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

#define FALSE 0
#define TRUE !FALSE

struct stock_data {
	char name[30];
	float buy_price;
	float current_price;
	};
	
void write_info(void);
void read_info(void);
void replace_info(void);

int main()
{
	char c;
	int done=FALSE;

	while(!done)
	{	
		puts("\nStock Portfolio Thing\n");
		puts("A - Add new stock\n");
		puts("L - List stocks\n");
		puts("R - Replace stock\n");
		puts("Q - Quit\n");
		printf("Your choice: ");
		
		c = getchar();
		fflush(stdin);		/* fpurge(stdin) */
		c = toupper(c);
		switch(c)
		{
			case('A'):
				puts("Add new stock\n");
				write_info();
				break;
			case('L'):
				puts("List stocks");
				read_info();
				break;
			case('R'):
				puts("Replace stock");
				replace_info();
				break;
			case('Q'):
				puts("Quit\n");
				done = TRUE;
				break;
			default:
				puts("?");
				break;
		}	
	}
	return(0);	
}

void write_info(void)
{   
	FILE *stocks;
	struct stock_data stock;
	
	printf("Enter stock name:");
	gets(stock.name);
	printf("What did you buy it for? $");
	scanf("%f",&stock.buy_price);
	stock.current_price = stock.buy_price/11;
	
	stocks = fopen("stock.dat","a");
	if(stocks==NULL)
	{
		puts("Error opening file");
		exit(1);
	}
	
	fwrite(&stock,sizeof(stock),1,stocks);	
		
	fclose(stocks);	
	puts("Stock added!");
	fflush(stdin);
}		

void read_info(void)
{
    	FILE *stocks;
	struct stock_data stock;
    	int x;
	
	stocks = fopen("stock.dat","r");
	if(stocks==NULL)
	{
		puts("No data in file");
		return;
	}

	while(TRUE)
	{	
		x = fread(&stock,sizeof(stock),1,stocks);  
		
		if(x==0) break;
		
		printf("\nStock name: %s\n",stock.name);
		printf("Purchased for $%.2f\n",stock.buy_price);
		printf("Current price: $%.2f\n",stock.current_price);
	}

	fclose(stocks);
}	

void replace_info(void)
{
    	FILE *stocks;
	struct stock_data stock;
    	int record,x;
	long offset;
	
	printf("Which record number do you want to find? ");
	scanf("%d",&record);
	
	stocks = fopen("stock.dat","r");
	if(stocks==NULL)
	{
		puts("Error opening file");
		return;
	}

	offset = (long)(record-1)*sizeof(stock);
	x = fseek(stocks,offset,SEEK_SET);
	if(x != 0)
	{
		puts("Error reading from file");
		return;
	}

	x = fread(&stock,sizeof(stock),1,stocks);  
	if(x==0)
	{
		puts("Error reading record");
		return;
	}
	
	printf("\nRecord: %d\n",record);	
	printf("Stock name: %s\n",stock.name);
	printf("Purchased for $%.2f\n",stock.buy_price);
	printf("Current price: $%.2f\n",stock.current_price);
	fclose(stocks);	
	fflush(stdin);		/* fpurge(stdin) */

/* read in new stock information */
	printf("Enter new stock name: ");
	gets(stock.name);
	printf("Enter purchase price: ");
	scanf("%f",&stock.buy_price);
	stock.current_price = stock.buy_price/9;
	
/* write stock information back to disk */
	stocks = fopen("stock.dat","r+");
	if(stocks==NULL)
	{
		puts("Error opening file for update");
		return;
	}

	offset = (long)(record-1)*sizeof(stock);
	x = fseek(stocks,offset,SEEK_SET);
	if(x != 0)
	{
		puts("Error finding record");
		return;
	}

	x = fwrite(&stock,sizeof(stock),1,stocks);  
	if(x==0)
	{
		puts("Error writing record");
		return;
	}
	fclose(stocks);
	fflush(stdin);	/* fpurge(stdin); */
}