added file error handling

#vendorInfo.c#

@@ -0,0 +1,437 @@
+/* 
+ * vendorInfo.c
+ *
+ * SEN-102 Intro to Programming - Pre-Assessment
+ * Program that simulates a market containing vendors.
+ *
+ *    Created by Win (Thanawin Pattanaphol), 28th August 2024
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <ctype.h>
+
+#define MAX_VENDORS 20
+#define MAX_FILENAME_LENGTH 4096
+
+/* STRUCTURES */
+typedef struct vendor
+{
+	char vendor_name[20];
+	char merchandise[15];
+	int inventory_count;
+	int item_price_baht;
+	int revenue;	
+	int duplicate;
+} vendor;
+
+// Return type for search function
+typedef struct search_r
+{
+	int status;
+	int item_id;
+} search_r;
+
+// Return type for purchase function 
+typedef struct purchase_r
+{
+	int status;
+	char vendor_name[20];
+	int price_owe_baht; 
+} purchase_r; 
+
+vendor vendors[MAX_VENDORS];
+
+/* FUNCTION DECLARATION */
+int getstr(char str[], size_t n);
+char *strnlower(char *s, size_t n);
+
+search_r search
+(
+	char query[], 
+	vendor vendors[MAX_VENDORS], 
+	int total_vendors
+);
+		   
+purchase_r purchase
+(
+	int item_id, 
+	int amount, 
+	vendor vendors[MAX_VENDORS]
+);
+
+int check_vendors(vendor vendors[MAX_VENDORS], int total_vendors);
+
+int main()
+{	
+	char file_name[MAX_FILENAME_LENGTH];
+	printf("Enter name of input file: ");
+	getstr(file_name, MAX_FILENAME_LENGTH);
+	
+	FILE *fp;
+	if ((fp = fopen(file_name, "r")) == NULL) 
+	{
+		printf("%s cannot be opened.\n", file_name);
+		exit(EXIT_FAILURE);
+	}
+
+	// Calculate the file size
+	fseek(fp, 0, SEEK_END);
+	unsigned long file_size = ftell(fp);
+	fseek(fp, 0, SEEK_SET);
+
+	// Dynamically allocate buffer for file content
+	char *file_buffer = (char *) malloc(file_size);
+	int index = 0;
+
+	// Reading the file with fgets and formatting them using strtok
+	while ((fgets(file_buffer, 50, fp) != NULL) && (index <= MAX_VENDORS - 1))
+	{
+		char *token = strtok(file_buffer, " ");
+		strncpy(vendors[index].vendor_name, token, strlen(token) + 1); 
+		
+		token = strtok(NULL, " ");
+		strncpy(vendors[index].merchandise, token, strlen(token) + 1); 
+				
+		token = strtok(NULL, " ");
+		vendors[index].inventory_count = atoi(token);
+				
+		token = strtok(NULL, " ");
+		vendors[index].item_price_baht = atoi(token);
+				
+		index++;	
+	}
+
+	if (ferror(fp))
+	{
+	  printf("");
+	}
+	
+	int total_vendors = index;
+	printf("\n>>> Read %d vendors from file %s\n", total_vendors, file_name);
+
+	// Print out each vendor's info - excluding duplicates. 
+	for (int i = 0; i <= (total_vendors - 1); i++) 
+	{
+		/*
+		  This is similar to a linear search algorithm
+		  i = the current item
+		  j = the item next to i
+
+		  i is being compared to j:
+		      - if i == j then mark both i and j as duplicates
+		      - if not, move on to the next two items
+	    */
+		for (int j = i + 1; j < total_vendors; j++)
+		{
+			if ((strcmp(vendors[i].merchandise, vendors[j].merchandise)) == 0) 
+			{
+				vendors[j].duplicate = 1;
+			}
+			
+			if ((strcmp(vendors[i].vendor_name, vendors[j].vendor_name)) == 0)
+			{
+				vendors[j].duplicate = 1;
+			}
+		}	
+
+		if (vendors[i].duplicate == 0)
+		{
+			char vendor_info[200];
+			sprintf(vendor_info, "%s sells %s for %d each",
+				vendors[i].vendor_name, 
+				vendors[i].merchandise, 
+				vendors[i].item_price_baht
+			);
+			
+			char vendor_stock[50];
+			sprintf(vendor_stock, "Inventory %d items",
+				vendors[i].inventory_count
+			);
+	
+			printf("%-50s %s\n", vendor_info, vendor_stock);
+		} 
+		else
+		{
+			printf("\e[31m%s\e[m\n", "Duplicate record detected!");   
+		}
+	}
+	
+	printf("\n");
+
+	while (1) 
+	{
+		if(check_vendors(vendors, total_vendors) == 0)
+		{
+			break;	
+		};
+	
+		char user_query[100];
+		printf("What do you want to buy? (DONE to end) ");
+		getstr(user_query, 100);
+
+		if (
+		    (strcmp(user_query, "DONE") == 0) ||
+		    (strcmp(user_query, "done") == 0)
+		) 
+		{
+			break;
+		}
+
+		if (strcmp(user_query, "") == 0)
+		{
+			printf("Please enter an item name\n");
+		}
+		else
+		{
+			// convert string to lowercase - each character one by one
+			int user_query_length = strlen(user_query);	
+			strnlower(user_query, user_query_length);
+			
+			struct search_r item = search(user_query, vendors, total_vendors);
+			if(item.status == 0)
+			{
+				char input[10];
+
+				printf("How many do you want to buy? ");
+				getstr(input, 10);
+
+				// If a character of a string was sent, the return value would always be 0
+				// If a negative number was sent, the return value will always be negative.
+				
+				if(atoi(input) > 0) 
+				{
+					int item_amount = atoi(input);
+					purchase_r response = purchase(item.item_id, item_amount, vendors);
+
+					if (response.status == 0)
