#include <stdio.h>
#include <stdlib.h>
#include "studlist03.h"

int main()
{
  char *filename="Student.txt";
  FILE *fp;
  int i;
  Record r;
  int n;
  //char c;
 
  /* initialize */
  head = make_1node( r, NULL );

  /* input data from file */
  if ((fp = fopen(filename, "r")) == NULL) {
    fprintf(stderr, "Cannot open %s!\n", filename);
    exit(1);
  }

  while (fscanf(fp, "%d %s %s %d", &r.id, r.surname, r.givenname, &r.age) != EOF) {
    if(insert(r) == NULL) printf("Error: %d appears twice in the file.\n", r.id);   /* ここのメッセージは適当。なくてもよい */
  }
  fclose(fp);
  listprint();

  while (1) {
    /* rewind関数をコメントアウトすると，想定されていない入力があった場合に */
    /* キーボードから入力された内容がバッファに残ったままになり，次のループ */
    /* で意図しない動作を引き起こすことがある． */
    /* 例えば以下のような例である． */
    /* Chose operation で 0 を入力 */
    /* Delete ID で A を入力（本来整数値のIDを入力すべきところに文字を入力 */
    /* 以降，無限ループで以下の出力が繰り返される（Ctrl-Cで強制終了できる） */
    /* Chose operation (1: Insert, 0: delete, ^D: Finish) -> Delete ID -> Error: Bad data format. */
    /* なぜこのようなことが起きるのか，またなぜrewind関数で問題の発生を防げる */
    /* のかは各自考えてみよ． */
    /* rewind(stdin); */
    
    printf("Choose operation (1: Insert, 0: Delete, ^D: Finish) -> ");
    if (scanf("%d", &n) == EOF) {
      printf("\n");
      break;
    }
    switch (n) {
    case 1:
      /* insert list member */
      printf("Insert new student data: (ID Surname Givenname Age) -> ");
      if (scanf("%d %s %s %d", &r.id, r.surname, r.givenname, &r.age) != 4) {
        printf("Error: Bad data format.\n");
        break;
      }
      if (insert(r) == NULL) {
        printf("ID %d is already on the list!\n", r.id);
      }
      listprint();
      break;
    case 0:
      /* delete list member */
      printf("Delete ID -> ");
      if (scanf("%d", &i) != 1) {
        printf("Error: Bad data format.\n");
        break;
      }
      if (delete(i) ==  NULL) {
        printf("ID %d is not found.\n", i);
      }
      listprint();
      break;
    default:
      printf("Error: undefined command.\n");
      break;
    }
  }
  
  return 0;
}

/* First, find item r, based on data ID */
/* If the ID is not found, insert r after the last node */
/* Return value: node(inserted), NULL(already exist) */
NodePointer insert(Record r)
{
  NodePointer newnode, n;

  if (finditem(r.id) == NULL) {
    /* item not found and new node creation */
    newnode = make_1node(r, NULL);

    /* trace nodes from head to tail */
    for ( n=head; n->next!=NULL; n=n->next );

    n->next = newnode;
    return newnode;
  }
  else return NULL;
}

/* find item by ID and delete that node if it exists */
/* return pos before(exist), NULL(not exist) */
NodePointer delete(int key)
{
  NodePointer x, y;

  if ((x = finditem(key)) != NULL){
    /* item found and node deletion */
    y = x->next;
    x->next = y->next;

    /* free the memory */
    if (y != NULL) {
      free(y);
    }
  }
  return x;
}

/* print all items in the list from head to tail */
void listprint(void)
{
  NodePointer n;
  int count = 0;

  printf("Head - \n");
  for(n = head->next; n != NULL; n = n->next){
    printf("  %7d %-12s %-12s %d\n", n->data.id, n->data.surname, n->data.givenname, n->data.age);
    count++;
  }
  printf("%d nodes exist in the list.\n", count);
  printf("\n");
}

/* find item id_data with given ID                      */
/*   if found, return the address of the previous node. */
/*   otherwise, return NULL                             */
NodePointer finditem(int sid)
{
  NodePointer n;
  
  for(n = head; n->next != NULL; n = n->next) {
    if(n->next->data.id == sid) return n;
  }
  return NULL;
}

NodePointer make_1node(Record r, NodePointer p)
{
  NodePointer n;

  if ((n = (NodePointer) malloc(sizeof(struct node)) ) == NULL) {
    printf("Error in memory allocation\n");
    exit(8);
  }

  n->data = r;
  n->next = p;
  return n;
}