#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <string.h>
#include <errno.h>

int main(int argc, char *argv[]) {
    if (argc < 4) {
        fprintf(stderr,
                "Usage: parent <max_replacements> <input1.txt> <output1.txt> [<input2.txt> <output2.txt> ...]\n"
                "  max_replacements: maximum number of replacements\n"
                "  input/output: pairs of input and output files\n");
        return -1;
    }

    if ((argc - 2) % 2 != 0) {
        fprintf(stderr, "Error: number of input/output files must be even (pairs of input/output)\n");
        return -1;
    }

    const char *max_replacements_arg = argv[1];
    int num_pairs = (argc - 2) / 2;

    pid_t *child_pids = malloc(num_pairs * sizeof(pid_t));
    if (!child_pids) {
        perror("malloc failed");
        return -1;
    }

    for (int i = 0; i < num_pairs; i++) {
        const char *input_file = argv[2 + i * 2];
        const char *output_file = argv[2 + i * 2 + 1];

        pid_t pid = fork();
        if (pid < 0) {
            perror("fork failed");
            // Wait for already started children
            for (int j = 0; j < i; j++) {
                waitpid(child_pids[j], NULL, 0);
            }
            free(child_pids);
            return -1;
        }

        if (pid == 0) {
            // Child process
            printf("Child %d (PID=%d) processing %s -> %s\n", i + 1, getpid(), input_file, output_file);
            execl("./task11", "task11", input_file, output_file, max_replacements_arg, (char *) NULL);

            // If exec returns, error happened
            fprintf(stderr, "Child %d: execl failed for %s: %s\n", i + 1, input_file, strerror(errno));
            _exit(-1);
        }

        // Parent process
        child_pids[i] = pid;
    }

    printf("Parent process waiting for children...\n");

    int ret_code = 0;
    for (int i = 0; i < num_pairs; i++) {
        int status;
        pid_t pid = waitpid(child_pids[i], &status, 0);
        if (pid < 0) {
            perror("waitpid failed");
            continue;
        }

        if (WIFEXITED(status)) {
            int code = WEXITSTATUS(status);
            printf("Child %d (PID=%d) exited with code %d\n", i + 1, pid, code);
            if (code != 0) {
                ret_code = code;
            }
        } else if (WIFSIGNALED(status)) {
            printf("Child %d (PID=%d) terminated by signal %d\n", i + 1, pid, WTERMSIG(status));
        } else {
            printf("Child %d (PID=%d) ended abnormally\n", i + 1, pid);
        }
    }

    free(child_pids);
    printf("All children finished\n");
    return ret_code;
}