+					{
+						printf("You owe %s a total of %d baht.\n",
+							response.vendor_name,
+							response.price_owe_baht
+						);
+					}
+					else
+					{
+						printf("\e[31m%s -- %s %s\e[m\n",
+							   "Sorry",
+							   response.vendor_name,
+							   "does not have enough items available"
+						);
+					}
+				}
+				else 
+				{
+					printf("\e[31m%s\e[m\n",
+						   "You must enter a positive whole number for the number of items"
+					);                      	
+				}
+
+			}
+			else if (item.status == 2)
+			{
+				printf("\e[31m%s\e[m\n",
+					   "This item has duplicate records, please choose another item"
+				);
+			}
+			else
+			{
+				printf("\e[31m%s %s\e[m\n",
+					   "No vendor in this market sells",
+					   user_query
+			    );
+			}
+		}
+	}
+
+	printf("\n>>> End of day details\n");
+	
+	// Print out remaining inventory
+	for (int i = 0; i <= (total_vendors - 1); i++) 
+	{
+		if (vendors[i].duplicate == 0)
+		{
+			char vendor_info[200];
+			sprintf(vendor_info, "%s made %d baht today",
+				vendors[i].vendor_name, 
+				vendors[i].revenue
+			);
+			
+			char vendor_stock[50];
+			sprintf(vendor_stock, "Remaining inventory %d items",
+				vendors[i].inventory_count
+			);
+	
+			printf("%-50s %s\n", vendor_info, vendor_stock);	
+		}
+	}
+		
+	fclose(fp);
+	free(file_buffer);
+	return 0;
+};
+
+/*
+	getstr: Custom read input function
+
+	Parameters: 
+	    - str = string itself
+	    - n = max amount of characters that the function is able to read into buffer
+
+	Reads one character at a time into buffer and adds a null terminator when finish reading
+*/
+int getstr(char str[], size_t n) 
+{
+	int ch, i = 0;
+
+	while ((ch = getchar()) != '\n') 
+	{
+		if (i < (int)n) 
+		{
+			str[i++] = ch;
+		}
+	}
+
+	str[i] = '\0';
+	return i;
+};
+
+/* 
+	strnlower: Convert string to lowercase
+
+	Parameters:
+		- s: String
+		- n: Length of string
+
+    Return values:
+	    - (char *): Lowercased version of the string. 
+*/
+char *strnlower(char *s, size_t n)
+{
+	for (int i = 0; i < (int) n; i++)
+	{
+		s[i] = tolower(s[i]);
+	};
+}
+
+/* 
+	Search function
+
+	Parameters:
+		- (string) query: search query
+		- (vendor) vendors: the vendor table
+		- (int) total_vendors: the amount of vendors
+
+	Return values:
+	    (search_r) response:
+	    - status: 0 (Found item)
+		- status: 1 (No results)
+		- status: 2 (Found duplicate item)
+*/
+
+search_r search(char query[], vendor vendors[MAX_VENDORS], int total_vendors)
+{
+	int i; 
+	for (i = 0; i < total_vendors; i++)
+	{	
+		// First, check if duplicate
+		if (strcmp(query, vendors[i].merchandise) == 0)
+		{
+			if (vendors[i].duplicate == 0)
+			{
+				search_r response;
+				response.status = 0;
+				response.item_id = i;
+				
+				return (response);
+				break;
+			}
+			else
+			{	
+				search_r response;
+				response.status = 2;
+				return (response);
+			}
+		}	
+	};
+
+	if (i == total_vendors)
+	{
+		search_r response;
+		response.status = 1;
+		response.item_id = 0;
+		return (response);
+	}
+};
+
+/* 
+	purchase: Purchase function
+
+	Parameters:
+		- item_id: The item id that the user is purchasing
+		- amount: How many items that the user is purchasing
+		- vendors: vendor table
+
+	Return values:
+	    (purchase_r) response:
+	    - status: 0 (Purchase successful)
+		- status: 1 (Vendor does not have enough items)
+*/
+
+purchase_r purchase(int item_id, int amount, vendor vendors[MAX_VENDORS])
+{
+	if(amount <= vendors[item_id].inventory_count)
+	{
+		// Decrease vendor inventory
+		vendors[item_id].inventory_count = vendors[item_id].inventory_count - amount;
+
+		purchase_r response;
+
+		response.status = 0;
+		strcpy(response.vendor_name, vendors[item_id].vendor_name);
+		response.price_owe_baht = vendors[item_id].item_price_baht * amount;
+
+		vendors[item_id].revenue = vendors[item_id].item_price_baht * amount; 
+		
+		return response;
+	}
+	else
+	{
+		purchase_r response; 
+		response.status = 1;
+		strcpy(response.vendor_name, vendors[item_id].vendor_name);
+		
+		return response;
+	} 
+};
+
+/* 
+	check_vendors: Custom function to check if all vendors are empty.
+
+	Parameters:
+	    - vendors[MAX_VENDORS]: (vendor) All of the vendors.
+		- total_vendors: (integer) Total vendors in market.
+
+	Return values:
+	    - (int) 0: All vendors are empty.
+		- (int) 1: There are still items left. 
+*/
+
+int check_vendors(vendor vendors[MAX_VENDORS], int total_vendors)
+{
+	int i;
+	for (i = 0; i < total_vendors; i++)
+	{
+		// Condition: Vendors that are not empty (Check if not marked as duplicates) 
+		if (vendors[i].inventory_count != 0 && vendors[i].duplicate == 0)
+		{
+			return 1;
+		}
+	}
+
+	if (i == total_vendors)
+	{
+		return 0;
+	}
+};

