/*
    progress-bar.c
    Jeff Ondich, 2 June 2019

    Keyboard setup Code adapted from http://www.linux-sxs.org/programming/kbhit.html, which
    in turn adapted it from "Beginning Linux Programming" by Neil Matthew and Richard Stones,
    Wrox Press.
*/

#include <stdio.h>
#include <stdlib.h>
#include <termios.h>
#include <ctype.h>
#include <unistd.h> // for read()
#include <pthread.h>


void initialize_keyboard();
void restore_keyboard();

void *workerThreadMain(void *arg);
void *progressThreadMain(void *arg);

pthread_mutex_t gLock = PTHREAD_MUTEX_INITIALIZER;
int gPrimeCount = 0;
int gProgress = 0;
int gProgressLimit = 0;

int main() {
    gProgressLimit = 1000000;
    fprintf(stderr, "We're counting the prime numbers <= %d\n", gProgressLimit);
    fprintf(stderr, "Hit X to cancel\n");

    pthread_t workerThread, progressThread;

    if (pthread_create(&progressThread, NULL, progressThreadMain, 0) != 0) {
        perror("Can't create progress thread");
        exit(1);
    }

    if (pthread_create(&workerThread, NULL, workerThreadMain, 0) != 0) {
        perror("Can't create worker thread");
        exit(1);
    }

    initialize_keyboard();

    char ch = '\0';
    while (gProgress < gProgressLimit && tolower(ch) != 'x') {
        read(0, &ch, 1);
    }

    fputc('\n', stderr);
    restore_keyboard();

    return 0;
}

// Returns true (1) if n is prime, false (0) otherwise.
// Uses a super-slow algorithm because we just want
// it to take a long time.
int isPrime(int n) {
    for (int k = 2; 2 * k <= n; k++) {
        if (n % k == 0) {
            return 0;
        }
    }
    return 1;
}

void *workerThreadMain(void *arg) {
    fprintf(stderr, "Worker thread starting\n");
    gPrimeCount = 1;
    for (int k = 3; k <= gProgressLimit; k += 2) {
        gProgress = k;
        if (isPrime(k)) {
            pthread_mutex_lock(&gLock);
            gPrimeCount++;
            pthread_mutex_unlock(&gLock);
        }
    }

    return NULL;
}

void *progressThreadMain(void *arg) {
    int previousBoxCount = 0;
    while (gProgress < gProgressLimit) {
        float percentage = 100.0 * (float)gProgress / (float)gProgressLimit;
        int progressBoxCount = (int)(percentage / 2.0);
        if (progressBoxCount != previousBoxCount) {
            fprintf(stderr, "(%02.1f) |", percentage);
            for (int k = 0; k < 50; k++) {
                if (k < progressBoxCount) {
                    fputc('x', stderr);
                } else {
                    fputc(' ', stderr);
                }
            }
            fprintf(stderr, "|\r");
            previousBoxCount = progressBoxCount;
        }
    }

    fprintf(stderr, "\n# primes less than or equal to %d: %d\n", gProgressLimit, gPrimeCount);

    return NULL;
}

// Keyboard management
static struct termios initial_settings, new_settings;

void initialize_keyboard() {
    tcgetattr(0, &initial_settings);
    new_settings = initial_settings;
    new_settings.c_lflag &= ~ICANON;
    new_settings.c_lflag &= ~ECHO;
    new_settings.c_lflag &= ~ISIG;
    new_settings.c_cc[VMIN] = 1;
    new_settings.c_cc[VTIME] = 0;
    tcsetattr(0, TCSANOW, &new_settings);
}

void restore_keyboard() {
    tcsetattr(0, TCSANOW, &initial_settings);
}