#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdint.h>
#include <errno.h>
#include <sys/time.h>

const char *LOCALHOST = "127.0.0.1";

#define SERVERDATA_AUTH 3
#define SERVERDATA_AUTH_RESPONSE 2
#define SERVERDATA_EXECCOMMAND 2
#define SERVERDATA_RESPONSE_VALUE 0

typedef struct {
    int32_t size;
    int32_t id;
    int32_t type;
    char body[4096];
} rcon_packet_t;

int read_env_int(const char *var) {
    const char* port_str = getenv(var);
    if (port_str == NULL) {
        fprintf(stderr, "error: %s environment variable not set.\n", var);
        exit(EXIT_FAILURE);
    }
    char* endptr;
    long val = strtol(port_str, &endptr, 10);
    if (endptr == port_str || *endptr != '\0') {
        fprintf(stderr, "error: invalid number format for %s.\n", var);
        exit(EXIT_FAILURE);
    }
    return (int)val;
}

int rcon_connect(int port) {
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        perror("socket creation failed");
        exit(EXIT_FAILURE);
    }

    struct timeval tv;
    tv.tv_sec = 2;
    tv.tv_usec = 0;
    setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv));

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_port = htons(port);

    if (inet_pton(AF_INET, LOCALHOST, &server_addr.sin_addr) <= 0) {
        perror("invalid address");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    if (connect(sockfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
        perror("connection failed");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    printf("connected to rcon server\n");
    return sockfd;
}

void send_packet(int sockfd, int32_t id, int32_t type, const char *body) {
    int body_len = strlen(body);
    int32_t size = 10 + body_len;

    size_t packet_size = sizeof(int32_t) + size;
    unsigned char *packet = malloc(packet_size);
    if (!packet) {
        perror("malloc failed");
        return;
    }

    packet[0] = size & 0xFF;
    packet[1] = (size >> 8) & 0xFF;
    packet[2] = (size >> 16) & 0xFF;
    packet[3] = (size >> 24) & 0xFF;

    packet[4] = id & 0xFF;
    packet[5] = (id >> 8) & 0xFF;
    packet[6] = (id >> 16) & 0xFF;
    packet[7] = (id >> 24) & 0xFF;

    packet[8] = type & 0xFF;
    packet[9] = (type >> 8) & 0xFF;
    packet[10] = (type >> 16) & 0xFF;
    packet[11] = (type >> 24) & 0xFF;

    memcpy(packet + 12, body, body_len);
    packet[12 + body_len] = 0;
    packet[12 + body_len + 1] = 0;

    ssize_t sent = send(sockfd, packet, packet_size, 0);
    if (sent < 0) {
        perror("send failed");
    }

    free(packet);
}

int recv_packet(int sockfd, rcon_packet_t *packet) {
    ssize_t bytes;

    bytes = recv(sockfd, &packet->size, sizeof(int32_t), MSG_WAITALL);
    if (bytes <= 0) {
        if (bytes == 0) {
            fprintf(stderr, "connection closed by server\n");
        } else if (errno == EAGAIN || errno == EWOULDBLOCK) {
            return -2; // Timeout
        } else {
            perror("recv size failed");
        }
        return -1;
    }

    if (packet->size < 10 || packet->size > 4110) {
        fprintf(stderr, "invalid packet size: %d\n", packet->size);
        return -1;
    }

    bytes = recv(sockfd, &packet->id, sizeof(int32_t), MSG_WAITALL);
    if (bytes <= 0) {
        perror("recv id failed");
        return -1;
    }

    bytes = recv(sockfd, &packet->type, sizeof(int32_t), MSG_WAITALL);
    if (bytes <= 0) {
        perror("recv type failed");
        return -1;
    }

    int body_size = packet->size - 10;
    if (body_size > 0 && body_size < (int)sizeof(packet->body)) {
        bytes = recv(sockfd, packet->body, body_size + 2, MSG_WAITALL);
        if (bytes <= 0) {
            perror("recv body failed");
            return -1;
        }
        packet->body[body_size] = '\0';
    } else {
        packet->body[0] = '\0';
    }

    return 0;
}

int rcon_authenticate(int sockfd, const char *password) {
    printf("authenticating with password: '%s'\n", password);

    send_packet(sockfd, 1, SERVERDATA_AUTH, password);

    printf("waiting for auth response...\n");

    rcon_packet_t response;
    if (recv_packet(sockfd, &response) < 0) {
        fprintf(stderr, "failed to receive auth response\n");
        return -1;
    }

    printf("received auth packet: id=%d, type=%d\n", response.id, response.type);

    // Check if authentication failed (id == -1)
    if (response.id == -1) {
        fprintf(stderr, "authentication failed - invalid password\n");
        return -1;
    }

    // Try to read second packet (may timeout, which is OK)
    rcon_packet_t response2;
    int result = recv_packet(sockfd, &response2);
    if (result == 0) {
        printf("received second auth packet: id=%d, type=%d\n", response2.id, response2.type);
    } else if (result == -2) {
        printf("no second packet (timeout - this is normal)\n");
    }

    printf("authenticated successfully\n");
    return 0;
}

char* rcon_command_multipacket(int sockfd, const char *command) {
    static char result[65536];
    result[0] = '\0';

    int cmd_id = 100;
    int dummy_id = 101;

    send_packet(sockfd, cmd_id, SERVERDATA_EXECCOMMAND, command);
    send_packet(sockfd, dummy_id, SERVERDATA_EXECCOMMAND, "");

    while (1) {
        rcon_packet_t response;
        if (recv_packet(sockfd, &response) < 0) {
            fprintf(stderr, "failed to receive command response\n");
            return NULL;
        }
        if (response.id == dummy_id) {
            break;
        }
        if (response.type == SERVERDATA_RESPONSE_VALUE && response.id == cmd_id) {
            strncat(result, response.body, sizeof(result) - strlen(result) - 1);
        }
    }

    return result;
}

int main(int argc, char **argv) {
    const int PORT_NUM = read_env_int("RCON_PORT_NUMBER");
    const char *password = getenv("RCON_PASSWORD");

    if (password == NULL) {
        fprintf(stderr, "error: RCON_PASSWORD environment variable not set.\n");
        exit(EXIT_FAILURE);
    }

    printf("=== RCON Configuration ===\n");
    printf("port: %d\n", PORT_NUM);
    printf("password: '%s'\n", password);
    printf("==========================\n\n");

    int sockfd = rcon_connect(PORT_NUM);

    if (rcon_authenticate(sockfd, password) < 0) {
        close(sockfd);
        exit(EXIT_FAILURE);
    }

    const char *get_player_positions_cmd = "execute as @a run data get entity @s Pos";
    printf("\nexecuting command: %s\n", get_player_positions_cmd);
    char *response = rcon_command_multipacket(sockfd, get_player_positions_cmd);

    if (response) {
        printf("\n=== player positions ===\n");
        printf("%s\n", response);
    } else {
        fprintf(stderr, "failed to get player positions\n");
    }

    close(sockfd);
    return 0;
}