to open %s\n", m->filename)

	TRY(png = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL),
		"png_create_read_struct failed\n")

	TRY(info = png_create_info_struct(png), "png_create_info_struct failed\n")

	png_init_io(png, file);
	png_read_info(png, info);

	png_uint_32 width = png_get_image_width(png, info);
	png_uint_32 height = png_get_image_height(png, info);
	png_byte color_type = png_get_color_type(png, info);

	TRY(width == m->chunk.bounds.size.x, "%s: width mismatch\n", m->filename)
	TRY(height == m->chunk.bounds.size.y, "%s: height mismatch\n", m->filename)
	TRY(color_type == PNG_COLOR_TYPE_RGB, "%s: color type is not RGB\n", m->filename)

	// uint32_t colors[100] = {0};

	png_uint_32 pitch = png_get_rowbytes(png, info);
	png_byte row[pitch];
	for (png_uint_32 y = 0; y < height; y++) {
		png_read_row(png, row, NULL);

		for (png_uint_32 x = 0; x < width; x++) {
			png_bytep p = &row[x*3];

			/*
			for (size_t i = 0; i < 100; i++) {
				if (colors[i] == color) {
					break;
				} else if (colors[i] == 0) {
					colors[i] = color;
					printf("#%06x\n", color);
					break;
				}
			}*/

			map_load_node(g, m, UVEC2(x, y), (color) { p[0], p[1], p[2] });
		}
	}

	fclose(file);
	png_destroy_read_struct(&png, &info, NULL);
	return true;
#undef TRY
}

void send_players(game *g)
{
	ARR_ITER(g->players, to) if (to->auth) {
		SEND_PKT(to->conn, CPKT_PLAYERS,
			ser_u16(&pkt, g->players.len);
			ARR_ITER(g->players, p) if (p->auth) {
				ser_str(&pkt, p->name);
				ser_entity_id(&pkt, p->id);
			}
		)
	}
}

// send_nudes when
void send_nodes(player *p, game *g, box2 bounds, int8_t z)
{
	SEND_PKT(p->conn, CPKT_NODES,
		ser_box2(&pkt, bounds);
		for (uint32_t x = 0; x < bounds.size.x; x++)
		for (uint32_t y = 0; y < bounds.size.y; y++)
			ser_node(&pkt, map_node(g, vec2_add(bounds.pos, VEC2(x, y)), z));
	)
}

void player_cleanup(player *p)
{
	peer_free(&p->conn);
	if (p->auth)
		free(p->name.data);
}

void player_remove(player *p, game *g)
{
	player_cleanup(p);

	bool auth = p->auth;
	entity_id id = p->id;

	ARR_REMOVE(g->players, p);

	if (auth) {
		remove_entity(g, entity_from_id(g, id));
		send_players(g);
	}
}

void game_exit(game *g, int ret)
{
	free(g->motd.data);
	free(g->passphrase.data);

	ARR_ITER(g->maps, m) {
		free(m->name.data);
		free(m->chunk.data);
	}
	free(g->maps.data);

	ARR_ITER(g->players, p) player_cleanup(p);
	free(g->players.data);

	exit(ret);
}

bool handle_hi(str pkt, player *p, game *g)
{
	str name, pass;
	if (! (deser_str(&pkt, &name) && deser_str(&pkt, &pass)))
		return false;

	if (!str_eq(g->passphrase, pass)) {
		printf("wrong passphrase from %.*s\n", PSTR(name)); // TODO: log ip ?
		SEND_PKT(p->conn, CPKT_FAIL, ser_fail_reason(&pkt, FAIL_WRONG_PASS);)
		return true; // valid pkt, but invalid passphrase
	}

	if (player_from_name(g, name)) {
		SEND_PKT(p->conn, CPKT_FAIL, ser_fail_reason(&pkt, FAIL_ALREADY_ONLINE);)
		return true;
	}

	printf("player authenticated as %.*s\n", PSTR(name));

	p->auth = true;
	p->name = str_clone(name);

	srv_entity *e = ARR_APPEND(g->entities);
	e->base.id = p->id;
	e->base.type = ENTITY_PLAYER;
	e->base.pos.x = e->base.pos.y = 0;
	e->z = 0;

