/** Karlstad University
 *  Course: Distributed Systems and Applications
 *  Course Code: DVGC15
 *  Authors: Cédric Poirot, Jaume Gelonch, Felix Grund
 *  Contents: Lab 1 : Part 1 : Unnamed Pipes : Token Game
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <stdbool.h>
#include <limits.h>

#define CONVERT_FAILURE -1
#define READ_FAILURE -2

int tokenvalue;
int players;
int winpoints;

void parent_signal_handler(int sig) {
    printf("\nMain process got signal");
    //kill(SIGTERM); HOW DO I KNOW THE PIDs OF THE CHILDREN??
    exit(EXIT_SUCCESS);
}

void child_signal_handler(int sig) {
    printf("\nChild process got signal");
    exit(EXIT_SUCCESS);
}

void print_header() {
    printf("\n=====================================================");
    printf("\n=========== Welcome to the magnificient =============");
    printf("\n======================= TOKEN =======================");
    printf("\n======================= GAME ========================");
    printf("\n=====================================================\n");
}

int read_value() {
    char read[20];
    printf("\n Enter value: ");
    fflush(stdout);

    if (fgets(read, sizeof(read), stdin)) {
        int number = CONVERT_FAILURE;
        sscanf(read, "%d", &number);
        return number;
    }
    else {
        return READ_FAILURE;
    }

}

int get_value() {
    int value;
    while ((value = read_value()) == CONVERT_FAILURE) {
        printf("\nAre you kidding? This is not a number, please do again...");
    }

    if (value == READ_FAILURE) {
        perror("\nFailure reading from input. Program exits");
        exit(EXIT_FAILURE);
    }
    else {
        return value;
    }
}

int child_process (int readpipe, int writepipe, int player_number) {
    printf("\nPlayer #%d is alive...", player_number);
    fflush(stdout);

    int mypoints = 0;
    int mytoken = INT_MAX;


    while (mypoints < winpoints) {

        read(readpipe, &mytoken, sizeof(mytoken));
        sleep(1);
        printf("\nToken was read by player #%d: %d", player_number, mytoken);
        fflush(stdout);
        if (mytoken > 0) {
            sleep(1);
            printf("\nNo win this time for player #%d. Passing decreased token to next player...", player_number);
            fflush(stdout);
            mytoken--;
            write(writepipe, &mytoken, sizeof(mytoken));
        }
        else {
            sleep(1);
            mypoints++;
            printf("\nPlayer #%d wins! He has now %d winning points! Next round...", player_number, mypoints);
            fflush(stdout);
            mytoken = INT_MAX;
            write(writepipe, &tokenvalue, sizeof(tokenvalue));
        }
    }

    printf("Game finished! Player #%d has %d winning points and is the winner.\n***** CONGRATULATIONS *****\n\nProgram exits...", player_number, mypoints);
    kill(getppid(), SIGTERM);
}

int run_game() {
    int i;
    int pipes[players][2];
    char buffer[players][30];
    pid_t pid[players];

    for (i = 0; i < players; i++) {

        if (pipe(pipes[i]) == -1) {
            perror("pipe");
            exit(EXIT_FAILURE);
        }
    }

    printf("\nPipes created...");
    fflush(stdout);

    for (i = 0; i < players; i++) {

        int readpipe, writepipe, pipe_number;
        pipe_number = i;
        writepipe = pipes[pipe_number][1];

        pipe_number--;
        if (pipe_number < 0) pipe_number = players-1;
        readpipe = pipes[pipe_number][0];

        if ((pid[i] = fork()) == -1) {
            perror("fork");
            exit(EXIT_FAILURE);
        }
        else if (pid[i] == 0) { // Child
            (void) signal(SIGTERM, child_signal_handler);
            child_process(readpipe, writepipe, i);
            break;
        }

        sleep(1);
    }

    write(pipes[players-1][1], &tokenvalue, sizeof(tokenvalue));

    return 0;
}

int main() {
    (void) signal(SIGTERM, parent_signal_handler);

    print_header();

    fputs("\nPlease Enter Token Value: ", stdout);
    tokenvalue = get_value();
    fputs("\nHow many players?: ", stdout);
    players = get_value();
    fputs("\nHow many winning points?: ", stdout);
    winpoints = get_value();
    printf("\nThe final settings of the game: Token Value = %d, Players = %d, Winpoints = %d", tokenvalue, players, winpoints);
    fflush(stdout);

    run_game();

    pause();

    return 0;
}