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

int main(int argc, char **argv)
{
    //If only one input then user has not provided a file name to calculate.
    if(argc == 1)
    {
        printf("No file provided. Please provide name of file needed to add.\n");
    }
    else{
        FILE *inputFile;    //file to be calculated
        double inputNumber; //each number in the file
        double answer = 0;  //final answer
        int count = 0;  //counter variable to make sure there are numbers in the file
        int forkCounter = 1;
        int addUpPipe[2]; //float array for pipe
        pid_t childPid; //id of child

        pipe(addUpPipe);    //create pipe

        /**
        for(int i = 1; i < argc - 1; i++){
            childPid = fork();
            if(childPid > 0){
                fopen("%s", argv[i]);   //Opens provided file name and stores in variable
            }
        }
        **/

        //Fork process for however many arguments are provided
        while((childPid = fork()) > 0 && forkCounter < argc - 1){
            fopen("%s", argv[forkCounter]);
            ++forkCounter;
            printf("Forked %d\n",forkCounter);
        }

        //Parent code
        //If parent, wait for children to finish then open pipe, add answers, then send to command line
        if(childPid > 0){
            int returnStatus;
            double value;
            double finalAnswer = 0;

            printf("%s\n", "Entered Parent");

            while(wait(&returnStatus) > 0); //Wait until children are finished
            printf("%s", "Finished waiting for child");
            //Reads the added value from pipe
            FILE* readPipe = fdopen(addUpPipe[0], "r");
            while(fscanf(readPipe, "%lf", &value) != EOF){
                finalAnswer += value;
            }
            printf("%lf", value);    //Print completed value to command line
            close(addUpPipe[0]);    //Close pipe
        }
            //Child Code
        else{
            //If file is null it cant be opened or doesnt exist
            printf("%s\n", "Entered Child");
            if(inputFile == NULL)
            {
                printf("Cant open file or file does not exist\n");
                return 0;
            }

            //Goes through file and adds each number together while increasing the counter variable
            while(fscanf(inputFile, "%lf", &inputNumber) != EOF)
            {
                answer += inputNumber;
                count++;
            }
            //If reached the end of file immediately without count increasing, must be empty
            if(count == 0)
            {
                printf("Error! No numbers in file!\n");
            }
                //Otherwise, print the answer
            else
            {
                //printf("%d", answer);
                write(addUpPipe[1], &answer, sizeof(answer));
                write(addUpPipe[1], "\n", 2);
                close(addUpPipe[1]);
                printf("%s", "Child done");
            }
            fclose(inputFile);  //Close file
        }
        return 0;
    }
}