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

#ifdef EBUG
#define DEBUG(m) \
  printf("debug: %s at line %d in file %s\n", \
    (m), __LINE__, __FILE__)
#else
#define DEBUG(m)
#endif

struct Staff {
  char name[50];
  int age;
  struct Staff * next;
};

const char * FILENAME = "staffList.txt";
struct Staff *	head = NULL;

/* Recursively print the content of <h>, in post-order. */
void printList(struct Staff* h) {
  if (!h) return;
  printList(h->next);
  printf(">> %s, %d\n", h->name, h->age);
}

/* Add <n> to the first node of <h>
   return the processed list
 */
struct Staff * addNode(struct Staff * h, struct Staff * n) {
  if (!n) return h; /* do nothing if n is NULL */
  n->next = h;
  return n;
}

void calcAvgAge(struct Staff * h) {
  int total = 0, staffNum = 0;
  for (; h; ++staffNum, h=h->next)
    total += h->age;
  printf("Average age: %.2f\n", (float)total/staffNum);
}

/* Recursively search for <name> in list <h> 
   Return the found node, or NULL if not found
 */
struct Staff * inList(struct Staff * h, char* name) {
  if (!h) return NULL; 
  char fname[200], lname[200];
  sscanf(h->name, "%s %s", fname, lname);

  if (strcmp(lname, name)) /* not found; keep trying */
    return inList(h->next, name);
  return h; /* found */
}

/* Write the content of list <h> into <FILENAME> */
void writeToFile(struct Staff * h) {
  FILE * outfile = fopen(FILENAME, "w");
  while (h) {
    fprintf(outfile, "%s:%d\n", h->name, h->age);
    h = h->next;
  }
  fclose(outfile);
}

/* Remove the node <r> from list <h>, if <r> exists. 
   Return the processed list
 */
struct Staff * removeNode(struct Staff * h, struct Staff * r) {
  struct Staff * prev = NULL, *head = h;
  while(h) {
    if (h == r) {
      /* special case: if the match found at the first node */
      if (prev == NULL) {
        h = h->next;
        free(r);
        return h;
      }
      prev->next = h->next;
      free(r);
      return head;
    }
    prev = h;
    h = h->next;
  }
}

int main() {
  FILE * infile;
  char line[257], name[256], toDel[10];
  int age;
  struct Staff * temp = NULL;

  /* if file open failed, exit with signal status 1 */
  if (!(infile = fopen(FILENAME, "r"))) 
    exit(1);

  DEBUG("Start processing the file");
  while (fgets(line, 256, infile)) {
    sscanf(line, "%[^:]:%d", name, &age);
    DEBUG("Populating the <temp> node");
    temp = malloc(sizeof(struct Staff));
    temp->next = NULL;
    strcpy(temp->name, name);
    temp->age = age;
    head = addNode(head, temp);
  }

  DEBUG("Start prompting...");
  /* prompt for a last name to search for */
  while (1) {
    printf("Enter a last name: ");
    scanf("%s", name);
    if (strcmp(name, "q") == 0) 
      return 0;
    if (strcmp(name, "w") == 0) {
      writeToFile(head);
      continue;
    }
    if (temp = inList(head, name)) {
      printf(">> %s, %d\n", temp->name, temp->age);

      /* prompt user to remove the found record */
      printf("Delete this person? [yes/NO] ");
      scanf("%s", toDel);
      DEBUG("Scanned user's input");
      if (strcmp(toDel, "yes") == 0) {
        DEBUG("Removing the person...");
        head = removeNode(head, temp);
      }
#ifdef EBUG
      printList(head);
#endif
    } else {
      printf("not found!\n");
    }
  }

  //printList(head);
  //calcAvgAge(head);
  return 0;
}