vendor2.data

@@ -8,6 +8,7 @@ Oat watches 9 120
 Lila jackets 7 380
 Mary toys 17 39
 Kitty dishes 11 67
+Win books 30 165
 Pat comics 22 18
 Jay shoes 22 300
 Mark dvds 10 200

vendorInfo.c

@@ -72,7 +72,7 @@ int main()
 	FILE *fp;
 	if ((fp = fopen(file_name, "r")) == NULL) 
 	{
-		printf("%s cannot be opened.\n", file_name);
+		perror("Error opening file");
 		exit(EXIT_FAILURE);
 	}
 
@@ -103,6 +103,12 @@ int main()
 		index++;	
 	}
 
+	// Error handling 
+	if (ferror(fp))
+	{
+		printf("An error occured while reading the file.\n");
+	}
+
 	int total_vendors = index;
 	printf("\n>>> Read %d vendors from file %s\n", total_vendors, file_name);
 
@@ -122,13 +128,11 @@ int main()
 		{
 			if ((strcmp(vendors[i].merchandise, vendors[j].merchandise)) == 0) 
 			{
-				vendors[i].duplicate = 1;
 				vendors[j].duplicate = 1;
 			}
 			
 			if ((strcmp(vendors[i].vendor_name, vendors[j].vendor_name)) == 0)
 			{
-				vendors[i].duplicate = 1;
 				vendors[j].duplicate = 1;
 			}
 		}	

vendorsmall.data

@@ -2,3 +2,4 @@ Win phone 1 50
 Peter books 1 70
 Amy teeshirts 5 100
 Deez computers 5 80
+kjflkfdl lkdfjlkslkfslklk sdfdsjf dslkfjdslfkjs