Implementation of functions LoginAsCustomer() and Login()

src/CustomerData.txt

@@ -0,0 +1,6 @@
+1234=example
+ID=1234
+forename=Max
+Surname=Mustermann
+password=example
+balance=0

src/CustomerProperties.h

@@ -0,0 +1,4 @@
+typedef struct Customer{
+	char *ID, *forename, *surname, *password;
+	float balance;
+}customer_t;

src/LoginCustomer.c

@@ -1,5 +1,97 @@
 #include "LoginCustomer.h"
+
 bool checkLogin(bool loginSuccessful)
 {	
 	return (loginSuccessful) ? true : false;
 }
+
+void collectCustomerDataForLogin(int attempts)
+{
+	customer_t c;
+	c.ID = calloc(15+1,sizeof(char));
+	c.password = calloc(15+1, sizeof(char));
+	char digitCharacterFromUser, passwordCharacterFromUser;
+	int IDLengthCounter = 0, passwordLengthCounter = 0;
+	const int IDMaxLength = 16, passwordMaxLength = 16;
+	
+	printf("Enter ID:\n");
+	while(((digitCharacterFromUser=getchar()) != '\n')&&IDLengthCounter<IDMaxLength){
+			if(digitCharacterFromUser>='0'&&digitCharacterFromUser<='9'){
+				*(c.ID+IDLengthCounter) = digitCharacterFromUser;
+			}
+			else{
+				printf("Character entered is not a digit. Aborting.\n");
+				exit(-1);
+			}
+		++IDLengthCounter;	
+	}
+	*(c.ID+IDLengthCounter) = '\0';
+	
+	if(IDLengthCounter>=IDMaxLength){
+		printf("ID entered is too long. Aborting.\n");
+		exit(-1);
+	}
+
+	printf("Enter password:\n");
+	while((passwordCharacterFromUser=getchar())!='\n'&&passwordLengthCounter<passwordMaxLength){
+		*(c.password+passwordLengthCounter) = passwordCharacterFromUser;
+		++passwordLengthCounter;
+	}
+	*(c.password+passwordLengthCounter) = '\0';
+	
+	if(passwordLengthCounter>=passwordMaxLength){
+		printf("Password entered is too long. Aborting.\n");
+		exit(-1);
+	}
+	customer_t *ptr = &c;
+	bool loginSuccessful = loginCustomer(ptr);
+	if(loginSuccessful ) {
+		printf("Welcome to the menu!\n");
+		//call menu()
+	}else if(!loginSuccessful && attempts < MAX_LOGIN_ATTEMPTS){
+		printf("You have %d attempts left.\n", MAX_LOGIN_ATTEMPTS - attempts);
+		collectCustomerDataForLogin(++attempts);
+	}else{
+		printf("Maximum number of attempts reached. Program terminates.\n");
+		exit(-1);
+		//call error()
+	}
+	
+}
+
+bool loginCustomer(customer_t *c)
+{
+	bool foundCustomerEntryInFile = false;
+	char *searchForThisString = generateCheckString(c->ID,c->password);
+	char *lineFromCustomerFile = calloc(40,sizeof(char));
+	FILE *readCustomerFile = fopen("CustomerData.txt", "r");
+	if(readCustomerFile==NULL){
+		printf("Could not find file. Aborting.\n");
+		exit(-1);
+		//call error()
+	}
+	while((fscanf(readCustomerFile,"%s",lineFromCustomerFile)!=EOF)){
+			if(strcmp(searchForThisString,lineFromCustomerFile)==0){
+				foundCustomerEntryInFile = true;
+				break;
+			}
+	}
+	
+	if(checkLogin(foundCustomerEntryInFile)){
+		printf("Login successful.\n");
+		return foundCustomerEntryInFile;
+	}else{
+		printf("Login not successful.\n");
+	}
+	fclose(readCustomerFile);
+	return foundCustomerEntryInFile;
+}
+
+char *generateCheckString(char *ID, char *password){
+	int checkStringLength = strlen(ID) + 1 + strlen(password) + 1;
+	char *checkString = calloc(checkStringLength, sizeof(char));
+	checkString = strcat(ID,"=");
+	checkString = strcat(checkString,password);
+	*(checkString+checkStringLength) = '\0';
+	return checkString;
+}

src/LoginCustomer.h

@@ -1,3 +1,10 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include <stdbool.h>
+#include <string.h>
+#include "CustomerProperties.h"
+#define MAX_LOGIN_ATTEMPTS 3
+char *generateCheckString(char *, char*);
 bool checkLogin(bool);
+void collectCustomerDataForLogin(int);
+bool loginCustomer(customer_t *);