	SEND_PKT(p->conn, CPKT_HI, ser_str(&pkt, g->motd);)
	send_players(g);

	pos ent_p = entity_pos(e);

	moved_entity(g, e, none_pos, some_pos(ent_p));
	send_nodes(p, g, player_sight(ent_p.xy), ent_p.z);

	return true;
}

bool handle_move(str pkt, player *p, game *g)
{
	dir d;
	if (!deser_dir(&pkt, &d)) return false;

	vec2 v = dir_to_vec2(d);
	if (vec2_iszero(v))
		return false;

	srv_entity *e = entity_from_id(g, p->id);

	pos old_pos = entity_pos(e);

	// yolo
	e->base.pos = vec2_add(v, e->base.pos);

	pos new_pos = entity_pos(e);

	moved_entity(g, e, some_pos(old_pos), some_pos(new_pos));

	// TODO: only send newly visible nodes
	send_nodes(p, g, player_sight(new_pos.xy), new_pos.z);

	return true;
}

bool handle_pkt(str pkt, player *p, game *g)
{
	pkt_type type;
	if (!deser_pkt_type(&pkt, &type))
		return false;

	if ((type == SPKT_HI) == p->auth)
		return false;

	switch (type) {
		case SPKT_HI: return handle_hi(pkt, p, g);
		case SPKT_MOVE: return handle_move(pkt, p, g);
		default: return false;
	}
}

int main()
{
	signal_setup();

	game g = {0};

	g.accept_fd = -1;
	g.next_entity = 1;
	g.motd = str_clone(S("Welcome to test server"));
	g.passphrase = str_clone(S(""));

	g.maps.len = 1;
	g.maps.data = malloc(g.maps.len * sizeof *g.maps.data);
	g.maps.data[0] = (map) {
		.filename = "assets/map_valley.png",
		.name = str_clone(S("Valley")),
		.type = MAP_VALLEY,
		.z = 0,
		.chunk = chunk_alloc((box2) { { -50, -50 }, { 100, 100 } }),
	};

	if (!map_load(&g, &g.maps.data[0]))
		game_exit(&g, EXIT_FAILURE);

	if ((g.accept_fd = socket_create("0.0.0.0", "4560", true)) < 0)
		game_exit(&g, EXIT_FAILURE);

	for (;;) {
		struct pollfd fds[g.players.len + 1];

		for (size_t i = 0; i < g.players.len; i++)
			fds[i] = peer_prepare(&g.players.data[i].conn);

		fds[g.players.len].fd = g.accept_fd;
		fds[g.players.len].events = POLLIN;

		if (poll(fds, g.players.len + 1, -1) < 0) {
			switch (errno) {
				case EINTR: break;
				default: perror("poll"); continue;
			}
		}

		if (signal_stop)
			game_exit(&g, EXIT_SUCCESS);

		for (size_t i = 0; i < g.players.len; i++) {
			player *p = &g.players.data[i];

			str pkt = peer_recv(&p->conn, fds[i]);
			if (p->conn.disco) {
				printf("player %.*s disconnected\n", PSTR(p->name));
				player_remove(p, &g);
				goto cont;
			}

			if (pkt.len > 0 && !handle_pkt(pkt, p, &g))
				invalid_pkt(&p->conn, pkt);
		}

		if (fds[g.players.len].revents) {
			int socket = socket_accept(g.accept_fd);
			if (socket < 0)
				continue;

			printf("new player\n");
			player *p = ARR_APPEND(g.players);
			p->auth = false;
			p->id = g.next_entity++;
			p->name = S("(unauthenticated)");
			peer_init(&p->conn, socket, &p->name);
		}

		cont: continue;
	}
}