/**************************************************************/
/**************************************************************/
/********************** Assigment 3 *****************************/
/**************************************************************/
/**************************************************************/                                              


#include<stdio.h>
#include<stdlib.h>
#include<string.h>



typedef struct student
{
    int id;
    char fn[30];
    char ln[30];
    float md;
    float final;
    struct student *next;
    }node;



/**************************************************************/
/* which add a node to a list in its correct order position   */
/**************************************************************/

void insert_in_order(node *p,FILE *in,FILE *out)
{
    node *t,*s,*curr,*prev;
    int flag=0;
    
    t=(node*)malloc(sizeof(node));
    fscanf(in,"%d",&(t->id));
    fscanf(in,"%s",t->fn);
    fscanf(in,"%s",t->ln);
    fscanf(in,"%f",&(t->md));
    fscanf(in,"%f",&(t->final));
    t->next=NULL;
    s=p;
    while(s!=NULL&&flag!=1)
    {
        if(t->id==s->id)
        {
            fprintf(out,"ID is already insert");
            flag=1;
        }
        s=s->next;
    }
    if(flag==0)
    {
        if(p==NULL)
            p=t;
        else if (strcmp(p->fn,t->fn)==1)
        {
            t->next=p;
            p=t;
        }
        else
        {
            curr=p;
            while (strcmp(t->fn,curr->fn)==1&&curr!=NULL)
            {
                prev=curr;
                curr=curr->next;
            }
            prev->next=t;
            t->next=curr;
        }
    }
}

/**************************************************************/
/* which removes a particular node from the list using ID     */
/**************************************************************/

void delet_node(node *p,FILE *in,FILE *out)
{
    node *prev=NULL,*curr=p;
    int id;
    fscanf(in,"id",&id);
    while(curr!=NULL&&curr->id!=id)
    {
        prev=curr;
        curr=curr->next;
    }
    if(curr==NULL)
        fprintf(out,"The ID not exist");
    else
    {
        prev->next=curr->next;
        curr->next=NULL;
        free(curr);
    }
}

/**************************************************************/
/* which lists all the records in the linked list            */
/**************************************************************/

void list_records(node *p,FILE *out)
{
    if(p!=NULL)
    {
        fprintf(out,"%d ",(p->id));
        fprintf(out,"%s ",(p->fn));
        fprintf(out,"%s ",p->ln);
        fprintf(out,"%f ",p->md);
        fprintf(out,"%f\n",p->final);
        list_records(p->next,out);
    }
}

/**************************************************************/
/* which calculates and returns the average of final exams   */
/**************************************************************/

float calc_average(node *p)
{
    static float sum=0;
    static int c=0;
    if(p==NULL)
        return (sum/c);
    else
    {
        sum=sum+p->final;
        c++;
        return (calc_average(p->next));
    }
}


/**************************************************************/
/* which findes and returns a particular record using the ID  */
/* you should print the whole record from the main .          */
/**************************************************************/

node *find_record(node *p,FILE *in)
{
    int id;
    fscanf(in,"%d",&id);
    if(p==NULL)
        return NULL;
    else if(p->id==id)
        return p;
    else
        return (find_record(p->next,in));
}


main()
{
    FILE *in,*out;
    node *p=NULL,*r;
    char ch;

    in=fopen("in.txt","r");
    out=fopen("out.txt","w");
    if(in!=NULL&&out!=NULL)
    {
        fprintf(out,"1)I for insert anew record.\n");
        fprintf(out,"2)D for deleting arecord from the array.\n");
        fprintf(out,"3)F for the average of final exam.\n");
        fprintf(out,"4)C for the smallest and largest score of the final exam.\n");
        fprintf(out,"5)S for sort the array by descending order according to the first name .\n");
        fprintf(out,"6)Q to quit the program.\n");
    
        fprintf(out,"Enter an opration cod:");
        fscanf(in," %c",&ch);
    
        while(ch!='Q'&&ch!='q')
        {
            if(ch=='I'||ch=='i')
                insert_in_order(p,in,out);
            else if(ch=='D'||ch=='d')
            {
                delet_node(p,in,out);
                list_records(p,out);
            }
            else if(ch=='L'||ch=='l')
                list_records(p,out);
            else if(ch=='C'||ch=='c')
                fprintf(out,"The average of final exams=%f\n",calc_average(p));
            else if(ch=='F'||ch=='f')
            {
                r=find_record(p,in);
                list_records(r,out);
            }
            else
            fprintf(out,"wrong operation cod...");
    
            fprintf(out,"Enter an opration cod:");
            fscanf(in," %c",&ch);
        }
        fclose(in);
    }
    else
        printf("The file not exist");

    return 0;
}