#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>

#define BUF_SIZE 256

typedef struct node {
  char* string;
  struct node* next;
} fifo;

void fifo_append(fifo* head, char* new_string);
char* fifo_read(fifo** head);

int main(int argc, char* argv[]) {
  if (argc <= 1) {
    printf("Too few arguments\n");
    return 1;
  }

  char name[strlen(argv[1]) + 2];
  strcpy(name, argv[1]);
  strcat(name, ".c");

  char path[BUF_SIZE] = "./";

  strcat(path, name);

  open(path, O_RDONLY, 0);
  
  if (errno == 0) {
    printf("File already exists.\n");
    return 2;
  }
  errno = 0;

  const int fd = creat(path, S_IRUSR | S_IWUSR | S_IROTH);

  int includes_n = argc - 2;
  int lines_n = 5 + includes_n;

  fifo* lines_head = (fifo*) malloc(sizeof(fifo));
  lines_head->string = "";
  lines_head->next = NULL;

  if (argc > 2) {
    for (int i = 2; i < argc; i++) {
      char line[BUF_SIZE] = "#include <";
      strcat(line, argv[i]);
      strcat(line, ".h>\n");
      fifo_append(lines_head, line);
    }
    fifo_append(lines_head, "\n");
  }

  fifo_append(lines_head, "int main() {\n\n");
  fifo_append(lines_head, "  return 0;\n");
  fifo_append(lines_head, "}");

  for (int i = 0; i < lines_n; i++) {
    write(fd, fifo_read(&lines_head), strlen(lines_head->string));
  }

  close(fd);

  char command[5 + strlen(name)];
  strcpy(command, "nvim ");
  strcat(command, name);

  system(command);

  return 0;
}

void fifo_append(fifo* head, char* string) {
  fifo* last = head;

  char* new_string = (char*) malloc(sizeof(char) * strlen(string));
  strcpy(new_string, string);

  while (last->next != NULL)
    last = last->next;

  fifo* new_node = (fifo*) malloc(sizeof(fifo));
  new_node->string = new_string;
  new_node->next = NULL;

  last->next = new_node;
}

char* fifo_read(fifo** head) {
  char* return_value = (*head)->string;

  fifo* prev_head = *head;

  *head = (*head)->next;

  free(prev_head);

  return return_value;
}